Does + _ wire positions matter on a fuel injector as one of my injectors is wire different to the other 3 thankyou

Silverado 1500 or 2500 or 3500 or HD? no pickup told
not told the job you are doing>??
remove them all ,or scope them or just what, no job told
no end goal or task told. sorry can guess it.

like most V6/8 now , it is a sandwich.
the service manual covers all,l buy it rent it.?
toss dice and land on 1500
the rail on this engine, fuel rail like all , intake manifold injectors used;. all injector held down by both rails. left and right
now the steps to off them if is the job,
pull the isolator seen photo 1, far below.
1: pull left rail and right rail
Remove and discard the fuel injector retainer clips by installing EN-51097 injector retaining clip installer and spreading both sides of the clip evenly.
Always use NEW fuel injector collars supplied with injector when installing the new injector. If reinstalling the injector, it is not necessary to remove the collars unless the collars are being replaced.
Replace the injector seals as needed. Refer to Fuel Rail and Injectors Cleaning and Inspection.
Note
Inspect the injectors to be sure that they are clean and free of debris prior to installation. Do NOT lubricate the injector seals. Rebuild the fuel injectors whenever the injector has been removed from the fuel injector rail.


now I will past the other page rails off per the manual read to you.
just bank 1, i am to lazy to post both
step 1 rail off bank1.
Note
Inspect the injectors to be sure that they are clean and free of debris prior to installation. Do NOT lubricate the injector seals. Rebuild the fuel injectors whenever the injector has been removed from the fuel injector rail.

1. Remove the fuel pump insulator. Fuel Pump Insulator Replacement
2. Remove the fuel injector intermediate pipe position?1. Fuel Feed Intermediate Pipe Replacement - Position 1
3. Clean the cylinder head pocket around the injectors of any dirt or buildup.
4. Disconnect the electrical wiring harness connectors from the fuel rail.
5. the fuel rail fasteners are retained in the fuel rail by keepers and may be difficult to remove.Remove the fuel rail fasteners?(1) securing the injector rail?(2).
   Install two sets of EN-49248 remover?(3).
6. Install one remover in each of the fuel rail fastener bores.
7. Remove by turning each section of the EN-49248 remover an even amount to pull the fuel rail and injectors out evenly.
8. CAUTION
9. Remove the fuel rail assembly carefully in order to prevent damage to the injector electrical connector terminals and the injector spray tips. Support the fuel rail after the fuel rail is removed in order to avoid damaging the fuel rail components.
10. Cap the fittings and plug the holes when servicing the fuel system in order to prevent dirt and other contaminants from entering open pipes and passages.
11. 1. Simultaneously lift both ends of the fuel rail?(2) and remove the fuel rail assembly from the cylinder head.
12. Remove and DISCARD the fuel injector seals.
13. Some vehicles were not originally equipped with fuel injector dust seals. A NEW seal must be installed when the injectors are removed.
    Remove and DISCARD the fuel injector dust seal (1).
14. NOTE
    Note
    Whenever the fuel injectors are removed from the cylinder head or fuel rail, they will need to be rebuilt. Fuel Rail and Injectors Cleaning and Inspection
    If replacing the fuel injection fuel rail, remove the fuel injectors. Fuel Injector Replacement

Installation Procedure, skipped me. the service manual lists 4 tools
per

Special Tools

1. EN-49248 Injector Rail Assembly Remover
2. EN-51105-1 Injector Seal Installer and Sizer
3. EN-49245-3 Fuel Injection Seal Installer Sizer
4. EN-49245-4 Fuel Injection Seal Installer Sizer

this is first. pull the isolator.

this one step is the GET TO ANSWEREd
Injector work 10x more complex and special tools needed x4

fuel filter, computer

Yes it does

They will spray fuel into the wrong cylinder,
at the wrong time

Could Hydraulic the motor & damage it

Just an at home chat room

You have to use the internet for info
or buy factory service manuals

Should have marked the connectors with a
sharpe & made note of wire colors on the PCM
side

Why replace injectors?
They leaked
They failed a test
They quite
Your guessing at a misfire

Sensor diagram for a 2000 toyota avalon and list of Pcodes

P0100 Mass or Volume Air Flow Circuit Malfunction
P0101 Mass or Volume Air Flow Circuit Range/Performance Problem
P0102 Mass or Volume Air Flow Circuit Low Input
P0103 Mass or Volume Air Flow Circuit High Input
P0104 Mass or Volume Air Flow Circuit Intermittent
P0105 Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction
P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem
P0107 Manifold Absolute Pressure/Barometric Pressure Circuit Low Input
P0108 Manifold Absolute Pressure/Barometric Pressure Circuit High Input
P0109 Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent
P0110 Intake Air Temperature Circuit Malfunction
P0111 Intake Air Temperature Circuit Range/Performance Problem
P0112 Intake Air Temperature Circuit Low Input
P0113 Intake Air Temperature Circuit High Input
P0114 Intake Air Temperature Circuit Intermittent
P0115 Engine Coolant Temperature Circuit Malfunction
P0116 Engine Coolant Temperature Circuit Range/Performance Problem
P0117 Engine Coolant Temperature Circuit Low Input
P0118 Engine Coolant Temperature Circuit High Input
P0119 Engine Coolant Temperature Circuit Intermittent
P0120 Throttle/Pedal Position Sensor/Switch "A" Circuit Malfunction
P0121 Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance Problem
P0122 Throttle/Pedal Position Sensor/Switch "A" Circuit Low Input
P0123 Throttle/Pedal Position Sensor/Switch "A" Circuit High Input
P0124 Throttle/Pedal Position Sensor/Switch "A" Circuit Intermittent
P0125 Insufficient Coolant Temperature For Closed Loop Fuel Control
P0126 Insufficient Coolant Temperature For Stable Operation
P0130 O2Circuit Malfunction (Bank #1 Sensor #1)
P0131 O2Sensor Circuit Low Voltage (Bank #1 Sensor #1)
P0132 O2Sensor Circuit High Voltage (Bank #1 Sensor #1)
P0133 O2Sensor Circuit Slow Response (Bank #1 Sensor #1)
P0134 O2Sensor Circuit No Activity Detected (Bank #1 Sensor #1)
P0135 O2Sensor Heater Circuit Malfunction (Bank #1 Sensor #1)
P0136 O2Sensor Circuit Malfunction (Bank #1 Sensor #2)
P0137 O2Sensor Circuit Low Voltage (Bank #1 Sensor #2)
P0138 O2Sensor Circuit High Voltage (Bank #1 Sensor #2)
P0139 O2Sensor Circuit Slow Response (Bank #1 Sensor #2)
P0140 O2Sensor Circuit No Activity Detected (Bank #1 Sensor #2)
P0141 O2Sensor Heater Circuit Malfunction (Bank #1 Sensor #2)
P0142 O2Sensor Circuit Malfunction (Bank #1 Sensor #3)
P0143 O2Sensor Circuit Low Voltage (Bank #1 Sensor #3)
P0144 O2Sensor Circuit High Voltage (Bank #1 Sensor #3)
P0145 O2Sensor Circuit Slow Response (Bank #1 Sensor #3)
P0146 O2Sensor Circuit No Activity Detected (Bank #1 Sensor #3)
P0147 O2Sensor Heater Circuit Malfunction (Bank #1 Sensor #3)
P0150 O2Sensor Circuit Malfunction (Bank #2 Sensor #1)
P0151 O2Sensor Circuit Low Voltage (Bank #2 Sensor #1)
P0152 O2Sensor Circuit High Voltage (Bank #2 Sensor #1)
P0153 O2Sensor Circuit Slow Response (Bank #2 Sensor #1)
P0154 O2Sensor Circuit No Activity Detected (Bank #2 Sensor #1)
P0155 O2Sensor Heater Circuit Malfunction (Bank #2 Sensor #1)
P0156 O2Sensor Circuit Malfunction (Bank #2 Sensor #2)
P0157 O2Sensor Circuit Low Voltage (Bank #2 Sensor #2)
P0158 O2Sensor Circuit High Voltage (Bank #2 Sensor #2)
P0159 O2Sensor Circuit Slow Response (Bank #2 Sensor #2)
P0160 O2Sensor Circuit No Activity Detected (Bank #2 Sensor #2)
P0161 O2Sensor Heater Circuit Malfunction (Bank #2 Sensor #2)
P0162 O2Sensor Circuit Malfunction (Bank #2 Sensor #3)
P0163 O2Sensor Circuit Low Voltage (Bank #2 Sensor #3)
P0164 O2Sensor Circuit High Voltage (Bank #2 Sensor #3)
P0165 O2Sensor Circuit Slow Response (Bank #2 Sensor #3)
P0166 O2Sensor Circuit No Activity Detected (Bank #2 Sensor #3)
P0167 O2Sensor Heater Circuit Malfunction (Bank #2 Sensor #3)
P0170 Fuel Trim Malfunction (Bank #1)
P0171 System Too Lean (Bank #1)
P0172 System Too Rich (Bank #1)
P0173 Fuel Trim Malfunction (Bank #2)
P0174 System Too Lean (Bank #2)
P0175 System Too Rich (Bank #2)
P0176 Fuel Composition Sensor Circuit Malfunction
P0177 Fuel Composition Sensor Circuit Range/Performance
P0178 Fuel Composition Sensor Circuit Low Input
P0179 Fuel Composition Sensor Circuit High Input
P0180 Fuel Temperature Sensor "A" Circuit Malfunction
P0181 Fuel Temperature Sensor "A" Circuit Range/Performance
P0182 Fuel Temperature Sensor "A" Circuit Low Input
P0183 Fuel Temperature Sensor "A" Circuit High Input
P0184 Fuel Temperature Sensor "A" Circuit Intermittent
P0185 Fuel Temperature Sensor "B" Circuit Malfunction
P0186 Fuel Temperature Sensor "B" Circuit Range/Performance
P0187 Fuel Temperature Sensor "B" Circuit Low Input
P0188 Fuel Temperature Sensor "B" Circuit High Input
P0189 Fuel Temperature Sensor "B" Circuit Intermittent
P0190 Fuel Rail Pressure Sensor Circuit Malfunction
P0191 Fuel Rail Pressure Sensor Circuit Range/Performance
P0192 Fuel Rail Pressure Sensor Circuit Low Input
P0193 Fuel Rail Pressure Sensor Circuit High Input
P0194 Fuel Rail Pressure Sensor Circuit Intermittent
P0195 Engine Oil Temperature Sensor Malfunction
P0196 Engine Oil Temperature Sensor Range/Performance
P0197 Engine Oil Temperature Sensor Low
P0198 Engine Oil Temperature Sensor High
P0199 Engine Oil Temperature Sensor Intermittent
P0200 Injector Circuit Malfunction
P0201 Injector Circuit Malfunction - Cylinder #1
P0202 Injector Circuit Malfunction - Cylinder #2
P0203 Injector Circuit Malfunction - Cylinder #3
P0204 Injector Circuit Malfunction - Cylinder #4
P0205 Injector Circuit Malfunction - Cylinder #5
P0206 Injector Circuit Malfunction - Cylinder #6
P0207 Injector Circuit Malfunction - Cylinder #7
P0208 Injector Circuit Malfunction - Cylinder #8
P0209 Injector Circuit Malfunction - Cylinder #9
P0210 Injector Circuit Malfunction - Cylinder #10
P0211 Injector Circuit Malfunction - Cylinder #11
P0212 Injector Circuit Malfunction - Cylinder #12
P0213 Cold Start Injector #1 Malfunction
P0214 Cold Start Injector #2 Malfunction
P0215 Engine Shutoff Solenoid Malfunction
P0216 Injection Timing Control Circuit Malfunction
P0217 Engine Over Temperature Condition
P0218 Transmission Over Temperature Condition
P0219 Engine Over Speed Condition
P0220 Throttle/Pedal Position Sensor/Switch "B" Circuit Malfunction
P0221 Throttle/Pedal Position Sensor/Switch "B" Circuit Range/Performance Problem
P0222 Throttle/Pedal Position Sensor/Switch "B" Circuit Low Input
P0223 Throttle/Pedal Position Sensor/Switch "B" Circuit High Input
P0224 Throttle/Pedal Position Sensor/Switch "B" Circuit Intermittent
P0225 Throttle/Pedal Position Sensor/Switch "C" Circuit Malfunction
P0226 Throttle/Pedal Position Sensor/Switch "C" Circuit Range/Performance Problem
P0227 Throttle/Pedal Position Sensor/Switch "C" Circuit Low Input
P0228 Throttle/Pedal Position Sensor/Switch "C" Circuit High Input
P0229 Throttle/Pedal Position Sensor/Switch "C" Circuit Intermittent
P0230 Fuel Pump Primary Circuit Malfunction
P0231 Fuel Pump Secondary Circuit Low
P0232 Fuel Pump Secondary Circuit High
P0233 Fuel Pump Secondary Circuit Intermittent
P0234 Engine Over Boost Condition
P0261 Cylinder #1 Injector Circuit Low
P0262 Cylinder #1 Injector Circuit High
P0263 Cylinder #1 Contribution/Balance Fault
P0264 Cylinder #2 Injector Circuit Low
P0265 Cylinder #2 Injector Circuit High
P0266 Cylinder #2 Contribution/Balance Fault
P0267 Cylinder #3 Injector Circuit Low
P0268 Cylinder #3 Injector Circuit High
P0269 Cylinder #3 Contribution/Balance Fault
P0270 Cylinder #4 Injector Circuit Low
P0271 Cylinder #4 Injector Circuit High
P0272 Cylinder #4 Contribution/Balance Fault
P0273 Cylinder #5 Injector Circuit Low
P0274 Cylinder #5 Injector Circuit High
P0275 Cylinder #5 Contribution/Balance Fault
P0276 Cylinder #6 Injector Circuit Low
P0277 Cylinder #6 Injector Circuit High
P0278 Cylinder #6 Contribution/Balance Fault
P0279 Cylinder #7 Injector Circuit Low
P0280 Cylinder #7 Injector Circuit High
P0281 Cylinder #7 Contribution/Balance Fault
P0282 Cylinder #8 Injector Circuit Low
P0283 Cylinder #8 Injector Circuit High
P0284 Cylinder #8 Contribution/Balance Fault
P0285 Cylinder #9 Injector Circuit Low
P0286 Cylinder #9 Injector Circuit High
P0287 Cylinder #9 Contribution/Balance Fault
P0288 Cylinder #10 Injector Circuit Low
P0289 Cylinder #10 Injector Circuit High
P0290 Cylinder #10 Contribution/Balance Fault
P0291 Cylinder #11 Injector Circuit Low
P0292 Cylinder #11 Injector Circuit High
P0293 Cylinder #11 Contribution/Balance Fault
P0294 Cylinder #12 Injector Circuit Low
P0295 Cylinder #12 Injector Circuit High
P0296 Cylinder #12 Contribution/Balance Fault
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder #1 - Misfire Detected
P0302 Cylinder #2 - Misfire Detected
P0303 Cylinder #3 - Misfire Detected
P0304 Cylinder #4 - Misfire Detected
P0305 Cylinder #5 - Misfire Detected
P0306 Cylinder #6 - Misfire Detected
P0307 Cylinder #7 - Misfire Detected
P0308 Cylinder #8 - Misfire Detected
P0320 Ignition/Distributor Engine Speed Input Circuit Malfunction
P0321 Ignition/Distributor Engine Speed Input Circuit Range/Performance
P0322 Ignition/Distributor Engine Speed Input Circuit No Signal
P0323 Ignition/Distributor Engine Speed Input Circuit Intermittent
P0325 Knock Sensor #1 - Circuit Malfunction (Bank #1 or Single Sensor)
P0326 nock Sensor #1 - Circuit Range/Performance (Bank #1 or Single Sensor)
P0327 Knock Sensor #1 - Circuit Low Input (Bank #1 or Single Sensor)
P0328 Knock Sensor #1 - Circuit High Input (Bank #1 or Single Sensor)
P0329 Knock Sensor #1 - Circuit Input Intermittent (Bank #1 or Single Sensor)
P0330 Knock Sensor #2 - Circuit Malfunction (Bank #2)
P0331 Knock Sensor #2 - Circuit Range/Performance (Bank #2)
P0332 Knock Sensor #2 - Circuit Low Input (Bank #2)
P0333 Knock Sensor #2 - Circuit High Input (Bank #2)
P0334 Knock Sensor #2 - Circuit Input Intermittent (Bank #2)
P0335 Crankshaft Position Sensor "A" Circuit Malfunction
P0336 Crankshaft Position Sensor "A" Circuit Range/Performance
P0337 Crankshaft Position Sensor "A" Circuit Low Input
P0338 Crankshaft Position Sensor "A" Circuit High Input
P0339 Crankshaft Position Sensor "A" Circuit Intermittent
P0340 Camshaft Position Sensor Circuit Malfunction
P0341 Camshaft Position Sensor Circuit Range/Performance
P0342 Camshaft Position Sensor Circuit Low Input
P0343 Camshaft Position Sensor Circuit High Input
P0344 Camshaft Position Sensor Circuit Intermittent
P0350 Ignition Coil Primary/Secondary Circuit Malfunction
P0351 Ignition Coil "A" Primary/Secondary Circuit Malfunction
P0352 Ignition Coil "B" Primary/Secondary Circuit Malfunction
P0353 Ignition Coil "C" Primary/Secondary Circuit Malfunction
P0354 Ignition Coil "D" Primary/Secondary Circuit Malfunction
P0355 Ignition Coil "E" Primary/Secondary Circuit Malfunction
P0356 Ignition Coil "F" Primary/Secondary Circuit Malfunction
P0357 Ignition Coil "G" Primary/Secondary Circuit Malfunction
P0358 Ignition Coil "H" Primary/Secondary Circuit Malfunction
P0359 Ignition Coil "I" Primary/Secondary Circuit Malfunction
P0360 Ignition Coil "J" Primary/Secondary Circuit Malfunction
P0361 Ignition Coil "K" Primary/Secondary Circuit Malfunction
P0362 Ignition Coil "L" Primary/Secondary Circuit Malfunction
P0370 Timing Reference High Resolution Signal "A" Malfunction
P0371 Timing Reference High Resolution Signal "A" Too Many Pulses
P0372 Timing Reference High Resolution Signal "A" Too Few Pulses
P0373 Timing Reference High Resolution Signal "A" Intermittent/Erratic Pulses
P0374 Timing Reference High Resolution Signal "A" No Pulses
P0375 Timing Reference High Resolution Signal "B" Malfunction
P0376 Timing Reference High Resolution Signal "B" Too Many Pulses
P0377 Timing Reference High Resolution Signal "B" Too Few Pulses
P0378 Timing Reference High Resolution Signal "B" Intermittent/Erratic Pulses
P0379 Timing Reference High Resolution Signal "B" No Pulses
P0380 Glow Plug/Heater Circuit "A" Malfunction
P0381 Glow Plug/Heater Indicator Circuit Malfunction
P0382 Glow Plug/Heater Circuit "B" Malfunction
P0385 Crankshaft Position Sensor "B" Circuit Malfunction
P0386 Crankshaft Position Sensor "B" Circuit Range/Performance
P0387 Crankshaft Position Sensor "B" Circuit Low Input
P0388 Crankshaft Position Sensor "B" Circuit High Input
P0389 Crankshaft Position Sensor "B" Circuit Intermittent
P0400 Exhaust Gas Recirculation Flow Malfunction
P0401 Exhaust Gas Recirculation Flow Insufficient Detected
P0402 Exhaust Gas Recirculation Flow Excessive Detected
P0403 Exhaust Gas Recirculation Circuit Malfunction
P0404 Exhaust Gas Recirculation Circuit Range/Performance
P0405 Exhaust Gas Recirculation Sensor "A" Circuit Low
P0406 Exhaust Gas Recirculation Sensor "A" Circuit High
P0407 Exhaust Gas Recirculation Sensor "B" Circuit Low
P0408 Exhaust Gas Recirculation Sensor "B" Circuit High
P0410 Secondary Air Injection System Malfunction
P0411 Secondary Air Injection System Incorrect Flow Detected
P0412 Secondary Air Injection System Switching Valve "A" Circuit Malfunction
P0413 Secondary Air Injection System Switching Valve "A" Circuit Open
P0414 Secondary Air Injection System Switching Valve "A" Circuit Shorted
P0415 Secondary Air Injection System Switching Valve "B" Circuit Malfunction
P0416 Secondary Air Injection System Switching Valve "B" Circuit Open
P0417 Secondary Air Injection System Switching Valve "B" Circuit Shorted
P0418 Secondary Air Injection System Relay "A" Circuit Malfunction
P0419 Secondary Air Injection System Relay "B" Circuit Malfunction
P0420 Catalyst System Efficiency Below Threshold (Bank #1)
P0421 Warm Up Catalyst Efficiency Below Threshold (Bank #1)
P0422 Main Catalyst Efficiency Below Threshold (Bank #1)
P0423 Heated Catalyst Efficiency Below Threshold (Bank #1)
P0424 Heated Catalyst Temperature Below Threshold (Bank #1)
P0430 Catalyst System Efficiency Below Threshold (Bank #2)
P0431 Warm Up Catalyst Efficiency Below Threshold (Bank #2)
P0432 Main Catalyst Efficiency Below Threshold (Bank #2)
P0433 Heated Catalyst Efficiency Below Threshold (Bank #2)
P0434 Heated Catalyst Temperature Below Threshold (Bank #2)
P0440 Evaporative Emission Control System Malfunction
P0441 Evaporative Emission Control System Incorrect Purge Flow
P0442 Evaporative Emission Control System Leak Detected (Small Leak)
P0443 Evaporative Emission Control System Purge Control Valve Circuit Malfunction
P0444 Evaporative Emission Control System Purge Control Valve Circuit Open
P0445 Evaporative Emission Control System Purge Control Valve Circuit Shorted
P0446 Evaporative Emission Control System Vent Control Circuit Malfunction P0441 and/or P0446

fuse power to rail injector must be good check fuses first.
is CEL glowing key ?
ok,no engine stated. this the 4 liter? I6? nah you said HEADS
not 2.5L I4
not 4.0 L I6
so must be V6, really
or the 2.1L diesel....>>>>
and 3 or 4 diffr. EFI systems, im not much help
why folks post engine free ,amazes me....

it takes 2 things.
fuel pressure over 30psi (generic)
and the noid lamp passing on injector.

and the knowledge that all jeeps,(cars) cut fuel (gas)
if the PCM see and errors with (crank for 5 seconds)
1: spark?
2: CMP?
3: CKP?
4: if IMMO , that too, no imm on 87, think , go lazy to look up.

If the NOID lamps fail x6 (no injection pulses)
then the ASD relay is dropping out)
87 is the really really old RENIX/Benicx injection system. on 4L
i had a 88. same car.
see alldata.com for permissive to inject.

on my old I6 4L Renix sys
the injectors are all grounded , that is correct
and the ECU drives this hot switched ! unlike most cars.
back then the ASD was called the LATCH relay.
if it dont pull in and stay , it will not run.

Ill stop there. until you say what engine and country car resides.
export jeeps are wired different (laws)

Are you sure it's not the fuel pump? I would be checking fuel pressure-the injectors need fuel under high pressure against them so they will spray out when pulsed.
What year is your Isuzu, and what size engine? Multiport injection has a higher pressure requirement than throttle body injection.
There should be a fuse for the injectors, check that. With key on, not start, the injectors would have power to them on the "injector drive circuit". In other words, constant power is supplied to the injectors when the key is on. The other wire at an injector is the ground wire. The ground wire goes into the engine computer. When the computer internally grounds the injector wire for a split second, the injector is energized and fuel is able to spray out.
Post back if you need help checking the injector circuit-both the power side and the ground side. You can check both with a test light.

Well, here it is anyway: ground a test light and probe the injector connector. With key on, one terminal should be hot-the drive circuit. Now move the test light lead to the POSITIVE battery post, and stick the test light probe into the injector terminal that did not light the test light-the ground terminal. Now have someone crank the engine over. If ground circuit is working, the test light should be blinking-meaning the computer is properly grounding the injector circuit. If both tests are good-a steady light on the power side (key on) and a blinking light on the ground side (engine cranking), the injector circuit is good.

The only V6 engine I could find in a Cherokee was in the mid 1980s and it was carb not fuel injected. The 4.0 straight 6 engines that were fuel injected used the same black wire for all 6 injectors to power them. Each injector has a different ground wire from the computer.
The injector in question should have the same input voltage as the others and then a ground signal on the other side when the computer commands it to open. All 6 injectors should also have the same resistance when the harness is unplugged.

This sounds like a fuel pump or fuel filter problem.
The 1988 Jetta has two fuel pumps. The "main" one under the car directly in front of the gas tank on the right hand side. The other fuel pum is in the tank. You can access that fuel pum by removing the round access panel in the trunk towards the back seat.

You'll need a fuel pressure gauge. You can usually borrow one from a large auto parts chain store.

FUEL DELIVERY & SYSTEM PRESSURES
System Pressure
Connect Pressure Gauge (VW 1318) between line from fuel distributor to cold start valve and
test port connection on lower chamber of fuel distributor, using Adapter Fittings (VW 1318/5).
Test port is sealed by a threaded plug. Bridge fuel pump relay with Jumper Switch (US 4480/3).
1.
Disconnect wiring from Differential Pressure Regulator (DPR). Open valve on pressure gauge
(points at cold start valve line when open) and activate fuel pump. System pressure must be 75-
82 psi (5.3-5.8 kg/cm2 ). If pressure reading is low and fuel pump delivery quantity is good,
replace pressure regulator.
2.
If pressure reading is high, disconnect fuel tank return line from DPR. Repeat test. If reading is
correct, check for plugged return line. If reading is incorrect with line open, replace DPR.
3.
Differential Control Pressure
Close valve on pressure gauge. Activate fuel pump with jumper switch. Leave DPR
disconnected. DPR reading should be 2.9-7.0 psi (.2-.5 kg/cm2 ) less than system pressure. If
pressure is incorrect, disconnect lower chamber return line and measure volume.
1.
Close open port to diaphragm pressure regulator. Activate fuel pump with jumper switch. Fuel
volume should be .14-.16 qts. (.13-.15L) for period of one minute. If volume is correct, replace
DPR. If volume is incorrect, replace fuel distributor.
2.
Close valve on pressure gauge. Install Test Harness (1315A/1) between DPR and vehicle
harness. Set multimeter to DCA 200 mA scale. Connect multimeter to test harness. Disconnect
wiring to coolant temperature sensor. Connect 15 k/ohm side of Test Resistor (VW 1490) to
sensor wiring.
3.
Turn on ignition and fuel pump. Differential pressure should be 10-17.5 psi (.7-1.2 kg/cm2 )
less than system pressure. DPR current should be 50-80 mA. If pressure is incorrect and current
is correct, replace DPR.
4.
If both pressure and current readings are incorrect, remove test harness from DPR. Ensure
resistance of DPR is 17.5-21.5 ohms. If reading is incorrect, replace DPR.
5.
If reading is correct, check ground from temperature sensor to cold start valve. If ground is
good, check power supply fuse. If fuse is okay, check terminals on ECU connector. If connector
is okay, replace ECU.
6.
Residual Pressure & Internal Leak Testing
Open valve on pressure gauge. Operate fuel pump for 30 seconds. Pressure can drop to a
minimum of 38 psi (2.7 kg/cm2 ) after 10 minutes. If pressure drops below specification, inspect
fuel pump check valve and all fuel fittings for leakage.
1.
NOTE: Pressure and leak testing does not include checking cold start
valve.
FUEL INJECTION SYSTEM - BOSCH CIS-E -1988 Volkswagen Jetta Page 1 of 3
http://www.ondemand5.com/mric/common/asp/printart.aspx 11/25/2011
If there are no leaks, check airflow sensor plate clearance. If plate clearance is correct, replace
diaphragm pressure regulator and repeat leak test. If pressure drop is not within specification,
replace fuel distributor "O" rings.
2.
Transfer Pump Delivery Volume
Check voltage supply to pumps. Connect Jumper Switch (US 4480/3) in place of fuel pump
relay, on relay panel. Remove fuel filler cap. Disconnect and plug off Black fuel line from
sending unit.
1.
Connect hose to sender port and place in measuring container. Turn on fuel pumps. Minimum
transfer pump delivery volume should be .42 qts. (.4L) in 10 seconds. Reconnect fuel line to
sender.
2.
Main Pump Delivery Volume
Check transfer pump (if equipped) and fuel filter. Disconnect fuel return line and place in
measuring container. Switch on fuel pump with jumper switch. Check fuel pump delivery
volume for 30 second period. Delivery rates are given with voltage reading at pump as volume
will change with different voltages.
1.
Minimum delivery volume for Fox, Quantum and Quantum Syncro models is .71 qts. (.68L) for
30 seconds with reading of 11.4 volts at fuel pump. Minimum delivery volume for other models
is .62 qts. (.59L) with 11.4 volts at fuel pump.
2.
Fuel Distributor
Check sensor plate adjusting lever and fuel distributor control piston for smooth operation.
Disconnect fuel injector lines at fuel injectors.
1.
Remove fuel pump relay and bridge fuel pump circuit. Use Jumper Switch (US 4480/3) in place
of fuel pump relay. When pressure has built up, turn off fuel pump. Move sensor plate from rest
position to end of travel.
2.
Uniform resistance should be felt during entire movement. No resistance should be felt on
quick return to rest position. Connect injector lines. Install fuel pump relay.
3.
Injector Quantity Comparison
Remove fuel pump relay, from relay panel, and install Jumper Switch (US 4480/3) in off
position in place of relay. Attach Fuel Quantity Analyzer (US 4480) to bumper and secure in
place. Remove injectors from cylinder head with fuel lines attached. Check and replace fuel
injector "O" rings as necessary.
1.
Check tightness of injector insert (2-piece inserts). If inserts are loose, remove and clean
threads. Use sealing compound when installing upper insert. Replace sealing washer that goes
against cylinder head below lower portion of insert. Lubricate injector "O" rings with gasoline
and install injectors, with fuel lines connected, into fuel quantity analyzer tubes.
2.
Ensure lines are not kinked or bent. Loosen fittings to align fuel lines and retighten. Remove
rubber boot from airflow sensor housing above sensor plate. Turn and lift setting screw and
adjusting slide of Sensor Plate Adjustable Holder (VW 1348/1) into upper position. This
simulates full throttle operation. See Fig. 11 .
3.
FUEL INJECTION SYSTEM - BOSCH CIS-E -1988 Volkswagen Jetta Page 2 of 3
http://www.ondemand5.com/mric/common/asp/printart.aspx 11/25/2011
Fig. 11: Sensor Plate Adjustable Holder (VW 1348/1)
Courtesy of AUDI OF AMERICA, INC.
Place sensor plate adjustable holder on airflow sensor housing with holder centered over plate.
Pointer on edge of holder base must point toward center of fuel distributor. Push adjusting slide
of holder down onto stop.
4.
Turn adjusting screw clockwise until magnetic end touches sensor plate retaining bolt. Activate
fuel pump with jumper switch. Turn adjusting screw of holder counterclockwise until any one
injector starts to deliver fuel. Turn off jumper switch and empty fuel quantity analyzer after
taking sample.
5.
Idle injection quantity is measured first. Lifting adjusting slide of holder to first stop simulates
idle position of sensor plate. Activate fuel pump until fuel level reaches 20 ml on scale of any
tube.
6.
Check that all injectors have identical spray patterns that are even and cone-shaped. If not, raise
sensor plate up quickly to full lift position and release. Repeat idle quantity test. Compare
amounts of fuel delivered by all injectors with analyzer held level. Maximum difference in
delivery quantity between injectors is 3.0 ml of fuel.
7.
If fuel delivery quantity differs between high and low levels by more than 3.0 ml, interchange
injectors and repeat test. If difference of delivery quantity changes with injectors, replace
injectors. If difference of delivery quantity does not change with movement of injectors, either
fuel lines are pinched or fuel distributor is defective.
8.
Measure full throttle injection quantity. Empty analyzer into fuel tank and reinstall injectors in
analyzer. Lift adjusting slide of holder to last stop to simulate full throttle position of sensor
plate. Activate fuel pump with jumper switch until fuel level reaches 80 ml on scale of any tube
of analyzer.
9.
Check that all injectors have identical spray patterns that are even and cone-shaped. If not, raise
sensor plate up quickly to full lift position and release. Repeat full throttle quantity test.
Compare amounts of fuel delivered by all injectors with analyzer held level. Maximum
difference in delivery quantity between injectors is 8.0 ml of fuel.
10.
If fuel delivery quantity differs between high and low levels by more than 8.0 ml, interchange
injectors and repeat test. If difference of delivery quantity changes with injectors, replace
injectors. If difference of delivery quantity does not change with movement of injectors, either
fuel lines are pinched or fuel distributor is defective.
11.
Check fuel injectors for leakage immediately after delivery quantity test is complete. Set sensor
plate in rest position. Activate fuel pump with jumper switch for 2 minutes. Injectors should not
drip. Replace injectors that drip.
See image. Fuel filter is probably located on the frame between the engine and fuel tank.

Without knowing the model car your working on I'll assume it's a standard Ford car fuel injection system. The injectors each have two wires going to them. All of the injectors are powered through a common wire. What make them work is the processor (computer). When the processor determines that it's time to open an injector, it grounds the wire coming from the injector. The processor uses a duty cycle to allow the injector to be on for a certain amount of time.

The processor determines when the injector should be turned on by using signal inputs from sensors. Oxygen sensors in the exhaust tell the processor if the air/fuel mixture is correct or whether it needs to add fuel or take away fuel. The fuel is pressurized by the fuel pump and typically measures 40-65 psi, depending on the vehicle. This high pressure fuel goes through the injestor and is atomized when it goes through the 3-4 small holes in the injector. The atomized fuel mixes with air and enters the combustion chamber to be compressed and burned to make power.

sounds like a short in the wiring from the fuse and the fuel injector junction block. GM like most fuel injection systems control injector firing by the computer providing ground to each injector in pairs or individually. The fuel injector fuse provides power to the injectors using splices therefore enabling one wire to feed 6 injectors. A shorted wire at any of these wires will blow the fuse. On one rare incident I found a faulty computer caused the fuse to blow. A shorted injector will just cause a rough running problem due to the injector stuck either open or closed.