1990 Ford F150 - Answered Questions & Fixed issues

Question edited for clarity and typo. Question moved to model category. It is a known issue. Lots of information in the link and also a video. https://www.google.com/search?q=1990+Ford+F-150%2C+Tachometer+sticks

That really sounds like a vacuum leak. Check all connections. don-ohio

copy and paste https://www.cargurus.com/Cars/Discussion-c5248_ds555900

None. Yes I said it right, None. Belive it or not in 1976 trucks were not required converters, air pumps and could run on leaded or unleaded gas. Man I've been doing this too long and I'm getting old.

One common problem is a vac leak or a sticking throttle plate.The computer controls idle speed by how much air is allowed into the intake. The idle control valve could be sticking even tho you have cleaned it, or have a faulty motor.

Check out the wires inside of the rubber that goes between the body and the door for damage. If the switch is good are check out the relays

What is the vehicle specifically? Jerking when letting off during hard or mild acceleration could indicate a problem with an engine or trans mount. More severe cases its indicative of a loose, worn, damaged drive shaft or pinion. If front wheel drive car, lean toward engine mounts. But to clarify again, we need details of your situation to help more effectively.

Dependant on your model specifics, either two or one tank assembly, the tanks themselves will have a sending unit inside. You can replace just the pumps for less but you MUST exercise care when removing reinstalling and cleaning. The orig sending unit can be brittle. The plastic parts to specify. If just trying to get a truck running, start with the rear tank, and if you cannot save the tank straps you can ratchet strap the tank to the frame to make it mobile. DONT DROP THE TANK OR LET IT HANG. While under the truck lean the back side of the tank off first and it will give access to the connections you need to remove to drop the tank

I think you need to replace the front fuel pump it has a bad check valve in it. Check with Ford there is a tech bulletin written for these and they have a modified part for repair. I hope this helps, Take care. If you have more questions for me use testimonial and it will show up in my email. Thanks

First make sure that it has plenty of good clean fuel. Old fuel will cause spark knock.

Kinda sounds like it works when fluid is thick and not after it warms up. If it has been awhile since trans fluid and filter were changed it is the most simple thing to change. The torque converter is a big pump, it may be going and not providing enough pressure. This could be checked on most transmissions by a shop expert. Sometimes pressure can be adjusted externally.

Sounds like a vacuumed leak, spray wd40 around the inlet manifold whilst on idle

you have 2 options 1--- put the fuel return line into the tank you are using 2--- install a balance line between tank 1 and tank 2 so that the fuel back to tank1 is allowed to balance back into tank 2 properly set up the tanks should be connected so that the fuel gauge reads the total fuel in the tanks and there is a need for only one fuel pump

fit a breather to the inlet pipe of the tank.

You need to do a OBD1 fault code test on the EEC4 engine control computer. follow the instructions at the link provided.

Here is the wiring

Lock cylinder is not properly engaging the ignition switch. There is a pushrod from the end of the lock cylinder that moves the slider on the switch. Make sure the pushrod is properly connected to both the cylinder and the switch.

which engine

There may be a fuelpump relay in one of the underhood fuseboxes. You can try some searches for 1988 F150 fusebox diagrams to find the location of the relay. The reset of the inertia sensor (safety switch) was a good try but if the fuel pump relay is bad, there will be nothing to reset because there will be no power. There can also be a crankshaft sensor which needs to generate a signal to tell the fuelpump to run.

https://s11.postimg.org/crrcun103/generator.jpg Click on the link. The diagram shows generator with internal voltage regulator and with external voltage regulator, at the moment, I don't know which one you have? The bat terminal at the generator should be hot even with the key off, is it, use a test light. If no voltage either the fusible link is faulty or the wiring circuit to battery +. You can see fusible links in diagram. Could be other issues, the generator probably needs excite voltage or it won't work. The excite voltage comes from charge indicator circuit. Does the charge lamp on the dash work?