20 Most Recent 1989 GMC C1500 - Page 6 Questions & Answers

Hey man my best guess would be that you have a bad relay in the system. Also it would be a good idea to inspect the wire for signs of damage or a short. hope that is helpfull.

ck to see that you didn't pull the connection off the flasher

Remove the vacuum lines on the bottom front of the throttle body with the engine off. Check each hose connection with a nail; small screwdriver or a small drill bit. Make sure they are not clogged. If they are clean them out carefully. If they are not clogged, then check to make sure the vacuum lines aren't obstructed. I refer to your idling up and down as hunting. Reconnect the vacuum lines and start the engine. If it idles smoothly, your found your problem. Good luck.

Sounds like your timing chain has jumped out of time, if the timing chain is old, the chain jump a few teeth putting it out of time having it fire at the wrong time when the exhaust valve is open. Check timing by pulling #1 plug - bring #1 piston to the top and line up timing mark , Ifind it easy to put thumb over spark plug hole and have someone bump the engine over and feel the pressure relief stop before you feel vacumm - timing mark should line up if the timing hasn't jumped

check fuel pump pressure at the throttle body

fuel pump, or fuel punp relay mounted on fire wall, check the fuse in relay, also check the ground wire from fuel pump (in tank) to the inlet pipe , under the truck, where you put gas in, fuel pump needs a good ground period. fuel pump could be on its last leg ! reason why I know this is cause I have a 1988 gmc 3/4 ton. to access fuel pump, I cut an access opening in truck bed, 12" square above tank at location of pump. better than dropping tank, besides the truck is how old ? makes a hard job easy. change your fuel filter also. good luck, ken

Sounds like a bad ignition switch or a bad main electrical connection between the battery and the switch. Check all the battery connections and grounds for clean tight connections. Check for power going to the switch.

That is normal for a 4WD. When in 4WD you cant do hard/sharp turns, the result is axle bind.

that should have throttle body fuel injection run the engine with the air filter off and watch the injectors spray fuel to see if there a cone shaped spray if ok check the fuel pressure i have seen the regulator rupsure and the fuel dumps into the engine

should be in the discharge line near the evaporator or out near the condenser

There should be a pigtail connector for trucks with or without rear bumpers. Did you look in the harness for a brown wire ?Same as the marker lights.

You'll have to figure out if it is a water pump, thermostat, or fan clutch problem.Could be other things too.One important question is how long does it take to boil over ?