20 Most Recent 1990 GMC C1500 Questions & Answers

Change ignition module in distributor and test coil

You need to remove first the power steering belt, the 3 or 4 screews, after that make sure you reinstall the new pump and bleed it correctly.

Did you also replace the fuel filter? May also check fuel injectors.

There are two relays , high and a low . they are under right side of dash below blower motor housing !

2,4,6,8 Front 1,3,5,7 1-8-4-3-6-5-7-2

If you are competent to do so you can.

If you have the same problem after the tuneup as before you may have an injector problem or possibly a mechanical one. Ie. valves, timing chain, valve train.

Worn timing belt or bad map sensor, weak ignition coil, worn distributor gear (usually starts hard with that) Leaking manifold gaskets all possible causes. Start with a new coil, spray starting fluid around manifold gasket while running, if it revs up in any certain spots, manifold leaking (intake only test), check vacuum lines for cracks and leaks,(MAP) replace sensor. Over 75,000 miles probably timing belt, recommended change interval is 60,000 miles.

Time for transmission rebuild.

check your spark wires if the insulation is not intact they could be shorting throwing off the timing then when you hit a bump they move enough to no longer be shorting

remove the taillights from the bed and check if you are geltting power from the switch. The circuit board the bulbs plug into sometimes goes bad. Lee

The inner part of the distributor is a relector,these have a high tendency for corrosion,and creates misfires,and rough idle.you will need to open the distributor and inspect it

IAC either dirty or bad

this could be many different issues. you could have a lower degree thermostat, if the block wasn't boiled and flushed you could have coolant restriction in the block causing less flow to the heater core,or you could have put your heater core hoses in reverse flow.

probly hav a weak fuel pump or pump regulator-in engine area--did u change plug wires and distributer cap-they go bad but dont show it--throttlebody area may need cleanin--egr valve cud hav an issue--and the fuel injection--its 20 yr old