CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

1989 GMC suburban V8 350 5.7L that will not start

I have a 1989 GMC suburban V8 350 5.7l that will not start. I have replace the following fuel pump and sending unit, fuel pump relay, ECM computer brand new, new fuel filter. When I go to start it the fuel injectors dont spray fuel into the combustion chambers verified fuel injectors still work by bypassing them and they spray fuel. Fuse’s are not blown. I have been told the oil pressure switch might be bad but I’m at my end of sanity on this. Any suggestions Thanks for the effort

Additional Details
Tried spraying fuel into the throttle body and still no fire, ignition module and ignition coil where replaced 15,000miles ago.

First thing to check- does the SECURITY lamp on the dash stay lit after the other ones go out?

It could very well be ^related^ to what @twinturbo suggests - some sort of vehicle disabling feature thinking the car is being stolen. That’s where I’d look first as well.

Are you getting spark at all? If you’re not and the injectors aren’t working, it could also be that the ECM is totally unaware that the engine is turning. Maybe a crank sensor or its wiring to the ECM?

The pick up coil may have failed and at $20 and easily replaced it might be worth trying. It would be worthwhile to replace the module while you’re in there. And look closely at the cap, rotor and wires because when those parts fail they take out the pick up and/or module.

Go with the oil psi switch. It turns off the fuel pump if the oil psi go to low. When they go bad it cuts power to the fuel pump. Its a common problem.

@TwinTurbo and @RemcoW I dont think it is a security issue it is a 1989 suburban and there is no security features that I’m aware of, I could be mistaken???
@RodKnox I have removed the ECM module will go get checked tmrw with autozone will post back later with results

@oldbodyman excuse my ignorance before hand but the oil psi switch will not allow the car to start when they go bad.

Thank you all for the help Im trying to get the damn thing running again so my Mom can drive her car again.

Do you have spark? This is a simple system, the ECM uses a signal from the ignition module to determine when and how to run the fuel injectors. If you have no spark and no fuel injection operation, chances are you have a bad ignition module or pickup coil in the distributor. The module is easily replaced, the pickup coil requires removal and disassembly of the distributor.

May seem stupid but is the distributor turning when you crank the engine?

Oil pressure switch has no bearing on fuel injector operation or spark output.

GM certainly had VATS on a lot of vehicles in that year. Pretty sure my 1988 2500 had it. I’m positive my 89 camaro did. If you prefer to assume that is not possible to be your problem, just hope you don’t waste a lot of time and money chasing other possibilities. It couldn’t be easier to verify…

@TwinTurbo confirmed no security lamp, that’s what I initially thought based on other GMC I have owned.

@asemaster and @RodKnox confirmed ICM was good at autozone bench test.
Confirmed no spark, my next step will be replace the pick up coil either tomorrow or thursday.
Is there any diagram available showing how to do this??

Now that I think of it this could have been the problem for a while, because the engine would be sluggish sometimes going around corners.

Next step replacing pick-up coil. will post back on thursday with results
Thank you all for the suggestions and guidance

To replace the pick-up coil remove the distributor, use a punch to drive out the roll pin in the drive gear, remove the drive gear and thrust washers, pull the shaft from the housing (often a shot of penetrating oil on the shaft and twisting while pulling helps get them out) then replacing the pick-up is straight forward. Of course you must mark the position of the distributor and the rotor before removal and drop it back in time being aware that the slotted oil pump drive might require you to do some jiggling,

These trucks have a low oil psi cutoff built into the oil psi switch. It turns off the fuel pump when the oil psi go’s to low. You said you had no fuel at the injectors till you put power to the fuel pump.

If you sprayed son gasoline into the throttle body, it should have momentarily started IF the problem was no fuel being delivered. This looks like ignition failure. Buy a “test plug” at any autoparts store, and verify that you have spark to the plugs…if not, the ignition module located inside the distributor becomes the first suspect…How may MILES on this vehicle? Perhaps the timing chain has slipped in which case it will not start. But it should “sound funny” when you crank it not the normal cranking rhythm, and back-fire while being cranked…

Update sorry the delay got held with work these last 3 weeks. Replaced the The whole distributor with new rotor and new pick-up. Changed spark plugs they where all fouled over, new spark wires. Replaced ignition coil also found by chance the ignition coil was failing after the car warmed up and would open up. My friend came over and dialed in the timing. The 350 V8 no sounds and runs like it should. Thank you for every-bodies useful information especially the pick-up coil.