My FIL has been having trouble with his 91 Chevy pickup (305 V8) Sometimes it will start but will die a couple min later, or it won't start at all. A new fuel pump, fuel filter and modulating valve on the fire wall. Still does the same thing. I'm up visiting and trying to help him out. Any ideas?
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Help w? a 91 Chevy 1500 Silverado Pickup
- Thread starter Arne73
- Start date
unpredictable1
Well-known member
Has he checked the IAC valve? (Idle Air Control valve)
That can cause hard starting, and then the only way to keep it going once started is to constantly apply throttle.
You can sometimes clean the one on there with brake cleaner, but they're usually not expensive to buy another and replace.
That can cause hard starting, and then the only way to keep it going once started is to constantly apply throttle.
You can sometimes clean the one on there with brake cleaner, but they're usually not expensive to buy another and replace.
StingRay
Well-known member
Have you checked to see if it has any codes? As far as fuel pressure goes a 91 is a TBI truck and has a fuel pressure reg in the throttle body. Have you done a fuel pressure check. It's not real easy unless you buy a fitting then it's not too bad. A factory service manual has some pretty good diagnosis and test flow charts. If you can find one I highly advise that you get it.
There is a member Chevytech over on www.67-72chevytrucks.com on the 88-98 board that is really helpful. Also some really helpfule people over on Fullsizechevy.
There is a member Chevytech over on www.67-72chevytrucks.com on the 88-98 board that is really helpful. Also some really helpfule people over on Fullsizechevy.
Lotek
Well-known member
Check for spark, the ignition module and pickup are notorious on those for failing. If you pop the cap off and see green corrosion inside, it's dead or dying, won't set a code.
Thanks-
I'll check easy stuff, the cap and rotor, we were suspecting the ignition module as well. As far as codes go as a 91 I didn't think it would have retrievable codes since it's OBD 1.
I'll see if the shop performed a fuel pressure test or replaced the IAC valve.
I'll check easy stuff, the cap and rotor, we were suspecting the ignition module as well. As far as codes go as a 91 I didn't think it would have retrievable codes since it's OBD 1.
I'll see if the shop performed a fuel pressure test or replaced the IAC valve.
slopdog
Well-known member
I,m gonna say Ignition Switch
ddawg16
Well-known member
Back to basics....if it quits running....pull the air cleaner and crank it....if you see the injectors firing then it's getting fuel. Start checking for spark.
You can get codes.....short pins one and two together....the CEL will flash and codes....a 12 means that it does not see any issues.
I have a 93 SBC in my jeep....most likely almost identical to what he has. I had a bad coil wire from the coil to the dist....it was open....but the jeep ran...and ran well except for an occasional miss.
You can get codes.....short pins one and two together....the CEL will flash and codes....a 12 means that it does not see any issues.
I have a 93 SBC in my jeep....most likely almost identical to what he has. I had a bad coil wire from the coil to the dist....it was open....but the jeep ran...and ran well except for an occasional miss.
Back to basics....if it quits running....pull the air cleaner and crank it....if you see the injectors firing then it's getting fuel. .
I'll have to disagree with Dawg just a bit. I just went through this on a '93 and it turned out the temp sensor was bad and that caused the computer to think it was -40* and it was flooding the engine. Still a good test though. If it will start you can watch the fuel pattern while it is running and see if the fuel stops flowing causing the engine to die.
On my rig it would start and had lots of black smoke out the tail pipe indicating a very rich mixture until it would die. Then no start till it was cold again.
lg
no neat sig line
ddawg16
Well-known member
I'll have to disagree with Dawg just a bit. I just went through this on a '93 and it turned out the temp sensor was bad and that caused the computer to think it was -40* and it was flooding the engine. Still a good test though. If it will start you can watch the fuel pattern while it is running and see if the fuel stops flowing causing the engine to die.
On my rig it would start and had lots of black smoke out the tail pipe indicating a very rich mixture until it would die. Then no start till it was cold again.
lg
no neat sig line
I had the same issue once....but that sympton is pretty obvious and the OP made no mention of it. What he describes does not sound like a rich condition.
steel 35
Well-known member
(Fuel pump relay) and I would bet a nickle. there is a way to test it by jumping
terminals. but I would have to walk out to the shop been more then two days; and I am tired a sunburned and they are cheap just go buy one.
terminals. but I would have to walk out to the shop been more then two days; and I am tired a sunburned and they are cheap just go buy one.
bgott
Well-known member
Cracked magnet in the distributor shaft will do all that.
mrbreezeet1
Banned
We had a lot of problems with the Chevy pick up at work, it's around that year. Kept replacing module's, and it would run well for a while, and act up, replace module, run well for a while, act up,
They were getting them from advance and auto zone, I finely got one from NAPA has been good ever since. Think it had a code, something to do with timing, can't recall.
They were getting them from advance and auto zone, I finely got one from NAPA has been good ever since. Think it had a code, something to do with timing, can't recall.
mrbreezeet1
Banned
Or yeah, when it won't start, see if it's getting fuel, as stated above, or spray a little carb cleaner in the TB and see if it tries to fire.
But IIRC the module on this truck somehow also controls injector pulse's.
We had to pull the distributor to replace the pick up coil.
But IIRC the module on this truck somehow also controls injector pulse's.
We had to pull the distributor to replace the pick up coil.
mrbreezeet1
Banned
Found this link.
How To: Test TBI Distributor Signal/Injector Pulse
http://www.gmtruckclub.com/forum/sh...To-Test-TBI-Distributor-Signal-Injector-Pulse
How To: Test TBI Distributor Signal/Injector Pulse
http://www.gmtruckclub.com/forum/sh...To-Test-TBI-Distributor-Signal-Injector-Pulse