"new" towrig, need TBI 350 help

[45acp]

Alright, here's the down low-

91 GMC 2500 4x4, 350 auto

I got this truck dirt cheap because it would randomly die and not restart until hours later when it had cooled down. Thought right away it was the ignition module. Put a new module on it and a coil for good measure and it ran like a champ for a day. Now it wont start at all. Been trying it off and on all day. Its getting fuel (you can see the injectors spraying as the engine turns over) but no spark whatsoever.

These things are new and have been checked as good-

ignition module
coil
cap
rotor
plugs
plug wires


My guess is its gotta be the distributor or the computer. Its a friggin TBI motor... it should run no matter what as long as its getting spark and fuel. Is there any way to test one of the old OBD1 computers?

[rocknbronco]

yeah get an scanner wal mart sells em and most major auto parts stores do.

[Mohadeab]

I don't think a scanner is going to help ya out with that problem..the old OBD1 don't do much...put you must check the inputs to the OBD..crank pos sensor and TPS..the air/fuel ratio won't make this problem happen..or the water temp sensor(this one causes a bad backfire and won't run very well)..if those all check good...then hell I don't know

[Pooge]

my buddies truck is doing the same thing, it would not start, then sit, and was able to start, now its dead in my driveway... 93 1500 with a 350. If anyone else might have info to save on the tow bill, maybe i can do it in my driveway for him.

its spraying fuel and has spark.... no idea why it wont start...

Doug

[Mechanos]

I don't think a scanner is going to help ya out with that problem..the old OBD1 don't do much...put you must check the inputs to the OBD..crank pos sensor and TPS..the air/fuel ratio won't make this problem happen..or the water temp sensor(this one causes a bad backfire and won't run very well)..if those all check good...then hell I don't know
'91 vintage GM TBI does not use a crank position sensor since it still uses a distributor. If it is spraying fuel, butterflies are opening and it's getting spark, then it should start or at least try to start. Is it throwing any codes?
I see the first post says it's not getting any spark. If you replaced the ignition module, coil, wires, cap, rotor, etc. Have you tested the pickup coil in the distributor? It's the little circular coil that goes around the distributor shaft and has eight little points on it and has two wires coming out of it that attach to the ignition module.

Is it a large cap (coil in the cap) distributor or a small cap (remote mounted coil)?

[45acp]

Its the small cap type dizzy. I found a spare loaner computer that im going to try tommorrow along with pulling the dizzy and checking it and the pickup coil. Hard to get to right now working 12 hour shifts but i should be able to figure it out this weekend.

[45acp]

my buddies truck is doing the same thing, it would not start, then sit, and was able to start, now its dead in my driveway... 93 1500 with a 350. If anyone else might have info to save on the tow bill, maybe i can do it in my driveway for him.99% sure its the ignition module. $25-30 at any auto parts store and takes 10 minutes to change. Most auto parts stores can even check your old module so at least pull it off and have it tested. Very common issue with the TBI trucks.

[45acp]

It was the computer. Hard to believe i could buy a truck and the computer would die 3 days later but it happened.