GMC / Chevy TBI help

[Corban_White]

I have a '91 GMC with a 350 tbi. The other day it died getting on the freeway and hasn't so much as attempted to start since. I thought it was the fuel pump but upon further investigation found that it was working and in fact the whole fuel system is working as I can see the injectors squirting gas while cranking. So, I checked the spark and low and behold there is none. I have gone through all of the checks outlined in the clymer manual (mostly ohm checks) and everything checks out as spec'd. But, there is no denying the lack of spark. Anyone have any ideas of what could have suddenly and completely crapped out? I have checked the fuses (unless there are more than those under the dash-I know the fuel pump one was tucked away in another spot). Any ideas on what to else check? I am at a loss. Thanks.

 

[Greg]

Replace the ignition module, in the distributor, under the rotor. They are a a semi-common issue with GM's that suddenly loose spark. That's where I'd start, report back if it fixes it or not, good luck!

 

[mbryson]

Replace the ignition module, in the distributor, under the rotor. They are a a semi-common issue with GM's that suddenly loose spark. That's where I'd start, report back if it fixes it or not, good luck!

That'd be my guess.


It COULD also be a fuse. There are two fuses in the GM harness that control spark. Check those out as well.

 

[Corban_White]

Thanks guys, I'll give that a shot.

It COULD also be a fuse. There are two fuses in the GM harness that control spark. Check those out as well.

Where might I look for these? Somewhere other than in the fuse panel?

 

[mbryson]

...Where might I look for these? Somewhere other than in the fuse panel?

It's in the fuse panel. I'm using a total GM harness but can't remember exactly which one it is. One to the computer is very low amp rating (maybe 2?) and the other is 15 or so? Check them both out.

 

[Corban_White]

Right, I saw both of those. Thanks though!

 

[zukking01]

Any updates. I swapped a 4.3 into my sammy with a howell harness. Ran and then 2 days later wont start. No spark but all the stand alone harness fuses are good. I have 12.6 on the coil but nothing coming from the cap. New cap and rotor that worked 2 days ago. I was going to check the module in the dist, and was wondering what the cause was on this thread?

 

[Corban_White]

Still haven't had time to get it done. Maybe today or tomorrow I will make it to the parts store. (depending how long it takes me to swap my Tacoma springs today and how long NPLD takes tomorrow) I will update this thread when it is fixed tho.

 

[Corban_White]

Replace the ignition module, in the distributor, under the rotor. They are a a semi-common issue with GM's that suddenly loose spark. That's where I'd start, report back if it fixes it or not, good luck!

That'd be my guess.

That fixed it! Thanks Greg and Marc!:thumbs::bow:

 

[zukking01]

That fixed it! Thanks Greg and Marc!:thumbs::bow:

X2 The 4.3 is up and running. I had another one is a broke dist. and it fired up as soon as the used one was in. Thanks. :bow::thumbs: