91 GMC K1500 Won't Start

[dstrick32]

Brad the black plugs tells you it's running rich. Have you checked the TPS (Throttle Position Sensor)? The TDC 22 that you said it throwed earlier is TPS voltage was under 0.2 volts for 2 seconds when the engine was running. Check the DTC's again and get back with the numbers. This site will help if you don't have a scanner:
http://www.troublecodes.net/GM/

[Brad_J]

Got it running again. Put 5 gal fresh gas in (~ 1/2 tank now) with no change.

I loosed dist and started from scratch again. I couldn't find any markings or notch described in the manuals. Lined rotor to #1 and it didn't start there. Ended up moving ~ 3deg before it would start. Was stumbing @ 4 deg ATDC and I got it running smoothly @ ~ 14deg BTDC. Noticed a blue spark once when i was moving the dist (probably coil wire). Set timing @ temp to 0 deg TDC and cleared ECM. Started again and was at ~ 20 BTDC. Running a little rough still but able to move around at least.

No codes have popped up since I replaced the battery and starter (they were really bad). I had checked the TPS before and it has a smooth rise from 0.5(?) to 4.5V. It would only set the Code 22 when stumbling at idle before.

It's hard to say if the plugs are black from it stumbling so much before I got it smoother. Do I need new plugs again?

I really need to check the fuel pressure before I go down any other dead ends. Can excessive fuel pressure cause rich running?

thanks all for your help.

[mudrunner80]

just a thought here but take a fuel pressure check. To me it sounds like a weak pump or a broken line some where. Some of the symptoms you described happend to my truck also. Mine had a broken line so it was'nt holding pressure and it would only idle. If you have one or know someone with one it won't cost anything. Good luck

[ronaldk]

Brad J

Go to (here in ck) post labelled 1996 gmc 4.3 distributor phase issue need help.
MT-2500 posted a http at which you will find the pix showing both 6 cyl and 8 cyl marks to line up you distrib rotor at TDC. This is a very clean pix and should help. It has date 9-28-09 MT-2500 . Ron, good luck

[Brad_J]

Ron,

Thanks for the pic. My old distributor looks nothing like that. Here's pics of top and bottom.





As long as I have the rotor pointing at #1 on the cap @ TDC before starting, that's all that should matter, right?

I found this thread where someone had a similar dilemma (http://www.truckforum.org/forums/che...stributor.html)

I'll have the wife crank while I check the timing again. Should have fuel pressure numbers tonight or tomorrow. I'll clean the plugs again since I'm sure their fouled.

[Brad_J]

Finally got fuel pressure readings:

Installed gage after fuel filter. Turn key to "RUN" = steady rise to 14psi for a few seconds, then I hear a click from engine bay and pressure steadily drops to zero (with key still in "RUN"). During cranking and the 30 seconds I got it to sputter (had to hold half throttle) the pressure stayed rock steady at 14psi. After it died (or didn't start) pressure steadily dropped to zero with key still in "RUN" position.

I'll try to check timing again once I have a helper to crank it over. When I checked plugs before, the back cylinders' plugs were wet w/fuel (not sure if that's normal or not for this engine). I also bought new plug wire separators since the old ones are broken.

Thanks everyone for their help thus far.

[ronaldk]

TBI system has a bleeder in regulator and can go to 0 psi. It should read 9-13 psi when running. Pump will only run about 2 seconds if eng stops running even with ign in run position, ecm controls pump staying on when it receives info that eng is running. I see the dist you have and they have a white painted area by cam gear and on gear there is a indent predrilled hole that should be lined up with crank at TDC. Sorry I have been busy and have not been here lately.hope this helps.