Hey All,

I have a '89 2500 GMC that has a fuel problem. The truck is a plow truck but generally well loved (its Canada, and yes I have lots of snow in the yard) and on a plowrun it just died. The truck always starts and runs well - 239,000Kms. I have read the Haynes Manual (Vague at best, sorry Haynes) and it was unclear on how to fix it. I think it's a fuel problem but can't be sure - This is what I have done.
Fuel Side
-Tested the Fuel pump using the ALDL terminal and a jumper - I have pump noise!
-Found and checked the Fuel pump fuse (pic is upside down in book) - OK
-Checked the Fuel Pump Relay (manual bench test, Power in, relay toggles)
Should I have fuel flow in the TBI when the key is on and you pump the gas? Mine does not.
Could the oil pressure switch be stopping the fuel pump and thus the starting of the engine? I cant find this anywhere - and to be honest makes me sad. I believe that if the switch is bad it should stop the fuel pump and thus kill me in motion. I continue to look for the switch (in both the manual and vehicle) but to no avail.
I even tried squirting fuel down the throat of the TBI and she would not start - seems weird - so this led to -

Electrical Side:
Tested Spark - None which again is weird (Had the truck running the other day at -34.7ēC and started second try - so no former signs of electrical problems) So no spark led to coil test (seems fine - tested as per manual instructions) and the pulling of the Dist cap. Yikes! - Really badly corroded - will clean and replace today (it's - 19ēC here today, it needs to warm up a bit, brave but not stupid!)

So this is where I am at, Just looking for general input - What am I missing? (no Sarcastic answers please) I believe the problem to be fuel, as I was driving and she died. It wouldn't even re-start. I need to do a Fuel pressure test (hopefully today) but I have no fuel at the TBI. Heck she wouldn't even fire up with the fuel squirt - The Dist cap is dirty but that is just because it has not been changed in like 10 years)
I continually use fuel line conditioner (It's cold here..) thus I doubt that it is a frozen line..

Thanks for your time -

 

The fact that you don't have fire to the plugs, it wouldn't start with a squirt of starting fluid and your cap is corroded would lead me in the ignition direction. There is a spark/ignition sensor in the distributor that can make your truck just stop like that. I had one that went out at a red light and the truck stayed right there until the tow truck came. I would recommend replacing that sensor and it sounds like while your there a tune-up is in order.
To test the fuel pressure on a TBI truck you need a fitting that replaces the fuel filter. It has a schrader valve on it to hook a gauge to. You might be able to borrow one from a mechanic if you know one around there. Also a good idea to replace the fliter while you have it off (unless you just did recently).
Good luck and let us know what you find.

 

Thanks for the advice, I have purchased a new Dis Cap and Rotor, but will wait for a bit warmer weather to put it on (was -30ēC this morning), so I will pass back the results of install - More to follow -

 

Hey all - Tonight I have actually gotten out and worked on the truck. So since we have last talked this is what I have done. - I have replaced the Dist Cap as well as the Ignition module on the back of the Distributor base. - Additionally I have replaced the fuel filter (and subsequently due to rust and hate, a high pressure fuel line) so I am confident that I have fuel up to the TBI. I have proved that the fuel pump works (hear the pump noise and I made it stop when I disconnected the Fuel Pump Fuse) So the TBI is supplied fuel but will not spray. When I roll the engine should the injectors squirt fuel? I continue to have no spark. Shamrock, at this point I am wondering if it is the Computer or the CamPac? To loose both the Spark and the ability to trigger the injector leads me to the belief that the computer may be dead. I did perform a diagnostic on the ADAL and no codes were stored. So would a bad computer tell on itself? the manual tells me that it would come up with a Code 51 or Code 52 but no codes reply. Your thoughts would be appreciated. A new computer is about $250 here and prior to buying this I am going to retrace my steps and see if there is something that I have missed. Thanks!

 

I had a similar problem such as yours in a Chevy Blazer. It had developed a leak on a fuel line close to the tank. So, after taking everything apart I eventually had to replace the tank, sending unit and fuel pump. A brand new Carter fuel pump was installed and all worked fine for approx 1500 miles after that it would intermittently and abruptly stall out without jerking, sputtering or bucking as you would think if it were starving for fuel. Seemed like an electrical issue the way it just cut out. At this point the Blazer was spending more time driving around on a flat bed than it was driving on the road before it was figured out. The problem was the Carter fuel pump and the fuel relay switch. They would run fine when started cold, after they got hot it would shut down, wait about 45 mins and it would start up again. Replaced those components with AC-Delco parts and it worked fine. The cost for the parts and labor on changing out both fuel pumps ( #1 replacement from the local mechanic, # 2 replacement from GM dealer service) totaled $2200.00. Hope your problem is more simple than mine was. Good Luck!

 

Usually when your ECM goes bad you will no longer get a SES light when you turn the ignition on and it will not have communication when you try to run a diagnostic. Are you getting spark now? I would check fuel pressure. Just because you hear it come on doesn't mean your getting the pressure or volume that you need.

 

Yes I agree wit Shamrock. A slight drop in fuel psi and it wont start or run.

 

You have a pickup coil on dist shaft. Test it should have 790 to 1200 ohms.
Take wires loose from ignition module . Set meter to ohms should read 790 to 1200 ohms.
If not it is bad. The wires are green and yellow if i remember right.
The oil sending unit is located behind dist. You should have fuel two second squirt
when key is turned on. Should have fuel when cranking on truck.
Make sure you are getting spark at coil , if so then at plugs.

If you are getting spark at plugs , good blue spark when you pour a little fuel down tbi should start.
Do not use starting fluid.
Fuel pressure should be 9 too 14 psi.

 

Good Day all! I thought I take a moment to update the truck. I had a bad coil within the distributor. When we took a closer look the age of the coil was clear as pieces were missing and severe cracks were evident. The repair was stalled by the removal of the bolt that holds the fork plate (and thus) the distributor. My problem was as the bolt has not been moved for 20 some odd years it was pretty stiff. I tried several methods (with various tools) with little luck. Finally I decided that it was better to replace the entire distributor than to sheer off the bolt in the block. So I bent up the plate the distributor sits on and used an impact wrench to gently work the bolt free. After this it was just a matter of getting a whole new distributor from a wrecker and re-assembling it all ($100.00). After about an hour of work the truck fired up on the first try. Nice! This is how I understand it - I had no fuel as the sensor on the Dist. was not receiving a signal from the coil within the distributor, (due to the break), so the fuel pump was not activated. Fix the coil, get the fuel - I wanted to thank everyone who chimed in and made me think about what the problem could be. It was the input of all here on the forum that gave me the confidence to go beyond the book and solve the problem. Thanks Guys! Now for the irony - no snow! - so I suppose I will continue to fix her up and wait for next years season! Thanks again - Map Guy

 

Nice, I am glad you got it fixed! Also thanks for posting your results!