Dies in gear when throttle applied

[Sabinoerc]

That's my gut feeling too but I am strapped for cash so looking to fully diagnose first if possible.

perhaps check/replace fuel filter? I don’t remember cost but I think not too expensive and easy to get to.

My reading was taken at the TBI feed line. I am leaning on the conservative side when I say 11 psi. It was between 11.5-12 psi based on the guage markings.

TBI feed line = between fuel filter and TBI, I assume? Did you check what pressure does when flooring throttle?

How has your experience with the AC del/Delphi fuel pump been?

No problems, about 7 years or so. I‘ve read negative comments about autozone/oReilly cheap pumps in forums but no personal experience on them.

a good hygiene thing is to check/clean all your grounds. bad ground to pcm can cause problems but i think unlikely in your description - but never know and easy/no cost.
good luck!

 

[92GMCK2500]

perhaps check/replace fuel filter? I don’t remember cost but I think not too expensive and easy to get to.

TBI feed line = between fuel filter and TBI, I assume? Did you check what pressure does when flooring throttle?

No problems, about 7 years or so. I‘ve read negative comments about autozone/oReilly cheap pumps in forums but no personal experience on them.

a good hygiene thing is to check/clean all your grounds. bad ground to pcm can cause problems but i think unlikely in your description - but never know and easy/no cost.
good luck!

Yeah, thanks. Changing out the filter was the first thing I did.

Yep, had the pressure guage right at the tbi unit. Pressure was steady at 11 psi at various throttle applications, tried gradual in 500 rpm increments, stabbed throttle, floored to 4000 rpm. In idle it held steady at 11 psi. In gear, it stumbles, splutters, then stalls.

 

[GrimsterGMC]

Yeah, thanks. Changing out the filter was the first thing I did.

Yep, had the pressure guage right at the tbi unit. Pressure was steady at 11 psi at various throttle applications, tried gradual in 500 rpm increments, stabbed throttle, floored to 4000 rpm. In idle it held steady at 11 psi. In gear, it stumbles, splutters, then stalls.

Just a thought but maybe try pulling the plug at the base of the steering column that tells the computer that you have shifted into gear and try driving like that. Mine was running great and I did some data logging and realised the computer wasn't seeing that I was in gear and when I fixed the wire it suddenly started going really rich at idle when previously it was fine. So I am thinking it is to do with the computer and not physical like fuel pressure exactly. Just my 2 cents worth but when all else fails look outside the box.

 

[92GMCK2500]

Since I can't tinker on the truck during the week, time for theories...

This truck is old, like 30 years old. The current engine has 285 000kms on it, or there abouts. It has been knocking for years, I had a local mechanic do quick look over a few years back, "possible suspected rod or main bearing spun".

It burns oil, you can see it in the exhaust gasses as blue tish smoke, when we did the plugs a couple years vsvj, cylinder 2 & 5 were oil fouled. Now, all plugs are oil fouled. It leaks oil pretty savage too.

Now, I've read the fuel pump is wired on the same circuit as the oil pressure switch. Could the ECM be cutting fuel delivery due to excessively low oil pressure?

Oil pressure gage reads mid range on cold start up but drops to low red line once up-to operating temp. When cruising for a while, like 100 kms distance or more, the CEL flashes sometimes. I am pretty sure this is the truck telling me that oil pressure is low. Happens to be when gage shows redline low. No codes gave shown up except the EGR code 32 mentioned earlier.

Ok, theory over.

 

[Schurkey]

The oil pressure switch can turn the pump ON. It cannot turn the pump OFF unless the fuel pump relay or relay harness is also defective. The oil pressure SWITCH is not the device that drives the gauge on the dash.

The MIL/CEL is not wired into the oil pressure system. You have something else going on. Connect a scan tool, see what you can find out--codes AND data stream. Verify the sensors and computer outputs.

 

[1990Z71Swede]

Careful quick clean with carb cleaner. Propane torch sounds much more fun.

I'll check that snap on tester out

Got this from the snowmobile guys, Toothbrush and Brake cleaner. Works every time, but consider it a quick fix to get you home, or to diagnose if new plugs are needed. I think that combo is enough to brake the "glaze" but just enough for the plugs to start working again. They are not going to be like new and sometimes they die again in short order.

Also, Have you replaced your PCV valve recently? Because: High Oil consumption and possibly high idle...

 

[Sabinoerc]

Yep, had the pressure guage right at the tbi unit. Pressure was steady at 11 psi at various throttle applications, tried gradual in 500 rpm increments, stabbed throttle, floored to 4000 rpm. In idle it held steady at 11 psi. In gear, it stumbles, splutters, then stalls.

Seems like you tested it well, thoroughly.
I am leaning more towards Shurkey now. If you are pretty sure fuel pressure is good and checked grounds, no vacuum leaks - so many things can cause drivability problems it can be really hard to figure out without some diagnostics. Sounds like you are I tried to keep fixing things on mine as it aged without diagnostics and chased my tail many times trying to figure something out. Finally gave up and invested time in getting into diagnostics and wish I had done it sooner. Seems you are at point that anyone who keeps one of these going eventually comes to - throw parts at it, get some diagnostic capability, pay someone to fix it for you, or get rid of it.

Two paths on diagnostic capability
Buy a scanner somewhere - I've no experience with that but many on here do.
2nd path is Tunerpro. If you are handy with laptop and inclined, Tunerpro is freeware/shareware. Plenty of people use it here and on gearhead-efi so you can get help - but it is an investment in time.

I would confirm EGR is OK. I've heard if they leak/fail they can cause problems but no personal experience.
Good luck!

 

[92GMCK2500]

The oil pressure switch can turn the pump ON. It cannot turn the pump OFF unless the fuel pump relay or relay harness is also defective. The oil pressure SWITCH is not the device that drives the gauge on the dash.

Good to know. Maybe there is hope! I started spiraling about having to do a mandatory engine overhaul.

I am just needing to drive this pig 20 kms to our summer camping spot where it will be parked for two months. That starts July 1st, so got some time...

The MIL/CEL is not wired into the oil pressure system. You have something else going on. Connect a scan tool, see what you can find out--codes AND data stream. Verify the sensors and computer outoutput

Roger that. Should be a great learning opportunity.

 

[92GMCK2500]

Also, Have you replaced your PCV valve recently? Because: High Oil consumption and possibly high idle...

Yes. PCV was replaced with ACD one a couple hundy kms ago. I do need to recheck the hose & grommet tho so good reminder.

 

[92GMCK2500]

Seems like you tested it well, thoroughly.
I am leaning more towards Shurkey now. If you are pretty sure fuel pressure is good and checked grounds, no vacuum leaks - so many things can cause drivability problems it can be really hard to figure out without some diagnostics. Sounds like you are I tried to keep fixing things on mine as it aged without diagnostics and chased my tail many times trying to figure something out. Finally gave up and invested time in getting into diagnostics and wish I had done it sooner. Seems you are at point that anyone who keeps one of these going eventually comes to - throw parts at it, get some diagnostic capability, pay someone to fix it for you, or get rid of it.

Two paths on diagnostic capability
Buy a scanner somewhere - I've no experience with that but many on here do.
2nd path is Tunerpro. If you are handy with laptop and inclined, Tunerpro is freeware/shareware. Plenty of people use it here and on gearhead-efi so you can get help - but it is an investment in time.

I would confirm EGR is OK. I've heard if they leak/fail they can cause problems but no personal experience.
Good luck!

Thanks for the words. I have an old scanner that I have never used, time to bust it out!