Dies in gear when throttle applied

[92GMCK2500]

Pressure seems a little low. Not holding pressure is totally normal on TBI.


The pump will "run" on less-than-optimum voltage. But it won't run RIGHT. Yes, I'd check the voltage near the pump, with the pump RUNNING. Also verify amperage draw of the pump, with the pump RUNNING.


Seems reasonable. Most folks prefer to be at the high-end of spec (~13 psi) but you shouldn't have stalling problems at 11 psi.

Is your gauge accurate? How do you know?


Pressure maybe varies when the engine stalls because the alternator quits charging, and the system voltage droops.


You haven't dicked with the tamper-resistant base idle screw, have you?


Wise.


Probably a waste of time and fuel.

Does low KOEO fuel pressure indicate anything in particular?

Excuse my rookie questions. Does conducting a voltage check with pump running require probing the 12V wire at the pump connector?

What about average draw? I can Google but thought I'd ask while here.

Can't verify fuel pressure on another guage right now. I rented the tool from the parts store.

No mucking around with idle screw. It's got the cap & will stay that way.

I am running the 'bad' gas for now. It wasn't randomly splattering when running in P/N, so mehhh, figure it's ok for now.

 

[udidwht]

9.5 is on the low side of what I believe is unacceptable.

 

[92GMCK2500]

9.5 is on the low side of what I believe is unacceptable.

This is at KOEO. Still unacceptable?

I am steady at 11psi with engine running otherwise. Except when it dies of course.

 

[92GMCK2500]

Well, double no dice.

Went to test EGR, my vacuum tester tool is broken. Spent morning trying to fix that. No luck. Time for a new one. I'll order one this week.

Pulled plugs. Clearly oil fouled, all of them to some degree. Cleaned and reinstalled. No difference. I knew they were bad but not that BAD! Could this be my problem?

 

[Schurkey]

HOW did you "clean" them?

A propane torch works pretty well...MOST of the time. Yellow flame is crap burning off, orange flame with no yellow is "done".

If the porcelains have conductive glaze on them, the propane torch is useless, they'll have to be grit-blasted or replaced.

I have a Mityvac vacuum tester that uses a Holley accelerator pump umbrella as a check-valve. No end of problems with it from the day I took it out of the box, until I replaced the OEM check-valve with a genuine Holley valve. While I still own this tool, it's rarely used now--bought a used Snap-On SVT270 from a seller on eBay--which works first time, every time, one-handed and beautifully balanced. Best I can tell, Snappy discontinued this tool, wasn't available for years...but has been re-introduced and is available again. Which means, all the replacement parts are also available. (Beware the cheap-junk counterfeits made from plastic. The Snappy is a metal, made-for-life job.)

 

[Sabinoerc]

I would change fuel pump/filter. Marginal fuel pressure can cause so many problems that send you down false paths. Idling well with lowish fuel pressure doesn’t mean it will be ok when in cell/demand is higher.

I had problem with stalling, studder on accel (93 5.7tbi). Fuel pressure was 11psi between filter and TBI at idle. I noticed that if nailed throttle momentarily fuel pressure would dip. I had replaced and checked about everything else and had saved the fuel pressure/pump for last because of the pain. Replaced with standard ACDelco or Delphi, can’t remember, and got a solid 13psi with any dip when nailing throttle. The drivability problems went away , no stalling, etc. as well as truck drove so much better overall.

I‘ve read that 11psi should be ok but in my case it wasn’t. Don’t know if just old engines with 200k are more demanding or something else. Someone posts about replacing std fuel pump with pump from vortex for better fuel pressure. If I we’re to do it again, I’d do that.
Good luck!

 

[92GMCK2500]

I would change fuel pump/filter. Marginal fuel pressure can cause so many problems that send you down false paths. Idling well with lowish fuel pressure doesn’t mean it will be ok when in cell/demand is higher.

I had problem with stalling, studder on accel (93 5.7tbi). Fuel pressure was 11psi between filter and TBI at idle. I noticed that if nailed throttle momentarily fuel pressure would dip. I had replaced and checked about everything else and had saved the fuel pressure/pump for last because of the pain. Replaced with standard ACDelco or Delphi, can’t remember, and got a solid 13psi with any dip when nailing throttle. The drivability problems went away , no stalling, etc. as well as truck drove so much better overall.

I‘ve read that 11psi should be ok but in my case it wasn’t. Don’t know if just old engines with 200k are more demanding or something else. Someone posts about replacing std fuel pump with pump from vortex for better fuel pressure. If I we’re to do it again, I’d do that.
Good luck!

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

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.

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

 

[92GMCK2500]

No progress during the week, work, kids, work, repeat.

I am ordering another vacuum tester and elec probes to continue the goose hunt

 

[92GMCK2500]

HOW did you "clean" them?

A propane torch works pretty well...MOST of the time. Yellow flame is crap burning off, orange flame with no yellow is "done".

If the porcelains have conductive glaze on them, the propane torch is useless, they'll have to be grit-blasted or replaced.

I have a Mityvac vacuum tester that uses a Holley accelerator pump umbrella as a check-valve. No end of problems with it from the day I took it out of the box, until I replaced the OEM check-valve with a genuine Holley valve. While I still own this tool, it's rarely used now--bought a used Snap-On SVT270 from a seller on eBay--which works first time, every time, one-handed and beautifully balanced. Best I can tell, Snappy discontinued this tool, wasn't available for years...but has been re-introduced and is available again. Which means, all the replacement parts are also available. (Beware the cheap-junk counterfeits made from plastic. The Snappy is a metal, made-for-life job.)

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

I'll check that snap on tester out

 

[Schurkey]

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

Propane flame is enormously more effective (unless you've got that conductive glaze on 'em.)

I'll check that snap on tester out

A few on eBay right now, starting at about $26 (needing repair) on up.