What are some tell tail signs that the lift pump is going bad?

I don't know if there are early signs of impending death. Its a weak little pump. It works or it does not. You can check flow rate at water drain with engine idling. But problems may be power supply, oil pressure switch, or fuel tank pickup etc. Maybe listen to it on the wts cycle for strange noise. Several people have added fuel pressure guage to keep eye on it. Just driving around light load the truck will run OK w/o the lift pump working.

I have had a bad PMD before but its nothing like that. Most of the time basic acceleration is fine. Steady 55 to 65 driving seams a little choppy.
Hard accelleration can produce some coppyness also. The lift pump is noisy.
It just all around dosnt feel quit right.

Is it an "s" engine? I've read here that EGR can cause that type of symptom

I dont remember how to identifie the engine. Its a 97 Suburban.

I dont remember how to identifie the engine. Its a 97 Suburban.

It's in your Vin...;)

Mark

Easiest way to tell is change your fuel filter! :D


If you cannot hear it when the key on then the pump is dead!

filter could also be clogged

You can hear the lift pump, over the engine. Its very rattlie.

If you can hear it over the rattle of your running 6.5, then I'd be shopping for a new one, IIRC your eigth didget in the VIN should be an "S" or "F"
an S engine has an EGR (which is the funny looking device mounted on the center of the intake)

No way I can hear it over the rattle of my motor.

Mine don't make any noise either, just a bumpy feel to the touch.;)

Mark

I can hear mine now too over the engine, never did before stalling problems started 2 days ago. I'm wondering if a bad pmd would cause lift pump to weaken- thought it might be the reverse. Or what else makes lift pump weak-perhaps repeated start and stalls could kill it?
Would louder sound mean lift pump is definitely bad or could it be ok as long as flow rate is normal? Is it likely fixing something else will make it sound "normal again"?

For all the aggravation they cause, just put a new one in if it starts sounding bad. Fuel filter BEFORE the lift pump wouldn't hurt either.

when you say "choppy" at 65 and up, are you talking about under hard accelleration? and it acts like it's running out of fuel? I was going to start a thread asking the same question. (just changed my fuel filter because of same symptoms)

I imagine that it's possible for a worn pump to not deliver enough fuel.

Yes its coppy under accleration. But I think I found the problem
THe retaining ring around the fuel filter wasnt tight. It never leaked fuel but the filter housing never filled up completely. When I openend it it was only half full, or half empty which ever way you would like to look at it.
There you have it problem solved.
Push pump is still noisy by the way.

THe retaining ring around the fuel filter wasnt tight. It never leaked fuel but the filter housing never filled up completely. When I openend it it was only half full, or half empty which ever way you would like to look at it.
There you have it problem solved.
Push pump is still noisy by the way.

You aren't the first guy that happened to.

Well thats How I found my bad lift pump I changed the furl filter, and as soon as I put a new one in it started right up, Oh yea 2 new batteries, the fact I ran the others down not knowing the lift pump was bad :lol: ,
Ofcourse now the PMD is going south

Sometimes it's just " Misery, Misery, Misery".

Yeah but arnt they fun when everything is right?!