New Fuel Pump Failure

Hi guys, I just replaced the fuel pump in my '96 Silverado (5.7L Vortec, 4x4, 5spd)2 days ago and it apparently has failed today. Pump purchased from Dealer part#25163473. After installing new pump, truck started right up, good idle, no hesitation on acceleration, took it for a quick spin around neighborhood, truck ran great so i parked it. I go to move it today and it starts up fine but as soon as I start to drive out, it wants to stall, then starts idling rough and practically dies when press down on accelerator ( basically all the symptoms it had prior to pump change). I rechecked fuel pressure from rail and it barely hits 40psi before rapid drop off back to zero when pump is cycled. There are no visible fuel leaks that i can detect or smell. I went with the dealer pump after much reading here on the fail percentage of aftermarket pumps, guess I was unlucky. Is there something else I'm overlooking here? Any advice would be greatly appreciated before i start tanking fuel tank out again.

Thanks in advance,
~David

Hi guys, I just replaced the fuel pump in my '96 Silverado (5.7L Vortec, 4x4, 5spd)2 days ago and it apparently has failed today. Pump purchased from Dealer part#25163473. After installing new pump, truck started right up, good idle, no hesitation on acceleration, took it for a quick spin around neighborhood, truck ran great so i parked it. I go to move it today and it starts up fine but as soon as I start to drive out, it wants to stall, then starts idling rough and practically dies when press down on accelerator ( basically all the symptoms it had prior to pump change). I rechecked fuel pressure from rail and it barely hits 40psi before rapid drop off back to zero when pump is cycled. There are no visible fuel leaks that i can detect or smell. I went with the dealer pump after much reading here on the fail percentage of aftermarket pumps, guess I was unlucky. Is there something else I'm overlooking here? Any advice would be greatly appreciated before i start tanking fuel tank out again.

Thanks in advance,
~David

on a vehicle this old replacement of the fuel pump relay is important,,these contacts get damaged over time and with the pump failing can get stressed out with higher amp's flowing..

another area of concern is the ground connection to the frame rail next to tank for the fuel pump...this must be cleaned and secure..

Thanks for the suggestions j_cAT, I'll double check the ground (though I think is ok because the pump does cycle). As for the fuel pump relay, I'll change it out, but would a faulty relay cause the pump to not hold pressure? I still get the feeling I'm going to have to swap the pump out...again ( i have to admit I did not particularly enjoy removing the tank, re-installing it was slightly less aggravating :biggrin: ) Anyway, I'll report back after I follow up on your suggestions, thanks again.

~David

Thanks for the suggestions j_cAT, I'll double check the ground (though I think is ok because the pump does cycle). As for the fuel pump relay, I'll change it out, but would a faulty relay cause the pump to not hold pressure? I still get the feeling I'm going to have to swap the pump out...again ( i have to admit I did not particularly enjoy removing the tank, re-installing it was slightly less aggravating :biggrin: ) Anyway, I'll report back after I follow up on your suggestions, thanks again.

~David

yes the rapid drop off is bad...
question is was the tank dirty///rust ????etc....excessive dirt can/ will damage pump...

Could also be the fuel pressure regulator.

Thanks for the replies

j cAT: The inside of the fuel tank was clean, no rust/debris of any kind, quite pristine. In fact I was a little surprised, but this truck has been very well taken care of. I also changed fuel filter when i did the pump, filter was maybe 3 yrs old at most since I last changed, was very clean as well. So I'm not inclined to suspect a blockage. To test repair I added about 7 gallons of fresh gas (gauge reading just above 1/4 tank) should have been more than enough to prevent running pump dry. As for the rapid drop of pressure, that's what makes me think the new pump has failed as opposed to a new or additional problem. Per your other suggestion I double checked ground connection on frame rail, it is clean and tight. I did not get to auto parts today for a fuel pump relay though, will go in the morning.

777Stickman: I had the regulator replaced 2 years ago. Since replacing right up till time of death of original fuel pump the truck performed great. Then as mentioned after replacing fuel pump, my truck was it's "rarin' ta' go" self, at least until day 3. Anyway my truck is not exhibiting any of the symptoms it had when original regulator was leaking. When it developed it's leak the smell of gas was quite obvious, especially after turning truck off and excess fuel was draining into lifter valley. That and I thought a slow drop in pressure was more indicative of a regulator leak,though I'm not sure about that. When i turn key on I hear pump, gauge climbs rapidly to about 40psi and then just falls off and is back at zero by the time pump has cycled for 2 seconds. Even the original pump would hold at around 15psi after it stopped working normally, it just wasn't making pressure, the new one just doesn't hold it.

Should I be testing the regulator? steps for trouble shooting are given in my manual, though i don't have a shut off valve which if i remember is required on the return line. Not to sure about wanting to tackle that myself if I have to modify the line to do so (doesn't really explain procedure for installing the shut off, just says it's needed).

Thanks again for your feedback, if you have any other suggestions or advice I would sure appreciate it.

~David

PS: The sooner I get this pump issue resolved the sooner I can post in the mileage thread, can't do it in good conscience when truck is tore up :)

Well I just finished removing the "new" pump, was much easier this time around.Took about an hour and without rushing (and no swearing) as opposed to 5hrs first time (3hrs of swearing, 1 hour of coffee drinking and about 2hours of actual work mixed in between :)).Well all jokes aside, I talked to the parts department at my local dealer (where i purchased the new fuel pump) this morning and they're gonna swap the pump out for me which I'm thankful for. Also on the shopping list is a new fuel pump relay, and new O-rings for supply and return lines. I didn't replace O-rings the first time, no leaks, but seeing as how it's apart again i figure I should. Will be checking fuel pressure with key on, then if good while running, this time before I just take it out for a test drive. I regret not doing this the first time as I would like to have known how the pump was performing while the truck seemed to be operating normally on first start up and test drive only to fail the 2nd time.

Anyway, I hope to get it buttoned up this afternoon, will post back with results. Thanks again for tips and advice, I'm glad I found this forum, ton's of info and friendly help available here, you guys rock!

~David

Well, here's more of my bad news. Swapped out pump, wanted to get a pressure reading before starting up, here's the results:

Key-on: 1st cycle peaked at about 63psi dropped back to about 57psi at end of cycle

2nd & 3rd: peaked at just over 60psi dropped to about 50psi but held

4th: pressure dropped to zero at key on *pump was running, now will not make pressure, as fuel is just leaking right back into tank.

Seems to be a repeat of the results I just experienced, only took less time to fail. No visible signs of fuel leaking no detectable odor. Documentation that came with pump identifies the part that connects the pump to the line as the "Fuel Pump Pulsator" has this been the culprit the whole time??? My Haynes repair manual makes no mention of this item, point of insertion for fuel pump is referred to as "rubber connector". No mention is made of this part in any of the trouble shooting steps for the fuel delivery system. New pump came with a short length of rubber fuel line and 2 plastic clamps, but it lists them for use only on vehicle that use this type of connection and not a pulsator.

Is it possible that after initial assemble when everything is firmly seated i get adequate pressure, but then as pump cycles the seal made by the pulsator begins to fail and then prevents any pressurization from occurring?

A quick google search and apparently the purpose of the pulsator is to dampen noise caused by the vibration of the pump, and one random forum thread I looked at suggests that it is acceptable to replace the pulsator with a fixed hose (such as what came with the pump). And that it can be the cause of poor pressure.

Uggh!!! looks like up dropping the tank AGAIN tomorrow. While I don't know for certain this is the root of the problem, I certainly feel it has the highest probability. I only wish I had not been ignorant of the possibility of the pulsator being the cause of inadequate pressure in the first place, makes me wonder if the original pump actually did fail (unfortunately it's garbage now, and well, I do have a new one...sigh) The fact is isn't even mentioned in the trouble shooting of the fuel system in my Haynes repair manual is distressing. Oh well live and learn. Will update progress tomorrow with results.

~David

Well this seems to have done the trick. After discarding the fuel pump pulsator, and replacing it with a hose and 2 clamps, the pump is functioning as it should. Key-on cycle: 62psi, truck idling: 54psi, peaks out about 62-64psi when I rev it up a little. After turning it off pressure eases down to 50psi and holds there steadliy for about 3.5 min before easing down any further. Test drove it, runs great, so it would seem that the issue has been resolved (crosses fingers, knocks on wood etc...) Still not thrilled about the fact my Haynes Manual doesn't include or even mention anything about the pulsator, could have potentially saved me a lot of headaches and not required me to remove tank and pump 3 times. Apparently the pulsator is an Illuminati secret no one talks about :sarcasm1:

Anyway, gripes aside, I guess the old "3rd time's the charm" was in effect, and I'm glad the problem is fixed. Thanks again for your tips and advice.

~David

when you removed the original pump was it made exactly the same as the NEW pump ????

trying to understand how the hayes manual messed you up...

the aftermarket manuals have many confusing directions...

so the GM pump had no instructions ??

Hi J cAT, the the new pump was identical to the original except for obvious discoloration of the plastic on the old one. My gripe with that manual is that the entire section on the fuel system is devoid of any mention of the "fuel pump pulsator". The step by step instructions for pressure testing the system should have at least identified this part, but really the fact that manual pretty much says if the pressure isn't within the listed limits to replace pump. There are additional trouble shooting steps that address potential for regulator/injector leaks, obstruction in a filter/line or leak there as well as possibility of a oil pressure senor (only found on some models) being cause for inoperative pump. But nowhere does it say anything along the lines of "a worn out fuel pump pulsator may result in poor or absent pressure...blah...blah..."

It was in fact the documentation that came with the pump that got me thinking it could be the problem after all. It does identify the part in a diagram of a typical unit. This is how I identified the part. BUT...the instructions clearly say that the included fuel hose and clamps are for vehicles that DO NOT have a fuel pump pulsator, but that have this hose instead. My vehicle had a pulsator, so I was not inclined to replace it with a length of hose. Though in hind site that's exactly what i should have done.

Now, I also did not initially even suspect the pulsator as part of or the source of the problem (back to "bad pressure bad pump"). I suppose it should have occurred to me that the way in which the pump connects to the supply line should be checked and/or replaced *this is where the manual should list this as something to at least consider. As I said in a previous post, once I began suspecting this part, a quick google search informed me what the pulsator does and that if it leaks it will cause poor pressure. Of course I'm not a mechanic by trade, I chose to undertake the repair myself and learned a good lesson from it.

Sorry for wall of text here, I just feel that the repair manual should include checking the pulsator in its trouble shooting process. On a positive note I've become fairly effecient at removing and reinstalling the fuel tank :tongue:

~David

A quick After though: the documentation that came with the pump clearly describes how to remove a fuel pump equipped with a pulsator, they were well written and easy to understand.

i have actually ran into that same problem at my work. that little rubber hose breaks down and swells up which will let pressure through sometime or it might not and will let pressure bleed off quicker than what it should. Good idea to replace that whenever new pump is installed. I don't see why the new pump didn't come with that anyways.

thanks for that great explaination.....where this is not a usual task, this can be confusing...

thanks for that great explaination.....where this is not a usual task, this can be confusing...

Your welcome, thanks for taking time to read it. I hope this thread will be helpful to anyone having fuel pressure problems where the pump is suspect. Maybe it'll save some time and headaches, especially for those doing this repair for the first time, or a reminder to those more experienced mechanics when offering trouble shooting tips as something not to overlook.

~David

Great write-up, it helped me pin point the problem on my sons 1994 Jimmy 4.3 Vortec. Had an issue with the SUV, it stalled on the highway, fuel pump fuse blew. Changed the fuses out and about a week later it bogged down ( no acceleration ). Started with checking the pressure, pressure registered just fine, both idle and just the key. Removed intake, checked each port, and each one shot when the engine cranked over (you have to disconnect the coil wire to do this, if you remove the connectors from the coil itself the ports will not work).

After reading your thread, I thought maybe the hose on the fuel pump on the pick-up assembly was loose and loosing some pressure as you indicated. It’s easier for me to get to the pump since the previous owner cut an access panel on top. Well the clamps were loose, but the bigger problem I found was rust. When I removed the fuel pump, the hose poured out brown thick rust. Changed the filter and the Jimmy is off and running again.

Next project, drop the tank and remove the rust.