New option for fuel pump replacement

[BigJohn]

Originally Posted by -=Jeff=-

sure 27 years ago.. I wonder if there is a replacement now that would work..

Besides, doesn't a pump shut off after a certain amount of time?

Fuel pumps normally shut off when you turn off car.
Fuel injected cars need steady high pressure, plus there is a return line to the fuel tank.

[-=Jeff=-]

Originally Posted by BigJohn

Fuel pumps normally shut off when you turn off car.
Fuel injected cars need steady high pressure, plus there is a return line to the fuel tank.

Yes I know that.

the LT5 has TWO pumps.. most find they have a bad pump because the car dies when pump #2 shuts off, Hence the Fuel Pump Jumper harness GC is selling

so.. When does the 2ndary Pump Operate and when does it NOT operate.

**
and not all Fuel injected cars need a return line, in fact many dead head form the pump..

[BigJohn]

Originally Posted by -=Jeff=-

Yes I know that.

the LT5 has TWO pumps.. most find they have a bad pump because the car dies when pump #2 shuts off, Hence the Fuel Pump Jumper harness GC is selling

so.. When does the 2ndary Pump Operate and when does it NOT operate.

**
and not all Fuel injected cars need a return line, in fact many dead head form the pump..

When secondary injectors come on for full power would be my guess.

[XfireZ51]

Well if you've eliminated the secondaries, the pump comes on right off idle aside than at first key ON.

[5ABI VT]

Originally Posted by mhobtr

I wouldn't replace a working fuel pump just as a precaution. There is a good chance the new one will not be as reliable as the one it replaced.

If you are worried about being stranded, get one of the primary/secondary reverse harnesses so if your primary pump dies, you can get home on the secondary.

Last year I replaced the entire pump assembly on my 91 with a NIB ACDelco unit. Never was pleased and turned out the check valves in both pumps were bad. Replaced the pumps and everything's great now.

BTW, if you buy new pumps, make sure the check valves are working as soon as you take them out of the box. If not, you can get a replacement or refund and not get stuck like I did.

I did change my pumps that were working fine and I do regret it. I have a slight hesitation that I noticed a few times last summer at wot shifting gears. It has me thinking about the clutch but the truth is if the clutch slips Rpms will rise and this is more of a hesitation or a ever so slight pause in acceleration after a hard fast shift. So.. one thing had bugged me from the beggining is one of the pumps I used had a completely different rattle to it and it's been in the back of my mind. I also did use the plastic clips and I'm wondering if they may have come off as well so I've been wanting to tear in there again and replace them while I'm in there with a high performance pump and use better steel clamps.

Originally Posted by Roadster

Interesting thread, a good read....
After reading some other fuel pump threads back in April, I started doing some research about the pumps. Although I have a back up set from Rock Auto, I wanted to check out more info on different pumps.
The one that caught my interest was the Denso Fuel Pump. I know at least one member has them installed. I think the units installed are:
DENSO #951-5016. So checking them out further my info showed me that this particular # is for the LT1 and not the LT5. And let me say that in no way am I referring that this person installed the wrong part. I am just posting the info from my research. And I am not implying in any way that this part # does not work on the LT5, because this member is using them and to my knowledge is very satisfied.
The number that I found to be for the 90-95 LT5 is: DENSO #951-5006
I don't know or have any knowledge of the specs for the two part numbers listed. Again I am just relaying the info that was relayed to me.
Both part #'s to my knowledge are direct fit units. The Denso units can also be a little more expensive, but not over the top.
The Fuel Pump Filters # DENSO 952-0094 are also listed for the LT5.

As of now the 951-5006 pumps are on National Back Order and should be available sometime in the near future for anyone interested.
Just thought I would pass this along......

This is interesting because I'm not sure but this may be me you are talking about ! I appreciate you posting the research. I had no idea and never cared to really look into the fuel pump part numbers. I had been planning to change my pumps because on install one pump had a distinct rattle that bothered me (think I posted a video of the rattle -if not will do it today) and I also didn't use the screw steel clamps. For some reason when I think about the plastic becoming brittle and being under stress if overtightened it only makes sense they can split and break easily leaving the hose free to shoot off (pretty sure that's what others have mentioned) . SO... I ordered the twin walbro pumps from Lingenfelter. Not cheap but I feel much more comfortable with Walbro pumps from them. Will post again when they come and I tackle it. Will also change my fuel filter again too.

[mhobtr]

I started suspecting my fuel pumps as a source of sluggish acceleration.

I pulled the pump assembly and was not pleased with the hack job someone had done on replacing the two pumps so I ordered a complete new ACDelco assembly thinking that would solve everything.

I didn't do my homework as I should so I didn't replace the plastic hose clamps and, not knowing any better, I didn't check the backflow check valves in the pumps.

Pressure checked good at idle but performance was not what I expected. I ruled out the pumps because they were new and looked elsewhere but eventually came back to suspecting the pumps. By then I was kicking myself for not replacing the plastic hose clamps so I pulled the assembly and found that the check valves on both pumps were bad.

I bought two new Delphi pumps from Rock Auto, with good check valves, installed them along with new stainless steel hose camps and I am very pleased with the results.

[5ABI VT]

Originally Posted by mhobtr

I started suspecting my fuel pumps as a source of sluggish acceleration.

I pulled the pump assembly and was not pleased with the hack job someone had done on replacing the two pumps so I ordered a complete new ACDelco assembly thinking that would solve everything.

I didn't do my homework as I should so I didn't replace the plastic hose clamps and, not knowing any better, I didn't check the backflow check valves in the pumps.

Pressure checked good at idle but performance was not what I expected. I ruled out the pumps because they were new and looked elsewhere but eventually came back to suspecting the pumps. By then I was kicking myself for not replacing the plastic hose clamps so I pulled the assembly and found that the check valves on both pumps were bad.

I bought two new Delphi pumps from Rock Auto, with good check valves, installed them along with new stainless steel hose camps and I am very pleased with the results.

Glad to hear you figured it out was it a hesitation like mine ?

I'm also going to take everyone's advice on the stainless clamps and do that for sure . I will feel happy to find a broken plastic clip but not expecting it!!
Here's a clip I made last year and while I have had other symptoms of my clutch being worn in this case it can be felt and my rpms aren't slipping and rising which is a common clutch -slip symptom but I can feel and hear the delay in acceleration when hitting the next gear and it has made me suspect the pumps. I have changed plugs, wires, coils, injectors, o2 sensors and the map sensor. This video was taken after it all. Leads me back to the beggining ..

Around 14-15 second mark in the video.

https://youtu.be/bH7F59FKPEU

[Roadster]

Originally Posted by 5ABI VT

I did change my pumps that were working fine and I do regret it. I have a slight hesitation that I noticed a few times last summer at wot shifting gears. It has me thinking about the clutch but the truth is if the clutch slips Rpms will rise and this is more of a hesitation or a ever so slight pause in acceleration after a hard fast shift. So.. one thing had bugged me from the beggining is one of the pumps I used had a completely different rattle to it and it's been in the back of my mind. I also did use the plastic clips and I'm wondering if they may have come off as well so I've been wanting to tear in there again and replace them while I'm in there with a high performance pump and use better steel clamps.



This is interesting because I'm not sure but this may be me you are talking about ! I appreciate you posting the research. I had no idea and never cared to really look into the fuel pump part numbers. I had been planning to change my pumps because on install one pump had a distinct rattle that bothered me (think I posted a video of the rattle -if not will do it today) and I also didn't use the screw steel clamps. For some reason when I think about the plastic becoming brittle and being under stress if overtightened it only makes sense they can split and break easily leaving the hose free to shoot off (pretty sure that's what others have mentioned) . SO... I ordered the twin walbro pumps from Lingenfelter. Not cheap but I feel much more comfortable with Walbro pumps from them. Will post again when they come and I tackle it. Will also change my fuel filter again too.

Yes Mike, it was you that I was referring too. Just didn't mentioned your name because I didnt want to imply that "I think you ordered the wrong part"
I have a habit of researching and double checking parts #'s and applications. Although I might not need fuel pump replacements in the near future, I did order the LT5 Denso pumps back in April. As mentioned they are on Natioal BO, but as of late last week, my order finally got submitted. So it seems like they are in production.
Will be anxious to hear your report on the pumps you just ordered.
Glad my earler post helped.....


Sent from my SM-G935P using ZR-1 Net Registry mobile app

[5ABI VT]

Originally Posted by Roadster

Yes Mike, it was you that I was referring too. Just didn't mentioned your name because I didnt want to imply that "I think you ordered the wrong part"
I have a habit of researching and double checking parts #'s and applications. Although I might not need fuel pump replacements in the near future, I did order the LT5 Denso pumps back in April. As mentioned they are on Natioal BO, but as of late last week, my order finally got submitted. So it seems like they are in production.
Will be anxious to hear your report on the pumps you just ordered.
Glad my earler post helped.....


Sent from my SM-G935P using ZR-1 Net Registry mobile app

Definitely helped thank you ! Just knowing that would have made me change them out regardless I definitely will post up! I checked after reading your post that they did show available on amazon.ca for the correct part number. But with the strainers (likely wouldn't need another pair) it would have been close to the cost of the lpe pumps which on their website shows are included for the cost so I went with that. I spoke with Ken at lpe briefly and I was convinced (lol). I figured no one really talks about walbro or performance brands much so I at the least I could add something to the forums regarding that setup.

[mhobtr]

Originally Posted by 5ABI VT

Glad to hear you figured it out was it a hesitation like mine ?

I'm also going to take everyone's advice on the stainless clamps and do that for sure . I will feel happy to find a broken plastic clip but not expecting it!!
Here's a clip I made last year and while I have had other symptoms of my clutch being worn in this case it can be felt and my rpms aren't slipping and rising which is a common clutch -slip symptom but I can feel and hear the delay in acceleration when hitting the next gear and it has made me suspect the pumps. I have changed plugs, wires, coils, injectors, o2 sensors and the map sensor. This video was taken after it all. Leads me back to the beggining ..

Around 14-15 second mark in the video.

https://youtu.be/bH7F59FKPEU

I doubt you will find a broken plastic clamp but they just don't clamp and seal well. The two pumps "Y" into a single outlet pipe so as the pressure builds, the pipe connections leak and, as time goes on, it gets worse. In my case, I believe I was experiencing the inability of the system to deliver adequate pressure during hard acceleration. I did not try taping my fuel gauge to the windshield but I bet it would have proven me right.

As to the check valves, they shouldn't make any difference when both pumps are running but when the secondary pump turns off during normal driving, the primary pump will short cycle back through the "Y" pipe, into and out of the secondary pump, which will hurt system pressure. In my case, I believed this caused my primary pump to begin intermittent failure. I could drive for short time and "run out of gas". I could then turn the ignition off and restart immediately because the secondary pump would kick in and deliver system pressure.

When I installed my primary/secondary reverse harness, the problem didn't go away because both pumps had the same issue with bad check valves.

When I put the new pumps in, with the steel clamps, the intermittent failures stopped and the performance increased dramatically.