New option for fuel pump replacement

[XfireZ51]

I think that if GM could have gotten away w a single pump, they would have.

[-=Jeff=-]

Originally Posted by XfireZ51

I think that if GM could have gotten away w a single pump, they would have.

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?

[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.

[mhobtr]

One of the more popular replacements is the PERFORMANCE ELECTRIC P240KC sold by Rock Auto. There are numerous posts about them and I don't remember any being negative.

They have been out of stock for a while but are now relisted at $19.22 each which is a great deal.

I just ordered two for spares.

[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

[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.

[Hog]

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

If you were able to view your WOT fuel pressure I'm thinking it would be ramping up during those periods when you are getting back on the throttle after you upshift.
As soon as you go WOT the ECM would be commanding very high pulsewidths, with all 16 injectors firing the fuel system is fighting to supply them with fuel and it takes a moment to get the fuel pressure back up.
Throwing some powershifts would eliminate your issue I'm guessing as the throttles remain open and there is no ramping up to full power. You would be looking for just under 52 psi at all times, IIRC the OEM regulator is set at 51.8psi for LT5.


A fuel pressure gauge taped to the windshield would tell the tale.


Cutting open fuel filters is a good idea as well. It doesn't take much to start to plug these high pressure fuel systems. I had a 66psi OEM GM system that woudnt rev over 4500rpm at WOT, I was surprised what was in the filter.






Mr Haibeck says that you require 51psi plus or minus 1 psi at WOT 3000-7000rpm. If you see less that 47psi of WOT fuel pressure, reduced power and knocking and possible codes can result. He agrees with talking her for a spin with the gauge taped to the windshield, he does make a good point to use a passenger though. The fuel pressure should snap up to 51 +/-psi (from around 43psi during normal driving when engine vacuum is high) when you stand on the throttle, then you know the FPR is working, or if you are at idle and you disconnect the vacuum supply to the FPR, you will see 51psi or so.

[5ABI VT]

Originally Posted by Hog

If you were able to view your WOT fuel pressure I'm thinking it would be ramping up during those periods when you are getting back on the throttle after you upshift.
As soon as you go WOT the ECM would be commanding very high pulsewidths, with all 16 injectors firing the fuel system is fighting to supply them with fuel and it takes a moment to get the fuel pressure back up.
Throwing some powershifts would eliminate your issue I'm guessing as the throttles remain open and there is no ramping up to full power. You would be looking for just under 52 psi at all times, IIRC the OEM regulator is set at 51.8psi for LT5.


A fuel pressure gauge taped to the windshield would tell the tale.


Cutting open fuel filters is a good idea as well. It doesn't take much to start to plug these high pressure fuel systems. I had a 66psi OEM GM system that woudnt rev over 4500rpm at WOT, I was surprised what was in the filter.






Mr Haibeck says that you require 51psi plus or minus 1 psi at WOT 3000-7000rpm. If you see less that 47psi of WOT fuel pressure, reduced power and knocking and possible codes can result. He agrees with talking her for a spin with the gauge taped to the windshield, he does make a good point to use a passenger though. The fuel pressure should snap up to 51 +/-psi (from around 43psi during normal driving when engine vacuum is high) when you stand on the throttle, then you know the FPR is working, or if you are at idle and you disconnect the vacuum supply to the FPR, you will see 51psi or so.

I looked briefly for a fuel pressure gauge to tape to the windshield but am not sure what the fitting size is etc. is it the same as an LT1 ? The car never hesitated like that before (few runway events on YouTube I have have no lag whatsoever) I have a few videos I won't post because we were being naughty on the highways at night but the hesitation was much more prominent. It still pulls decent with the hesitation but something is going on.

[Hog]

Originally Posted by 5ABI VT

I looked briefly for a fuel pressure gauge to tape to the windshield but am not sure what the fitting size is etc. is it the same as an LT1 ? The car never hesitated like that before (few runway events on YouTube I have have no lag whatsoever) I have a few videos I won't post because we were being naughty on the highways at night but the hesitation was much more prominent. It still pulls decent with the hesitation but something is going on.

I took a quick look and it looks like the LT1 and Lt5 fitting should be the same. I have no idea on what the fitting size is, all GM stuff was the same, my gauge came with the correct size.


Used on everything GM from 1991-2012.
Description
"Fuel Rail Pressure Relief Valve Distributor-Breakerless ignition"

US$18.26
GM p/n 12570619






This thread throws around some possible sizes.
http://www.zr1.net/forum/showthread....=fuel+pressure


Whatever your issue is, the engine sure recovers quickly afterwards. I can totally understand thinking it might be a clutch issue.


After much digging, I found a thread that specifies the correct un regulated or WOT fuel pressure of 50.76 psi. So if you find 51 psi plus or minus 1 psi at WOT your golden. It was tpepmeie who reported the actual LT5 fuel pressure of 50.76psi. At 50.76psi of fuel pressure, the stock injectors will flow 22.14 lb/hr and at 43.5psi they would flow 20.5 lb/hr.


This is the thread where I was referencing Mark Haibecks info.
http://www.zr1.net/forum/showthread.php?t=14739