Re: New option for fuel pump replacement
 

Ok, in the process of more research.....really makes your head spin...
What I would suggest is to make sure your getting the product you need and at the best cost possible.
Case in point, Mike checked Amazon and the Denso 951-5006 unit is listed there for under $20, but their site mentions that it doesn't fit the LT5. The same (think they are the same) units I ordered are more than $20, and are a direct fit for the LT5. The one Denso listed on Amazon is made in China, the Denso unit that Mike used is made in Mexico. I am calling tomorrow to check where the units I have on order will be made.
We would all like a quality product regardless where it is made and hopefully that is what we purchase. I would like to see more USA units made, as with some of the China based automotive products have been in question over the years concerning quality and reliability. That being said, ineffective quality control could take place anywhere.

Also take note that there are many sites that do not distinguish the difference between the LT1 and LT5 fuel pumps in their specs. One exception appears to be Rock Auto that does show a difference in part #'s for the two engines. But one thing I found very interesting is that the
PERFORMANCE ELECTRIC P240KC fuel pumps that are popular are listed for both the LT1 and the LT5, while other brands on their site do show different part #'s pertaining to the different engines.

IMO, this is one of many instances where you really need to check everything out before making a purchase.

Re: New option for fuel pump replacement
 

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.

Re: New option for fuel pump replacement
 

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.

Re: New option for fuel pump replacement
 

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


http://www.rockauto.com/info/321/125...mary__ra_t.jpg



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


http://i185.photobucket.com/albums/x...PtestLarge.jpg