Engine/Transmission (1998.5 - 2002) Hot fuel killing lift pumps?

[GWedekind]

I have been reading the posts for cooling fuel to help make the VP44 last longer and realized that this is a strong possibility as to what killed my relocated Carter 4601HP's and is now affecting my pressures on my Holley Blue.



Last month I put a 190 deg stat in because my original stat failed and the truck wouldnt run past 160 or so. Since the replacement stat was installed and I now run about 190 I have been loosing fuel pressure when hot and pressure has become erratic.



The Carter and the Holley both have a steel bypass valve that floats inside an aluminum pump housing. Two dissimlar metals that expand at different rates. BINGO... this could be why we are loosing relocated Carter 4601's after a few months!



I bet the FASS has more heat absorption abilities because of larger size of the billet aluminum pump body and filter base.



My holley gets so hot that I cant touch it after a few hours of driving. I realize that some of that heat is from the pump running but with all the testing that I read on other posts we have an inherent heat issue with return fuel and with that being identified this could be affecting the 4600, 4601 and Holley lift pumps.



Another wild opinion here is that the original factory Carter type lift pump that was block mounted doesnt seem to fail as often when relocated to the frame by the tank. Maybe the original style has a modified bypass valve in it so that it wont stick when subjected to heated fuel and I bet the replacement aftermarket 4601's dont have the same clearances/specs when compared to the factory type carter pump.



I have a 4601HP that is stuck and wont produce pressure and will cut it open and see what it looks like. If anyone has a stock factory style pump that wants to help out in this experiment please let me know.

 

[keimmmo]

I am participating strongly in cooling the fuel to the VP. I relocated my factory LP just in front of the tank years ago thinking that electric pumps are made to push, not pull. Also, it seemed logical that it would last longer without the heat and vibration of the motor. I ran 80k on the last LP... not great, but no real complaints.



While I hadn't really thought of it, I have to agree that fuel temps could very well be what is killing the LPs as well as the VPs! I like the way you are thinking!!!



Steve Keim

 

[lumberjack98]

I also have a recently failed carter 4601hp @ 7,000 miles very interested i'll see if i can find my old lp.

 

[WestTN]

I think running the tank level too low before filling up allows too much sloshing away from the pickup. The resulting slugging hammers the bearings out of the pump. DC motors really rev up when the pump loses prime. . AC motors don't have the same speed gain and they can be damaged by slugging. I never use more than 26 to 27 gallons from the 36 gallon tank before refilling. I am still using the original pump at 101,000 miles and the fuel pressure is the same as when I installed the pressure gauge at about 2,000 miles.

 

[Gary - K7GLD]

I have a 4601HP that is stuck and wont produce pressure and will cut it open and see what it looks like. If anyone has a stock factory style pump that wants to help out in this experiment please let me know.



NO need to reinvent the wheel - already been there, done that:



https://www.turbodieselregister.com/forums/showthread.php?t=108275

 

[GWedekind]

interesting..... Thanks Gary for the link!



I still think that there is a difference in the stock LP and the 4601HP. We seem to get more life out of stock ones than we do out of the 4601's.



I did have one 4601 that had a rotor failure ( plastic bushing stripped out ) but the last 2 were bypass issues. I even tried soaking it in gasoline and beat it sensless to try and get the bypass unstuck. No luck.



I wonder if the bypass spring fails from heat issues or does it pop out?

 

[GWedekind]

Just came back from the shop and i cut the 4601HP pump apart and there appears to be a difference in the bypass valves from a stock LP and a 4601HP. Mine was stuck open and the piston rod looked bent.

 

[GWedekind]

pic of the assy before i removed the bypass valve

 

[rivercat]

I for one would like to see a poll of sorts to see if there are trends in fuel problems assosiated with: long beds (longer distance to VP) , towing or traveling long distances (potential for lots of heat in fuel to be returned many times over long trip), Warm climates in general (desert states) I think if any of these qualifications are met the potential for heat related faulure is greater.

 

[Gary - K7GLD]

HMMmmm - that 4601 bypass valve looks totally different in design from the stock DC LP I took apart and posted pics of in the pointer up higher in this thread...

 

[GWedekind]

That has to be why the relocated 4601's dont last very long. Im getting the feeling that the stock LP relocated to the lower frame rail is a viable option for mild or stock trucks.



Anyone have a stock LP that they want to cut up and take detailed pics of just the bypass?