Engine/Transmission (1998.5 - 2002) Hard starting RASP

[dieselboy25]

I installed my RASP from DTT with the help of Tony of Welch Performance Diesel last September. Everything was working and starting great. I had 6 psi at with lift pump running (truck off), 14. 5 psi at idle and rock steady 15 psi at just about any boost or rpm level.



Two months after I had the RASP installed, the truck would start great, but die about 10-30 seconds right afterwards. I would have to crank for 20-40 seconds for the engine to kick over.



Once the engine restarted, everything the engine would run fine, but my fuel pressure would start at 0 slowing climb up to 12 at idle. I can pull it down to 9 under a good load now. I was not getting any fuel pressure from the just the lift pump running so I figured my lift pump finally went bad. I replaced the lift pump to no avail. I hear the new lift pump running, but I do not get any pressure until after the truck starts for the second time.



The truck is hard to start regardless of the outside temperature, engine temperature or duration of time between starts. Keep in mind, I do not drive my truck very often (less than once a week).



I love the RASP once my truck is running, but I need to solve this hard starting issue. I have no codes and my mods in the signature.

Thanks,

Eric

 

[steved]

I'm not to up onthe RASP, but, I would check the electric LP for operation and I believe there is a checkvalve in the loop somewhere (to isolate the electric LP when the RASP takes over)... that might be stuck open.



Just a couple ideas... could also be a cracked line letting air into the system... or a serious restriction in a line... have you replced fuel filters lately??



Again, just throwing out some ideas... I don't know much about the RASP other than what I have read...



steved

 

[dieselboy25]

The lift pump is running (making noise), but I am not ruling it out.



I have checked the system for leaks a few times, but I have not found any. I am not leaking any fuel when running.



I first thought it was a priming issue, but it is hard to start even if I shut it off and start it right back up.



I have thought a lot about a block or check valve somewhere, but it does start every time (with lots of cranking) and is fine once it starts for the second time.



I replaced the fuel filter when we installed the RASP and I only have about 2000 miles on it since then.



Keep the ideas coming.

Eric

 

[steved]

The lift pump is running (making noise), but I am not ruling it out.



I have checked the system for leaks a few times, but I have not found any. I am not leaking any fuel when running.



I first thought it was a priming issue, but it is hard to start even if I shut it off and start it right back up.



I have thought a lot about a block or check valve somewhere, but it does start every time (with lots of cranking) and is fine once it starts for the second time.



I replaced the fuel filter when we installed the RASP and I only have about 2000 miles on it since then.



Keep the ideas coming.

Eric

I know from experience that the LP can run and not pump anything. . so your are wise to not totally rule it out... if the check valve is open, it might make it hard for the RASP to prime itself. That's what it sounds like... lots of cranking indicated to me it is losing prime.



Or your VP44 is on it's way out...



steved

 

[BarryG]

DB:

I also am leaning towards one of the check valves sticking open partially(could be a piece of crud blocking it from closing). The truck might be starting right off because of the residual fuel in the vp and injector lines. Then die until the rasp or lp has primed the fuel system backup before the vp. As you know I was also having this problem but it doesnt sound like it is nearly as bad as yours. Mine only did it on fairly cold mornings and only the first start of the day. I also have checked for air leaks and I may have found my culprit but since it only does or at least has done it when it is fairly cold out I may have to wait until next fall to find out for sure. I know the next thing I am going to do is take those check valves out and carefully inspect them or possibly even just replace them to rule them out.

 

[24V-DSL]

Have you talked to Bill or Stefan?

 

[rweis]

Did you "cut" any check valve springs?



I cut the bypass checkvalve spring to fit exactely the psi I wanted, and since the cut spring end was positioned on only a point instead of a rolled spring end I needed to flatten the cut end to form a better seat for the rest of the spring.



Bob Weis

 

[Supermod56]

Plug the side of the regulator that returns fuel to the tank with a #6 alum cap, we use the same type of reg on the race car, we constantly have to "reset" the piston in the reg, they get out of round pretty easy, and if there is any crap on it, it will bypass fuel when you don't want it to. Start there.



Tom