Engine/Transmission (1998.5 - 2002) Do you have to run a stock lift pump with the RASP?

[Blacksdieselhp]

I have an RASP on order and was wandering if you have to run a stock lift pump with it or can it be ran by itself. The truck it is going on, has had the stock lift pump system removed and replaced with a frame mounted pump at the tank. So should I run it with the existing pump or just run it solo?

 

[DBartoli]

I am by no means an authority on these diesels. I put a RASP on my truck 18K ago. It is my understanding an electric pump is needed for start up. As it was told to me there is a circuit that drops the pump pressure down to 3psi for starting. If the pressure is less it sucks air and if it is more the it is hard to start. I purchased the entire kit that had all the hoses and one way check/pressure valves included. I also put on a column mounted fuel pressure gauge. Once I got it all together and stopped all the leaks it has worked perfectly. I have 14psi at all times running. Full throttle up a hill at 95mph I still have 13. 5 psi. Idle is about 11psi.

Dave

02, extended cab, 8'bed, 24v HO, Cummins Jake, K&N intake, Banks 4" exaust, 6spd, fiberglass toneau, RASP, 60 gal Aero tank & 3. 54axle

 

[Fishin Guide]

If you had a way to maintain a positive pressure or just have fuel in the VP, it will fire. Question is, how long before you see pressure? I would venture a guess that the lift pump is not "required" at all. Especially with check valves in the feed line.



In my eyes, the lift pump is a "backup" in case the RASP has a failure. This way, the truck still runs, but you are on the secondary system.



Maybe someone that has run the system without a pump can chime in.



Dave

 

[BarryG]

I bought my RASP from Bill K at DTT. He actually recommends you run the stock lift pump without the rasp (after install) for 20-30 minutes. Then hook up the belt and unhook the electrical leads for the stock pump so that you are just using the rasp for a couple days. He said this way you know for a fact that after install each pump works and it works indpendantly of each other. I have run my rasp without the lift pump for long periods of time (I had not tightened down one of the electrical leads on the hobbs switch good enough apparently and found that thing just sitting loose not attached to anything for who knows how long). Truck has always started just fine.



I do right now however have an issue. Intermittently, right after a cold startup (truck has sit for at least 10 hours and is very cold outside, and so far only in my driveway) it will start right up and then die and then take 20 seconds of cranking to fire up. Am looking for loose fittings/air leaks now but so far nothing I can say was it. Its intermittentness(is that a word) makes it hard to track down. I do not think it is related to the rasp or lp. Runs great, pressure is great. Been to darn cold and dark to go out and take the belt off even though it is only a 2 minute job and verify lp operation is still good on its own.

 

[AHire]

I put my rasp on about 8000 miles ago and run it 7500 miles without the lp. No problems yet.

 

[dieselboy25]

I do right now however have an issue. Intermittently, right after a cold startup (truck has sit for at least 10 hours and is very cold outside, and so far only in my driveway) it will start right up and then die and then take 20 seconds of cranking to fire up. Am looking for loose fittings/air leaks now but so far nothing I can say was it. Its intermittentness(is that a word) makes it hard to track down. I do not think it is related to the rasp or lp. Runs great, pressure is great. Been to darn cold and dark to go out and take the belt off even though it is only a 2 minute job and verify lp operation is still good on its own.

I am having the same issues. Let me know if you figure it out.

Eric

 

[BarryG]

Eric:

I went through and checked all my fittings and tightened a few up(none were dripping wet but a couple were slightly damp). I did not have the issue for a couple days. Then it happened again. So I rechecked a couple that I just wasnt sure I had done good enough mainly because I was using long wrenches and the space was very tight. I rechecked those two in question and did tighten them up a hair more. Now I honestly cant remember if it acted up after that or not but it has not done it for a couple weeks now. The weather has warmed up quite a bit since I was having the problem though so it is possible that it is temperature related. Will see when it gets cold again. Though I am liking the 50-60 degree days instead of normal 20's for the past couple weeks.

 

[Supermod56]

The electric pump is needed to prime the system after a filter change, or in case the belt falls off, which happened to me once. Supposedly it's needed for start up, but as long as you have an air-tight system, I doubt you need it. On the AN fittings, you need to re-snug them once in awhile, you should use AN wrenches on them, they are easy to break, trust me!!



Tom

 

[BarryG]

Supermod:

I have seen the AN wrenches and considered some before. I know I have also broken a fitting or two over the years and now just try to be careful but with my latest snugfest I was constantly second guessing myself if I should go tighter or not. However I have no experience or even seen an AN wrench in person just pictures. How do they differ from say a regular open end wrench? What keeps them from over torqueing a fitting? I didnt really worry about it before as I only had a couple of those type fittings. Now though with the rasp I have quite a few in that plumbing and realize the need to check occassionaly and resnug when necessary. Might be time to get a couple at least of the couple sizes I have.

 

[Supermod56]

They are made out of aluminum and are real thin, the theory is they will "spread" before you over-tighten the fitting. And they won't scratch the anodized fittings. Longacre racing makes some real nice ones, not cheap, but nice. You can get a whole set or just the -6 to fit the RASP.



Tom

 

[dieselboy25]

BarryG,

Are you still having this issue with your RASP? I replaced my lift pump today and still have the same starting and dying issues. The warmer weather has certainly cut down the number of times it dying right after starting up.

Thanks,

Eric

 

[BarryG]

DB:

Actually yes I am still having the problem. It does seem to be temperature related though. So here is my theory as strange as it may be. Since it only does it when it is pretty cold I think I am getting air into my system. I think that because of two reasons. First going from hot to cold creates a vacumn and I think when it is pretty cold the vacumn effect is increased and that vacumn is letting air get sucked in. As opposed to it being relatively warm and the cooldown is slower and does not create enough vacumn to suck in the air from wherever it is coming from. The second reason is really just an addon for the first. My fuel pressure gauge is hooked in line between my ff and vp with a 3ft stretch of hose going to my a needle valve and my sender. My needle valve weeps pretty good(if fuel can weep out air can get sucked in). I am getting ready to pull it out and see what happens.

I also think that must be where the leak is because when it does do it it starts and runs for just a second or two then quits. And after about 20 seconds of cranking it will fire up so my thought is that the air must be in the line between the ff and vp. If it was in the filter canister or prefilter it would run longer I think. Just my current theory. I still have not unhooked the rasp belt to verify that my lp is good and I suppose it may be bad or weak but I have had the lp unhooked for thouands of miles before and not had the problem and also had the problem so I dont think that is it but will check it soon. It is warming up here I just havent had the time in warmer weather to mess with it yet but I think this weekend is supposed to be ok and I wll be home.

My theory is probably full of holes that I havent thought about but air is getting in somewhere somehow.

 

[dieselboy25]

I thought that same thing about an air leak, but I have checked and checked for an fuel leak while running and I have not found one. I know if I do not have a fuel leak running, then I could not have an air leak since fuel can more through a smaller hole than air can. Make sense?



I have noticed that if I start driving right away, that my truck surges slightly, but stays running. If I just start and idle, it always dies. Still trying to figure this one out. I got a code for Crank Position Sensor, but I am not sure if that is related this or not.

Eric

 

[Fishin Guide]

I thought that same thing about an air leak, but I have checked and checked for an fuel leak while running and I have not found one. I know if I do not have a fuel leak running, then I could not have an air leak since fuel can more through a smaller hole than air can. Make sense?



I have noticed that if I start driving right away, that my truck surges slightly, but stays running. If I just start and idle, it always dies. Still trying to figure this one out. I got a code for Crank Position Sensor, but I am not sure if that is related this or not.

Eric

I would pull that sensor yesterday! And have a new one in hand. If it's chewed up, your tone ring has come loose and it's gonna get worse.



CHECK IT TODAY!!!!



Dave

 

[Fishin Guide]

DB:

Actually yes I am still having the problem. It does seem to be temperature related though. So here is my theory as strange as it may be. Since it only does it when it is pretty cold I think I am getting air into my system. I think that because of two reasons. First going from hot to cold creates a vacumn and I think when it is pretty cold the vacumn effect is increased and that vacumn is letting air get sucked in. As opposed to it being relatively warm and the cooldown is slower and does not create enough vacumn to suck in the air from wherever it is coming from. The second reason is really just an addon for the first. My fuel pressure gauge is hooked in line between my ff and vp with a 3ft stretch of hose going to my a needle valve and my sender. My needle valve weeps pretty good(if fuel can weep out air can get sucked in). I am getting ready to pull it out and see what happens.

I also think that must be where the leak is because when it does do it it starts and runs for just a second or two then quits. And after about 20 seconds of cranking it will fire up so my thought is that the air must be in the line between the ff and vp. If it was in the filter canister or prefilter it would run longer I think. Just my current theory. I still have not unhooked the rasp belt to verify that my lp is good and I suppose it may be bad or weak but I have had the lp unhooked for thouands of miles before and not had the problem and also had the problem so I dont think that is it but will check it soon. It is warming up here I just havent had the time in warmer weather to mess with it yet but I think this weekend is supposed to be ok and I wll be home.

My theory is probably full of holes that I havent thought about but air is getting in somewhere somehow.

Air can and does into the stock VP fuel system. If you were to pull the overflow, you would find an air bleed hole. This is to allow the lift pump to purge the air in the system.



Have you checked for codes? How about fuel pressure? Where is it monitored at?



Dave

 

[BarryG]

Fishin:

No codes. Fuel pressure is after the filter less than a foot from the vp. I have taken the plumbing for my gauge out and have the sender attatched directly to the fuel line. My pressure is good. It is 12psi at idle and goes up from there depending on rpm due to the RASP. I have recently installed an Edge Juice and the fuel pressure sensor for it is matching what I was seeing with my spa fp gauge. As mentioned I have removed the additional plumbing and needle valve as it was weeping. It has not done it since I removed that but it hadnt done it before that since it has warmed up. Really seems to have something to do with cold temp (ie below 20). Might have to wait until next winter to find out if it it is really fixed. Also I have not removed the rasp belt but if I bump my starter I can hear the lp run and watch my [pressure go up so I think my lp is working ok. Should still remove the belt and verify that it works good though I suppose.