well i finally got around to installing the new lift pump. i installed it in series with the cummins lift pump. the cummins pump works but didn't have the umph at volume..well the new pump does..the lowest i could get was 27psi at WOT. that is to say put the pedal to the floor and leave it...from 20 -60 MPH. at idle it was more than 30psi.

i am think this is too high? am I right..or should I just leave it as it is.

-dkenny

 

No, you're right- it's too high. I don't think I'd leave one anywhere over 16 or 17 psi at idle. The VP44 will have problems starting with pressure that high, and you'll be fighting leaks in any component that's in less than perfect shape.

 

Did your new lift pump come with a regulator?

 

it should be limited to 14psi. according to the specs. its a holley blue. since I bought it used I have no idea what the prior owner might have done to it.
so today i'll take it apart and check the pressure relief valve.

edit:
well it turns out the PO change the relief spring to one with more tension. I changed to one with less tension. now the pressure ti 17WOT and 24 idle..still a little higher than I would like..now to find a weaker spring..

-dkenny

 

I think 24 as a max is acceptable. Most guys say that below 25psi you're not going to blow the top off of the FF canister. If you have stock wiring running to the pump (pump off until you actually crank the engine) you shouldn't have any starting problems.

 

I use a holley black and ran mine like that for 2 years. I started to notice low power problems and bypassed the stock lift pump and got my power back. So now I only run the holley. You can bypass the stock pump without buying anything also the line will reach the filter housing

 

I wired the holley pump in parallel with the existing pump..so if the cummins lift runs so does the holley( through a relay of course). I still thinking about cutting the spring to lower the pressure a few psi. I'd like to 20 as a max.

starting today seemed harder than before but I didn't wait for the 'wait to start' to go out. also I'm about B70 at the moment.

it sure is nice to drive and not worry about the psi going too low..pedal to the metal..man lets move! makes the truck fun to drive..now for RV275 injectors..better VP..more power

I thought about running the pumps in parallel instead of series..might change back to the parallel in the future.
-dkenny

 

I ran my 24v with 24psi at idle for 4 years

 

Anything over 4 psi at wot is a pump working for nothing.

 

nitrousn,
what do you base this opinion on?

from what I have read, I not an expert here.., seem to think that around 10psi WOT is best.. sure i still think my pressure is too high but way better than 1psi.

much to learn about my truck..but that's part of the fun with a new toy..the learning
-dkenny

 

Mine runs at 21psi at idle and dropps under full throttle. I think that if you can keep it below 25psi you will be fine.

 

heres the specs more than 24 psi will cause problems with vp44

 

PSI=pressure to resistance. As long as there is pressure even if it is 1 psi means you are still supplying more fuel than what you can burn.

 

Running the LP in parallel would put back pressure on the stock pump, unless your running a check valve, but then the check valve would close off the lower pressure stock LP. I wold think this would damage the stock pump. Are you running a check valve? Wouldn't back pressure also damage the stock LP? I don't believe these pumps have a bypass.

 

With this logic, you'll be replacing the IP before long.