Engine/Transmission (1998.5 - 2002) Too much fuel pressure?

[EthanWhite]

My 98. 5 24v has a ddrp plus a carter lift pump which together produce 30 psi (according to gauge) fuel pressure Ive heard the vp pump doesn't like that much pressure is this true? I am monitoring pressure with a p. o. s. westach gauge from Genos I hate it, it lazily moves and I don't think it gives accurate readings.

 

[EForbes]

I think anything over 20 psi, could damage the vp, i may be wrong on that. If you installed the DDRP, you dont need the carter. I frame mounted my DDRP by the tank, and used 1/2 inch fuel line, and it gets 17psi, and never drops below 12 psi at wot.

 

[EthanWhite]

Alright, im fed up with that westach gauge (electronic type) im going to use a test gauge to verify.

 

[Cummins Thunder]

Alright, im fed up with that westach gauge (electronic type) im going to use a test gauge to verify.

I feel the same way about my Westach f/p gauge#@$%!

 

[JLandry]

Alright, im fed up with that westach gauge (electronic type) im going to use a test gauge to verify.

Getting a "second opinion" with a pressure test gauge is always a good idea, but just so you know, others have reported routinely running fuel pressures as high as 25-30 psi without any ill effects. Personally though, I wouldn't run that much pressure on my truck because if it were such a great idea, you'd think Cummins are Chrysler would have set it up that way in the first place. All the VP44 needs is positive pressure at all times for proper operation. Most agree that 5 psi minimum (under heavy load with a wide open throttle) is adequate and anything above that is just icing on the cake... to a point of course. Too much of anything can cause problems.



It's worth noting that the ECM reduces lift pump output pressure during engine cranking by operating it on a 25% duty cycle. For some reason the VP44 doesn't handle high inlet pressure very well during starting. High VP44 inlet pressure during starting can result in hard starting.



John L.

 

[AWeaver]

bluechipdiesel.com has a good article on fuel pressure and your vp... this is an excerpt from one of his articles... "We proved on a dynomometer in 1998 that if you have 5 PSI, under load, you can make all the power available from a VP44, and 5 psi will provide plenty of return fuel for pump lubrication. We do not recommend running more than 12-15 PSI as that does NOT help the fuel system in any way. In fact higher pressures could diminish fuel delivery to the rotor and make the truck run worse at high RPM and possibly overheat and damage the fuel bypass solenoid. " ... just something to think about.

 

[fox]

STOP posting facts on the pressure, or you will start a war!!!!

I run 15psi.

 

[KLockliear]

I run 21psi (idle) and 6-7psi (WOT), but we did have some trucks using the 12v lift pump making 45+psi and never had a problem. 550+hp on #2 and 740 wtih N2O.

 

[AWeaver]

STOP posting facts on the pressure, or you will start a war!!!!

I run 15psi.

OK OK OK... I run 17 idle and 10-11 wot (w/ a clean fuel filter)... I dont know the limits on the max fuel pressure since nobody can seem to agree on a number, but from all the info I have read and heard 5 psi is pretty much the consensus on the lowest you can run w/o damaging the vp.

 

[EthanWhite]

Well have any else of your guys had a westach that was sloppy and sluggish in needle movement?

 

[BDaugherty]

I run 20-21 psi at idle and as low as 10-12 at WOT. From what I've been told, the reason not to run too much pressure to a VP44 is that it uses a small solenoid to turn fuel on/off to the rotor. Higher fuel pressure isn't necessary for cooling or lubrication or power production. However, it does make the fuel solenoid work harder.

I'm not condemming high fuel pressure. Personally, I try to keep my fuel pressure above 10psi under all conditions. With my fuel system, it takes 20-21 at idle to keep me from dropping under 10 at higher RPMs standing on it with the Juice on level 6. I also like the added security of using a 5 micron filter instead of the stock 10 micron.

As far as fuel pressure gauges go, I've never used the westach gauge. I've been very happy with the electronic gauge on my Attitude monitor.

 

[JHudson]

I install the DDRP two weeks ago. I had the original mounted on the frame using the pump relocation kit from Geno's. The reason why I did this is I thought that the Westac fuel sender was failing as the carter pump would be at 15psi at idle then drop down to 10psi just sitting there. After a bit it would return to normal again. I installed the Westac back in 2000 when they offered only one gauge the 15 psi one. It has worked always worked perfectly and I thought okay it must be time to replace it. Well to make this story short, I also have the Blue Chip FMS which has a low fuel pressure warning also. It activates at under 5 psi. Guess what driving back to the campground the Westac gauge drops to zero and FMS fuel pressure comes on to. I turn my fuel box off limp back to the campground and change back to my original lift pump in the morning. This pump was on the truck for its first 60000 miles. Its pressure was down to 10 psi under load and I thought it would make a great backup and it did. When I installed the backup, pressure was back to 12 at idle and 10 under load on the Westac gauge. Well it was not the gauge it was the pump in my case.



Just some notes that I have discovered with the Westac. When I first installed it in 2000, I tapped into my transmission temp gauge power. This cause major needle swings of 2 to 3 psi. If you would turn on your lights the guage would read higher readings. It was kind of crazy as more accessories you would turn on the guage would read high.



I solved this problem by running a power line directly to the battery. I didn't want to take any chances with the ground, so I also work on it at the sender and gauge.



Well the Westec fuel pressure gauge has worked perfect and now with the DDRP in place, 17 psi at idle and 15 under light load, but mainly just sits at 17 psi. My original lift pump is back under the rear seat if I ever need it again.



I guess my opinion of the Westac Fuel pressure gauge is it has worked great for me, and saved my VP44 with the help of the FMS low pressure warning as I thought the sender had failed.



Jay