Puke

My question is: when it is hot (summer) is your fuel pressure less than it is in winter??? Lately, my fuel pressure at idle is around 11 psi, bumping it to 2000 rpm gives me about 9psi, and if I don't start the truck, it will put out about 12 psi. This is on the vp44 side of the fuel filter,..so I know the fuel filter could change it a little. ALSO, about 8 months ago I put in an earlier model (I think from a 95 or 6) fuel filter (spin on type) and what goes with.

I do recall, that USUALLY, with a new lift pump (I have gone through 5 or 6 of these)..it was usually around 13 to 14 psi at idle...(this was before I changed to the earlier model of fuel filter.)...and as the pump aged it went down. When it got to 6 or 7 lbs at idle I would change the lift pump. I could always tell it was getting time to change the lift pump because the motor sounded different. I could tell immiediately, when I changed to the earlier screw on filter...that the motor immiediately sounded different,.. and I might not be able to tell when the fuel pressure is getting low enough to change the lp.

I really love the earlier spin-on filter setup, ..does anybody else have experience with this? Is the earlier style filter more restrictive,..causing a lower fuel pressure?

Anyway, just thinking out loud,.. The older I get, the harder it is to change LPs and filters (actually,..this spin on filter is cake to change.).. So, I guess I'm looking for someone to chime in and tell me to wait till it gets down to 6 or 7 at idle,..
ok,
thankx,

I guess I also need to ask if there is a hose I can buy (or sensor) that allows me to bring my fuel pressure guage inside the cab...right now I'm running a glycerin filled 0-25 guage that screws right into the filter housing with the banjo piggy back bolt...which is a bit of a pain.

Greg Reed

Probably the best thing to do is get a good aftermarket pump. I went through 6 of the stock pumps. Another thing you can do is relocate the stock pump back near the tank. Makes for much easier replacement. As I recall, pressure with the stock pump did go down a bit in the summer. To run the gauge into the cab, nylon air brake tubing works good. Put a needle valve near the attachment point on the engine and just barely crack it open. You can also get gauge snubbers.

cougar

The stock lift pumps don't put out enough pressure and volume to keep a VP44 cool causing a premature death. Get an after market pump that puts out a minimum of 90gph and set it between15 and 20psi.

johnh

iv'e been running mine at 5psi for years with no problems ...when under load my low pressure warning light comes on,(less than 2psi)

Puke

I think I'm going to change mine tonight. I've got my spare anyway, might as well put it on.

Puke

Well, I changed the lift pump. The pressure with the new one is exactly the same as the pressure with the old one. So that leads only one direction. My fuel filter is getting dirty. And I don't want to put a autozone fuel filter in there. (Might be ok, I donno).. I have a cummins on the way I ordered the other day.

I hope the pressure goes back to normal after I change it.

Puke

Is the old style fuel filter harder to push fuel through??????????

cougar

https://mopar1973man.com/cummins/art...tion-pump-r21/

Puke

OK, I installed a new fuel filter, It was now at 12 pounds idling rather than 11.????

Ran it for a few hours, it's near 100 degrees outside,.. checked it idling when HOT and it is at 7 pounds pressure.

Am I to assume that my check valve (or return valve or whatever you call it) is going bad???? I didn't think these return valves ever go bad? Wish I knew how to tell for sure other than replace it and see.

Anybody on here know?

SIXSLUG

Mine fluctuates around a bit, kinda inconsistent, usually about 3 psi or so. Hot here too. I'll see what it does after work and post back.

Puke

OK,
I ordered a new overflow valve. I don't have a warm feeling that it is the problem, but I need to start somewhere. If it's NOT..the overflow valve.,.....IS THERE A FUEL PRE-FILTER i DON'T KNOW ABOUT ON A 24 VALVE TRUCK THAT COULD BE DIRTY??? if not,..then might it be a dirty intake sock on the fuel intake tube in the tank? My understanding is that if the overflow valve is letting the pressure go down,.. It's not much of a danger (as long as it doesn't go to zero) because it's just letting more fuel go through the VP 44 and cool it. Anybody with any other ideas?

Kerley

There is another fuel filter inside the fuel/water separator, Cummins Fleetguard part #3845400-J, I discovered this in a Genos Garage Tech Article. I ordered the part from Cummins, cost $8.83+ postage. The Fleetguard Filter #3845400-J arrived today but does not fit anywhere in my fuel filter, I do not understand because Cummins ask for My Engine serial number to verify the correct part.

high bid

Older thread but searching for an answer on the reason for low fuel pressure.
I've been going through quite a bit of fuel lateley... 100 gal about every 2 weeks. I have the factory fuel filter and also a Baldwin BF957 spin-on filter mounted on the frame. Lately the fuel psi has been getting low 4-5psi, noted by the mechanical gauge and idiot light sensor. I've changed both the factory filter and the spin-on, still the same low fuel psi. I then changed the lift pump and put on another new Airtex pump thinking it was going bad (last one lasted 100k mi). This pump provides a solid 15psi. I still have the same low fuel psi; at idle it's about 8-10psi and then under empty load acceleration it drops down to 4-5 or sometimes even lower. Is there another filter, screen or place I should possibly check for a potential fuel line clog?
I have a larger fuel line from the factory filter to the VP44 and the banjo bolts have been increased in size for better flow but I'm at a loss of what to check next?????
Any ideas would be appreciated!

AlpineRAM

I'd check on the suction side, maybe the metal lines exiting the tank are corroded.

The in-tank module has a screen and a valve, they should not play much of a role when the tank is full, but at less than 1/4 full they can lead to fluctuations in the fuel pressure.

high bid

Following up... disconnected the fuel lines from the factory filter to the VP44 all clean. Blew the line from the factory filter back to the tank... all seemed to be clear and clean.
I guess it's possible the diesel I have is so dirty it almost instantly clogs the two filters, Baldwin spin-on on the frame and the factory filter. I've changed both twice and still get 8psi at idle and down to almost 0 under empty acceleration. New Airtex pump also installed.
Guess I'll have to keep changing the filters till I burn through all this junk fuel.... any other ideas?