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fuel pressure and fuel pressure guage

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Old 06-29-2017, 07:23 PM   #1  
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fuel pressure and fuel pressure guage

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.
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Old 06-30-2017, 09:19 AM   #2  
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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.
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Old 06-30-2017, 11:26 AM   #3  
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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.
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Old 06-30-2017, 01:20 PM   #4  
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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.
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)
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Old 06-30-2017, 07:25 PM   #5  
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I think I'm going to change mine tonight. I've got my spare anyway, might as well put it on.
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Old 06-30-2017, 09:39 PM   #6  
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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.
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Old 06-30-2017, 10:27 PM   #7  
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Is the old style fuel filter harder to push fuel through??????????
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Old 07-01-2017, 10:56 AM   #8  
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Old 07-05-2017, 12:40 PM   #9  
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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?
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Old 07-05-2017, 12:45 PM   #10  
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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.
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Old 07-10-2017, 04:12 PM   #11  
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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?
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Old 03-09-2018, 07:11 AM   #12  
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Fuel Filter

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Originally Posted by Puke View Post
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?
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.

Last edited by Kerley; 03-10-2018 at 03:56 PM. Reason: Update
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