Lift Pump Pressure
 

I just installed a new Carter (I know) lift pump on my 93 6.5 Turbo Diesel. Before I switched I installed a pressure gauge between the fuel filter and the IP, which read anywhere from 5 to 6 psi at idle.
Now that I have my new LP installed, the psi is exactly the same. From what I understand should it be closer to 10 to 12 psi at idle?
Its a Mechanical IP but like I said the gauge is before the IP. Is this psi ok or should I be looking elsewhere for a problem?
It also has a new fuel filter installed.
It starts great, runs at idle forever, then dies after driving a few minutes. Typical yes, but trying to figure this fuel pressure out before anything else. Thanx

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Even better....
After letting it idle at 6 psi, I ran it up and down the driveway a few times and actually got a vacuum, what?
There a no noticable fuel leaks, defiantely lost. Had to walk away for the day:argh:

As long as you have pressure, the IP will be somewhat happy.

A vacuum indicates the pump is not working or not working up to snuff as the IP is demanding more flow than the pump can deliver.

Not sure on mech lift pumps, but the numbers you quoted (IE: 10 psi) is more like what an electric LP puts out.

Guys get all wrapped around the axle about PSI, the important thing is flow (IE: GPM, GPH, etc) but that's a bit harder to measure so it's referenced off PSI....

Thanx Great White!!
U misread a lil, I was said my IP was Mechanical but of course my LP is 12V driven.
And yes, I completely understand we shouldn't get to hung up on exact LP psi, but maybe to explain it a lil better;
The LP is brand new out of the box, yes a Carter but it is reading the exact same readings as the older LP I took off. Exact same symptoms. Today I put a brand new OPS on, but it changed nothing.
So further, I dropped the tank, and empty all fuel, sock on the sending unit is great shape, to see if the was any obstructions in the tank. After letting the fuel set to seperate, very lil sediment, but a good percentage of fuel was actually water.
Would an excess of water cause a pressure drop? Tomorrow plan to re-hang tank change some hoses and see what happens.:humm:

I installed a mechanical fuel gauge between filter and pump and it read 11 psi .. under load it went down to 6-7 .. the lift pump was changed out 7 years before so I installed a raptor 100 and the preshure at idle was 17 psi and under load 11-12 psi hope i didn't waste money

Sounds like a plugged line before the lift pump. Check for a smashed hard line or a collapsed rubber line. The rubber line may be hard to see since the core can separate and collapse.

that sounds good to me, on a ds4 IP you want 11-15 psi at idle and 6-7 under load

Hi, I think I have one of these rubber fuel lines collapsing & robbing me of fuel pressure. Where can i get a new one?

:hijack:

Its not hijacking a thread to ask where to get a new fuel line, when I have the same probable, you ass.

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:(

You need to turn the raptor down!

They can build much more pressure than the ip can handle.

There is an adjustment screw on the side of the pump body.

If you bought the kit for a 6.5 it should have come pre adjusted for about 8-10 psi.

Much more than that and you're risking the seals inthe pump and possibly ending up with fuel in the crankcase.

How do I know?

Well:

http://i40.photobucket.com/albums/e2...l/DSC04084.jpg

I run one on my 1998.

:)


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Pre filter manager you need to buy from the dealer. It's a braided stainless hose/steel line combination.

After the filter manager up to the ip is just fuel rated hose iirc.

I could be wrong on that one though, I converted to aeroquip fittings and braided stainless from the fm to the ip and 1/2 eaton Pushlok hose from the tank to the fm....


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As long as you don't drop to "0" at wot, the lift pump is keeping up just fine.

Ideally you'd like to see around 5 psi at wot, but 2 or 3 is even good.


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Do you have a fuel pressure gauge under the hood or somewhere you can see it while driving? What is the LP pressure after it warms up? And finally, have you replaced the fuel pickup assembly or specifically the strainer on it? I had the same problem, and after chasing it for months off and on, and burning up my IP, it turns out it was a strainer designed for gasoline that came on my new pickup assy. Glowshift makes a cheap electrick fuel pressure gauge that can be mounted in the cab, I installed one of those to wnsure my supply pressure is good before frplacing the $1,000 IP. So far, so good with the ACDelco diesel strainer (coarsed mesh and a pressure relief valve) as far as how the truck runs, but the gas one took a little while to clog up. My pressure at WOT with the engine hot and under load drops to zero, which is why I found this thread...