Lift Pump and still having air in fuel symptoms

white69mach1 · **Joined:** Wed Feb 24, 2010 11:15 pm **Posts:** 29

I have a 2005 CRD, it has the the updated fuel head and an inline lift pump. I have tested the lift pump and its still operating correctly, the fuel head plunger is still hard. However the engine is running rough and has the same symptoms as air in the lines. The Jeep ran fine for about 20,000 miles with the lift pump. Any ideas what it could be guys.

Auberon · **Posted:** Fri May 03, 2013 11:28 am

Are there any quick-connects in the line?

Rich · **Posted:** Fri May 03, 2013 6:18 pm

Not always air in the line.

Have you started to diagnose the many other parts of the fuel system?

https://docs.google.com/file/d/0B8HRaBS ... yM4B&pli=1

DOC4444 · **Posted:** Sat May 04, 2013 4:37 am

No sig. What kind of lift pump and where is it installed?

DOC

Hexus · **Posted:** Sat May 04, 2013 6:22 am

white69mach1 wrote:

I have a 2005 CRD, it has the the updated fuel head and an inline lift pump. I have tested the lift pump and its still operating correctly, the fuel head plunger is still hard. However the engine is running rough and has the same symptoms as air in the lines. The Jeep ran fine for about 20,000 miles with the lift pump. Any ideas what it could be guys.

Could be a sticking injector. Could be a clogged fuel filter.

TJ2 · **Posted:** Sun May 05, 2013 1:28 am

Could be a sensor.

kjjet · **Posted:** Sun May 05, 2013 9:00 am

Lift pumps do not fix leaks. A good tight fuel system needs no lift pump.

white69mach1 · **Joined:** Wed Feb 24, 2010 11:15 pm **Posts:** 29

It has a facet fuel pump in the engine bay. I have replaced the quick disconnect lines with rubber lines and still have the same problem. It will run good as long as the engine is cold once it warms up it will run like there is air in the line and will run still run rough if you bleed the lines.. I can bleed the air out start it, let it run for a few minutes and when I crack the bleeder valve air will come out. I will do the check list next time a get a chance. Either way once its running its being sold.

DOC4444 · **Posted:** Sun May 05, 2013 2:25 pm

That's what I suspected, lift pump in engine bay. Unless you have replaced ALL the lines ALL the way to the tank with non-compression unions, you may be drawing air into the fuel.

An in-tank lift pump is more trouble to install, but is more effective as the compression unions age. As has been stated, the OEM fuel lines used by MOPAR are for an injected gas motor running a high pressure pump in the tank. The unions are prone to leak air under suction.

Let us know when you put your KJ up for sale.

DOC

papaindigo · **Posted:** Sun May 05, 2013 4:32 pm

You might want to temporarily splice a bit of clear vinyl tubing into the line from the tank which I presume runs to the pump and then to the filter. If you put the tubing in place before the pump and the fuel filter head you can do a visual check on whether air is coming into the system between there and the fuel tank as opposed to somewhere between that point and the injectors.

I do find it curious that you say the engine runs fine when cold but runs rough once it's warmed up. That does not sound like a typical air in the fuel issue.

DOC4444 · **Posted:** Sun May 05, 2013 5:49 pm

Richer mixture when cold masking air in fuel? Obviously, many things can cause rough running. To pick up off of Pap's idea, how about running a loop of clear line out of the corner of the hood through the driver's open window to see if there is air in fuel under load at highway speed?

DOC

msilbernagel · **Posted:** Sun May 05, 2013 9:04 pm

I think Doc's right - putting a smaller pump between the CP3 and the tank doesn't really address the problem of introducing air at the junction between the tank lines and the lines that carry fuel forward from the tank.

Those are the culprits quite often, and it's caused by fittings not suitable for a *vacuum*. This is why putting the pump before those fittings is so effective - it pressurizes them and eliminates vacuum related air leaks from the point of the lift pump all the way to the engine.

Mark

Rich · **Posted:** Sun May 05, 2013 10:16 pm

the link I posted above is a step-by-step fuel system test, flow chart included. It was developed by a member who spent literally months with the FSM, talking with GDE and people on this forum, while he fought his way to diagnosing his fuel issue.

Use a google log-in to see the file, it will be well worth your effort.

Auberon · **Posted:** Mon May 06, 2013 2:00 pm

And so the worm turns.
Your description describes the gradual accrual of a quantity of air that has to be evolving from events like the ones I describe below.

If any new members read this I would go out on a limb and strongly suggest that a "lift" pump should actually push the fuel through the line to the fuel head and permit fluid flow in failure.
If air can be bled from the system it must be getting in somewhere - it always does.
If you are new to diesel - check the obvious first and follow the KISS principle.
If papas suggestion pans out, then may I suggest:
start at the tank and look for anything in the sequence that will leak - especially under even low negative pressure.
This sounds like a diesel fuelling problem not a KJ Jeep problem.
I would suggest starting at the rear and working forwards.

Apart from that:
Does the bleed nipple seat & seal properly?
Is the heater & heater connector sealed?
Is there an extra (read old) seal in the head?
How loaded is the fuel filter....You could try attaching a fuel P gauge in a T...I run the Racor 245 with a Holley unit in spare port so I know if the filter medium is loading. If that is the case, then it will simply bypass and leak at the seal.
I assume it was fuel hose (some try to use heater and it eats it especially with low S fuels)?
Does the hose collapse?
Dirt will cause an increase over 4-6 psi Max and cause seal failure.
ROV (roll over valve) - is this functional - normally open?
Is tank venting otherwise clear?
Are the air bleed holes in the cap clear?
Any restrictions will obviously cause fuel starvation and poor driveability.
Do the WIF & HTR (heater) e connectors seal?
Any breathing restrictions will cause hose or any hose clamps to be tested to collapse and a gradual build up of negative P in the line resulting in air ingress.

Do you know the P neg in the line on the inlet side at idle?
As you probably know it works at 4-6 psi on the inlet side but if there is a flow or venting restriction the 20" vacuum? can be applied to the fittings, seals etc

crdjoe · **Posted:** Sun Jun 16, 2013 1:36 pm

I always had lag and I read one of the LJs bleeding the filter head daily I still do this and get air out each time but this doesn't fix it the amount air doesn't change much always 2-3 bleeds so I ordered the 2nd generation pump head and disassembled it when to Lowes bought a 2 inch long brass 1/4 inch pipe tapped the fuel pickup on the bottom of the filter head and reassembled I think I used red loctite they had some kind of sealer that hardened, I cannot stress enough how clean the reassembly has to be ! debris will flow right to your 1200.00 front pump ! Now I have no lag at speed it pulls fuel below the airpocket in the filter head . This didnot completely solve the lag from stop and go its alittle better, I have ordered the intank airtex pump and will be installing. Its just another idea in our love-hate relationship! :JEEPIN:

car0430a · **Posted:** Sun Jun 16, 2013 3:48 pm

Intake lift pump is the only way to go IMHO. I would have been up doo doo creek when my gen one head started leaking without it. And with it it only took popping the hood to see where fuel was spewing from, instead of the motor sucking air into the lines and running like crap. It took me a while to tackle the install, I have done others on gas vehicles before. The one thing that does make it easy is the quick disconnects, the bad side there prone to leaking and failure.

Lift Pump and still having air in fuel symptoms

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