Air in fuel

CRD4U2 · **Posted:** Wed Mar 25, 2015 8:14 pm

I need to know your guys opinion on the subject. I find out that I get air in the fuel, primed it this morning, lots of air and primed it after work(50kms drive) and lots of air too. I know the best way to get rid of the air is the in tank fuel pump, is it still available? Should I start by changing the fuel filter head first with an aftermaket one and which one? Money is a little short this days(new thermostat, samco hose, GDE hot tune, 2003 libby V6 for mags, air box and lift pump wiring). I know I could just get a Kennedy lift pump but I would rather wait and install an intank pump(later on). Is the racon filter head and upgrade to the oem one and are the fuel filter easy to get?

flash7210 · **Posted:** Thu Mar 26, 2015 2:46 pm

It all depends on the condition of your current fuel filter head

Do you still have the factory original filter head?
If so, the fuel heater has probably burned up and that is what is creating your leak.
Pull both wire connectors off and inspect them. If you see any indication of a fuel leak at those connectors, thats your problem and you need to replace with the new upgraded mopar filter assembly with wire kit. It is available from Mopar dealers. I got mine through ebay.

Another possibility is the fuel line connector back at the tank. These are known to leak but you will never see any fuel come out of them. When they leak they only let air in.

The best lift pump is the in-tank one. But its kinda expensive and a pain to drop the tank.
You can use a Facet or GM fuel pump (from a GM 6.5L diesel) any where in-line between the tank and fuel filter.

I have no idea what Racor filter will fit. For most people here the mopar one has been good enough.

papaindigo · **Posted:** Thu Mar 26, 2015 3:06 pm

The 2n gen OEM filter head has a bright blue heater element plug on the right when viewed from the front. If you don't have that filter head I'd recommend getting it (http://idparts.com/catalog/product_info ... ts_id=4723). There is nothing inherently "wrong" with the CP3 as a fuel pump being located in the engine bay, engine bay pumps have been around for decades, but it can be a problem if the fuel line from the tank to the CP3 is not "solid". IMHO if a 2n gen filter head does not solve your problem then the cheap and simple fix is to drop the tank (see parts of http://www.auerbach.ca/kj/lift_pump/) and simply cut out the 2 IIRC fuel supply (not return) quick disconnect fittings and replace them with a couple of short lengths of marine grade diesel rated fuel line and appropriate clamps which should be enough to make the fuel line essentially solid.

rankom · **Posted:** Thu Mar 26, 2015 5:16 pm

my opinion is to install in tank pump rl143160 and harness from gas liberty, 1st i made mistake replacing ff head and fuel lines in my case problem was inside fuel sending unit (module ) so lift pump was only solution. Its up to you what you want to do in your case first.

rankom · **Posted:** Thu Mar 26, 2015 7:56 pm

please fix your air in fuel problem , or your injector will fail do to lack of lubrication ,my engine stumbled at idle or slow speed . it was ok on the highway, but i learnt hard way ( injectors are very expensive . so my advice , don't drive till you fix air in fuel asap

WWDiesel · **Posted:** Thu Mar 26, 2015 8:36 pm

Review these two threads, they will provide you some guidance.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=78950
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=80342

If you have any questions, just ask, very many knowledgeable people on this forum willing to help... :wink:

The in-tank pump option is the only 110% option to keep any air out of your fuel if you have the time, otherwise a pump close to the tank can be a viable option. Any leak or leaks on the suction line side of a fuel pump, lines,fittings, etc... of any fuel pump mounted anywhere other than inside the fuel tank can inject some air into the fuel system. Anything to keep air out of the fuel system is a positive approach... :roll:

CRD4U2 · **Posted:** Fri Mar 27, 2015 12:46 pm

I will be getting the Carter fuel pump from ebay and I have a libby V6 for part at home so I will be taking the pump harness from it. I shouldn't need anything else, don't want to be running all over the place to find parts?

GordnadoCRD · **Posted:** Mon Dec 12, 2016 6:45 pm

I just did an experiment this morning, on how much air the CP3 has to deal with under "Normal" conditions.

My CRD Libby has been on a lift since September, and the fuel in the tank was put there in Redding CA in mid-august, during 100F+ weather, so it's KNOWN summer fuel mix, and right here right now its 20f and dropping. Expected to hit +5F tonight. Not fuel I want to deal with when starting this thing.

I borrowed a Bosch fuel pump from an old Ford 6.9 diesel. (Good fuel pulling ability) I unplugged the fuel line to the CP3, and clamped that line to the inlet of the Bosch, and ran an outlet line to fill a couple of Jerry cans that were available. With this setup, the Bosch would pull the fuel from the tank all the way through the system exactly as the CP3 would, and I could see how much air is introduced in a system that had no known problems with the fuel system.

I powered the Bosch first to 6v 2a setting on the commercial charger, so it was turning very slowly, perhaps 2gph estimate, and the fuel was drizzling, but clean and clear, then switched to 12v 2a, the fuel was flowing slowly from the line, rather than drizzling but still clean and clear.

Then I switched to 12v 10a setting for normal operation, and the fuel was flowing at more like 15gph, but was suddenly so full of tiny air bubbles that it looked more like milk than fuel. Not just bubbles on top like one sees when filling at a station, but bubbles clear through. I ran some onto a sheet of plastic that was nearby, and it took several seconds for the bubbles to come to the top, combine, and begin to dissipate.

This system was functioning without problem when the vehicle was running, so it's likely this is normal for a vehicle with 100kish miles on it. There are so many possible points of entry, from the filter head, the priming pump, the connections in the lines to the tank, even though there is no evidence of fuel leakage in any of those places, when under vacuum, air can still get in.

With this evidence I can see where under this condition, the priming pump at the filter head really is a necessary feature when there is no in-tank pump. With the cp3 pulling aerated fuel through the system, and the system is shut off, the air in the fuel in the filter rises to the top. if sufficient, when this larger amount of air hits the supply pump in the cp3, it loses it's ability to draw fuel through. we have to do it by hand with the priming plunger at the filter head.

I guess one moral of this story is IF you choose to use a lift pump that is NOT located in the tank, get it as close to the tank as possible, and take every measure you can to seal the connections / lines between the tank and the pump against air entry due to vacuum.

With the 20second supply the pump puts out when you turn the key on, it would move any air in the fuel filter past the cp3 supply pump and enable the vehicle to start and run normally.

Air in fuel

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