Easy Air in Fuel Elimination

dan86 · **Posted:** Mon Apr 13, 2015 4:31 pm

I've been suffering with air in fuel for about 2 weeks now. It got to the point where I had to bleed the system every single day just to get the thing to even start. Not good.
So today I took steps to prevent that.
There are 2 plastic pipes that come out of the top of the fuel tank. A feed to the filter head in the engine bay, and a return from the engine back to the tank. They have quick connect style couplings and have a tendency to leak air. This job is to do away with those couplings and the plastic hoses.
There is an access panel to the top of the fuel tank underneath the carpet in the boot.
So the first step is to remove the rear carpet.

There are 2 rivets in each corner that need to be drilled out

Once the head of the rivet is drilled off, you will likely end up with the rest of the rivet sticking out the floor. Just take a punch and knock them out

You only need to remove the rear most 2 to be able to pull the carpet back far enough to gain access, although I did end up removing 3 corners.
pull the carpet back, and this is what you will see

The is a 10mm head nut in each corner of the panel under all that sealant. So the first job is to chip it away by whatever means possible. I used away hammer and chisel

Once the nuts are removed, you then need to chip away all the sealant around the panel itself. It takes a while!

Once done, you'll see the top of the tank

Now you're ready to start removing and replacing the pipes. I started with the outlet which is the bigger of the 2 and the one closest to the rear of the vehicle. Just press both sides of the quick connect coupling in simultaneously and pull it off. Then go underneath and remove it from there.

Grab your new hose and slide it onto the connector on the tank first. Be careful when pushing it on as the elbows on the tank are plastic. If you break them off, you're gonna have a bad day! The size of hose you need for the outlet is 8mm id (inside diameter) before sliding it onto the tank, be sure to put your new clamp on first!

tighten the clamp up but be careful. You want it to be tight, but bear in mind the elbow is plastic and could easily break.
Once that's done, head underneath, cut your hose to size, put another clamp on and tighten up. This end is going onto a metal pipe, so tighten it up good.
Once you've done that, it's just a case of repeating the process for the return pipe.
Whilst not strictly necessary to replace both, for all the time it will take, I did it anyway. The only difference for the return pipe, is that you will need 7mm id pipe.
Once done, it should look a bit like this

Congratulations. You have now successfully replaced the stupid plastic pipes and quick connects.

Read on for how to replace the outlet pipe from the filter head down to the cp3 pump.

First job is to remove the plastic engine cover.
Things you'll need to do this job
3/8" id pipe, 2 new clamps, 15mm spanner, ratchet, small extension, a screwdriver, and 10mm socket

This is the pipe you will be replacing

First step is to gain gain a bit more access to the cp3. Do this by removing the alternator bracket
Start by removing this 15mm nut

Then these 2 10mm bolts

Deep down under the bracket you will see the other end of the pipe. Just!

Unscrew both clamps, pull the hose off the cp3 and filter head and throw it away.
grab your new 3/8" hose and measure the length you need against the old piece

Remember to slide both clamps on your new hose then push it onto the filter head first and tighten the clamp up. Then feed it down and just before you push it onto the cp3, pump up your filter head till only fuel comes out. Then just push it onto the pump and tighten up the clamp. It will be tight to push on, but that's a good thing!
it'll look a bit like this

Now just put the alternator bracket amd engine cover back on. Just before you try and start it, open the bleed screw on the filter head and give it a few pumps just to make absolutely sure there is no air in the sysyem. Then just turn the key! with air my luck it will start!
Congratulations. You have now successfully replaced all the pipes that are likely to let air into the system

Since doing mine, it has started first time every time.
I do also plan on fitting a lift pump which will be a separate write up.
Hope this helps somebody.

2003 KJ Liberty 2.5 CRD

user113 · **Posted:** Tue Apr 14, 2015 10:08 pm

I am so jealous. The 2005 U.S.A. models do not have the access hatch. But this is definitely something I need to do. Do you know how approximately much hose is needed for the tank connections? Looks like about 50 cm each, but I would hate to end up buying it too short. (I'm also jealous of the Racor fuel head.)

dan86 · **Posted:** Wed Apr 15, 2015 3:04 am

The length of the pipes that came off don't exceed 50cm each. I bought 2 metres of each just so I had loads left. Pity you weren't closer, or I'd have just given it to you.

2003 KJ Liberty 2.5 CRD

RogerR · **Joined:** Sun Jan 19, 2014 11:03 pm **Posts:** 3

I have an 2006 CRD, 102K with the replacement fuel head.

Recently I have had increasingly frequent PO093 codes and limp modes. Bleeding and resetting the code lasts only a few miles now. After reading all of the posts on this it looks like the only option is to have the tank dropped and rubber replacement hoses installed. The local dealer suggests $650 is the price but will not guarantee.

Has anyone had a replacement fuel head cause a problem? Mine is still on warranty. I have only 9,000 on the fuel filter, could it be a problem? I use only gas station diesel fuel, not bio.

I did try taking some silicone seal and smearing the joints I could reach under the hood and where the metal tube converts to plastic? under the rear. I could not reach the tank top (no access hatch) so could not try to seal there.

Any help stopping this problem would be appreciated as we are facing a 1,000 mile trip next week. On the way here we stopped 11 times to burp and still had to run many miles on limp mode. Took a lot of extra hours at 50 to 55 between safe places to bleed the air out.

pjigar · **Posted:** Sat Sep 12, 2015 5:16 pm

I had no air in fuel issues but I replaced following items to make the fuel supply system Rock solid reliable

Rubber hoses from tank to hard lines - require dropping tank
In tank lift pump - require dropping tank
Rubber lines to and from fuel head - requires cutting old crimped line to hard metal line

If you do all three then you will never ever have air in the fuel.

Sent from my iPhone using Tapatalk

RogerR · **Joined:** Sun Jan 19, 2014 11:03 pm **Posts:** 3

Did you drop the tank yourself? I have no access to a lift so would have to work from Liberty on ramps. Probably with no help and I am not so young anymore. But - $650 is a big chunk of change!

If you did drop it could you relate how hard, any special steps to save work or frustration. Thanks!

pjigar · **Posted:** Thu Sep 17, 2015 5:20 pm

I dropped the tank myself without any help. I used ramps on the back wheels to get some working room. I removed the three star screws holding the fuel cap to have better wiggle capabilities on the fill hose. I also used speed jack with paint can on it to get it high enough for supporting the tank bottom. I also used long extensions to reach the bolts holding the tank straps. The most important thing in the whole operation to have tank almost empty. I had only 3-4 gallons of fuel in the tank when I dropped it. It was really easy. The whole operation took me 3 hours.

69Hcode · **Posted:** Mon Apr 25, 2016 1:01 am

I just replaced the rear line on mine yesterday. Ran fine until this evening getting on the freeway. Acted like it was sucking a ton of air. Could only drive a couple of miles between bleeds. Turns out I pinched the rubber line when I reinstalled the tank. Ran fine for my wife all morning.

Just make sure the line isn't pinched when bolting the tank back up.

undrgnd · **Joined:** Sat Mar 26, 2016 4:47 am **Posts:** 194

69Hcode wrote:

I just replaced the rear line on mine yesterday. Ran fine until this evening getting on the freeway. Acted like it was sucking a ton of air. Could only drive a couple of miles between bleeds. Turns out I pinched the rubber line when I reinstalled the tank. Ran fine for my wife all morning.

Just make sure the line isn't pinched when bolting the tank back up.

Hi 69Hcode, for our 2006 models, what size hose did you use and length? I have it as 1/4" and 5/16" with 2.5 feet of hose for each. Is this correct?

Cheers,

Chris

undrgnd · **Joined:** Sat Mar 26, 2016 4:47 am **Posts:** 194

pjigar wrote:

I had no air in fuel issues but I replaced following items to make the fuel supply system Rock solid reliable

Rubber hoses from tank to hard lines - require dropping tank
In tank lift pump - require dropping tank
Rubber lines to and from fuel head - requires cutting old crimped line to hard metal line

If you do all three then you will never ever have air in the fuel.

Sent from my iPhone using Tapatalk

pjigar,

Do you have a pic for #3 (Rubber lines to and from fuel head - requires cutting old crimped line to hard metal line)?

Cheers,

Chris

WWDiesel · **Posted:** Mon May 02, 2016 9:33 am

Absolute best method to prevent any air from getting into the fuel system is to install the in-tank lift pump mod. There are quite a few threads on this forum as to how to do it! Once done, ANY leak anywhere in the system will be evident very quickly as the lift pump puts the entire system from the top of the tank to the back of the CP3 pump under positive pressure. Unless you find a fuel leak with the lift pump installed, there is no need to replace any of the hoses or the o'ring fittings as they are designed to seal with a positive pressure, NOT vacuum. The fittings do seal very well under pressure, there are untold hundreds of thousands of them in service today on gassers for which they were designed. If Chrysler had not cheaped out on the CRD and installed the lift pump as original equipment, we would not be having any of these discussions.... :wink:

sanchez · **Posted:** Wed May 18, 2016 3:00 pm

I will try to put in tank pump this weekend on my 2004 Crd. I bought one from 2003 3.7 gas Cherokee. The assembly looks completely same. Has anyone tried this mod?

Sent from my ASUS_T00J using Tapatalk

WWDiesel · **Posted:** Thu May 19, 2016 11:03 am

sanchez wrote:

I will try to put in tank pump this weekend on my 2004 Crd. I bought one from 2003 3.7 gas Cherokee. The assembly looks completely same. Has anyone tried this mod?

Sent from my ASUS_T00J using Tapatalk

DO NOT use a pump for a gas vehicle, it pumps at a much higher pressure, way to high to use on a diesel system!!! Diesels use a low pressure pump!!!!
You must get a pump for a diesel like the one used in the Dodge Cummins Ram trucks.
Seth sells the pumps and wiring harness on his web site, https://shop.sasquatchparts.com/
https://shop.sasquatchparts.com/products/in-tank-lift-pump-for-jeep-liberty-crd-carter-p76148m/
Look for these pump part numbers: AIRTEX-E7181M, CARTER-P76148M, DELPHI-FG1224, MOPAR-5143160AA if you have to source one in your location....

sanchez · **Posted:** Thu May 19, 2016 2:01 pm

3.7 fuel system pressure is regulated to 45psi by mechanical in-tank regulator. Cp3 internal LP pump 75psi. There is return line to tank from cp3. Why I should not use it with diesel?

Sent from my ASUS_T00J using Tapatalk

flash7210 · **Posted:** Fri May 20, 2016 8:01 am

sanchez wrote:

3.7 fuel system pressure is regulated to 45psi by mechanical in-tank regulator. Cp3 internal LP pump 75psi. There is return line to tank from cp3. Why I should not use it with diesel?

Sent from my ASUS_T00J using Tapatalk

I dont know how to explain why the gasser 45psi pump is a bad idea, but look at it this way...
The Dodge Cummins in-tank pump was designed for a Cummins diesel engine with a CP3.
And given all the experience here on this forum, seems like to best choice.

In a perfect world, the in-tank pump would not be needed because the CP3 has its own pump to draw fuel from the tank. The only reason for the lift pump is to pressurize the fuel line from tank to CP3 and keep air from getting in.

WWDiesel · **Posted:** Fri May 20, 2016 11:43 am

sanchez wrote:

3.7 fuel system pressure is regulated to 45psi by mechanical in-tank regulator. Cp3 internal LP pump 75psi. There is return line to tank from cp3. Why I should not use it with diesel?
Sent from my ASUS_T00J using Tapatalk

From an older post, but this is why you do not want to use a high pressure feed pump!!!
The reasoning is very sound!
A low pressure positive feed pump is all that is needed to prevent any air from being ingested into the fuel system.
Another point; the more you work diesel fuel, the more heat it will generate and absorb, to that end several of us CRD owners on this forum have installed in-line coolers in the fuel return line to prevent heat build up in the fuel tank.... :wink:

Understanding the CP3.

The CP3 is a 3 piston metered inlet pump. By metered inlet that means that the Fuel Control Actuator valve (also called Fuel Pressure Regulator or Flow Control Valve) controlled by the ECM meters fuel going into the pumping chambers to control how much fuel the CP3 pumps and thus the engine rail pressure. This is in sharp contrast to other pressure control systems that divert large amounts of PRESSURIZED flow OUT of the pump back to the tank. The FCA meters how much fuel actually gets pressurized in the first place. Very neat and efficient.

In order to meter the fuel into the chambers, the CP3 has an internal metering/lift pump built right into it. This pump takes the fuel at supply pressure and boosts it to pressures between 80 and 180 PSI depending on what is required. This fuel is fed to the FCA via the cascade overflow valve located on the side of the pump. The cascade overflow valve's (COFV) purpose is to prioritize the fuel flow between the pump itself (ie feed the FCA), then flow excess fuel to the lubrication flows to cool and lubricate the pump and finally divert any flow above that to the return line.

The COFV prioritizes the flow in that order. If the flow rate is low, only the FCA will get fed. No cooling or return flow will be provided. If the flow rate increases, the pump will get cooled. Any more flow than that and some fuel will get sent out the return line. Note that this prioritization happens AFTER the internal supply pump and there is NO passage from the CP3 inlet to the CP3 return line. The inlet feeds the internal supply pump. Unlike other pumps where the fuel supply pump inlet may feed the internal cooling passages and make its way back to the return line.

BTW: The Dodge shop manuals say the COFV isn't "field serviceable" they have been removed before, disassembled and re installed with no problems.

So... the internal supply pump is a constant displacement gear pump. This pump is actually capable of developing enough suction to draw fuel through a filter right from the tank. It actually does this on Duramax installations.

Being a constant displacement pump means that it you can't hook just any supply pump up to it. Whereas an injection pump like a P7100 can tolerate a large difference in flow rates to/through it with relatively little pressure change, the CP3 cannot. If you try to push too much fuel to the CP3, the pressure will skyrocket. There are no internal relief valves in the CP3, only a direct feed to the supply pump. Conversely, if there isn't enough flow to it, the pressure will drop and the supply pump may actually start developing a vacuum in an attempt to get enough fuel.

Supplying the CP3

Users needn't worry about pushing fuel to a CP3 at a high pressure. Because it has a built in supply pump, the CP3 only needs to be supplied at a low pressure OR VACUUM and it will handle supplying the pumping chambers from there. Whereas previous pumps had to be somewhat pressurized, the CP3 handles its own pressurization.

Conversely, users do have to worry about getting enough fuel to the CP3. Remember the COFV ? It prioritizes the flow and when there isn't enough fuel to the CP3, it shuts off internal lubrication and cooling flow. This is very bad news for the longevity of the CP3. Diesel fuel viscosity and lubricity falls dramatically with an increase in temperature. Hot fuel within the CP3 is bad.

Basically, one needs to get enough fuel from the tank to the CP3 inlet to keep the CP3 well fed, yet not over pressure it doing so.

sanchez · **Posted:** Sat May 21, 2016 5:17 am

Thats interesting. But I had installed gassers pump today. And it does the job, I dont need it all the time, only for 30 sec maybe, so after some time I'll put a time relay. After connecting pump to the battery I noticed leak through the filter knob (a have a Racor filter) but then it has stopped.

Sent from my ASUS_T00J using Tapatalk

sanchez · **Posted:** Sat May 21, 2016 5:40 am

Also would be interesting to know exactly what is the Low pressure in psi for the pump. Because 45psi is quite low if you compare it to 18000psi :-)

sanchez · **Posted:** Mon May 30, 2016 5:44 am

After week of no air in fuel, I had removed fuel pump from tank. I've put a lot of grease into the priming pump knob and around. Also installed NRV as close as possible to filter inlet so it prevent fuel draining back to tank. Looks like the main problem is the seal on the priming pump rod that is not included in Racor seal kit. Thats it.

Sent from my ASUS_T00J using Tapatalk

Easy Air in Fuel Elimination

Who is online