Air in fuel system

lesconley · **Joined:** Fri Sep 22, 2017 4:59 pm **Posts:** 4

I have air getting into the fuel system somewhere, So far the filter assembly, heater harness and turbo lines have been replaced. There has been a fuel pump installed in the tank and the connections on the fuel lines have been checked and appear to be good. Jeep starts fine and will run great for a time, the problem first started when pulling a small trailer. It has been getting progressively worst and any kind of added load (going up a hill etc) will either shut the engine down or cause a severe lack of power. There are usually no engine codes when this happens but occasionally a fuel system error pops up. It will also sometimes just go into the loss of power mode for no reason run like that for a time then magically come back to full power. Sometimes shutting it off and letting it sit for a few minutes will return it to normal. This jeep was likely run on farm dyed diesel since new. it's an 06 with 120,000 kms (62000m)on it. Anybody got any ideas?

joe_ · **Posted:** Fri Sep 22, 2017 6:11 pm

If you have a functioning in-tank lift pump, there should be no way for air to get into the lines since the fuel will by under pressure. If anything, you'd have fuel leaking out.

What fuel system code does it throw?

lesconley · **Joined:** Fri Sep 22, 2017 4:59 pm **Posts:** 4

The code is P0093, the mechanic said he was getting air in the system but could bleed it out then it would be fine for a short time. He put an in tank fuel pump in it. when he took it for a test drive it went into the low power mode within 4 blocks. This is after the fuel pump install. Thanks for your thoughts!

papaindigo · **Posted:** Mon Sep 25, 2017 6:22 am

If in fact he dropped the fuel tank added wiring and put something inside it get the specific part number of what was installed. If he installed what the Jeep parts manual lists for the CRD he did NOT install a fuel pump as the listed stock part is a fuel gauge sending unit only no fuel pump. Secondary check have someone stand back by where you put fuel in the tank with the filler cap off. Turn ignition on but without starting engine. Should be able to hear pump run for 5-10 seconds. If no run no pump.

WWDiesel · **Posted:** Mon Sep 25, 2017 12:55 pm

If you truly have an in-tank fuel pump installed, there is NO way air can get into the fuel system! Any leak would be immediately self evident as fuel would be leaking out, not air leaking in.... :roll:

The P0093 is a code for a problem on the HIGH pressure side of the CP3!
It could be a problem with fuel starvation on the LP side of the CP3 caused by a stopped up fuel filter or crimped suction fuel line..

From the OBD-CODES:
When the computer sets this code it senses a large fuel leak in the high pressure section of the engine. The ECM in a diesel always monitors and controls the fuel pressure from the fuel injector pump to the injectors as long as the engine is running. To set a code P0093 the ECM must sense a sudden large drop in fuel pressure within the system. This drop in fuel pressure can be internal, external or caused by a faulty sensor signal to the ECM. When this happens, the ECM sets the code, goes into fail-safe mode which will suspend the fuel injector pump operation and allow one minute to pull over before it shuts the engine down. It will remain in fail-safe mode until the key is off.

Read more at: https://www.obd-codes.com/p0093
Copyright OBD-Codes.com

lesconley · **Joined:** Fri Sep 22, 2017 4:59 pm **Posts:** 4

Thanks WWDiesel! this is awesome information I will pass it on to my mechanic, and yes it is a real fuel pump they installed not the fuel sensor only.

WWDiesel · **Posted:** Mon Sep 25, 2017 9:58 pm

lesconley wrote:

Thanks WWDiesel! this is awesome information I will pass it on to my mechanic, and yes it is a real fuel pump they installed not the fuel sensor only.

If that's the case, then unfortunately you must have another issue going on..... :roll:

Good luck and keep us posted as to what you discover....

GordnadoCRD · **Posted:** Mon Sep 25, 2017 11:30 pm

P0093, in order if costliness
could
among other things, be
Fuel Pressure Sensor Wiring / connectors
Fuel Pressure Sensor it's self (get the stored data from the DTC scanner. Rail pressure is one of the stored data bits)
Fuel Quantity Solenoid (low likelihood.) You can test this by unplugging the connector at the rear of the CP3. it will pop an open circuit code and make it smoke a lot as it puts all the fuel regulation duties on the Fuel Pressure Solenoid at the rear of the rail, but it will run, and may reveal if there is truly a large leak.

Fuel Pressure Solenoid wiring / connectors
Fuel Pressure Solenoid it's self
This operates by variable PWM voltage, where increase of voltage results in raise of fuel pressure (less bleedoff) in the High Pressure Common Rail. Any corroded connection or such that will increase resistance / cause voltage drop, will cause the fuel to bleed away & drop pressure, which appears to the ecm, like a large fuel leak. A solenoid with failing coil insulation, or worn/scored valve will also cause excessive bleedoff or reduced magnetic force and reduced fuel pressure. This is doesn't take much, as fuel doesn't compress like air does. Any bleeding by at all, causes an immediate drop in pressure as well as many other problems.

There are other things, but if you don't have fuel leaking externally, those are the main culprits you should look to. The FSM has many pages of pin checks to do at those solenoids and at the ECM end of those wires.

Checking wiring is bloody tedious, but most problems are somewhere there, and way cheaper to fix that to start changing parts. .....ask me how i know.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=86360

lesconley · **Joined:** Fri Sep 22, 2017 4:59 pm **Posts:** 4

Thanks a Bunch GordnadoCRD! we were just considering replacing the high pressure pump, so this gives us something to pursue before going there!

papaindigo · **Posted:** Thu Sep 28, 2017 3:41 pm

How about a leaky injector? lesconley just because I'm a somewhat cynical and suspicious person humor me with a simple test with 2 people. With ignition off open the fuel filter bleeder screw but do NOT pump primer; switch ignition on but do NOT crank engine; does fuel squirt out of bleeder screw? If yes the in tank pump is pumping if no.....

Screaminjeapin · **Joined:** Thu Aug 10, 2017 11:50 pm **Posts:** 2

hello i recently aquired a crd. it has its problems for example, a leaking injector seal :dizzy:

but this post is to help me get answers on my air in fuel problem i found out where the air is getting in. i started it today and it immediately shut off popped the hood and i thought i saw the little fuel heater connector spark. my brother said no no that was only fuel bubbles. and it was i pumped the primer and bubbles came out the plug. i continued to do so as i did not have the sockets at home to losen the bleeder. i did this till the bubbles stopped. as i beleived my brother i plugged the wire back in and drove it to the garage, when i got here and popped the hood the plug was smoking so i unplugged it. that fixes the fire hazard for now but not the fact that ive got obviously got a hole for air to get into the fuel. now what do i do. plug the whole with some chewing gum till i can get a new filter head, and lift pump but as for lift pump does any one know any cheap ones that work like under 20$ and ill probably get a fuel pressure sensor and keep a spare pump with me in that case

WWDiesel · **Posted:** Fri Sep 29, 2017 11:56 am

Screaminjeapin wrote:

hello i recently aquired a crd. it has its problems for example, a leaking injector seal :dizzy:

but this post is to help me get answers on my air in fuel problem i found out where the air is getting in. i started it today and it immediately shut off popped the hood and i thought i saw the little fuel heater connector spark. my brother said no no that was only fuel bubbles. and it was i pumped the primer and bubbles came out the plug. i continued to do so as i did not have the sockets at home to losen the bleeder. i did this till the bubbles stopped. as i beleived my brother i plugged the wire back in and drove it to the garage, when i got here and popped the hood the plug was smoking so i unplugged it. that fixes the fire hazard for now but not the fact that ive got obviously got a hole for air to get into the fuel. now what do i do. plug the whole with some chewing gum till i can get a new filter head, and lift pump but as for lift pump does any one know any cheap ones that work like under 20$ and ill probably get a fuel pressure sensor and keep a spare pump with me in that case

For a temporary repair on the fuel head heater plug in leak, clean the area good with brake or carb spray cleaner, let dry and fill whole plug area completely with some good automotive silicone sealer and let it dry for several hours. This will seal the air leaks until you can replace the fuel head which you will still need to do. DO NOT try to plug the fuel heater connector back in, that is a fire hazard, just leave it unplugged until you can replace the fuel filter head unit. :roll:

As to fuel pump, there are no good cheap options, only an in-tank fuel pump can reliably put the entire system under positive pressure thus preventing NO AIR ingestion into the fuel system... :wink:

papaindigo · **Posted:** Fri Sep 29, 2017 12:27 pm

Screaminjeapin - if you want a lift pump there are 2 options 1) in tank but that's going to be well over $20 or 2) in line still a bit over $20 but you can find a Facet 40109 for under $50. If you want my personal opinion 1) replace fuel filter head ASAP which should solve the air in fuel problem but if not then 2) drop fuel tank and replace both quick disconnect fittings on the fuel supply line (not the return line) with some marine grade diesel rated fuel line and good small "T" bolt clamps for ca. $20 in parts.

WWDiesel · **Posted:** Fri Sep 29, 2017 1:36 pm

Just beware, ANY fuel pump mounted outside of a fuel tank can possibly suck air into the fuel system on the suction side of the pump. :roll:

Only a true in-tank pump puts the ENTIRE fuel system under positive pressure from inside the fuel tank all the way to the back of the CP3 injection pump thus preventing ANY possible air ingestion into the fuel... :mrgreen:

papaindigo · **Posted:** Fri Sep 29, 2017 1:59 pm

WWDiesel is correct up to a point. I will, again, merely observe that front mounted "suction" fuel pumps existed for decades before electric in tank pumps and those front mounted pumps did not have air in the fuel problems. Why you may ask? Simple, those pumps were connected to the fuel tank pickup by a SOLID line with NO leaky quick disconnect fittings. Eliminate those fittings on the CRD and there is NO possibility of air in the fuel between the tank and the filter head inflow short of running the tank dry and sucking air. Place an inline pump between the tank and the filter head if you wish to pressurize the filter head and fuel line from there to the CP3 which is likely a good idea; won't eliminate leaks but if there are any leaks diesel will leak out as opposed to air leaking in.

I have nothing against an in tank pump. Install one if you want it's fine by me. I just think there are less expensive, in parts cost, solutions. Unfortunately either way the only way to get rid of those pesky quick disconnects is to drop the tank for access to them.

PS my 05 (now Chance's) and my son's 06 are both running fine with no air in the fuel issues since we installed 2n gen filter heads on both. Never bothered to install lift pump as they were not needed. Gave Chance my inline to do with as he desires.

WWDiesel · **Posted:** Fri Sep 29, 2017 3:19 pm

papaindigo wrote:

WWDiesel is correct up to a point.

Up to a point of what? Why do you think most every vehicle manufacturer in the world went to the newer technology in-tank fuel pumps?
More reliable and less problematic!
I am only trying to offer sound advice based on many years of experience! Don't like it, simple, don't follow it, it is your vehicle and you can do whatever you chose to do to it.
But if you search this forum for advice or reading on fuel pumps, you will see most people opt for the newer technology in-tank setup.... band-aid approach or do it right and fix it once and for all.....

Even Dodge saw the light and now ONLY offer a retrofit IN-TANK fuel pump replacement module with pump and new harness for all 1998-2002 Dodge diesel trucks that came OEM from the factory with the externally mounted fuel pump because they were so problematic and unreliable.... They will not even sell you the externally mounted fuel pump anymore, they discontinued it totally! :roll:

papaindigo · **Posted:** Fri Sep 29, 2017 5:03 pm

Whatever. Engine mounted mechanical fuel pump, not to be confused with a high pressure fuel injection pump, on my 1993 Dodge Cummins diesel was still running fine at 150,000 miles when we sold it. As to which is better it's a rather pointless debate given that the 2 sources of air in fuel on the CRD are 1) a badly designed fuel filter head heater that burns out and 2) DCJ being cheap and using the gasser fuel lines with quick disconnect fittings that leak air in if not under pressure. But for the latter cheap design I doubt the filter head heater would have been a problem as it would have been submerged in fuel not air and unlikely to overheat.

GordnadoCRD · **Posted:** Fri Sep 29, 2017 10:17 pm

Both PapaIndigo and WWDiesel are correct from their own perspective.
Everyone's choices are their own to make.
Their prioritized considerations involved in those choices are theirs alone.
Regardless of where each one of us has chosen to land on this issue, I think we've given lesconley and Screaminjeapin a fairly complete list of our personal opinions, so whatever thing they choose at this time, That's theirs.
It may not be the path I personally chose, but now my interest shifts to helping them make the best of their choice. Or in the words of Steve Dulcich, "to take the least bad way through a potentially bad situation."
I believe most people's approach (at least those who fall under the CRD's sweet siren song) is to address whatever problem with the best solution that they can afford when they are pressed to take action. This is where differences happen based on current issues, and current resources and priorities.
My observation of WWDiesel's approach is basically the pinnacle of preventive perfection. When something fails (torque converter, for one example) the only answer is the SunCoast TC.
PapaIndigo I know less well, but observe in his list of mods, that he basically takes the same path. In this case it seems you both want these guys to be aware of ALL options (+&-)so they can make their own informed choices.
:2cents:

{EDIT}
Hopefully in near future, There may be some light shed on how the CP3 OFV deals with purging air-in-fuel. I suspect the amount that it can deal with when only the prime pump is pulling fuel, vs when there is a lift pump applying advance pressure, is more than we collectively suspect.
Courtesy of Thermorex, I have a NON-OP CP3 that he sent me to dissect. :pepper:

Even if it's not functional, we can go through it and run a couple of camera batteries dead finding out why.

Air in fuel system

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