Air at Bleeder Valve.

BlackLibertyCRD · **Posted:** Sat Nov 04, 2006 6:38 pm

My CRD started doing more bucking while driving and felt to me like fuel problem. I checked the bleeder for the first time and found lots of air in there. I had to pump it alomst ten time to get all the air out. Now the question is, how in the world did the air get in the system? Could it been there all along? It has 12,500 mile on it and I don't know if this solved the problem. I will keep a tab on it. If the problem is gone I let everyone know, if it comes back after awhile I will check for air again.

RFCRD · **Posted:** Sat Nov 04, 2006 11:02 pm

BlackLibertyCRD wrote:

My CRD started doing more bucking while driving and felt to me like fuel problem. I checked the bleeder for the first time and found lots of air in there. I had to pump it alomst ten time to get all the air out. Now the question is, how in the world did the air get in the system? Could it been there all along? It has 12,500 mile on it and I don't know if this solved the problem. I will keep a tab on it. If the problem is gone I let everyone know, if it comes back after awhile I will check for air again.

One of the potential problems with this fuel system is the lack of a check-valve ahead of the fuel filter. Because of this, any suction leak will cause back-draining to the tank (when the engine is off) and an air pocket will form in the high spot (which in our case is the top of the filter). Start looking for signs of a leak, most obviously chaffed lines, damp fittings, oily hose clamps, and filter hardware. I have also read about hardware (plasticware is more accurate) problems near the tank which will case a suction leak (sucking air) resulting in the same air pocket.

BlackLibertyCRD · **Posted:** Sun Nov 05, 2006 12:13 pm

Thanks RFCRD I checked over the fuel lines and don't see any damp spots, near the tank look like connectors with clips and orings possible and they are dry. The only clamps I can get to was at the filter and they seemed tight enough to me. I can see spring clamps on the fuel pump but can't get to them without removing the fuel filter. If I get air in it again I will replace the filter and replace them with worm clamps. I ran it today and the bucking is gone, if it comes back or one week I will check for again for air. If new clamps don't fix it, then it will be the dealer problem. :roll:

BLake · **Posted:** Sun Nov 05, 2006 3:14 pm

Timely post. I've been having problems consistent with air in fuel. There is no CEL or codes so of course it is my imagination according to the dealer. I primed the pump and it took two cycles to get the air out. I do have some fuel around the clamps at the fuel filter. The fuel will attract dust and that is the clue. From my experience working on my GM diesels, I know that a fuel line leak on the suction side can be too small to let fuel out but still allow air to get in. Since this system is all suction up to the pump, the air leak can be anywhere.

The manual says:
AIR IN FUEL SYSTEM
Air will enter the fuel system whenever fuel supply lines, separator filters, injection pump, high-pressure lines or
injectors are removed or disconnected. Air trapped in the fuel system can result in hard starting, a rough running
engine, engine misfire, low power, excessive smoke and fuel knock.
Inspect the fuel system from the fuel tank to the injectors for loose connections (Refer to 14 - FUEL SYSTEM -
WARNING). Leaking fuel is an indicator of loose connections or defective seals. Air can also enter the fuel system
between the fuel tank and the fuel filter. Inspect the fuel tank and fuel lines for damage that might allow air into the
system.
Trapped air or leaking lines may also be identified by placing a clear piece of fuel line between the fuel supply hose
to the filter and the fuel supply hose to the high pressure pump. If a steady stream of large air bubbles are visible
in the clear hose while the engine is cranking or running the air intrusion is occurring before the high pressure
pump.
With the scan tool connected to the vehicle, select Engine and then select Sensor Display. Page down to view Fuel
Pressure Set Point and Actual Fuel Pressure. Start the engine and observe the Fuel Pressure Set Point and the
Actual Fuel Pressure. If the Actual Fuel Pressure Oscillates above and below the Fuel Pressure Set Point in a
regular cycle, inspect the fuel system for air intrusion.
If the Actual Fuel Pressure gradually drops below the Fuel Pressure Set Point then spikes well above the Fuel
Pressure Set Point, replace the fuel rail pressure solenoid (Refer to 14 - FUEL SYSTEM/FUEL INJECTION/FUEL
PRESSURE SOLENOID - REMOVAL).

Here is the bleeding procedure from the manual if any one is interested.

My notes: The bleeder screw is a silver thing with a nipple on the end. I used a section of clear hose to catch any fuel. The screw took more than 1/8 turn to bleed, just cracking it wasn't enough.

PRIMING FUEL SYSTEM
CAUTION: Cranking the engine for an extended
period with out a fuel supply may result in damage
to the high pressure fuel pump. DO NOT force the
plunger when priming the fuel system. Damage to
the plunger or fuel filter/water separate will result.
NOTE: Should the vehicle run out of fuel, the fuel
system must be re-primed in order to start. Factors
such as temperature, how long the vehicle
has been sitting, and engine cranking speed will
influence how quickly the engine starts. If the
water in fuel light is illuminated in the instrument
panel, refer to the water in fuel sensor for draining
procedure.
The fuel system must be primed if the fuel system has
been serviced. This is done using the fuel primer button
located at the top of the fuel filter/water separator.
1. With service completed on the fuel system.
2. Depress the fuel primer 20 consecutive times then open the bleeder screw on top of the housing to dispel
trapped air.
3. Close the bleeder screw and continue the step above until the primer button becomes slightly harder to depress.
4. Turn the ignition to START and crank the engine a maximum of ten seconds.
NOTE: If the engine does not start with in ten seconds, repeat the priming procedure. The engine will typically
start within ten seconds; the engine may idle, idle rough, or stall, purging any trapped air from the
lines and filter.
5. Tighten bleeder screw to 10.8 N·m (96 in.lbs.).

BlackLibertyCRD · **Posted:** Sun Nov 05, 2006 5:10 pm

Wow, I sure did that wrong. I open the bleeder and pump the plunger about 10 times to get the air out and then closed the bleeder. Maybe I got away with it because I didn't run it out of fuel.

RFCRD · **Posted:** Sun Nov 05, 2006 5:25 pm

BlackLibertyCRD wrote:

Thanks RFCRD I checked over the fuel lines and don't see any damp spots, near the tank look like connectors with clips and orings possible and they are dry. The only clamps I can get to was at the filter and they seemed tight enough to me. I can see spring clamps on the fuel pump but can't get to them without removing the fuel filter. If I get air in it again I will replace the filter and replace them with worm clamps. I ran it today and the bucking is gone, if it comes back or one week I will check for again for air. If new clamps don't fix it, then it will be the dealer problem. :roll:

Good luck, this can be one of the most elusive and frustrating problems you will ever see on a diesel. I've had suction/loss of prime leaks on Detroit Diesel powered buses that I chased for over a year before the source got bad enough to spot the problem.

This style of fuel line and fittings wouldn't be my first choice if I had to build one from scratch and the position/aim of the lines is problematic when changing the filter. One of the worst thing you can do for re-priming to is distrub the fuel lines while changing a filter. I wanted to change this arrangement on mine but took it in for the LBJ and F31 recalls and just had them change the fuel filter while they have it. BTW, they still have it as the F31 reflash didn't take and now waiting on a replacement TCM.

BlackLibertyCRD · **Posted:** Sun Nov 05, 2006 5:36 pm

That is really a bummer. I sure glad that the f31 recall don't show for my vehicle on the Jeep Web site. I'm going to wait for the notice in the mail before getting the ball joints done. Right now the steering is to good to mess with.

Goglio704 · **Posted:** Sun Nov 05, 2006 5:41 pm

I purged quite a bit of air out of mine the first time I did it, and it hasn't returned. I suspect you could also wind up with air in the filter from running real low on fuel. Low as in sloshing around and getting aerated.

BlackLibertyCRD · **Posted:** Sun Nov 05, 2006 8:23 pm

Goglio704 wrote:

I purged quite a bit of air out of mine the first time I did it, and it hasn't returned. I suspect you could also wind up with air in the filter from running real low on fuel. Low as in sloshing around and getting aerated.

Now that is something to think about. I usally fuel soon after the light comes on, about 17.5 gals worth. Maybe I have to burb it everytime I fill up. :-)r

RFCRD · **Posted:** Sun Nov 05, 2006 9:22 pm

BlackLibertyCRD wrote:

Goglio704 wrote:

I purged quite a bit of air out of mine the first time I did it, and it hasn't returned. I suspect you could also wind up with air in the filter from running real low on fuel. Low as in sloshing around and getting aerated.

Now that is something to think about. I usally fuel soon after the light comes on, about 17.5 gals worth. Maybe I have to burb it everytime I fill up. :-)r

I wonder if anyone had the need yet to drop the tank and look inside. On many diesels, it's not uncommon to "loose prime" climbing a steep hill or driving across a grade where the fuel collects away from the pick-up tube. One of the mystery leaks I found on a bus turned out to be a split pick-up tube. The manufacturer used a clear vynal hose inside the tank for a pick-up tube which dried out and cracked over time. As long as the tank was mostly full everything was fine, but when the fuel level got to @ 1/4 tank, it started sucking air and all kinds of wierd things happened.

BioJeep · **Posted:** Mon Nov 06, 2006 3:11 pm

An air leak on mine was recently fixed. I would get tons of air at the bleeder valve (along with stumbling, stalling, & limp mode) but only after running it hard. Seemed non existent as long as I took it easy. Drove about 6000 miles like that. FWIW, my leak turned out to be at the tank, either at the tank module or the connection between the steel line & the line running to the tank. It was apparently quite a headache for the dealer. Took 2 trips w/2 weeks in the shop, & it may be that they never found the specific cause; they replaced both the line & tank module & it sounded as if it may have been out of desperation.

BlackLibertyCRD · **Posted:** Mon Nov 06, 2006 4:19 pm

I travel to Dover, DE and back today, about 130 miles total and felt the bucking as I got off the turnpike. I check for air at the bleeder and sure enough there was lots. I started out with nearly a full tank and still reads more than 3/4. This time I bleed it as per BLake instruction so that won't be the blame if it happens again. Oh yeah! When I bleed it both times bucking went away.

BLake · **Posted:** Mon Nov 06, 2006 4:26 pm

Last time my low fuel light came on, I drove 1 more mile to the station. It took 20.2 gallons :shock:

The manual says the tank is 19.5 gal. I don't go much past 1/4 tank anymore. That may be where some of the air came from.

BLake · **Posted:** Mon Nov 06, 2006 4:29 pm

BlackLibertyCRD- Are you getting good mileage or is it less than you expect? Any smoke from the tailpipe when you accelerate hard?

BlackLibertyCRD · **Posted:** Mon Nov 06, 2006 4:43 pm

BLake wrote:

BlackLibertyCRD- Are you getting good mileage or is it less than you expect? Any smoke from the tailpipe when you accelerate hard?

I just got 31 MPG on the trip, I know much lower before. I know I had white smoke when hitting hard before but don't know right now or while it's bleed. I thought that once you had the fuel system bleed that trapped air on the pressure side would go to the return back to the tank harmlessly. :?:

no-blue-screen · **Posted:** Mon Nov 06, 2006 6:39 pm

I get loads of smoke when I get on it hard. I thought this was pretty much normal for this engine. Is there anyone out there who doesn't get smoke on hard accelleration?

RFCRD · **Posted:** Mon Nov 06, 2006 11:13 pm

BlackLibertyCRD wrote:

BLake wrote:

BlackLibertyCRD- Are you getting good mileage or is it less than you expect? Any smoke from the tailpipe when you accelerate hard?

I just got 31 MPG on the trip, I know much lower before. I know I had white smoke when hitting hard before but don't know right now or while it's bleed. I thought that once you had the fuel system bleed that trapped air on the pressure side would go to the return back to the tank harmlessly. :?:

That air pocket has to get through the pump to return to the tank. It's entirely suction fed, through the filter all the way to the pump. You definately have a suction leak at or ahead of the filter if you are trapping air in the top of the filter while driving.

BLake · **Posted:** Tue Nov 07, 2006 8:17 am

I'm trying to track down the reason for my poor mileage. Air in the system will mess with the mileage. The dealer is essentially useless. They took it for a ride around the block and declared it perfectly normal to get 20MPG. No diagnostic scan performed though it clearly states what and how to check in the Service Manual. I have to do the dirty work myself.

There is exhaust smoke and then there is excess smoke. I don't know where the line is on these. I do know that excess smoke equals wasted fuel. There is either too much fuel or not enough air/boost. My 6.5L Suburban with 100k miles does not smoke nearly as much as the CRD and it is the best 1980's technology. It also gets nearly the same mileage around town with more than twice the displacement and 2000 more pounds of weight.

Suction feed is the worst for air leaks. It is nearly impossible to find an air leak because a leak can be too small to let fuel out but big enough to let air in. All you can do is replace every hose and fitting up to the pressurized point and hope you fix the leak.

BlackLibertyCRD · **Posted:** Tue Nov 07, 2006 5:07 pm

My wife used the CRD today to Philly and back, about 130 miles. Wasn't having the bucking problem at the time but I check for air at the bleeder anyway. Sure enough there was air there and the tank is still over 1/2 full. If it's not the spring clamps at the fuel pump, then it has to be the quick disconnect o-rings ta the tank. I called the dealer and made an appointment for Tuesday.

Edit: I went and got hose clamps and expecting to see a fuel pump to the right of the filter and seems to be near the front under the intake. While I had the filter and bracket assembly pulled up, I disconnected the wire to the WIF sensor and found it went more then 1/8 turn tighter using just my fingers. :shock:

I tighten it as tight as I can with my fingers and reconnected the wire and mounter it back to the firewall bracket. Maybe I found something, I bleed it again and we will see. :roll:

BlackLibertyCRD · **Posted:** Sat Nov 11, 2006 11:29 pm

Started bucking again and had to bleed again. Seems like every hundred miles it gets enough air in the fuel to cause trouble. I wonder if there is a hose clamp at the fuel pump inlet???? If not there it would have to be at the fuel tank. I filled the tank today to help with the process of elimitination. Maybe tomorrow I take off the front skid plate to see if I can get at the pump to tighten or replace the clamp. I know it's going to the dealer Tuesday but who believes that they would care enough to fix it. :roll:

Edit: The engine and transmission sure is smooth with the air out of the fuel system.

Air at Bleeder Valve.

Who is online