Symptoms of air in fuel?

flash7210 · **Posted:** Sat Oct 03, 2009 7:30 am

Ok, I know I have been sucking air into the fuel lines because I found some
loose clamps and fittings. I just want to know if my symptoms correspnd to
this.

Symtoms:
1. Hard starting, takes a lot of cranking
2. Sudden drop in fuel mileage

And I mean sudden!
Like going from 26 mpg to 18. No changes in driving style. Just normal
commute. It was enough to make me think I had a fuel leak which is how
I found the loose clamps and fittings.
Only thing is, all the loose fitting were DRY. No fuel leaking OUT.

I plan on tightening every thing up today and just wanted to know if
there is anything else I should look for.
Thanks

BTW, I did install a Facet lift pump (not in tank) about a year ago and
this is the first time I have ever had any fuel issues.

FormerlyBankNote4x4 · **Posted:** Sat Oct 03, 2009 8:20 am

Hard starting and jerking while you drive, the jerking can get severe if there's alot of air- feels like your towing a vehicle with a rope.

Where is the lift pump? If its by the fuel tank your fittings would be pressurized outward-ie you'd see fuel if it were leaking.

If its by the engine you still have a vacuum and leaking would be drawing in air.

Air collects in the fuel filter head.

Try pumping the fuel head and crackig the bleeder- you'll hear the air rush out.

RJM · **Posted:** Sat Oct 03, 2009 10:10 pm

Bad fuel??

Diggerfreek · **Posted:** Sat Oct 03, 2009 10:48 pm

When was the last time you changed your fuel filter? It could be bad fuel if it was sudden to ........................

dgeist · **Posted:** Sat Oct 03, 2009 11:34 pm

Diggerfreek wrote:

When was the last time you changed your fuel filter? It could be bad fuel if it was sudden to ........................

X2 on the fuel filter. That's how I knew mine needed replacing after I gelled some biodiesel a couple years back. The mileage dropped by about 5 immediately following and didn't go back up with warmer weather and ULSD.

Dan

BlackLibertyCRD · **Posted:** Sun Oct 04, 2009 5:54 pm

I had to replace my fuel filter Thursday because it would miss on cold start, lost power and once shut off at full throttle. Got filled at Hess instead of BP this time, ran better but not as good as when I change the filter. I cut open the filter and it was like a roll of TP totally slimed until the very middle last inch. I unrolled the entired lenght of it and Napa had a replacement in stock. Bad fuel, maybe, clogged filter, yepper.

flman · **Posted:** Sun Oct 04, 2009 9:21 pm

Yeah, I threw in the towel today, new fuel head, new heater plug new filter, hopefully no more P0093 codes. Funny the factory filter went 25K, maybe the fuel system gets a residue with age. From now on, any fuel problems gets a new filter ASAP.

e_poirier2004 · **Posted:** Mon Oct 05, 2009 10:21 pm

Just opened my oem fuel head today and found something funny. The heater is made of 2 aluminums plate with 3 ceramic discs (resistors) sandwiched in between. Funnily enough, the connection where the aluminum plate connects to the positive was so pitted that it was desintegrated. The reason is the bad connection between 2 different metals. The crimp connection is not good enough and when it get loose, it start to pit and just desintegrate. The problem is that in the process, the pin gets heated and melts the plastic (cheap) housing. I find that out today when I cut off the fuel temperature sensor connector in order to reuse it with my racor head. I ordered a thermistor from allied electronic (about 3$), got a brass plug (5$), had some brass rod 1/4" and I made the sensor instead of buying it from omega and saved about 100$. Works great. I even managed to save the old thermistor from the oem fuel head to keep as a spare.

warp2diesel · **Posted:** Mon Oct 05, 2009 10:50 pm

....I though I got all the air out with my lift pump, WRONG. I made it to the street and stalled, when I tried to restart, it ran on one cylinder. I put on the four ways and shut down the engine. I, cracked open the bleeder with the lift pump running and got a bunch of air. After I got all the air out it ran fine and had a little more pep. Next time it started with in two strokes of the engine instead of four strokes.
Next filter change will be a Racor filter (I had the Mopar filter on the shelf paid for) mounted on my OEM head. I will make the adapter on my lathe, 1" threads on the OD and 16mm X 1.5mm ID. To seal it up, I will put in an O ring grove where it kisses the OEM filter head, put in a green O ring, loctite on the inside threads and crank it on (Gear Head Rocket Science).
The Water in Fuel sensor has 12mm x 1.5mm threads, again, I will make an adapter on my lathe.
When I get it worked out, I will post the drawings.

e_poirier2004 · **Posted:** Tue Oct 06, 2009 5:00 am

Even if you would change the filter, I doubt it would do much good. when you open the bleeder, you got bubbles pushed to the filter with the pump which means it must leak before the filter. I would check all the connections first. Then if you're still not sure, get the Racor filter head. Don't try to modify the oem head, major pita and it will never work the way it should. Once you will be done, the heater will leak from the connector. I had the cat 2 filter mod and still, the head gargle air like mad from the heater connector. The racor is modular and comes with a part list, much better product. At least, if something goes, you can change it without changing the whole head.

AZ CRD · **Posted:** Tue Oct 06, 2009 7:12 am

When I had an issue with air in the fuel it was like the motor went into limp mode. I could depress the go pedal to the floor and the rpm's/mph would not increase. The proximate cause of mine was a combination of bad fuel and fuel filter needing to be replaced. The underlying issue was the fuel vacuum system sucking air in through the pressure fittings of the fuel line. Cummins in-tank lift pump seems to have solved the issue.

warp2diesel · **Posted:** Tue Oct 06, 2009 7:46 am

e_poirier2004 wrote:

Even if you would change the filter, I doubt it would do much good. when you open the bleeder, you got bubbles pushed to the filter with the pump which means it must leak before the filter. I would check all the connections first. Then if you're still not sure, get the Racor filter head. Don't try to modify the oem head, major pita and it will never work the way it should. Once you will be done, the heater will leak from the connector. I had the cat 2 filter mod and still, the head gargle air like mad from the heater connector. The racor is modular and comes with a part list, much better product. At least, if something goes, you can change it without changing the whole head.

I installed a lift pump after having problems with air leaks. Since the lift pump, the only time I had air in the fuel is when I changed the fuel filter. I drove over 24,000 miles with no air in fuel problems.

Joe Romas · **Posted:** Tue Oct 06, 2009 7:51 am

warp2diesel wrote:

I installed a lift pump after having problems with air leaks. Since the lift pump, the only time I had air in the fuel is when I changed the fuel filter. I drove over 24,000 miles with no air in fuel problems.

X2

I had bad air leaks and since the in tank lift pump install there has been no more air and the fuel head is still the original at 28k miles. The filter is not the only part of the fuel system that can leak. I suspect the worst culpret is the plastic disconnects back by the tank :shock:

flash7210 · **Posted:** Tue Oct 06, 2009 8:05 am

My follow up...

My Facet lift pump is mounted under the hood, attached to the engine with
a home made bracket.
With the engine running and pump running I could see bubbles coming out
past a loose hose clamp at the filter head inlet.
The brass fittings I used for the pump inlet had all vibrated loose and one
even had a tiny crack around the threads. I didn't think my installation
was too rigid for this to happen, but... :roll:

Anyway, I removed the pump, put everything back to stock and hand
primed. Right now everything is running good. I put 400 miles on it over
the weekend and it all seems well again.

I suspected the fuel filter too, but I wanted to put another 5K miles before
replacing it. We will see how it goes.

My reported MPG drop was exaggerated. I blame the crappy fuel gauge. :wink:

flman · **Posted:** Tue Oct 06, 2009 4:56 pm

I was wondering, should we be plugging this new fuel heater back in since it has the improved connector?

Symptoms of air in fuel?

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