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Topic: Air in Fuel System Problem Starting (Read 571 times) previous topic - next topic

Air in Fuel System Problem Starting

Well replaced line from tank to first filter housing on frame about 2 years ago, last owner replaced line from primary to secondary filter.  Replaced all filters, lift pump, check valve on return line. Replaced all fittings. After priming system and  starting, she'll go down the road without an issue. No smoke, no loss of power. if coach sits for a day or so, and is on a forward angle, as per my driveway in front of the shop, it will start, run for a few seconds, and turn off. Will not restart unless primed again.
Had tank out twice already to inspect fittings and top of tank where it draws from.
The problem still exists and Im running out of summer, patience and ideas !!

ANY HELP WOULD BE GREATLY APPRECIATED !!    Thanks Folks
Jimmy A.
1997 Foretravel U295 40'
Build # 5146

Re: Air in Fuel System Problem Starting

Reply #1 –
This may sound strange to you, but your symptoms are similar to something I've seen before,  I'd check to see if there is only one rubber gasket under the primary filter and there wasn't one stuck up in there when you changed your filter.

jk
Jack and Cathy
1992 U280 Unihome 36' Build #4034
Cummins 8.3 /  Allison MT647/ PacBrake
Apopka, FL / Barre Center, NY

Re: Air in Fuel System Problem Starting

Reply #2 –
What about the line from the secondary to the injector pump, banjo fittings loose?
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Air in Fuel System Problem Starting

Reply #3 –
Air is the culprit but finding the source can cause a few grey hairs to grow. Return line to the tank could be leaking past the valve that keeps pressure at the injectors.  If you have a Bosch P pump, check the valve on the back side of the pump. Or, one leaking injector can cause loss of pressure in the system requiring priming. Fuel pump may be leaking, even causing diesel to get into the crankcase.  Check hose at the clamps including the fuel tank. New clamps of the wrong type may damage the line. They should be the full wrap, Euro style.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Air in Fuel System Problem Starting

Reply #4 –
A question, not a proclamation...

What would be necessary to gently PRESSURIZE  the supply line, where a person could look for leaks?

Thinking...  Plastic wrap over the secondary filler, a bolt in the tank vent, a sacrificial gas cap with an air fitting installed...

The a person could LOOK for the fuel dribble, not be chasing air.
Matt B
1998 u-320

Re: Air in Fuel System Problem Starting

Reply #5 –
Many leaks are so small that it's probably not going to show any fuel at a leak. And, a leaking injector or fuel valve allowing the fule system to lose pressure could not be found that way. Small sections of the fuel system could be isolated and then tested with a Mity-Vac with a vacuum pulled and then watching for the gauge to move. https://www.harborfreight.com/mityvac-vacuum-pump-39522.html

Easy to go to a Pick N Pull yard and buy a electric fuel pump off a fuel injected car. They put out about 50-60 psi, just right for priming the system or when changing fuel filters and perfect as our Detroit's lift pump puts out about 55 psi when the engine is running.  I like the Bosch pumps used on MBZ, BMW, VW, etc. About $15 at a yard.  5 or 10 seconds with a momentary switch  would be plenty if the system has a little air in it..

Here is the valve that had a crack on ours in Tom Hall's web page. It let air in and made for hard starting. He has a good diagram for how to install the electric fuel pump. Tom Hall

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Air in Fuel System Problem Starting

Reply #6 –
Till every line from the tank to the engine was replaced, one after another I too had the start and die symptoms.
And anytime I parked without a full tank, the engine would start, run, a 10-15 count and die.
Dave Cobb
Buckhorn Lake Resort The Club, #6202, Kerrville TX
check the map.  I do rent it out when I am traveling!
2001, U320, 36' #5887, in Kerrville, FT Club #17006, (7/23 to present)
2024 Jeep Grand Cherokee L, Summit, white
EX: 98 U295, 36' #5219, (mid door), (4/13-10/23)
EX: 93 U225, 36' (4/11 to 4/13)

Re: Air in Fuel System Problem Starting

Reply #7 –
Interesting, I'm told that could indicate a leak in the pickup tube in the tank also allowing air into the system.  Im considering getting my tank inspected as well as replacing all the fuel lines and filters. Hopefully that'll keep me off the side of the road ??
Jimmy A.
1997 Foretravel U295 40'
Build # 5146

Re: Air in Fuel System Problem Starting

Reply #8 –
Quote from: Jimmy –
1.  I'm told that could indicate a leak in the pickup tube in the tank also allowing air into the system.
2.  replacing all the fuel lines and filters.

Jimmy,
1. The way the pick up tube is made and installed in your tank it is highly likely that your problem is elsewhere.
2. With the age of your coach this is where you should be looking for the air leak. If you have the Racor 200200 fuel filter the "O" rings are suspect not just the filter element and it's gasket.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."
 

Re: Air in Fuel System Problem Starting

Reply #9 –
Quote from: Jimmy –
Interesting, I'm told that could indicate a leak in the pickup tube in the tank also allowing air into the system.  Im considering getting my tank inspected as well as replacing all the fuel lines and filters. Hopefully that'll keep me off the side of the road ??
Last things first.  Being on the side of the road is not such a bad thing when you're at home.  Sometimes a few road flares to warn traffic is in order but you always have time for a cup of coffee.
First thing second.  "I'm told" to me is ærobic exercise.  What I see is what i got.  There isn't that much to a fuel system, it's a finite number of potential leaks.

Starting fresh with all new flexible fuel lines is, in the long run, cheap.  Then take what has been said previously and make a list and order it from one end of your fuel system to the other.  It's grunt work, but then again so is life.

Art

Unnecessary verbiage:

I've spent 5 weeks so far tracing wires in the Studebaker, connecting them properly and removing the previous owner's additions to keep the car on the road.  It's a job I dreaded because there's no way to plan, as in no firm end date, but it needed to be done.  We took a 160 mile road trip to bring home a generator, which is replacing the one-wire alternator, and in the pouring rain, on a down hill run I pulled the accessory headlight switch and everything stopped.  Turning everything off then back on again brought the electrical system back on line, but Lynn was sitting next to me, so I had no choice but to trouble shoot the electrical system.  It is nice to have everything work as it should.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.