The clear plastic pre-filter, the one that connects before the canister fuel filter, I see air bubbles geting sucked up on their way to the IP.

My 603 nails much of the time, but sometimes it's very quiet too and runs more smoothly.

Do I have a problem, or am I just perinoid?

Sooty:

It's normal for there to be some air in the pre-filter and to see it slopping around, but air actually going up the line into the lift pump is not.

I had to replace all the fuel lines around the lift pump/pre filter last year, they leaked. I used normal fuel line.

If you have fuel down there, even a trace, yours are probably bad, too. They get small cracks, and that allows air to get sucked in instead of fuel from the tank, and if it's pretty bad, you will get excessive injector noise and some extra smoke, along with low power.

When they get really bad, you will have hard start problems, too.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Peter

I believe I saw, in another post you (or Leathermang) recommended pressurizing the tank with about 1 LB of air pressure and looking for leaks. How would you do that, maybe a hand pump on the vent line, have you done it. I would hate to give it too much and "blot" the tank. I finally got a pump for pressurizing the cooling system (and caps) to find leaks. I would think that sort of pump might work for pressurizing the tank??

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Psfred and Stevo

Thanks for those tips. No, it must have been Leathermang. I'll test my fuel supply tubes and see what's up. I can rig an old fuel cap with a hose barb and regulate a small amount of air into the tank.

Sooty

I was thinking that since the vent line has to be plugged it might be easy to hook up the air pump there. Its either the 8mm or the 10mm line coming out of the tank on the driver side. Of course just clamping the rubber vent line and using the fill neck to apply pressure could work too. Let us know how the test goes.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Sooty does the fuel foam in the pre filter? Before you do anything replace it, mine was foaming inside the filter and I could see bubbles in the clear spin on filter inlet line. It could be a bad pre filter.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

This morning I removed the fuel cap and when I did so I heard what sounded like a small vacuum wooosh. This isn't the first time I've heard this and this shouldn't be. As was mentioned there is a vent and I wouldn't think there should be any vacuum, or maybe it was pressure pushing out?

Maybe I'm wrong! There are a lot of bubbles in the filter, not quite foam, but close.

When I have time this weekend, and I cant drive the car until my replacement front turn signal arrives ups, it popped out and got crushed under my wheels last night! I'll really check into this air in fuel stuff and let you guys know what I've found.

Has anyone ever had the fuel heater pose such a problem? It's on my list for things to check.

I was mistaken, there is foam happening in the pre-filter and you can watch a steady stream of tiny air bubbles flow through it.

Hi,
You made mention that you should not have a vacum effect that would show itself when you remove the fuel cap.
I have always noticed that there is a 'whosh' of air into the fuel tank when I remove the cap on my '87 300d. Are you saying that that is not normal? My engine is running a little rougher then normal and am wondering if this may be an indicator of a problem.
Thanks,

ICEMAN

No, I'm not implying that the woosh is not normal, I'm trying to find out if it is, or isn't normal. I don't know!

The vent, I would think would make this impossible, but maybe not. The vent is there for fill up, so it dosen't take for ever!

I think the woosh is normal, mine does it. So did my Camry, and my moms Olds. Sooty get some 5/16 clear PVC hose, the cheap stuff availible everywhere. Splice it in, one side to the hard fuel line that comes up from the tank by the pre-filter. Put the other end on the fuel pump, this will by-pass the heater and pre-filter. Start the car and look for bubbles. Their shouldn't be any. But what you describe sounds like what mine was doing. I bet your pre-filter is bad.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

HATTERASGUY

That sounds like a good idea, I'll try that.

I disagree,
The MB fuel tanks have a vent line which should prevent any pressure or vacuum build-up. Check that the vent is clear of obstructions.

If you are getting air in the fuel system, the vacuum in the fuel tank may be contributing, allowing air to enter the fuel lines at weak points between the tank and engine.
To check: With the engine running and your stream of bubbles flowing, remove the tank cap and watch to see if the stream of bubbles reduces. Be sure to let it run for several minutes, to ensure that any air in the line to the tank is drawn out.
If they stop, change the flex line from the metal line to the prefilter first (easy job) If not the problem, do the one from the tank to the metal fuel line.
Happy hunting

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

The tank will hold some pressure -- it's whooshing OUT, not in! Vent the tank before removing either fuel line in the engine compartment, or fuel will push out. I know, I got soaked in a parking lot once while trimming the leaky bit off the end of the return line.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

If you have a fuel tank holding a vacuum or pressure you have a problem. All are vented, if vent systems fails and pressure builds from fuel & fume expansion (gassers, remember vent to charcoal canister) it can be dangerous when fueling a gasser. Also it will not allow for proper delivery of fuel as engine runs and creates a vacuum in the tank eventually stopping fuel flow or it sucks air some place in the fuel lines cause poor performance.

I've actually seen a couple of fuel tanks that have buckled spots from vent being plugged. One Dodge sockermom van required channel lock pliers to remove fuel cap. Yes the tank had to be replaced.

We have a wasp in this part of the country called a "dirt dobber" and these things can pack mud (drys into very hard crap) into the most unexpected places, including evap drains on cars that sit durring days because the owner works nights.

__________________
'10 Chrysler T&C Stow-N-Go White. Grandpa's ride.

'13 Chrysler 200 Touring Candy Red. Grandma's ride.

Age and cunning will always over come youth and vigor.