puzzling lack of fuel

[buckstersdad]

I have an interesting and puzzling fuel issue. 98 E300 D. When the fuel level is low, (1/4) tank or less, and not necessarily with the low level light on yet, I sometimes can't start engine without excessive cranking, perhaps up to 2 minutes.

The first time this happened was when I was having A/C serviced. After they replaced the compressor and lowered the car down on the lift it wouldn't start without excessive cranking. The tech said I shouldn't ever run the car down to the low level light. Never had this problem till then.

Well it happened again today when I went to start after sitting overnight. Not even in the low fuel warning, but in the last quarter. I have driven the car down to low fuel warning on occasions and it runs fine even with the light on for 20 or so miles until fill up. There are no leaks anywhere that I can see.

Last night I did park the car slightly nose up. Why would it seem that fuel tank level brings on this problem? What should I look for?

[scottmcphee]

They mixed up the supply and return lines for fuel when servicing the car and putting it back together. A/C is in the area.

You are now actually drawing fuel from the return spout at the tank, which is part way up the tank.

Find the two hard lines to fuel tank under the hood, and reverse the rubber hoses on them.

[buckstersdad]

Thanks Scott. Good point. I will check them this evening. I believe I saw something about that possibility in a fuel line replacement thread.

But, having said that I have, since the first incidence on occasion driven the car down in the low level light on zone. If the lines had been switched would the car run when the tank was that low?

[kerry]

Originally Posted by scottmcphee

They mixed up the supply and return lines for fuel when servicing the car and putting it back together. A/C is in the area.

You are now actually drawing fuel from the return spout at the tank, which is part way up the tank.

Find the two hard lines to fuel tank under the hood, and reverse the rubber hoses on them.

X2

[scottmcphee]

Hmmm.. run 'til light on would not be possible with switched lines, unless you have a defective float/sensor as well.

Maybe you're getting a fuel tank vacuum happening with temperature flux, that is pulling fuel back along both lines. Creating a dry start.

Loosen the fill lid, get a whoosh (suck) sound?

You're tank vent could be plugged.

You can add a check-valve up front on the supply hose for about $10, that prevents pull back / drain back.

Tighten all the fuel hoses a crank or two on the clamps under the hood.

Maybe you're just sucking air, on a loose re-fit of some hose.

Or fuel restricted: replace filters, and make sure the main filter is not leaking / has a good seal. It could be sucking air there.

[buckstersdad]

Got a new fuel filter coming tomorrow morn. Wish I had taken the time to look at the fuel lines when it wouldn't start. Could possibly have narrowed down some possibilities. I don't think I replaced both O rings when I last changed the fuel filter. (Few months and 5K mi. ago). I'll make sure both get replaced this time.

I like the idea of a check valve in the return line. Have you done yours that way? If so where did you source the valve, and how is it installed?

Stopped and re-started the car a few times today, with no issues. Staying close to home with a few errands today. Still less than 1/4 of a tank. Just trying to get the issue to repeat itself.

[nelbur]

You may have an air leak into the fuel system, that allows the fuel to return to the tank. A full tank could have enough head to keep the air out. Parking with the nose high helps the fuel run back to the tank. I would guess that parking with the nose down would allow use of all the fuel, and nose down with a full tank might show where the air leak is, as fuel should leak out there as well.

When my neighbor owned my car, he had it towed away three times in a week because it wouldn't start. He parked nose up in his driveway and the shop was on flat ground so they had trouble duplicating the problem. I think they fixed it, but he soon sold it to me and I have a flat drive, so maybe that leaking O-ring I recently fixed on top of the lift pump was the problem.

[buckstersdad]

I agree Nel: I was thinking the exact same thing, so I topped off this evening and parked nose down. Will inspect fuel lines, etc. before starting tomorrow morning. Hopefully something will show. I have a fear however, that a leaky O ring may allow air to leak into a line but may be a good enough seal to keep fuel from leaking out. The lines are original, and 187K, but seals were just replaced 5K ago.

I believe Hunter mentioned in some thread that there could be micro crazing/cracks in the lines letting air in but still intact enough to keep fuel in.

I've got a good light and inspection mirror for a thorough check in the morning.

[whunter]

Originally Posted by buckstersdad

I agree Nel: I was thinking the exact same thing, so I topped off this evening and parked nose down. Will inspect fuel lines, etc. before starting tomorrow morning. Hopefully something will show. I have a fear however, that a leaky O ring may allow air to leak into a line but may be a good enough seal to keep fuel from leaking out. The lines are original, and 187K, but seals were just replaced 5K ago.

I believe Hunter mentioned in some thread that there could be micro crazing/cracks in the lines letting air in but still intact enough to keep fuel in.

I've got a good light and inspection mirror for a thorough check in the morning.

That is correct.

Here is a list of the common issue lines and O-rings for your model.
http://www.peachparts.com/shopforum/mercedes-parts-reference-library/291250-om606-962-1998-99-e300-turbo-diesel-plastic-injection-pump-lines.html
Be sure to replace the Seal ring, shutoff valve to injection pump


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