Stalling when parked nose-up
 

When I park my car at an upward angle and restart the engine it sputters and dies. The car runs fine when parked on a flat surface or downward angle. I've checked the filters, the tank screen, the tank vent, cleaned all the check valves and banjo bolts and lengthened the spring on the fuel pressure valve, and replaced several possibly suspect fuel hoses.
Of note also is the prefilter, which is only about 1/2 full no matter how much I hand prime it. Small bubbles appear as well. Could my lift pump be bad?
Car is a 1973 220D.

Yes it could be the Fuel Supply/Lift Pump.

Do you have the new style Hand Primer on the Fuel Supply/Lift Pump? The old style hand primer one has a hard plastic knob on it that is usually white. Also when you pump on them whe worn out they usually leak fuel and become a source of an air leak.

If your hand Primer is by your canister fuel filter (if you have that type of fuel filter) I don't know if it is possible for them to get air leaks.

The bubble in the plast filter is normal as long as you do not see bubbles moving into the Fuel Supply/Lift Pump.

It's got the newer style hand pump.

I know a bubble in the prefilter is normal, but this is large enough that the air in it can get sucked into the pump.

The pre filter bubble I consider a constant. The small bubbles transiting through the pre filter are an abnormality.

When you park the car with the front higher it is reasonable that more air gets pulled into the system. Simply because the suction force is higher.

This car is old and the rubber hose at the back near the tank is suspect. As well as some line leakage at a clamped hose joint or the line itself.

The pre filter is before the lift pump and the primer pump so they are not where the bubbles are being created by air entering the system. Sometimes it is even a cracked prefilter or a clamped hose line entering it is allowing air in.

Park the vehicle nose down.

Take the fuel return hose and pinch it closed...

Pressurized the fuel tank about to 10 psi, then look for the fuel seeping out.

Fix whatever is seeping fuel...

What size(s) is the little hose that runs from the tank to the hard metal feed line?

I've replaced just about every rubber fuel line. Nothing appears to be leaking. I don't think it's the lift pump because it runs fine until the engine is shut off.
Yet it still does it.
Any ideas?

Do you still have a stream of bubbles going through the pre filter? If so air is still getting in some where..

73220: That little piece of fuel hose is 10mm on one side and 8mm on the other, it is available from Pelican.

It probably is time to rebuild/replace the lift pump.
Most likely the o-ring/check valves in the lift pump have worn out after many years of faithful service, and you are (partly) losing prime as a result.

I believe your lift pump is MB part number 001 091 53 01, Bosch number 0 440 007 014.
Still available new, not to bad a price considering it comes with a new primer pump

You will also need a new fuel pump gasket, MB part number 0000911780.

Edit: You can test for losing prime overnight.
Park uphill and install a fuel line clamp on the rubber fuel feed line just before the lift pump.
If it starts up in the morning without issue, right after you have removed the fuel line clamp, you will have found the cause.

Hope this helps.:)

I know I saw a rebuild kit for the lift pump not long ago but now I can't seem to find it.

No complete kit for the 0 440 007 014 lift pump according to this thread:
http://www.peachparts.com/shopforum/vintage-mercedes/370355-75-240d-om616-lift-pump-part-numbers-parts.html

Here are the unblocked images of the Bosch 0 440 007 014 lift pump and the Bosch parts list for the 0 440 007 014 lift pump:

I am looking at my DGK306 rebuild kit I have and it does have the pressure spindle o ring and some other o rings that would be used for our pumps. The only problem i see with the kit is it has a mounting gasket for the MW or 3 hole lift pumps and not the M or 2 hole lift pups. Which can be ordered on it's own.

I did notice that there are numerous air release holes in the bag that holds all the components; that smaller o ring could easily fall out.

Changing the valves and O-rings in the lift pump fixed it.
Thanks for the help!

Congrats, thanks for reporting what solved your problem, not every one does.

After a couple hundred miles the problem has reappeared. I'm fairly confident either the pump wasn't bad in the first place and I've just been very lucky for a couple weeks, or air is being let in from somewhere else. I can see bubbles in the clear line that runs from the bottom of the secondary fuel filter to the injection pump, and they would seem the originate from the IP itself. After a couple miles of driving I can see very slight seepage from out of the round things that connect to the hard injector lines. Might this be the cause?

Yes, this is probably the cause.

There should not be any fuel seepage...ever.
If fuel can get out, air can get in.

Can you post a photo of the "round things"?
I'm not exactly sure what it is you are describing.
Perhaps, you mean the fuel injectors??

http://i.imgur.com/y4O6Ke7.jpg
These things.

Ah, those are the delivery valve holders.

The air incursion leak is probably at the union where the ball of injector hard line fitting attaches to the cup of the delivery valve holder.

To test:
1) on a cold engine - clean the area both ends of the hard line injectors throughly with brake cleaner and let them air dry completely.
2) test for dryness by touching the tip of a dry tissue to the union of the injector hard line flare fitting with the delivery valve holder.
3) if the fitting is completely dry - run the engine for a few minutes
4) shut engine off and re-test for seepage at the union with a dry tissue.

If you find a leaky flare nut fitting, just tighten it a bit more with your flare wrench (17mm?).
If the fitting still leaks after re-testing, then disconnect the line clamps securing one hard line to the other, then loosen the injector hard line flare nuts with your flare wrench and remove the suspect injector hard line completely.
Inspect the end of the injector hard line that seats on the delivery valve holder for any corrosion, scratches or deformations that would prevent a good seal from being established.

Clean, repair(polish) or replace any damaged injector hard lines.
Make sure to cover the open injectors and delivery valve holders to prevent foreign matter from being introduced.

On reassembly, carefully start the flare fittings by hand to avoid crossing the threads.
Once both ends of the injector hard line are loosely attached, press the hard line onto the delivery valve holder and hand tighten the flare fitting.
Do the same with the other end of the injector hard line at the injector on the engine.

After the flare nuts are as hand tight as you can get, then tighten the flare nut with your flare wrench to avoid rounding the flare nut.
Re-attach the line clamps.
Re-test to verify the leak(s) are gone.

Hope this helps.:)

It could also be air getting in at the secondary fuel filter, or elsewhere. There are 2 types of filter housings with different seals used in each. The best place to look for air in fuel is a temporary clear pvc line in place of the cigar hose (return to tank). It should have a solid, bubble free non foamy stream of fuel at all times, engine running or not (as in overnight and longer). Any air that gets into the system will end up there.

Have you pressurized the fuel system yet?

It is vital that you put it under pressure and find the fuel leak.

My bet is the secondary fuel filter can is rusted through.

I checked the flare nut ends and found one that looked rather rough. I also cross-threaded it when screwing it down so it's getting replaced regardless. As to pressurizing the fuel system could you go into little more detail about what that entails? I know the leak is past the fuel pump so is it as simple as taking an air compressor and connecting it to the lines or is it more involved than that?

Alright after replacing that hard line no difference was noted. I then attempted to pressurize the fuel system. I clamped the return hose shut and then hand primed it. The only real leak was from the delivery valve holders. I suspect the last person to adjust the timing forgot to replace the washers. Would this be enough to cause this issue? I should also note that the bubbles I see in the line run from the pump to the fuel filter housing as though the leak originates in the IP.