posted this on tech help but maybe you fellow dieseler's can help...
I have an 84 300TD and I have some issues with the fuel delivery system. I have replaced both fuel filters, injector bypass lines (they were leaking a lot) and the fuel lines in the engine bay and directly in front of the tank. I recently discovered the small (reserve?) tank behind the spare but have not replaced the lines to it. My car didnt have a fuel strainer in the tank. After issues with the primer pump on my fuel pump leaking a lot (now need new engine mount) I replaced that with an updated model. However, my car STILL runs out of fuel! It will be fine and I can drive for 10 miles or so at various speeds and then the thing just runs out of gas (diesel I know)! I have to get out and pump the primer pump for a while, usually til I can feel there is fuel in the lines again, and then I can 'usually' start the car right back up and go again for another 10 or so miles. When it does start back up, its just barely running and I have to pump the pedal a bit until it gets up to speed and then I can go. Im baffled. IP? fuel pump? Posted this problem on the other list with no help. Anyone ever hear of anything like this? I did buy a fuel pump vavle replacement kit, but havent had the guts to try installing it yet.
Help!

when it runs out of fuel, is the clear primary filter full or empty? (a small bubble at the top is ok)

when it runs out of fuel are you usually going up a hill?

I believe its sucking a small amount of air from somewhere, takes some time for it to kill the engine.

Is any part of the fuel system leaking at present?

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Cheers,
Robert

If the fuel line was leaking did you replace ALL of it or just patch it? If any of the original line is still on there chances are there is a pinhole leak that is sucking air, probably under a clamp or in some other hidden spot where you would never find it in a million years.

Running out of fuel this fast shouldn't happen. Have you checked to see if the tank is venting? Doesn't quite match what I experienced. Open that fuel cap and see if there is a strong vacuum? If so your vent is probably clogged

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My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory

the prefilter still has fuel in it (with a small bubble). It doesn't really matter if Im going uphill or not, but it does seem to make it happen earlier if Im having to start from a full stop and accelerate or accelerate more to go up hill. I did completely replace the fuel lines (the rubber any way, not the steel) except for the lines I just discovered in the spare tire bay leading to the small (reserve?) tank that is behind the spare. There is evidence of some fuel leakge there. Plan on replacing those this weekend. I haven't messed with the fuel cap or vent, but will give that a shot. thanks!

This response sounds like a restiction to me. It is not unlike getting a fuel filter plugged. I would be checking for something plugging up the works, maybe reverse blow the fuel line with air.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

yep, have tried that too. I imagine that since I do not have a fuel strainer, there could be crud in the tank that builds up to form a stoppage? But then why would simply pumping the primer pump get it going again?

You may be starting to make a good case for a very weak lift pump a possibility. Test it with pressure gauge while cranking to see if up to spec. Oh yes driving with the fuel cap off will eliminate the possibility of a tank vaccum problem. One post suggested a vaccum problem as a possibility..

You are sucking air, and by the looks of the prefilter having a small air bubble, I can bet that the problem will be after the prefilter. I have experienced a cracked prefilter where the air leak would allow air into the fuel line to the lift pump, but not into the prefilter. This was exacerbated by the prefilter being partially clogged.
I doubt that you have a leak from the main filter, you would have a noticable fuel leakage when at idle.

Replace the prefilter and the small rubber hose which connects it to the lift pump and report back to the Forum.

Tony
The Wizard of Oz.

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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.

Tony I have experienced the same thing. The outlet of my prefilter had a hairline crack in it. Mine would never die from lack of fuel, but would stumble after sitting at a stoplight or intersection for a while.

But, in the original post it says he has replaced both fuel filters, but doesn't clearly indicate if this problem was occuring before the fuel filter change.

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Keep everything as simple as possible-but no simpler--Albert Einstein

It didnt really happen at all until one day it just ran out of fuel. That prompted the filter changes. Even after changing both filters, I couldnt get it started, then I noticed the PO's rig on the last bypass line had blown off. I capped that off with a vaccum cap, and then it started. Shortly after that the primer pump stated leaking terribly, so I replaced that. The prefilter is only a few bucks so maybe Ill see about replacing that again.

Have to agree that there is probably air getting in somewhere, had a similar problem with my 190D a few weeks ago.

My first ride was a 55 Ford pickup (gasser) that developed a similar problem, except that it would quit randomly. After replacing filters, fuel pump, fuel lines, etc, I finally resorted to pulling the gas tank and found a maple leaf drifting around inside. Would wrap around the fuel pickup and stall the truck. Once engine was dead the damn leaf would float away from the fuel line and all was ok with the world until the bloody leaf would drift into place again.

Replaced the pre-filter and the bit of hose between it and the fuel pump today. Wouldnt you know that the hose clamp closest to the fuel pump was quite bent and had put a hole all the way through the line! I probably bent it up installing the primer pump.
So, put the new prefilter in, bled the system til it "buzzed" a bit and went for a spin. Ran great for about 20 min. and then 'almost' died on me. I pulled to the side and sat there for about 10 mins with the pedal floored. It didnt shut off on me, but it sure wanted to. After a little while the pressure seemed to build back up and she was running fine. I got her parked and checked out the new prefilter just to see. No air bubbles! Is this a good thing? I hope so. Gonna take her for a spin tonight and see if she stalls on me again.
PS: Even though there was only about 3K miles on the replaced prefilter, I had been running SVO, and all I have to say is thank dog for pre-filters! If you're running SVO in your cars you better filter it and then filter it again!

i wonder if it can be related to the missing tank strainer. why is it gone? may be it wass removed to solve a problem in the tank. i would replace it immediately. they put those there for a reason. this might not solve your problem but still i think there must be a relationship.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I'm going to say the lift pump is weak since you're still having problems, I wonder if the SVO put a little too much strain on it or something. Doesn't sound like it's sucking air to me, sounds like fuel starvation though. And yes, put the strainer in the tank!

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k