Napa has the updated pumps fo2 $20 why pay more on Ebay...or deal with a leaking old style pump...

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

might help...
Here's my payback! Diesel Primer Pump Replacement

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

pressurized, I had pumped until I was fed up with pumping. Drove to town a while ago and coming back home, up a very steep hill, pulled the selector into "S"(what do they mean 'slope' - this is a mountain!) and floored the pedal. The engine began runnung out of fuel. We stopped, turned the fuel filler cap to take it off and then had to forcebly remove it. raised the hood and the prefilter was almost completly full while running at idle. Prior to this you could see no fuel at all(even tho it would run fine at speed. Must be a good pump on that IP....

Finally found the vent outlet, evicted the dirt dauber and all is heaven again!

Thanks to everyone - I hope I can contribute something in the future.

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car

kept running out of fuel. Tomorrow, out comes the pickup screen! Will post results.

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car

I don't think it ever hurts to clean something like that... also gives you a chance to look at lines, clamps, and note any snakes or critters which may be living up under the car..
But the idea it can get up to 79 mph and run out of fuel due to a clog in the main tank is a long shot .... But it will be clean and you won't have to worry about it the rest of this diagnosing exercise.... LOL

then I slowed to 70mph. A few seconds later it began slowing down. I pulled off in the grass the other to the right of the emergency lane, popped the hood and the primary filter was empty(Took the filler cap off and got no indication of vacuum OR pressure). The engine never did quit. Closed the hood, sat a minute or two and got back out on I-40. ran it back up to 70 for another 10 miles and it slowed down a couple times on it's own. Stopped to do some errands for a half hour or so and proceded back home with no further issues. The trip home was 45 miles but the speed was 55mph or slower.

Opened the hood and the filter(primary) was3/4ths full. You folks ain't gonna tell me I have an IP going on the fritz, are you??

No further starting problem since ridding the vent hose of it's tenants. Filter has plenty fuel in the mornings.

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car

If that primary filter was full of air and not fuel when you lost power your problem is an air leak between the tank and that filter.....keep in mind you CAN have an air leak without a fuel leak.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Originally I thought the tank may have a vaccum problem that was sucking air into the system after the engine was turned off. This air you would compress up in the injection pump area everytime you hand pumped. The return valve on the pump was probably not opening or with great difficulty as you had to overcome the vaccum in the tank as well as try to build enough pressure with that little pump and that has limits.Thats probably is why the only way you could get the car to start was to pump like mad. The pump was not up to it otherwise. The moment you stoped pumping of course some fuel was pushed back to the tank a little as the remaining air decompressed Plus the additional contribution of the vaccum from the tank pulling the fuel back as well and perhaps even more air into the system. Leaving you with the indication of a lesser quantity of fuel than normal in the pre filter. That sympton has probably stopped or lessoned now or partially so by elimination of the vaccum problem. But part of the problem may still be there. There is still the matter of the place the air originally was sucked in. Now perhaps the lift pump or the injection pump as well if it has some suction capacity is pulling air in the same place either constantly or at a variable rate or intermittently when running. The car probably starts everytime now unless it quits and you then are back to pumping but not as much as before or it really will not quit or refuse to start anymore just looses power now. You could pull the filter from the tank but a test can be done just by removing the hose back there and seeing if fuel flows out pretty good. If so go and find that breech in the system thats driving you crazy. Has to be between the tank and the pressure relief valve on the pump If it exists. So if you pump the fuel up and it stays there instead of backdraining down to a small quantity in the prefilter still go to work. If you have or can borrow a mityvac and find a way to match it to the end of your fuel line it should hold high vaccum. Or use the lift pump by cranking the engine to establish test vaccum with just vaccum gauge if you do not have a mityvac. I believe there is a check valve in the lift pump to stop back draining and to check it out just disconect secondary side of lift pump to verify check valve is ok by the high vaccum holding for at least 15 minutes to be safe. If you hold high vaccum there move next to the line at other side of lift pump and see if you hold high vaccum there but you will have to use a mityvac at that location I think but perhaps not. A bad tank filter could agravate the problem though by making the lift pump work or pull harder again another possibility for air being sucked in someplace. Then again the tank filter internal volume is pretty large so you should flow at least a pint out of the tank to make absolutly sure filter is clear without removing it. If you read through all of this you are older now. Naturally it is only my opinion and I am probably wrong but think it's time for applied mental effort to try to help resolve your problem. It of course will turn out to be easy, simple, and understandable once you have found it. Hindsight is beautiful. Also allow me to be wrong as above just my opinions. Old cars are also just a hobby (addiction?)for me when I get time. But I meet the nicest people. If you have another pre filter sub it in as it could have a hairline crack and would fit your present symptoms perfectly. This crack could even be so small as to miss it easily.

This is an excellent observation. A hole so small that it sucks in air but doesn't leak diesel would be really hard to see. Also, have a really close look at the hoses between the prefilter and the metal fuel line, and the primer pump and the prefilter. There could be a leak at the tank, too. It's even possible that the metal line itself is leaking somewhere, if it's been hit or is rubbing against something. It's a longshot, but I've seen stranger things before.

__________________
1982 300D, black w/ palomino leather, 203K
2001 E320, champagne, 105K (Mom's)
1999 Dodge Dakota, squeaky & battered, 142K

because I did not replace my primary filter until today. I discovered the PO had installed it backwards(don't know if that is important or not). It was badly gunked up. We blew air back into the tank and through the fuel,then installed a new filter. NAPA here only had gasoline filters. Figured that would be better(temporarily) than the dirty one that was on there. Will give it a good run tomorrow & holler back.

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car

......

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car

I would watch the new pre-filter for any rapid dirt build up. That is if it is the clear plastic type. If it becomes noticeable attention to getting the fuel tank in good condition would be on my list. Also if you have money to burn might want to put on a new style finger pump. Always easier to deal with problems when not away from home and much cheaper there as well. Some of it is just preventative maintenance as it is correcting things before they become problems. Anyways glad the initial problem is gone.

tar now. Driving the 300SD. Will take care of the 240D tank shortly. I have already changed the primer pump to the new style. Going to try to clean up the fuel level sender at the same time.

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car