My 300D is stalling out. It will start and run for a couple minutes then lose power and eventually stall. I think it is a fuel delivery problem or that there is air getting in the lines. I replaced both fuel filters and the fuel lines. I did not replace the clear lines that go from the primer pump to the secondary filter. There seems to be an air bubble in the primary(clear) filter. When it's idling it looks like it is just a bubble. I can't really tell if it is getting into the line. Is it normal to have a visible bubble in that filter?

Bubble in primary filter is normal. Could be a weak lift pump. Check to see how much it is pumping.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Is there an easy way to check that?

You are aware the 77 300d has an idle adjustment on the dash? Usually if set too low the engine kind of quits just as it starts or comes of the starter when cold or will not start at all.

If your primer pump is the old style with a white cap I would change it just as a general preventative thing. They can leak air. The new design is a push plunger type also that has a black smaller top and does not require you to unscrew the cap before using. Price shop this item. Somewhere around twenty dollars should get one new.

Does the car keep running if you start it with just a slight amount of pedal? My 77 300d would keep running with a visible stream of small air bubbles entering and leaving the pre filter when I had a rear air leak. Yes the primary bubble in the pre filter remains. A little rougher in the idle and a slight bit harder for the engine to catch. Yet it would stay running.
So if you have a fairly heavy air leak it just about has to be that primer pump. Or the little hose. The no bubbles transiting the pre filter show it is not before the prefilter. After the lift pump everything is under pressure so you would have a fuel leak.

If you have no knowledge of when the valve clearances where last checked, at least check them. Sometimes a cold engine will die out if valves clearances are far too tight. What I think occurs is the valve stems warm prior to the head. A lot less mass in a valve stem. If valve clearances were tight cold the new valve stem expansion keeps one valve or some off their seats. Compression drops and the engine quits. Eventually a valve can even be damaged by never checking the clearances. The important clue here is the engine runs a couple of minutes before it quits. Thats about the right time for some expansion to occur whith a valve stem.

Disconnect the outlet line and crank the engine with the outlet hose in a container. Brian Carlton has a number of posts where he lists the approximate appropriate volume.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I replaced the clear plastic lines on my 300D with 1/4 inch fuel hose. I had to heat the hose on the banjo nipples with a butane lighter to soften them to yank them off.
If it will run a while at idle and start to stall while ideling; before it stalls try pumping on the hand primer and see if it runs better.
An old hand primer can be a source of an air leak.

__________________
84 300D, 82 Volvo 244Gl Diesel

Do you have a oring or a crush washer sealing the fuel filter bolt? Replace it with a new one when you changed it?

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

check your pcv system for blockage

__________________
'81 300D - swapped to a 617.951 turbo motor with a 150 amp alt.

I'm thinking it might be the primer pump. when I pump it fuel leaks out of the top of it and it doesn't seem to pump very well. So I'm figuring that is a tell tale sign. It is the old style also. This seems to be a common problem, can I bypass it completely?

Need to install a new one. Less than $20.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13