Changed the entire lift pump assembly a few days ago.
Haven't driven the car since.

Started right up yesterday and let it warm up for 15-20 min.
Then **** down the engine.

Later wanted to go for a cruise and felt a sudden loss of power and then stall.

Pumped the lift pump a few times and started right back up.

Pulled into the garage to examine.

Everything looked fine. Plastic filter is clear.

Could this be an issue of air getting into one of the lines?

This was a new lift pump assembly with original style aluminum/plastic hand pump.

Wondering if the plastic on the hand pump is brittle and leaking air.

It's an old unit bit never used.

Any ideas?

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1983 300CD Turbodiesel

The old hand pump with a screw knob seals with an o-ring if is screwed down c.w. If you don't screw it c.w. it will suck air. I hate that thing since it spills a lot of fuel when priming. The best place to check if you have air is a temporary clear PVC line in place of the cigar hose.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I did re-use a crush washer when I transferred the barbed fitting from the old pump assembly to the new one. didn't have a new one on hand. just flipped the old one over.

not sure if that could be the problem.

I may change that crush wash, and change the fuel hose around the clear filter.

perhaps even change the primer pump to the new style.

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1983 300CD Turbodiesel

Copper crush washers can be re-animated by heating them with a propane torch before use.

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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

the puzzling thing is that the car started right up and idled for until warm.

then lost power when throttle was applied.

clear fuel filter looks clean.

don't know if those are symptoms of air getting in, or perhaps clogged strainer?

seems like too much of a coincidence that this is happening after a new pump...

although I did have some intermittent sputtering before changing out the pump assembly.

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1983 300CD Turbodiesel

Why not just try and bleed the lines and see what happens. I'm pretty sure after a lift pump replacement, I haven't done one before, but I'd imagine you have to bleed tbe system because your introduce air just like replacing a fuel filter.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

wouldn't that show when trying to start the car though?

it starts and idles just fine.

I was actually surprised that it started so easily after pumping the primer and hitting the ignition switch.

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1983 300CD Turbodiesel

tried running a diesel purge and no fuel coming from return line.

aborted the diesel purge and reconnected lines.

pumped the hand primer a bunch and drove.

still getting shaky/almost stalling at idle.

also the transmission is shifting weird. didn't have these issues with the old lift pump assembly.

I am suspecting either the old style hand pump, or the fuel pressure relief valve.

anything else to look at?

as mentioned, this was a new old stock lift pump. I think the pump valves are ok, since the hand pump will pull fuel and return fuel from the big filter.

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1983 300CD Turbodiesel

Air in your fuel system can cause all your symptoms.
The old style primer pump is the most likely culprit, especially if it leaks fuel when you use it.
Unlikely to be the fuel relief valve, unless you opened or loosened that connection.

Do the check that funola recommended.
Temporarily install a clear line in place of the cigar hose return line, and run the car.
There should be no air in the clear line while the engine is running or the next day after prolonged shutdown.

Of course, any fuel connections that were recently opened or loosened are suspect.
Crush washers on banjo bolts, the secondary fuel filter o-rings (or o-ring and crush washer) and the rubber hose to the lift pump.

Over time, the rubber hoses in the engine compartment get almost vulcanized and seal with a very firm grip.
If you re-use an old rubber fuel hose, it may leak air into the fuel especially on the suction side of the lift pump.
If you can cause a rubber fuel hose to turn when you grasp and attempt to twist it, you need to tighten the hose clamp and/or replace the hose.

If your symptoms persist after addressing the above potential problem areas, it is unlikely...but there may be a dried or damaged o-ring in the NOS lift pump.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

My bet is that the "new" lift pump is bad.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

You mean the whole assembly?
Or just the hand pump?

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1983 300CD Turbodiesel

And why erratic shifting all of a sudden?

Power related.

I've got delayed shifts, flaring, slipping

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1983 300CD Turbodiesel