It also indicates that the valves in the lift pump are working, but indicates nothing about the engine-driven portion of the pump.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

so, has anyone experienced the engine driven portion of the mechanical fuel pump being bad?

what would be the symptoms and more importantly the cause.

As mentioned in another thread, this was a new old stock unit. Even had the old style aluminum hand primer.

I switched that out thinking it was the culprit, but nope

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1983 300CD Turbodiesel

I have experienced the suction/discharge valves sticking, in which case fuel pressure is drastically reduced. Fuel just moves back and forth instead of steadily in one direction.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

I think I've ruled this out since manual pumping moves fuel in one direction rapidly. but maybe things are not what they seem

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1983 300CD Turbodiesel

Not easily, but generally if you have them reversed, your car will appear to "run out of fuel" when there is still about 1/4 tank left. If you refill the tank and restore performance, and then run out again when the gauge still shows fuel, then try swapping the lines BEFORE you fill the tank. If that restores performance, then you've solved that problem.

If you don't have the patience for that, you need to start at one end of the car and either (1) trace fuel lines to be sure you have them correctly connected or (2) pull off either line and blow air through it, check to see which line has air coming out at the other end of the car.

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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

I've never seen mine full, that sounds normal.

__________________
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

I suspect what was meant was the injection pump driven part of the lift pump. The IP has a little camshaft inside, driven by the engine, which operates the lift pump as well as the pump elements that send fuel through each delivery valve to each injector. If that camshaft is damaged, your lift pump won't work, and the symptoms would be what you are experiencing. This would also explain why two different lift pumps exhibited the same problem. I suppose you could remove the lift pump and observe the camshaft or push rod to make sure it goes in and out while rotating the engine by hand.

__________________
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

I didn't have this issue with the old pump.


I bought one, and planned on rebuilding the old one and having a spare.


this all started shortly after changing the assembly

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1983 300CD Turbodiesel

it has been my experience that these old cars reveal problems when things are replaced.

or

it could just be a bad pump.

but it seems that its never the new part that's bad but rather something else that just coincidentally broke shortly after

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1983 300CD Turbodiesel

Well there it is! Put the old pump back in, problem should be solved.

__________________
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

When you replaced the lift pump, did you swap over the primer pump? If so, there should be one copper washer under the primer pump, not 2, not zero, and should be dry there.

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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

yeah, I eventually swapped my old bosch primer with a new copper washer.


initially I thought the aluminum primer was the leak source. but its acting the same with the new style primer

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1983 300CD Turbodiesel

I did years ago.
I had intermittent fueling problems. Chased it right down to the tank. Not the filter screen! The was what looked like a piece of baby-blue balloon in the rubber line exiting the tank. It would billow around and block the flow, then settle out and allow fuel to pass once again. 99 cents worth of diesel fuel line took care of that.

Your issue may be something else-but check carefully!

Cheers,

snapped_bolt

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'81 240D For now, a good place to borrow new parts
'80 300TD Probably will be put back into service!
'79 240D BACK IN SERVICE SINCE 09/16; limited use, oil leak. Guide pin r/sealed/replaced. Still a leak. Front crank seal....

Changed both filters

The clear one had some black particles, not much.

The spin on liquid was clear, emptied it out and didn't see any sediment.

Did the same drive approx 50 miles.

Noticed some hesitation but made it all the way.

Siphoned by mouth from the supply line and got fuel. So not sure if it's obstructed.

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1983 300CD Turbodiesel

What did the temporary clear cigar hose look like?

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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