For Alastair -

CLERK: One warranty card for primer pump with white handle, filled out by DinNC.

DinNC: I don't even know what this is. This sort of thing ain't my bag, baby.

CLERK: One book: Primer Pumps with White Handles and Me: This Sort of Thing Is My Bag, Baby, by DinNC.

Sixto
87 300D

This is a proven fact millions of times..

Fuel Delivery:
Diesel Fuel Delivery:

Diesel Injection:
Diesel Injection:



Have a great day.

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1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Disagree with mobetta or BC?

I too am moving the hand pump to the back of my to-do list, driving home yesterday something went wrong in the rear (more on that later)..arent these cars fun?! I am still going to the yard and pulling off injectors, handpump, injector pump, power steering pump, radiator..you know everything I can! I will start reading through all of the information available to try and figure out my fuel issues, just so you know the cars runs like a champ once its warm!

I'm not sure exactly what you proved by referencing a bunch of threads that are not relevant.

I can certainly prove that a leaking primer pump will function just fine in most cases. They don't leak when the threaded handle is returned to the parked position. The leaking occurs when fuel manages to get past the piston diaphragm. That components is out of the loop when the handle is threaded in place.

On the older style Hand Primers I think some people do not know the handle needs to be screwed back in to seal. So the hand primer is leaking while you pump and you do not screw it back in you have a good chance to have an air leak.

My first time seeing the Newer Style Hand Primer was when I bought my Mercedes. I was at first baffled as to why the handle would not unscrew!

__________________
84 300D, 82 Volvo 244Gl Diesel

On my 78 i had the screw type, but with a metal handle. I liked that pump.

__________________

1996 E300 110,000
1985 300TD 212,000
1980 300D 238,000

I agree.

Apparently, some experienced folks don't know about that screw in feature as well.........

Any air leak in the diesel fuel system is BAD for the injection pump = starvation and lack of internal lubrication.

I have tested, and confirmed thousands of these primer pumps sucking air with the handle screwed in.

Replace any unit that leaks while priming, before you are stranded.

The design of the primer pump doesn't allow air to leak with the handle screwed in........so your statement of "thousands" might just be incorrect.

While you are certainly free to believe the pump is leaking air........the design of the pump doesn't support your contention.

Furthermore, there are thousands of old style primer pumps still on 617 engines and they all leak when the piston is unthreaded. None of them are stranded.

Thousands is correct, in thirty five + years.

I am stating fact, backed by years of experience/testing.
They can and do leak air into the system, age, damage, environmental factors, and manufacturing flaws defeat even the best design.
There are two separate sealing systems involved, when the first fails, the second (in most cases) takes over until failure.
Many are driving on only the second seal, and it with minor air leakage = direct performance loss...
I have personally rescued hundreds of 617 owners on the roadside with leaking primer pumps = replace it, prime and send them down the road happy.

Note: roadside rescues for this issue have become more common in the last ten years.

That's the whole point of the design. The second seal is designed to prevent air intrusion into the system. Granted, it can also fail...........but, the fact that the piston leaks when the primer pump is utilized is not the determining factor for an air leak........and that was the whole point of the discussion.

When the primer leaks "while priming" = it can suck/pump air/foam into the fuel system = making it more difficult or impossible to prime the system...

The fastest/cleanest diesel fuel system prime is always achieved with a primer pump that does NOT leak.

The damaged primer should always be replaced as soon as possible..

The second seal is not the primary.

The second seal is essentially an emergency backup seal to get you to a repair facility when the primary seal fails...

Guys, everything wears out or deteriorates with age; including both of the Old Style Primer Pump Seals.

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84 300D, 82 Volvo 244Gl Diesel