Lehman Injector Leak

Motor is a Ford Lehman, American Diesel Corporation variant model ADC 136N. Boat is a Marine Trader 35 Sundeck. Injector is Minimec.

OK, so tomorrow, I am calling Brian at American Diesel for this part. Any marine mechanic expert care to walk me step-wise through the exchange procedure?

I was told by Bob Smith that this is an easy change. But he did not yet say how. I will ask Brian tomorrow. Part is called a "pulsator diaphragm" I have looked it up but have not seen a clear schematic - of the specific part. Lots of the injector assembly, but not so much the part itself. Not sure why.

As I am a rookie at this, I will ask about eight times ("measure twice, cut once"?) until I feel confident to the molecular level. Thanks in advance!

Ben,
That's a knob on the side of the injector pump for bleeding air out of the supply lines when loosened (as I recall). Have you tried tightening it?


1983 Present 42 Sundeck
Twin Lehman 135's

Forkliftt said:

Ben,
That's a knob on the side of the injector pump for bleeding air out of the supply lines when loosened (as I recall). Have you tried tightening it?

1983 Present 42 Sundeck
Twin Lehman 135's

Click to expand...

Sent same video to Bob Smith of American Diesel. Said I had a faulty pulsator diaphragm. Said it's not common, but can happen. But I will be on boat tomorrow and check it's fit. You do see the fuel spurting out of the center of the diaphragm and a small hole, right?

Ha ha. Yes, pretty dramatic, I know. Has me waiting in the slip on parts. Today was 74 in Carolina Beach, was VERY hard not to cover it with a rubber glove and cruise around. Ah, but oh well.

Greetings,
Mr. B. Just got a note from the all powerful Oz. Was told:

Tell him to take the correct size wrench and unscrew the diaphragm. Screw the new one in. Use fuel proof thread sealer but not teflon tape.
It is not much more involved than changing a light bulb.

I trust this man's knowledge. Go for it.

I have an identical problem with my FL 135 and my research brought me here. I hope you guys won't mind help me out with following questions:

1) I can't see where the fuel can leak from the diagphram, to the naked eye it looks like a small solid wheel that can be turned. I don't see any spurting or squirting, only a steady drop from the lower part of the small disc. How does it leak?
2) I tried tightening it but it still leaks, so I guess I need to go one step further. Did the replacement diagphram solve the problem for OP? Was it hard to install, ie should I get a mechanic to do it, or is it safe for a DIY rookie?
3) Is American Diesel the sole supplier of the spare part?

I hope your memory of this issue is still fresh!

It was easy to do. It was also 4 years ago. Order that part - pulsator diaphragm- and it’s wrench off the old and wrench on the new. Cost I recall was like 7 bucks? Replace time was 10-15 minutes. Good luck!

Awesome, I will. Did your research reveal what that thing actually does and how it can leak when it appears to be a solid disc with no holes?

Injection pumps get a sharp pressure spike when the bleed off port on each plunger opens up on each stroke. Super high pressure fuel gets vented into the pump body. Root of a lot of the noise that comes from injection pumps.

I suspect the damper is in there to minimize that noise, or the effect on valving, etc. Just a theory on my part.

As a quick update out of respect to the folks who have helped me here and to the benefit of folks who may find this post in the future as I did: I changed the diaphragm on my starboard engine and the leak stopped. The change was indeed as easy as changing a lightbulb. The old diaphragm doesn’t show visible sign of holes or other source of leakage but it somehow did and the new one doesn’t.

If you get this problem, get in touch with Brian from American Diesel. He quickly confirmed that it was likely I had a leaking diaphragm when he saw the short video I sent him, he had plenty in stock and he sent me two at $115 a pop. Service was good and fast.

I have run the engine for 1 hour at varying revs and there’s no leak. If I get problems later I’ll post here again, so if you see no follow-up post it means all is well.