Strange IP Failure
 

Today, as I was driving my 1981 wvo powered 240D to school, I experienced a slight loss of power. Having not changed my fuel filters in a while, I suspected that at least one of them was clogged. (I had a bit of an algae problem before I switched over to vegetable oil, and now the algae seems to be winding up in my filters.) I didn’t think much of it until I returned to my car this afternoon to find that it would not start.

I tried to eliminate obvious possible causes by removing one of the high pressure lines that runs from the injector pump to the fuel injectors. Much to my surprise, when I cranked up the engine, the injector pump was pumping absolutely nothing. When I repeated this procedure with the other three lines, I got the same results.

The car has 204,000 miles on it, that last 7,000 of which have been on wvo with an Elsbett conversion kit. I have an excellent, water-free source for my wvo, and I am always very careful about filtering it.

So, is it possible that I could have destroyed my injector pump that quickly, or are there other forces at work here? Do injector pumps just die like that, or do they steadily decline over time?

they can do either. Maybe its your lift pump that failed

Is your fuel tank strainer clogged?

Is the vacuum shut-off device working or is it stuck.....?

Lift-pumps can go bad, the springs inside can go weak or just break, then there' the two valves in there that can fail....

yah i would check the lift pump first,

I would start at the tank filter and work from there, including the lift. If you had a "bit of an algae problem" that tank filter will be pretty clogged.
You can even get algae clogging the lines, just like plaque in our arteries from eating all those fried foods so you can have your fuel.

There are very very few failures of the IP on these cars, although with wvo that will probably be increasing in the future.
Problems pretty much always lie in filters, tank strainer, primer pump or lift pump. [primer pump allows air into fuel system]

I have determined that my lift pump was sucking in air, I think because of a small hole in one of the lines near the prefilter. I changed the line and bled out all air and it magically started right up! That explains the power loss but not why it wouldn’t start. I guess it could have just been pumping air, but I would think that if it was pumping air I would have seen air squirt or bubble up out of the IP when I removed the high pressure lines

It doesn’t seem like my strainer is totally clogged at the moment, but it probably will be in the near future.

Also, if the power loss comes back, I would be quick to suspect that the primer pump is the culprit. About a year ago I installed the Bosch upgraded primer pump, and when I ordered it, it specifically said “not rated for use with biofuels”. Of course, neither was the original primer pump, so I don’t know what I would do if it did go bad.

Lift Pump
 

If the lift pump cannot fill and pressurize the IP barrel fill chamber with a solid fuel charge due to input leaks... then the IP plungers just compress the air in them resulting in no real output from the delivery valves....
Air is compressable ....liquids are not....
When placed under pressure...air just gets squeezed.....liquids move.....
As told to me by an IP rebuilding shop owner.....
I have not tried this but it sounds correct.....

Ah, of course! That makes perfect sense