Fellow shade tree mechanics.....
This is sort of a convoluted story, please follow it all the way through
before rushing to an answer.
Three years ago my M35A2 cargo truck lost the ability to idle. Plenty of
power, ran good at speeds above 1200 rpm, but below that it shut down (just
like if you pulled the fuel shut off). I replaced the injection pump (we'll
call this "Pump A") with a spare I had on the shelf. The truck has been
running fine since.
I sent "Pump A" to an injection pump shop, where it was cleaned "adjusted"
and pronounced ready to work. I put it on the shelf as a spare.
Eighteen months ago I bought a M292A2. It wouldn't start. With ether, it
would start, and run until the ether was exhausted. Further investigation
showed that there was no fuel leaving the pump head.
I replaced the hydraulic head on the pump. The truck would then start,
grudgingly, after many revolutions and use of the flame heater. The truck
then smoked profusely. Then after driving a half mile or so, it would develop
a knock (much like a loud pre-ignition knock) and power would fall off
quickly and dramatically.
I then removed this injection pump (we'll call this "Pump B"), and installed
"Pump A" (remember, the one pronounced fixed). After having to crack the
line to injector 5 to bleed it, the truck now starts easily, no smoke to
speak of, no knock and hurtles down the highway at 60 MPH.
BUT, it won't idle. (same problem that this pump {Pump A} had 3 years ago).
If I turn the idle screw up enough to keep it running, 1200 rpm, the pump
"hunts" and runs up and down gradually from 1200 to 2400 rpm.
I now send "Pump B" to a different injection pump shop (being less than
thrilled with the work done on PUMP A).
They check it, says it was dirty internally, and pronounce it A-OK. I now
remove "Pump A," and reinstall "Pump B." Now, the truck requires ether to
start, idles rough, has low power, smokes, and the power falls off rapidly
after driving a half mile or so, just as it did 18 months ago.
What do you all think is the problem?
My hunch is that the engine itself is OK, since it ran so well with "Pump A,"
but could there be a problem with the injectors themselves, as well as the
pumps, or is it strictly a pump problem. Any ideas on "breeding" the two
pumps? Thoughts in general (other than finding a 3rd pump shop, or reducing
truck to scrap metal)?
Thanks,
David Doyle
This archive was generated by hypermail 2b29 : Mon Feb 05 2001 - 07:13:50 PST