From: ke6myk@sbcglobal.net
Date: Sat Mar 06 2004 - 18:41:38 PST
"Amnon" <amnon@deltaforce.net> wrote:
> Drove the Deuce today to a meeting, and realized I have to keep the
> hand throttle pulled out a lot now in order to keep the engine
> running. If I drop it below 1100rpm the engine dies.
That sounds similar to the problem I had with one of my deuces that I
got from GL a few months ago. At first, I had a lot of trouble
starting it. It would turn over and then "catch" once fuel got to the
cylinders, but then immediately die. I found that with many, many
repeated attempts to start it, it would do a little better each time,
until I eventually got it to start as long as I gave it enough
throttle. At that point, it would only run if I kept the RPM over
around 1000. It ran just fine while it was running, and everything
seemed to point to the injection pump just failing to deliver enough
fuel below a certain RPM, and even then only after a lot of attempts
to start it. I tried all of the usual tricks on the pump head without
any luck.
>From the symptoms, the best guess I could make was that something in
the fuel rate governing mechanism(s) was binding, sticking, or
otherwise garfed up a bit, so that it couldn't deliver enough fuel at
low RPMs.
A list member suggested that the fuel density compensator could be
bad, because that seemed to be the culprit in one of their trucks with
similar symptoms. They fixed it by changing the fuel density
compensator settings to effectively disable it. I studied the diagrams
in the injection pump manual for a while, and convinced myself that a
malfunctioning FDC might cause my truck's symptoms, due to the way it
interacts with the governor.
I would have preferred to simply bypass the FDC, but the line from the
fuel filters to the FDC wasn't long enough in that truck to bypass the
FDC without replacing the line, and I didn't have the right fittings
or tubing laying around. So, figuring I had nothing to lose, I decided
to mess with the FDC settings. There's a needle vale adjustment on the
FDC, under a threaded lock nut which is in turn covered with a metal
tube, which is in turn safety-wired in place with a lead seal. Take a
look at this picture:
http://www.qsl.net/ke6myk/forsale/04D98671/p1000238.jpg
Notice the metal tube with the flared end which is safety-wired in
place.
I do not remember whether I had to close the valve or open it further
to disable the FDC. In either case, to adjust it you would cut the
wire, pull off the metal cover, unscrew the first nut that's under it
to expose the adjustment screw, then use an Allen wrench on the
adjustment screw with a combination wrench on the remaining hex jam
nut (which locks the adjustment screw in place) to lock/unlock the
adjustment screw as necessary. Then put everything abck together and
wire the cover back into place.
Killing the FDC that way greatly improved the way that truck works. I
still need to use a bit of hand throttle for a short while when it's
cold, but once it starts to warm up it runs just fine, and I was able
to adjust the idle speed back down to around 900 RPM. I may need to
adjust the fuel rate cam (the pair of safety-wired hex nuts closer to
the injection pump body in that picture), but I haven't messed with it
yet. I or a future owner of the truck may need to get inside the
injection pump someday and fix it the "right" way, but since I don't
have the knowledge or equipment to properly calibrate the pump myself,
and it's running well now that the FDC is disabled, I decided to put
that off until it's really necessary.
Of course, as the manuals say, messing with the injection pump
settings if you don't know what you're doing and have the right
equipment is not advisable. I chose to do it in this case because I
figured I had nothing left to lose, and I'd have to pull out the pump
and have it rebuilt anyway if I couldn't make a simple on-engine fix
like disabling the FDC or freeing up the pump head plunger.
I don't know if your truck is suffering from the same malady, but I
hope that this description helps.
Ok, time for a shameless plug: The truck I described happens to be for
sale! It's located near Riverside, CA, I'm asking $3,500 for it, and
despite the issue that I had with the injection pump I think it's in
fine shape for that price. Although I'd prefer cash, I may consider a
straight trade for some other interesting vehicle. Here are the
details:
http://www.qsl.net/ke6myk/forsale/04D98671/index.html
Please contact me off-list if you have any questions about this truck.
-- Mark J. Blair, NF6X <ke6myk@sbcglobal.net> PGP 2.6.2 public key available from http://www.keyserver.net/ Web page: http://www.qsl.net/ke6myk/
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