| [GMCnet] Home again home again higgledy pig [message #77787] |
Tue, 23 March 2010 19:52  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma:
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Senior Member |
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After a well-spent yesterday ad a wasted morning today, I finally got back
to the GMC before noon. During my hiatus, my memory recovered enough to
suggest that the fact that there are TWO injector fused in the Howell EFI
harness might mean I did NOT blow another ECU driver.
Sure 'nuff, the right injector fuse was blown. With that replaced, the
rebuilt standard EFI installed, and my spare ECU from the Olds installed,
the engine ran pretty good all the way home. The coach is resting quietly
under it's shelter on its "high chair" (rack). Hallelujah!!! After a
couple of days away from the frustrations, I'll get back to doing an
organized, logical diagnosis of the situation and get it running right --
maybe.
Needing to turn to something else, I decided to have a look at the Troy-Bilt
generator I installed before starting the Cad 500 project. That
installation was essentially completed and working well when I wandered away
from it. Except for one little problem: After about 1-2 minutes of running
the engine always died. It would aways start right up and run for a similar
length of time, but never for a useful period. I'd always figured it was a
fuel line or pump problem and hadn't worried about it since I didn't really
need it (until I was stuck with the acting-up engine and weak batteries).
Today I watched it run and stop a couple of times, with a timing light
connected to show spark status at shutdown. The first clue I got was that
just before shutdown, the exhaust would become black. Ah Ha! A little pair
of lockgrip pliers clamped on the fuel line just before the carburetor (or
FI?) was my diagnostic tool. An hour later, the engine was still running
smoothly with two 120 vac lamps, two 1500 W heaters, and the refrigerator
running -- about 3800 W total load -- more than enough to run the roof A/C,
my ultimate concern. It's amazing to me how little effect the additon or
subtraction of load has on that little 305 cc B&S engine! I can't hear any
change in the frequency nor load change in the exhaust sound, and the freq
meter is pegged at 60.7 Hz.
Now how do I regulate the fuel pressure? The pump I'm using is that from
the removed Generac 36G, itself a little one-lunger. I figured that would
be a low enough pressure pump for this application, but I was wrong.
Considering that the Troy-Bilt design had a big flat tank gravity feeding
the engine from only inches above, I guess I need only 1 psi or so at the
carb. In fact, mathematically: 6.3 lb/gal * 7.5 gal/cu ft / 144 sq in/sq
ft = 0.33 psi at the bottom of 12" of gasoline; or, 0.1 psi at the bottom of
a full 4" deep tank. Hmmm -- Is there a pump or regulator rated that low?
Or even as low as 1 psi?
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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