Home » Public Forums » GMCnet » [GMCnet] Home again home again higgledy pig
| [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: 9
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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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| Re: [GMCnet] Home again home again higgledy pig [message #77800 is a reply to message #77787] |
Tue, 23 March 2010 21:21  |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
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Senior Member |
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Ken wrote.
> Is there a pump or regulator rated that low?
>Or even as low as 1 psi?
Ken,
I have a catalog from PegasusAutoracing.com that lists several FACET (the brand on the original Onan's) fuel pumps. New learning for me, was they have them with different pressure and flow ratings. (hope the formatting survives).
Typical Max Fitting
Type Max Press. Flow Flow Size Part # Price Notes
Cube 2.5 - 4.5 15 @ 1 psi 28 1/8 npt 1102 46.99
Cylin- 4 - 5 23 @ 2 psi 36 1/8 npt 1105 89.99 "Silver Top"
drical psi
Cylin- 6.5-7.5 35 @ 2 psi 45 1/4 npt 1106 99.99 "Blue Top"
drical psi gal./hr. gal./hr
Cylin- 1.25 - 1.75 1 @ 0.5 psi 20 1/8 npt 1107 99.99 low pressure
drical psi gal./hr. gal./hr. (Onan RV gen.)
So, if you can come up with an old original Onan fuel pump w/ 1/8" fittings it should meet your needs. I never realized the Onan version was a low pressure one. I put the one cube one in as it seems "close" on typical pressure (but the flow is much higher) and is cheaper if you were thinking of buying one new. With all the old dead trolls out there, there should be a lifetime supply of the original ones somewhere, though.
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: [GMCnet] Home again home again higgledy pig [message #77802 is a reply to message #77787] |
Tue, 23 March 2010 21:31 |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
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Senior Member |
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>Is there a pump or regulator rated that low?
Ok, my table spacing didn't survive the posting, but here is a more direct link for the Onan replacement #1107 Facet pump that gives more information on it.
<www.pegasusautoracing.com/productdetails.asp?RecID=2698>
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: [GMCnet] Home again home again higgledy pig [message #77826 is a reply to message #77803] |
Wed, 24 March 2010 09:31 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| GMCWiperMan wrote on Tue, 23 March 2010 22:41 |
Matt, Jim, Craig,
Thanks for all the suggestions. Of them, the AutoZone 2517 sounds like my best option. I've got several near-suitable small pump for spares if that regulator will indeed regulate to 1 psi (maybe less?). Being in stock at the local store is a plus too. 
Ken H.
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Ken,
What you have has actually been a pretty common problem for a while (evidence the regulators that are available).
The max pressure service of any float/needle/seat set is not very high and many pumps - even designed for the service will over power the level control.
The Bendix clicker (as in what lives on the side of every old Onan) was designed for a 2~3psi output pressure. People adding them to a system would often notice that they got better flow when installed upside down. Problem - If installed upside down, they deliver at 3~5 psi and there would be exactly the problem you have seen. Yes, they are that sensitive.
The later version with a T03 case (big transistor) case on the side were designed at Bendix and the division was sold to Facet. Facet made the original version and then a "high (something)" version that was also too high a pressure for many old carburetors still in service. The model numbers got changed - too - and I lost track about there.
So, if you have spares of little electric fuel pumps, there is a about an even bet that one is right for your job.
The regulator was always my first choice fix because it is simple (cut the line and clamp it in) and fast.
Let us know how it goes. (Not that I am worried about not hearing, but it is always good to know.)
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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