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Stretch · 02-01-2006, 03:22 PM

I think we broached this subject some months ago. However I have a specific problem that has plagued both Alpines we have owned, ( an 00 and 03). If the generator has not been used for a week or so, when I start it, it runs for max 2 minutes and stops. Trying to restart wont work unless I prime for a long time (2 minutes at least) then it starts by running on 1 then 2 then all three cylinders. obviously it lost fuel prime and was starving for fuel. I have called the Onan dealer and (over the phone)they think it is a leak in the supply line. I have my doubts because I carefully checked every connection on the 00 Alpine and found nothing. Anybody else having the same problem? Were you able to get it fixed? And if so, what was the problem?

Stretch · 02-01-2006, 03:22 PM

I think we broached this subject some months ago. However I have a specific problem that has plagued both Alpines we have owned, ( an 00 and 03). If the generator has not been used for a week or so, when I start it, it runs for max 2 minutes and stops. Trying to restart wont work unless I prime for a long time (2 minutes at least) then it starts by running on 1 then 2 then all three cylinders. obviously it lost fuel prime and was starving for fuel. I have called the Onan dealer and (over the phone)they think it is a leak in the supply line. I have my doubts because I carefully checked every connection on the 00 Alpine and found nothing. Anybody else having the same problem? Were you able to get it fixed? And if so, what was the problem?

VAGABONDMAN · 02-02-2006, 09:55 AM

I have experienced the same problem on my '03: it happens whenever I have run the fuel tank down below 1/4 full. My conclusion is that the fuel runs back into the tank and we lose prime. It's a big nuisance and I have no suggested fix.

Jim A · 02-02-2006, 11:49 AM

Vagabondman might be on to something there. I rarely let my fuel tank drop below 1/4 (I never trust gas guages very much), and I have never experienced the described problem with the generator. My generator has often sat idle for weeks, and has not had the problem when I finally start it up.

EngineerMike · 02-02-2006, 12:30 PM

Could try adding a low pressure check valve fitting near the tank; that'd minimize the volume of air accumulating in the line.
My experience w/diesels is that a small volume of air can be introduced into the Injection Pump & run thru w/out substantial trouble (it mostly gets pushed back to the tank in the fuel return line @ top of IP), but a lot will break the continuity of fuel reaching injectors and thereby shut down the motor.

Stretch · 02-02-2006, 02:53 PM

Hi Mike: I tried a check valve on our OO 40fdts. It suffered the same problem and the check valve did no good..........

Stretch · 02-02-2006, 02:56 PM

Thanks vagabond man:
Mine will fail at any fuel level. That is if I do not use the gen for several days

EngineerMike · 02-03-2006, 08:31 AM

Stretch- Thanks for plowing the row on the check valve. I wonder if the gen has a lift pump; sounds like not, and that it could benefit from 6psi or so constant fuel pressure to the IP when activated. In pick-up diesels, the IP can pull fuel at idle sufficiently so no performance issues are notable. But at speed, the IP can't pull enough fuel to avoid engine fuel starvation.

Stretch · 02-03-2006, 11:37 AM

Hi Mike:
Well I know the QD generator has an electric pump, cause I ca hear it running. I dont know if the injector pump has a mechanical pump also. But my system is getting air somewhere, In other words the line should be ful of fuel all the time. It is not, cause the engine wont start. If its not fuel in the line, what is it. got to be air,,,,,,,,,,

EngineerMike · 02-03-2006, 03:35 PM

Stretch- Its two different things to have air because of leak-back to the tank, and to have air because the line or fittings leak. The former you can solve w/a search & destroy effort following the line; the latter takes a different tactic (I'd start w/a complete one-line diagram for the gen fuel system, then stare at it till thought I had all possible failure causes listed, then attack them based on cheap & easy first).

Stretch · 02-03-2006, 08:01 PM

I will respectfully disagree. There is no way for the fuel to leak back into the tank UNLESS there is air getting into the lines somewhere. A vacuum is what keeps the fuel line full. If air gets in.....no vacuum...then the fuel can leak back to the tank. But where is the leak? I cannot find it. Perhaps it is a defective component in the fuel system leading up to the injector pump? I am stumped.

SteveS · 02-04-2006, 04:33 PM

I'd bet the feed line between the pump and the tank or input side of the pump has a slight leak. If it is very slight, you might not notice fuel but after there is enough time for it to settle, it could slowly return to the tank whild 'sucking' air in the line to replace the fuel. If it is very slow there would not be enough time for much fuel to return to the tank when the gen is turned off for a short time. Setting days would allow time for enough air to enter.