From: John De Armond
Subject: Re: 92 bounder generator fuel pickup problem
Date: Mon, 12 May 2008 04:35:07 -0400
On Sun, 11 May 2008 22:28:05 -0700, "Barry Streets" <firstname.lastname@example.org>
>Thanks to all for all of the good idea's, I run the engine in the generator,
>and the main engine every two weeks while its parked. I've had this RV for
>about 9 years, and never had a problem. I forgot to add that execpt for the
>hose between the tank and the line all other hose's have been replaced. I
>also replaced the fuel filter and fuel pump. This seem to make things
>somewhat better. Now it takes almost an hour before I start losing fuel
>flow. I'm not lookig forward to dropping the tank to replace the one hose.
>I will let everyone know how it turns after I drop the tank and replace all
>of the rubber lines. This will be in three weeks when I have a short break
>from my volunteer work. ( I am a corner worker for several race tracks)
Before you start changing parts willy-nilly, might I suggest that you narrow
the problem down a bit more? The very act of removing and replacing all that
hardware could make an obstruction-related problem go away. Temporarily, of
The problem is repeatable, though after a fairly long delay, so pinpointing
the problem should be easy.
Knowing only what you've reported about your system, my approach would be to
install a fuel pressure gauge between the electric pump and the carb, a
compound pressure/vac gauge before the electric fuel pump and perhaps a
voltmeter on the pump's supply. These gauges, made for such troubleshooting,
are quite inexpensive. K&D is the brand I have but the brand doesn't really
matter that much.
Run the generator until it acts up while observing the gauges. If you don't
want to sit there and watch them for an hour, set up your camcorder and
position the gauges where they're all visible at the same time to the camera.
A camcorder is a most powerful diagnostic tool for time-related problems.
If you see the pressure decrease AND the suction pressure develop much of a
vacuum then either the supply hose is collapsing or the gas tank has
insufficient venting. A third rather remote possibility is something solid in
the tank that gets sucked onto the generator feed tube inside the fuel tank,
stopping it up. I've seen that happen with a car exactly once. I suspect
that someone pranked the customer by stuffing some cello wrap into his tank.
If the pressure drops but the suction pressure remains nearly at zero then it
is time to suspect the fuel pump itself. Having a voltmeter attached will
tell you whether it's the pump itself or if the pump is losing power for some
If both pressures remain normal then disassemble and closely inspect the fuel
system from the pump to the float bowl. Look for bits of rubber or other
debris that can collect and clog the small passage leading to the float valve
inside the carburetor. If the carb has a banjo fuel inlet fitting, take that
apart and look at the small holes for clogs. More than once I've seen
relatively long narrow strips of rubber shed from the hose gather and clog the
One last thought regarding the fuel filter. Is it metal or plastic? I like
the clear plastic bodied filters because I can see inside to see if debris are
clogging it up. I've cut more than one metal-bodied fuel filter open after
pin-pointing it as the problem, to find manufacturing debris inside that would
get sucked up to block the outlet tube.
The filter that I use on my small engines is a Fram G2 (marked G2DP on the
package reverse), available at Wallyworld for a few bux. I normally would not
recommend ANYTHING Fram but in this case, it looks just like the AC Delco
counterpart. I suspect that it's made by AC and private labeled for Fram.
Interestingly enough, the filter itself is made in Israel. Sourcing it from
Wallyworld means that I can get a replacement any time, anywhere.
From: John De Armond
Subject: Re: 92 bounder generator fuel pickup problem
Date: Wed, 14 May 2008 00:26:13 -0400
On Tue, 13 May 2008 18:10:02 -0700, "Barry Streets" <email@example.com>
>Status so far
>I've replaced fuel pump, filters and all rubber lines I could get to. There
>are clear see thru filters on both the input and output of the new pump.
>When I start and run the generator 30% loaded I can see that the fuel flow
>to the input filter tapers off. If I disconnect the hose its dry and no fuel
>flow at all. (Normally fuel flows very well)
>My second test after waiting 15 minutes was to leave the gas cap off and
>cover the open filler with a rag to keep dirt and things fron gettinto the
>tank. Same results.
>So I believe all that left is the hoses to the tank, or something inside the
>tank. And since the hoses are 16 years old its a good idea to replace all of
>them while I have the tank down
>Thanks everyone for all of the good suggestions and I'll report back once I
>get the tank low enough on fuel to lower it down.
That kinda sounds like a combination of collapsing fuel hose and partially
blocked pickup element in the tank. Usually if the hose collapses by itself
enough to completely kill the engine, it'll stay that way and the engine won't
restart. What this sounds like is something blocking the inlet tube in your
gas tank enough that the fuel pump creates enough vacuum to collapse an
already weak hose. When the engine stops, the hose relaxes slowly and the
line refills with fuel, ready for the next round.
A fuel pressure/vacuum gauge at the tank would tell the tale for sure.
Something that you can try to diagnose a stopped up pickup is to remove the
hose from the gas tank and GENTLY blow some compressed air back through the
line. By gentle, I mean only a few psi. If you use a blow gun, hold it back
away from the opening an inch If there is crud clogging the screen, this will
blow it away from the screen, hopefully to settle to the bottom of the tank.
It's possible that the screen is corroded enough that the clog is fixed in
place and can't be blown away. In that event you'll have to look inside the
The generator fuel pickup can vary. On my older rig, the gas tank has a
fitting (probably silver-soldered) attached to the side of the tank about a
quarter of the way up the side. No internal pickup at all. I can shine a
light in and see the other side of the tank.
Others that I've worked on, primarily later model rigs, have the generator
pickup as part of the integrated pump/level gauge/main pickup assembly that
inserts into the tank as one assembly. This is the kind that requires you to
either cut a hole in the floor of rig or drop the tank to access it. That is,
unless you're REALLY lucky and the mfr included an access hatch.
If blowing on the pickup line clears things out then you'll need to think
about cleaning and flushing the gas tank. That can range from fairly easy to
very difficult, depending on the tank design and whether it has a drain plug
in the bottom.
If I were working on your rig I'd drop one of my little color lipstick video
cameras down the fuel filler and look around inside the tank. These little
cameras are very cheap now and most are self-illuminating. If I saw rust then
I'd drain the tank and haul it down to the radiator shop to have it boiled
out. I might also coat the inside of the tank with a gas tank coating
designed to seal the metal to prevent future rust. Standard auto parts store
If the metal is not rusty but there is gunk in the bottom then I'd mostly
drain the tank down to the level of the gunk, add a few bottles of Tecron
cleaner and lacquer thinner and let it sit for a day or two. Then, fueling
the engine from a portable tank (outboard motor tank, for instance), I'd drive
around a bit to slosh the mix. Drain the tank and flush with clean gas and
I've used this technique several times on classic cars to clean out gunk and
varnish from old fuel being allowed to sit and dry up. It works quite well.
If the tank doesn't have a drain plug then I'd pump out as much gas as I could
and then take the thing to the radiator shop and let them worry about getting
the last bit of fuel out before boiling out the tank.