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Old 07-15-2004, 01:52 PM   #1
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fuel problem

getting air in the fuel line from the tank. is there AN INSPECTION PLATE UNDER THE REAR BED TO ACCESS THE PICK UP TUBE AND THE SENDING UNIT FROM INSIDE THE COACH?
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Old 07-15-2004, 02:33 PM   #2
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Shinola345,
Welcome to the forum! As far as I know (and I've had the bed out) there isn't a hole in the floor over the tank - but I've not pulled up the carpet or removed the water tank back there yet.

When you say "air in the fuel" how do you know this? I'm not questioning your troubleshooting just trying to help as I've chased down a fair number of fuel issues on my 345.

Clogged filters are a common issue on the 345 (there are three to clog) along with the electric fuel pump in the rear. Let me know if I can help.

PS - We vacation every summer in Rye Beach, NH in our 345.
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Old 07-15-2004, 04:00 PM   #3
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No inspection plate. You have to drop the tank. If you drop the tank, take the time to reseal all plugs, and cover, at top of tank to avoid future gas odor/leak, it will eventually happen. Also replace the "rubber" fuel hose with fresh hose. Be sure you carefully insert/not jam the float level upon reinstall. Or you will, like me , have to drop the tank a second time to free it.
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Old 07-15-2004, 06:12 PM   #4
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Air? I pulled the gas line from the carb. conncected a 1/2" clear ply hose 30' foot long and ran it out the window to the gas cap. First cranked it over Air passed through the line. Then hot wired the Electric pump ,key off and ran the pump for 5 min's and again air passing in the line. I read all of your past fuel problems and will now check other places where it my be comming in. She runs out of fuel when the demand is high, 55 to 65mph or about 3,000 constant rpm's. Let up on the gas and she is good to go another few miles. I'm on the ground also, but it's 75 today.
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Old 07-15-2004, 06:56 PM   #5
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I have not experienced it but others have. In the vintage of MH you have there was a flaw in the fuel system. The electric pump could not with where it is located draw the fuel all the way from the rear tank to the carb. An additional electric fuel pump mounted near the tank will help this tremendously.

One of the things that you really need to verify is if all of the fuel filters have good gaskets. With the suction that the current fuel pump is making to draw the fuel the bulk of the system is under a vacuum, not under pressure.
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Old 07-15-2004, 07:05 PM   #6
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First.....

Quote:
Originally Posted by shinola345
....She runs out of fuel when the demand is high, 55 to 65mph or about 3,000 constant rpm's. Let up on the gas and she is good to go another few miles. I'm on the ground also, but it's 75 today.
Fairly classic rear electric fuel pump problem......

If you don't already have an electric fuel pump just forward of the fuel tank (external, not internal)...you need to get one, as Brett G indicated. The 345 chassis is just too long to suck the gas all that distance......also, if there are any age cracks in the line (there probably are), air is easily drawn in through the cracks, displacing the gas.

If a rear electric fuel pump is already installed......

I would first try to disconnect the outlet of the electric fuel pump, and then again hotwire the rear fuel pump....the electric pump is located just forward of the fuel tank. There should be a fuel filter located just to the inlet of the pump....The output of the pump would indicate if your problem is upstream or downstream of the pump......also, there should be a pressure bypass in the mechanical fuel pump - the second line takes the excess gas back to the tank - the internal pressure regulator could have failed "open"...sending almost all of the gas back to the tank.

Some of the 345's have an oil pressure permit switch to prevent the rear electric fuel pump without the engine being on.....some don't. If yours does....a failure in the swtch could manifest itself as you had described above.

Keep the forum up to date with your successes and failures...
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Old 07-15-2004, 08:47 PM   #7
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87mh ,swebster And Others. Fuel Problem

THANKS FOR ALL YOUR HELP. The electric pump is wired to the oil pressure sendind unit. ALL OF A SUDDEN I HAVE NO POWER TO THE PUMP. PERHAPS I DO HAVE A FAULTY SENDING UNIT AND BAD FUEL LINES. THESE WILL BE CHECKED OUT AND REPLACED IN THE AM. IS THERE ANY WAY THE PICK UP TUBE COULD BE FLOATING IN THE TANK ?
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Old 07-15-2004, 10:30 PM   #8
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The pickup is the same piece of tube inside and outside of the tank. The float is hooked to it so if your gas gauge is working the pickup is probably ok.

John
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Old 07-15-2004, 10:45 PM   #9
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I think Dennis is on the money. Start at the rear fuel pump and test for air. Move forward through the regulator..then into the hard lines. There is a secret fuel filter located on the inside frame rail (pass side) right behind the battery locker. Replace your hoses and filters as you go. I've heard of old fuel hose collapsing under suction causing poor fuel delivery. I ended up replacing the electric pump, hoses, filters, mechnical pump and rebuilding the carb before it was over. Now I get too much fuel to the engine (still running rich) but she runs to 70 MPH and can climb hills again.

You'll find it and chances are it'll be something simple.
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Old 07-16-2004, 08:25 AM   #10
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Tank was out in the summer of 02 because of a leaking fuel line at the top of the tank. The shop did not clean the tank so it still had rust in it. Later that year I pulled the drain plug, emptied the fuel and ran a garden hose for over an hour flushing the tank. Reversed my vacume and ran it for an hour or more to dry it out.
Installed a water seperator filter just outside the tank to pick up any big chuncks left behind then to an, inline clear, filter then to the electric pump and on to the the next filter by the steps.
The plot thickens. Last year my gage stoped working shows full . The generator also would not start, no fuel. I ran a new line off the water seprator and is't been OK .I do keep in mind I could run it too low and be stuck.
When testing the pumps with a clear poly line off the carb to the filler neck , air shows in the first clear filter as well as in the entire line. Could be a bad hose up stream to the pick up on top of the tank, I hope not ! I have a full tank I'll check all the lines again and by pass the all the filters and go to the tank dirrect to check for air.
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Old 07-16-2004, 08:32 AM   #11
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Whatever it is please report back for us. More than a few of us have chased down fuel delivery issues. It would be great if you could add your experience to the forum.
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Old 07-16-2004, 08:36 AM   #12
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I would replace every peice of rubber line on it. Ruber gas line has a nasty habit of having the inside surface start to come off in flakes. The flake will act like a valve and cut the flow off on the line.

A little bubbling in the line from airation by the pump is not a big deal as long as it has a good flow. When it hits the carb the air will leave via the vent and the gas will sit in the bowl. Now airaiting from a line on the suction side of the pump pulling air is only going to get worse.

Now from experiance change the filters including the one IN the carb. I have had simular problems on several older GM vehicles with Quadrajets. Crud and sediment in the tank breaks up and plugs the filters.

I have had two old 4x4 that after some rought trails and all the fuel sloshing this happen. At one point I was changing filters ever 3-4 days. A few $1.25 filters in the carb is sure a lot less hassle then dropping the tank. after about 3 months I never had a problem again. I just started changing the filter ever other oil change.
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Old 07-16-2004, 01:23 PM   #13
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What a great forum," What a country"
Foud "3" COUNT EM (3) ! BAD LINES, ALL IN AND OUT OF THE FILTERS. BY PASSED ALL FILTERS AND THE LINE CLEARED UP. THIS WAS AFTER JUST B/4 I STARTED TO SIZE UP THE INSPECTION HOLE I WAS GOING TO CUT UNDER THE BED TO GET TO THE PICK TUBE. THOUGHT IT MAY BE LEAKING AS WELL.
LINE IS CLEAR UNDER ELECTRIC OPPERATION, HOWEVER WHEN I ADD CRANKING POWER TO THE SYSTEM ,TURNING THE MOTOR OVER , AIR REAPEARS IN THE LINE ? I COULD BE PULLING AIR FORM THE RETURN LINE AT THIS POINT AND AS STATED THE VENT IN THE CARB MAY TAKE CARE OF THIS.

MY NEXT PROJECT IS FIND OUT WHY THERE IS NO POWER GOING TO THE ELECTRIC PUMP ANYMORE. WHEN I FIRST STARTED LOOKING INTO THE PROBLEM I COULD HEAR THE OIL SENDING TRIP THE PUMP AND THEN SHUT DOWN. I PUT A TROUBLE LIGHT ON THE HOT SIDE OF THE PUMP TO LOOK FOR POWER AND IT LIT AS THE KEY WAS TURNED ON THEN WENT OUT. AT THIS POINT I HAVE NO POWER TO THE PUIMP I'LL START AT THE PRESSURE SWICH ON THE OIL SENDING UNIT AND WORK BACK.

AS SOON AS THIS IS CORRECTED I'LL CLOSE THE DOOR , GET ON THE ROAD, AND KICK HER IN THE ASS AND SEE WHAT HAPPENS.

THANKS TO EVERYONE FOR YOUR HELP. WITH OUT ALL THE RESPONCES I WOULD NOT HAVE LEARNED AS MUCH. AND WOULD MOST LIKELY BE ON THE SIDE OF THE ROAD WITH A SHOT GUN IN MY MOUTH ,TRYING TO REACH THE TRIGGER WITH MY BIG TOE. OR EVEN WORSE TAKEN HER TO THE SHOP FOR REPAIR.
THANKS AGAIN... IF ANY OF YOU ARE IN NH OR MAINE ... THE LOBSTER IS ON ME..
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Old 07-16-2004, 04:40 PM   #14
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Lobster! I'm there!

Some of the 345's seem to have the oil pressure cutout and some don't. Mine does not...it's wired to the ignition on. 87MH has also spent some time back there fixing this wiring. Not having that pump on will cause fuel starvation on climbs and under load...just too much distance between the tank and that carb for the mechnical to work.

I often have "air" in the line when I first crank the engine. I've read on this forum that the QJet's will let the fuel back into the line and empty te bowl. You may want to consider an inline fuel pressure gauge from Jegs or Summit Racing. I think they are under $30 for a 15 psi gauge. It would certainly let you know what the carb was getting for pressure.
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