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Old 01-25-2006, 03:16 PM   #15
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Quote:
Originally Posted by guy99
I have a hard time seeing why a weak fuel pump won't cause other symptoms of fuel starvation.

If the floats are sticking, why do they unstick and why don't they ever stick except when the MH has been parked overnight?

I wasn't implying at all that the problem was not caused by the fuel pump. It certainly sounds like that's probable. I was simply relaying that there has been a problem with some carbs with the floats getting "saturated" (talking about plastic floats in particular) while they sit, and then causing the fuel shut-off symptoms. When that does happen, the floats typically will work correctly once they get freed up during the running of the engine. I'm not an expert on carbs, just relaying an experience that happened to me, and had similar symptoms to what our friend is having. A weak or erratic fuel pump certainly would be my first suspicion.
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Old 01-25-2006, 04:21 PM   #16
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A weak fuel pump will cause these problems. It allows the fuel to drain back to the tank when not running and then has a hard time repriming itself. When the engine calls for more power it can't supply the fuel fast enough. I am not sure what type pump your unit has, but if it is a diaphram type, a small pin hole in the diaphram would cause this.
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Old 01-25-2006, 06:26 PM   #17
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Weak Fuel pump

Jim,

Thanks for your posts. I'd really like to figure this out.

I follow how this might cause my morning hard/non start problem. But I am not having any other fuel starvation symptoms. Maybe the defect is small enough that it's not showing up when the engine is running?

Guy
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Old 01-25-2006, 06:31 PM   #18
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Quote:
Originally Posted by noiva
I wasn't implying at all that the problem was not caused by the fuel pump. It certainly sounds like that's probable. I was simply relaying that there has been a problem with some carbs with the floats getting "saturated" (talking about plastic floats in particular) while they sit, and then causing the fuel shut-off symptoms. When that does happen, the floats typically will work correctly once they get freed up during the running of the engine. I'm not an expert on carbs, just relaying an experience that happened to me, and had similar symptoms to what our friend is having. A weak or erratic fuel pump certainly would be my first suspicion.
Tim,
Thanks for your posts. I'd really like to figure this out but I'm having trouble following. If the float was "saturated" wouldn't it sink and fail to shut of fuel flow when the float chamber was full? Seems like this should cause flooding, not starvation, if I understand correctly.
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Old 01-25-2006, 07:02 PM   #19
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Quote:
Originally Posted by guy99
Tim,
Thanks for your posts. I'd really like to figure this out but I'm having trouble following. If the float was "saturated" wouldn't it sink and fail to shut of fuel flow when the float chamber was full? Seems like this should cause flooding, not starvation, if I understand correctly.
You're correct, of course. In my haste to get a message written that could possibly help you I didn't explain this problem intelligently at all , sorry. There are really 2 conditions I've seen (rarely) that have affected the operation of carbs on my vehicles in the past. The first is "saturated" floats, which you have correctly observed cause the vehicle to flood. Since you're NOT smelling gas, that's definitely not your problem. After going back over your posts more carefully , I should have written about the remote possibility (which I've experienced once) of the floats sticking in the "up" position, which cut off the gas even though there was none in the carb bowl. THAT is the only way this float thing could be affecting you. I really apologize for not reading more carefully, and causing this confusion. I've appreciated and gotten valuable info from your posts, and certainly didn't mean to cause any more problems for you. In the future I'll be more careful to read fully, and not comment unless I can do a better job than I did on the "saturated" float entry. Please let us know what you finally discover. I am concerned, and have good intentions in spite of that very poor post .

Tim
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Old 01-25-2006, 07:12 PM   #20
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Guy, I think you are fairly close to solving this, I would definitely follow the trail on the fuel pump(s) now. I have seen symptoms you are describing on two previous automobiles I have owned, both were due to weak valves in the fuel pump allowing the fuel to drain back to the tank. In the case of a motorhome it is a VERY long run back to the tank, so it makes sense it would be very difficult to get the pump to prime.

Not sure of your exact setup, i.e. if you have a pump at the engine and a pump back on the chassis, it is entirely possible that if you have both, one has failed entirely and the other is just managing to provide enough fuel to keep you going. The suggestion to check fuel pressure, and whether it leaks down is absolutely right, although at this point if there are doubts as to the condition of the mechanical pump on the engine I'd be tempted to change it out immediately - one less variable to worry about.

Incidentally, weak fuel pump valves often exhibit this kind of behavior, leak down of the fuel overnight but able to provide enough flow once the engine is actually running. One of the tricks to get mobile if you have the problem is what you already have discovered - cautious use of starting fluid or small amounts of fuel into the carb to get the engine to start, often then it will keep running as the pump will pull enough fuel at the rpm's the engine is turning when running (as opposed to the very low rpm's it turns on the starter) Such an appoach is suitable to get you home
but you'll still need to replace the offending pump.

Good luck, sounds like you are much closer to home now anyway.
John
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Old 01-25-2006, 07:31 PM   #21
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Could be fuel leaking out of the bowl overnight (time for a carb rebuild) or your mechanical pump is not drawing enough from the tank to crank. I can't remember if the 310's have an aux electric pump on them. I know the longer coaches do which basically act as a "pre-pump" to get fuel pressure up to the mechanical pump.

If you do have an electric boost pump double check the filter between it and the mechanical pump. Also check to see if the electric pump is coming on and pumping fuel (you can remove a line into a bowl and have someone turn the iginition to "ON". Also check the vent on the fuel tank for a blockage.

If you don't have an electric boost pump, make sure there are no leaks in the flex lines or connection. Also check for old rubber fuel line as it can collapse under suction.

You hard starting in the morning could also be related to failing oil control seals on your valves or worn valve guides letting oil down into cylinders overnight. Makes for a hard start, runs rough (puffs of white smoke from the tailpipe) then clears up and runs all day long.

Pull a plug or two in the morning and check for oil. Run the engine, then check it again. If the oil is gone and it starts right up you might have your source.
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Old 01-25-2006, 08:22 PM   #22
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My 310 does have two pumps

I can hear the rear (electric) pump come on when I turn the key.

Where is the front pump and how hard to replace?
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Old 01-25-2006, 08:57 PM   #23
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Quote:
Originally Posted by guy99
I can hear the rear (electric) pump come on when I turn the key.

Where is the front pump and how hard to replace?
At great risk , I'm going to tell you that on my last 454 Chevy engine it was on the lower right front of the engine. Held on with 2 bolts. Unscrew the fuel line, then the two bolts. The pump has a gasket against the lower block. Fairly simple to do, IF you can get under your MoHo. BE VERY SURE THE ROD THAT IS IN THE BLOCK IS FULLY UP INSIDE WHEN YOU PUT A NEW PUMP ON. Sounds basic, but I actually bent one of those 20 years ago - so badly it couldn't be removed. Anyway, just reverse the process to mount the new pump.
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Old 01-25-2006, 11:26 PM   #24
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Tim is right on the money about the pump. There is not a lot of access to it in the P30 (from below or through the passenger fender well).

There are three hoses on it, the supply, the feed and the return. In my case, getting the old hoses off took longer than removing the pump due to access contraints. Obviously this would be a good time to replace those hoses.

Getting the pushrod in the right place takes some patience. After I replaced mine I read a post about using some grease to "hold" the rod up in the engine on the cam to make the installation easier.

Before you go too far, check those plugs in the morning. They may tell the tale (lean, rich, oily, perfect, etc).
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Old 01-26-2006, 08:06 PM   #25
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Update

Well, its not the fuel pump. Unless they fix themselves.

Last night we stayed at Doc's RV Park and Service Center in Las Cruces, NM. Rather than crawl around in the gravel and goat heads hoping they wouldn't notice, I decided to have them replace the fuel pump. When I described the symptoms, they didn't think it was a fuel pump. So I had them come to my site to witness the problem. Pulled off the dog house, took the top off of the air cleaner and sat down in the driver seat. I pushed the accelerator to the floor once and released it. Then I turned the key, almost immediately the engine fired and died. Second try, it started right up and ran normally. The mechanic and I looked at each other and scratched our heads. I said that since it wasn't failing and he didn't think the symptoms sounded like a fuel pump I'd just be on my way.

My wife pointed out that it hadn't been very cold over night (high 40s) unlike the nights when we did have a problem (low 30s). Maybe that has something to do with it.

We headed out and drove the rest of the day without incident. Tonight we're in Gila Bend, AZ. Will see what happens tomorrow morning.
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Old 01-26-2006, 09:58 PM   #26
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The Choke.

The choke plate may be sticking open, or partly open. This will cause it to not want to start and stay running first thing in the morning, and it will be worse if it is cold out, as the engine needs the choke almost completely closed to run when cold. fter it is warm, the choke could be hanging partly closed, causing it to run rich, and start to stutter and belch black smoke.
It could be that the choke is stuck in one position, too lean to start when cold, and too rich to run good when hot.
In the morining, before you stsart the engine, push the gas pedal down once, release it, and observe the choke plate position. It should be almost entirely closed, with only a few thousandths of an inch opening. After it starts, the choke plate should open up slightly, if it doesn't, you have a bad choke pull-off. If the choke doesn't move at all , you may have a bad choke thermostat, or the electrical stove is not getting power. If you have a mechanical in stead of electrical unit, you should see a small pipe running from the intake manifold to the rear of the choke thermostat housing. If this is not connected, or is broken, you will also have these problems.
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Old 01-27-2006, 07:14 AM   #27
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Me thinks Terry is going to win the prize on this one.
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Old 01-27-2006, 08:11 AM   #28
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Agree

Quote:
Originally Posted by swebster
Me thinks Terry is going to win the prize on this one.
I agree with Terry and SWebster. I had a Honda motorcycle years ago with exactly the same symptoms - and a broken manual choke. Fixed the choke, cured the problem.

Tin Lizzie
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