Hi all, I am new to the board but looks like my answere might be here. I have an 83 motor home with a 351w. I pull a little jeep withit almost any where I go. It has worked well for me until recently. Last Thursday, the temp here was 105 degrees I headed out going through Fort Collins to Red feathers which is about 7500 ft altitude. I ran the A/C from Greeley through Fort Collins. It started acting like it was going to vapor lock after the stop and go traffic and it just got worse as I climbed in altitude. At some points it was all I could do to keep it running at 5 mph. The curious thing is that there was a strong smell of fuel keep in mind that once it started acting up I had to keep pumping the pedal to keep it running. This has never happened before and it did act up a little as I was coming home today. Temp was abou 97 and I was coming down in altitude. The real funny thing is that the water temp never went above "A" on the gauge. Any ideas would be a great help as I am heading toward Yellowstone in 2 weeks and don't really have time to play with it much. Every thing is in stock configuration.

 

I would start with the obvious and change the fuel filter. The fuel pump would be next. When you change the filter, knock it on a piece of wood and see how much rust is in it. If it seems like alot, keep an eye on it, and check it again. You may have a rusty fuel tank clogging things up. I bet it would be easy for that to happen if it sets around most of the year not being run.

 

Thanks for the reply Dave, I replaced the fuel filter. It didn't look to bad. I will try the pump. Does rerouting the line do any good and I also thought about an electric pump.

 

I thought about re-routing the fuel line, but if it's factory stock, it should be ok. Now if you have modified the exhaust or anything else you can think of that would create more heat, then by all means insulate or re-route the fuel line. Bascially you will only have to worry about vapor lock on the suction side of the pump. And a electric fuel pump would help if nothing else does, since you can mount it near the fuel tank, and it will push the fuel all the way up front, which will help it if it is vapor locking.

 

"the temp here was 105 degrees I headed out going through Fort Collins to Red feathers which is about 7500 ft altitude"

There's the most likely answer right there.
7500 feet is up there a ways, and if its running a little rich to begin with???

As you climb in altitude, the air gets thinner.
As the temp rises, the air also gets thinner.
Combine the two and your carb is in for trouble!

On a truck with EFI the FUEL INJECTION system adjusts fairly well for the thinner air and has a fuel return line to cycle the fuel to the tank preventing vapor lock.
The carbureted models do not, and tend to run WAY TOO RICH in the thinner air, not to mention the fuel sits there in the line heating up on its way to the carb, and liquids boil at a lower temp the higher your altitude gets anyway.

I fixed up a truck and sold it to a guy and when he got home, it would not start again, boy was he pissed!
Called me up yelling that I sold him a lemon!
Then he wanted me to drive up to Arrowhead from long beach and fix it?

ARROWHEAD!

It was jetted and the choke was adjusted perfect for SEA LEVEL, not way the heck up in the clouds in Arrowhead.
He got a local mechanic who confirmed this and helped him out, but he was not happy as it was supposed to be his commute to LA three times a week to do some pick up and delivery work.

Perhaps they found a half way adjustment/solution.

I have flown out of some small "HIGH ALTITUDE" airports that once it heats up, you cant get off the ground loaded well enough to do it safely, if at all!

 

I've got an '82 motorhome with a 460 - same thing happened to me last weekend (July 6th). Going through Ogden, Utah (~4500' elevation, maybe 90 in the shade), the rig was running good until I pulled off for gas (a fairly frequent duty with these land yachts). It stalled at the bottom of the off-ramp, at the stop light, and barely chugged into the gas station. It pulled out of the station alright (with much pedal pumping and mild swearing), and I proceeded to Evanston, WY (~6400') with no problems other than a pronouced gas smell coming through the open windows. That went away once I got into cooler air to the east.

This rig has electric fuel pumps and a hot fuel return, so I don't think the fuel line is the problem. I figure the fuel might have tried to boil in the carb bowls since the engine bay was so hot. Like Jeep71, the cooling system temperature was never outrageously high.

It's got a Carter carb that a previous owner installed. I would bet it's jetting is straight out of the box (i.e. sea level), so it's likely far too rich for Wyoming high desert. Maybe the unburned fuel in the exhaust was drawn back in to the open windows, since the A/C was turned off for the long haul up the mountains.

 

I am going to try something a guy here in Denver at Dan's Corner Garage told me they do. They put a tee in the line as close to the tank as possible. Then run another fuel line from there to the carb. Again put a tee in the line as close to the carb as you can. Leave the stock fuel system alone. In the new line as close to the tee by the tank add an electric pump and when you have trouble hit the switch for the electric. I had some questions about this but he claimed they installed this system on vehicles all the time for the same problem. I put it all together and will give it a shot. This motor home has been in the Greeley area and used in the mountains in the area all its life so I beleive the jetting and such should be good for the altitude. A couple weeks earlier and about 20 degrees cooler we headed over Isenhaur pass and it ran great all the way. I will post findings on the extra fuel line as I am headed to Yellowstone next weekend.

 

Cycling the fuel around, using the fuel line as a radiator to dump heat while the stock pump keep's going?

But it should drop your fuel pressure and if you run it too long the carb might get low on fuel and that's not good either.

You should put a pressure regulator at the carb that has a fuel return, and bring that back to your fuel tank (I did it once and added a return line real low and the internal portion was pointing down towards the tank in a fuel filler neck) so to cycle the fuel and keep it cool.

 

Just got back from a 2550 mile camper cruise with Clyde. Two years ago we did basically the same trip: MN, IA, NE, KS, CO and back ... the trip from hell! Headwinds both ways!! Overheated constantly, couldn't use AC, vapor locked in Grand Island, NE on a 110* day.

This year with new 4-core radiator, rebuilt carb, recurved distributor, recharged AC ... AND ... an insulated fuel line we had no problems! We still had headwinds though.

After the trip from hell I was talking to a Ford mechanic and he said there was a recall on vapor locking and Ford had sent out a recall kit that was essentially some thin and shiny thermal insulation material that snapped (literally) around the fuel line on top of the engine. He had a couple left over in his tool box (from the late 80's no less) and I installed them both, covering everything from the carb to half-way down the block. No problem this year and we ran again in the +100*s.

My two problems this year were minor in comparison. My AC kept freezing up and the fuel in my front tank was BOILING!! in the tank on more than one occassion. I dealt with the fuel by using the front tank first while it was still cool from the underground storage tank. At 6-7 mpg it never really heated as bad as if I used the rear first as I usually have. Will have to look at insulation or shielding ... kinda scary to hear hissing from a boiling gasoline tank!!!

 

Hi all,

I've also got an 82 e350 with 460 motorhome.

I have never had any of these problems but my trips are only 100 miles one way so far.

How do I know if I have this cool fuel return? I know mine has a mechanical fuel pump but it might have an electric pump as well? Are they in the tanks or on the frame?

Can anyone explain this system?

TIA

Dave

 

Dave98 - near as I can tell, I have an electric fuel pump in each tank. No mechanical pump in sight, although the fuel lines go through the same area a mechanical pump would occupy. To tell if you have the fuel return setup, there is a tee in the fuel line on top of the motor. Mine is about 18" away from the carb. It has an inlet and two outlets, and looks like a fuel filter (that's why I took it out once - my real fuel filter is along the frame about midway back to the fuel tanks). If you trace the fuel lines back to the tank, there is a big can with lots of fuel lines and wires that is your tank selector switch. This switches the fuel tank feed and also shifts the fuel return - so you don't drain one tank into the other while you're going down the road.

Let me know if that's the system you have. The fuel return tee has a little brass screen in it that can get plugged, as well as a spring check valve to allow only some of the fuel to recirc back to the fuel tanks.

 

Ok, I'm going to check it out this weekend when I do my radiator (motorhome is in storage lot now)

I don't think I have the cold fuel or electric pumps (bummer)

I know I have a mechanical pump (or at least looks like a mechanical pump)

Maybe I've got the old system.

Thanks Again

Dave

 

Had similar problem with 1982 F-250 with same engine. To make a long story short, I finally after trying different cures ended up installing an electric fuel pump . Replaced the manual pump twice, replaced fuel filter and rubber hoses on both tanks and coil and ignition module. This cured the problem. Have heard that vapor lock is very rare now days with the new gasoline as it has a higher boiling point than the older gas of the 1960's. My problem was intermittent and would happen either going up hill or down.