RV won't start. Possible vapor lock. Help needed!

[SyrenSkywolf]

Sunday we were moving to another campground, and as much as I hated it, we had to do it in 90 degree weather, 15 highway miles, and then 12 miles at 30mph. In that 12 miles at 30mph, we had to stop twice to let the motorhome cool down, which I somewhat expected but hoped against. The first stop was for about 1 1/2 hours, the second was for an hour. The motorhome started up both times.

The last mile or so was somewhat slower than that (dirt back road), plus the time it took to cruise around the campground looking for a decent spot. It stayed running long enough to get into the site, but was running pretty hot. Yesterday and today I tried starting it up, with absolutely no luck. It doesn't look like any fuel is making it into the carburetor, so it seems like it might be vapor lock, but wanted opinions on this.

If it IS vapor lock, what can I do to get it running for now? I can remedy the situation later to try and prevent it from happening again, but for now I want to know it will run and we will actually be able to get it out of the campground. It is a backwoods federal campground, so getting it hauled out is an iffy subject. Details would be definitely beneficial if you know where stuff would be located, as I don't know the engine compartment of the mh very well yet.

It is a 1978 Tioga with a Dodge 440. Thanks guys!

[Dave78Chief]

Quote:

Yesterday and today I tried starting it up, with absolutely no luck. It doesn't look like any fuel is making it into the carburetor, so it seems like it might be vapor lock, but wanted opinions on this.

In order to be vapor lock (Yesterday and today), the engine would have had to be running in order for the fuel lines to get hot enough. Once they cooled down. the fuel condenses back to a liquid state. Possible causes:

1. Dirty Fuel filter.
2. Bad Fuel Pump.
3. Dryed/cracked rubber fuel line at tank (fuel pump sucking air vs gas)
4. Fuel tank pickup sock clogged up.

You can get starting fluid at a auto supply to see if it really is a fuel related problem. You spray a 2 second burst down the carb then try to crank the engine. Ifit starts then dies it is a fuel related problem.

Dave

[Jim-in-Hope]

This doesn't sound like vapor lock if you have had the coach in hot climates before and did not experience the problem. I would suspect that you have a bad / crached coil. They get hot then fail and when they cool down (1 to2 hrs.) they work find. Look under the hood in the dark and see if there are sparks jumping around.

Jim

[wa8yxm]

How old is your rig (Don't bother answering me as I'll explain)

What is vapor lock?

Vapor lock is when the fuel in the line from the tank to the pump gets hot enough to vaporize and the pump is thus "Sucking fumes" instead of liquid fuel.

Why is age of vehicle important? Modern vehicles the fuel pump is usually an electric pump that is INSIDE the fuel tank, drown in liquid fuel, and thus vapor lock is IMPOSSIVLE,, IN addition there is a circulaiton line (Since this pump pumps way more than the engine needs) that circulates excess gas back to the tank if the fuel in the lines vaporizes the pump will continue to pump liquid into the line as the vapor is sent back to the tank, so the engine will always have a supply of LIQUID gas.

Older engines the fuel pump was often mounted on the engine, driven by the cam shaft, and thus.... Vapor lock was a possibility.

Other issues I HAVE SEEN with my own eyes. (Other than the ones listed in someone else's post)

On a older (ENgine mounted pump) car the fuel line from the tank to the pump had "Gotten religion" (Very HOLY or is that Holey, it had become) and thus the pump was sucking genuine AIR... I found it when I disconnected the fuel line from the carb and shived it into a glass (Genuine glass glass, gasoline proof) cranked the engine and got a dribble of gas but lots of "Blow" (Air) Replaced the fuel line and VARROOM!

[wayneew1]

ck fuel filter you man have 2 filter 1 at carb on fram by driver side
how hot did you get it

[GOLDWINGER2]

My '76 Dodge chassis Class C had the second filter on the frame on the passenger side. It also had old air sucking hoses. Once all hoses and filters were changed everything was lovely.
J

[SyrenSkywolf]

It had been running near the overheating marker on the last stretch to the campground for about 10 minutes or so, but I never saw it go over the line. She started sputtering like she does when she is running too hot. The only other time I had driven it in hot weather was a week earlier when we ran out to get an oil change and new tires, and she didn't like it then either. Anything under 75 or 80 degrees and she runs just fine. No fuel problems whatsoever.

I didn't think vapor lock would last this long, but the camp host, who usually owns nothing but vans, including older Dodges, said he's had them get vapor lock for a day or two before, which is about how long it was when I made this topic.

[nbounder]

Ford F 53 chassis with the 'old' 460 gasser can most certainly go into vapor lock. Mine and a zillion other guys can attest to that. Simply put, the pump gets so hot in operation that the adjacent fuel volatilizes, and whammo - stall out city. A sure way to verify this is to let it cool down for at least an hour and try a re-start. If it fires up, runs for a bit, then dies, you likely need a new $600 fuel pump. Worked wonders for me....pert near drained my emergency fund though.

[HD4Mark]

Kinda sounds like the fuel pump or a filter to me too if there isn't any gas getting to the carb.

That said I have had two experiences with vapor lock. A long time ago I had a Jeep Wagoneer that would vapor lock. It was a winter rat (for those of you from warm climes it is a junky car you drive in the winter to save your good car from road salt that will rust it) so I didn't get too carried away with investing money in it. All I did was carry a jar of gas to pour some right in the carb to get it going. Once the flow went, it ran OK. The second was DW had a small pickup that only needed a hole drilled in the gas cap. Just loosening it worked temporarily.

If the fuel pump is a mechanical pump on the engine, one time to get a car to the shop to get a gas tank replaced we attached a fuel line to it and stuck the other end in a small gas can strapped right into the engine compartment. Wasn't the safest thing in the world but for kids with about $2 to spare it got us to where we had to be without a tow truck.

Now days I take vehicles to the shop and let Mr. Visa worry about it.

[Triker56]

I had a old P30 with the 454. Fuel pump on the motor. It would vapor lock all the time, until I installed a 12V pump back by the fuel tank to push fuel to the engine one. No problem after I done that.

No one said anything about your getting hot problem.
Sounds like the radiator needs a good cleaning with maybe a thermostat change. 90º weather shouldn't make it run hot.

[SyrenSkywolf]

I'm going to investigate it all this weekend, when I am at the campground all weekend and not at school when it is light out. I have until next Sunday (Sept 11th) to get it running or we are screwed. 14 day limits at federal campgrounds and all.

[SyrenSkywolf]

Ended up being the fuel pump (mechanical). Quite an interesting fix to learn how to do. Also noticed the choke rod wasn't connected on the carburetor, so I reattached that. Took a while to get the gas through the never-ending fuel line, but once it hit the carburetor, she fired right up and runs a heck of a lot smoother now than it ever did since we got it.

Thanks for the input guys!