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FlyLikeABand · 07-06-2009, 11:51 AM

All,
I bought this RV (1985 Allegro 27' Chevy 454) a few years ago in good condition and took it on several trips. The last two trips the RV would not start and I had to pour gas down the carb to get the fuel to prime. So, I thought fuel pump, replaced the fuel pump and same problem, actually it appear worse now since before it would always start if it had been recently running. Now, it seems like it can stop running while idling and then the vapor lock occurs and no gas to carb. I have taken off the gas cap, I thought maybe the vent was clogged. Drove the RV around the block a few times, came back, it stalled backing into the parking space and wouldn't start again. I checked for fuel filters but can't find any. I want to pull the gas line going into the carb and see if the fuel pump is working, maybe I got a bad one.
Any other suggestions, I hate to take to a repair place for a simple problem, I am worried about the filters in the gas tank itself, not easy to pull the gas tank,
Any suggestions would be appreciated,
JT

blacktie.shooter · 07-06-2009, 12:15 PM

I really hate to be a sorehead, but I have to suggest the possibility of something floating around in the fuel tank, eventually being sucked into the outfeed and clogging it, then floating back up when the engine is not drawing fuel - which enables it to run again- for a little while.

When I first saw the thread, I suspected incorrect starting procedure for a carbureted Chev/GMC engine, but it does not appear to be that.

Really do hope you find a simpler solution. Good luck.

RV Trax · 07-07-2009, 06:28 PM

Try to manually close the choke inside the air cleaner when starting. If it cranks, it sounds like a bad accelerator pump in the carburator. The accelerator pump is most likely your problem as you described. Vapor lock with this engine will usually cause poor throttle response while driving. The new fuels contain alcohol, and it does cause fuel starvation when hot and driving. This problem would require a inline fuel pump as close to the fuel tank as possible. Vapor lock is a result of heat and a vacuum in the fuel line from the tank to the manual fuel pump. Vapor lock will not occur when the fuel line is pressurized.

sknight · 07-07-2009, 08:20 PM

I'd also suspect the bowls leaking down under the carb. It drains out while sitting, is a pita to start, then runs more or less normal once the bowl gets filled.

There is a filter, the big nut the line screws into has a filter under it. Remove that nut, and you will need to carry it to the parts store to match it up. They had short and long filters and they rarely know by application.

Sammie · 07-07-2009, 08:46 PM

On that year rig I would suspect that where the fuel line connects to the fuel tank there would be a piece of rubber fuel hose that is so old and possibly even cracked. When trying to start or even while running you are sucking air and some fuel which will cause vapor lock.

Sammie

Bruce H · 07-12-2009, 11:33 AM

I owned a 1986 Paces Arrow 454 for 17 years. I had issues with fuel pumps, one was the electric pump as the fuel line comes out of the tank behind the rear right wheel (on mine) there is also a fuel filter in the same location. I also had the mechanical engine pump go bad. The electric pump pushes the fuel to the mechanical pump. Once I had to drop the gas tank and replace the rubber fuel lines after about 8 years as Sammie suggested.

LVJ58 · 07-12-2009, 12:24 PM

If you have a Rochester Quadra-Jet carb, they're notorious for leaks from plugs in the bottom of the fuel bowl. Also the composite float over time absorbs fuel and rides low in the bowl. The symptom you describe sounds if the accelerator pump isn't working. I would first start with having the carb rebuilt and replacing the fuel screen where the fuel line attaches to the carb.

I had an old 84 Airstream and I installed an electric Mallory fuel pump back near the tank. Virtually eliminated vapor locks..

Best of luck, Jim

FlyLikeABand · 07-12-2009, 10:51 PM

Thanks all for you help. Turned out to be the fuel filter was clogged which caused my new fuel pump to go bad. Replaced filter, replaced fuel pump and would not idle still. Found burnt vacumn hose leaking and replaced, idles fine now. I just hope no more starting problems, we will see, looks good so far. Will check with her in a few days to see if she starts again.

Again thanks all for the help.