Roger Janke, (a great and helpful Barth owner). has sent me a copy of GMC Truck Service Bulletin #85-B-80 dated May, 1985, which discusses vapor lock on the 7.4L 454. It has specific guidelines to repair the condition.

I am trying to find a way to put it on the web site so that it is legible. Until I do, I will send a copy of it to anyone who emails me their address.





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Shortcuts Always Take Longer

I have an 85 28 foot with the 454. I have only owned this unit for 3years. When I bought it, it had 12,000 original miles, 30 hours on the generator, and had been sitting up for nearly 9 years. I did alot of work on it and the longest trip I have taken in it was to arkansas for a duck hunting trip. Well three weeks ago I let a friend borrow it to travel to the west coast. This is the first trip it has seen of great distance and in hot temperatures. My friend had continuous trouble with the engine loosing power due to lack of fuel supply, this would happen about every 3 hours. He would stop, replace filters, he replaced both the manual and elec. fuel pumps. But every time a few hours later, it would start loosing power. At one point he opened the fuel cap and fuel sprayed 5 feet out the filler tube. After careful evaluation of the symptoms and problems, he finally figured out the problem. It seems it was a design problem from the manufacture or something a muffler shop had done. The fuel line ran down the inside of the frame right next to the exhaust. And at the engine the fuel line ran right next to the manafolds. The fuel was getting vaporized before it even got to the engine. My friend ran a new fuel line on the other side of the frame, and he said the coach ran perfect for the last 3 days of the trip without any problems.



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