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Home » Public Forums » GMCnet » VAPOR LOCK and FUEL BOILING. (Trip Report)
VAPOR LOCK and FUEL BOILING. [message #139825] Thu, 18 August 2011 13:58 Go to previous message
djeffers is currently offline  djeffers   United States
Messages: 219
Registered: June 2004
Karma:
Senior Member
Hello all,

Late last saturday afternoon, 13 Aug 11, we left Dunnellon, FL in north central Florida, for Shipshewana, IN in very northern Indiana, going north on I-75.

We made it to Valdosta, GA and overnighted. We found some very low priced gas, filled up and spent the night at Walmart.

Got on the road around 10:30 a.m. the next morning. It was a pretty hot day. After driving for a while, the coach began to stumble and shortly thereafter began to backfire and the engine quit.

Coasted over to the shoulder on I-75. The engine would not restart, just cranked and backfired. About 20 or 30 minutes later the coach started right up and we resumed our drive north.

I pulled into another gas station and topped off the fuel. When I took the gas cap off I could HEAR the fuel bubbling and boiling. The coach took only about 10 gallons of fuel. The fuel filler sounded similar to what it does when filling the tanks and the fuel is nearly full and it takes a while for the fuel to drain down.

Got back on the road and about 20 miles later the same thing; stumble, backfire, quit and coast over to the side of the road. Not safe!

Got on the road again 30 minutes later and we changed the fuel filters at a rest stop. Back on the road and sure enough, 20 or so miles down the road the same thing. We made it off the Interstate and coasted onto an uphill off ramp at the Johnstonville Road exit, still in south GA.

I thought maybe we had a second fuel pick-up sock obstructed, as we already have one sock obstructed that we have blown out once. The wiser mind, Susan, was not so sure and observed that the problem seemed temperature related.

I walked up the hill on the off ramp and found a peanut stand next to a fairly large paved parking area across from the only other structure around, a Marathon gas station. Asked the the individuals working the stand (Peanut and David) if I could pull the coach into their lot.

Peanut and David, father and son southern gentlemen that they are, said yes and that they would help us any way they could. They told us to pull up on a slab on the lot and we could put our awning out, relax and work on our coach all we needed to. Peanut and David were a Godsend.

While I was working on the coach Susan checked the Black List and found a GMCer just 16 miles north, Chuck Chambers.

I called Chuck and expressed my need (I thought) to drop the fuel tanks and replace the socks and fuel lines with new. I thought too maybe the alcohol in the newer fuels had taken its toll on the older rubber.

Chuck told me that 20 or 25 GMCers at a recent Georgia meet had experienced the very same symptoms and that it was VAPOR LOCK caused by the new fuels.

I was a little reluctant to believe that diagnosis as we have been in the desert heat at high altitudes with the coach and never had a problem. We also have an electric fuel pump to help overcome vapor lock conditions.

Chuck advised that we wait until the roads cooled down before continuing on. It was already about 7:30 p.m. or so and it had been a long hot day.

Wiser heads prevailed, (Chuck's and Susan's). So Susan and I drove the toad a couple of exits down to a Waffle House and had a meal. By then it was after dark.

We left the Johnstonville Road exit about 9:30 p.m. and took off running hard and fast to check the vapor lock hypothesis. Sure enough the coach ran great in the cool of the evening.

I ran as much of the bargain gas out as I could and refueled with name brand gas, hoping that might help any vapor pressure problem. We drove straight through the night at 60 to 65 mph to Knoxville, TN and overnighted again.

Chuck was apparently correct; it was a combination of the newer fuels and the hot day and roadway that caused the problem.

It seems the fuel we had bought may have had a lower vapor pressure boiling point making the coach fuel tanks susceptible to the radiated heat from the hot roadway. We did not have the problem the afternoon before in hot Florida.

The next day in north Tennessee was about 20 degrees cooler than when we were on the road in south Georgia. We continued on without problem to Shipshewana and National RV Refrigeration, arriving in the late evening. We slept in the coach.

The next morning Leon Herschberger of National RV Refrigeration arrived and we left the coach with him to rebuild our Dometic 3 way refrigerator.

Many thanks to Chuck Chambers, Peanut and David as well as Roger Black for all their help.

The GMC adventure continues!


Don & Susan Jeffers
78 Eleganza II

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