| VAPOR LOCK or What?? [message #282344] |
Fri, 17 July 2015 15:38  |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
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I think I have read every forum post about vapor lock over the past 13 years that I have been driving this coach. But I had never had the first hand joy till last week. Not sure that is my problem.
On a trip from Red Bluff to Lake Almanor; about 70 miles rising from 300" elevation to 5600" and back down to 4500', temp about 95 in the valley down to less than 80 at the lake the engine seemed to be intermittently starving for fuel on the hills. Ran fine on the flats and minor grades. While at almanor I replaced the inline fuel filter. The old on was clear and has only been in use since the engine rebuild.
This is a regular route in the gmc. Have driven it dozens of times over the years in much hotter temps- towed my Jeep Cherokee many times. Never a problem in the past. Did not tow the Jeep on either of the recent trips.
The week before the trip I had dropped the rear tank to replace all the fuel, vent, vapor separator, and onan fuel lines. So I thought maybe I had pinched the fuel line. Dropped the tank again yesterday to make sure lines are free. Found nothing wrong. Pulled the carb to check the filter-There is none installed.
Drove up to Almanor yesterday afternoon and the starvation symptom(if that is what it is) was worse).Started the trip at +/-100deg. Slowed to 25-30 mph in 2nd gear on the multi-mile 6% grades.
Symptom is a momentary hesitation/slowing/surging only the grades. Runs fine otherwise.
455 has about 15000 miles on it since rebuilt. Headers, single muffler, 3 in exhaust 3:70 final drive, 180 deg thermostat, new mechanical fuel pump when engine rebuilt, elec fuel pump was turned ON . Filled up with fresh fuel (Arco 87) immediately before each trip. Engine temperature never rose above +/- 195.
I replaced the carb a few months ago. Not sure but I think this is the first time up this route since changing the carb. However I have been over The Grapevine(much longer 6% grade) on I-5 while towing the jeep with no problem since changing the carb.
Could this be electrical issue rather than vapor lock? I have spare ignition parts and can change.
Any one have any suggestions?
Thanks
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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