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My 91 Bounder (Ford 460 gasoline engine) has severe power loss problems when hot. I am unable even to drive downhill and need to put trans in 1st gear and race the engine. Eventually, after trying to accelerate from a stop the engine surges and bucks and backfires through the intake.
After it cools down engine runs fine.
Did Tuneup replacing plugs, air filters, fule filter, egr valve, dist cap, rotor pickup and ignition control. Checked for vapor lock.
The problem with your motorhome is classic vaporlock. It is caused by low fuel pressure. Most likely you need a new intank fuel pump. The fuel pressure at the fuel rail needs to be 30-32 psi at idle and 37-42 underload. If it does not hold at least 37psi then replace the pump with a Ford part # F6PZ-9H307-DA You will also need an update harness kit with the pump.
Your explaination about the loss of power in your 91 Bounder is exactly what happen to me in the summer of 1998. During very hot temperatures my 1992 Bounder had sever loss of power too. Mechanics said it was a vapor lock that had occured. When I fueled up and did not let the gas tank get less than 3/4's full, loss of power did not occur. Try to keep your fuel tank as full as you can during very hot days.
Sounds like vapor lock. Make sure lines have not been re-routed by a previous owner. They must be away from exhaust and other heat souces. My MH has a return line from the manual pump that is designed to return any unused fuel back to the fuel tank. I got my hoses crossed once while working on the tank and that caused problems. Check the complete lines for any leaks. You do not want any air getting in. Drive the MH, when you don't have to get somewhere, when it does get hot, take the hose off at the carb., carefully not to spill, and check the flow into an approved container. If it is spitting instead of a constant flow, it is probably vapor lock. Good luck.
1987 motorhome with Ford 460/ Holly Carb
Suspect vapor lock problem as motor stalls and refuses to start in high temps. Have spent considerble $$ on this problem but still persists. Temps must be in excess of85-90 F before problem exists. Have alternative fuel installation (propane),- motor functions perfectly on this fuel but need the gasoline fuel working as propane hard to find in some areas. Any ideas?
Thank you.
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