Stranded/broke down
Pulling through the city of Calgary, on the bypass. Had just filled with fuel 3 miles back. ¼ tank to full. Pulling up hill, gauges all normal, cruise set. Start to lose power and slow down. I reac...
Forum Discussion
So I have been fighting this high-temp shutdown problem for about a year now. Thought I had it licked last fall when I replaced the ignition control module, but the problem returned in the spring. Thought I had it licked when I replaced the distributor (and thus PIP sensor), but just had a week long trip ruined when it died in 95F+ heat just to Chattanooga, after a 2 hour run with the AC on.
Engine just sputters and dies. Backfires through the intake. Any attempt to give gas makes it worse. Eventually it dies trying to idle.
Saw this video:
https://www.youtube.com/watch?v=g6rf9oPDq1I
Exact same symptoms and motor.
I have already replaced the in-tank pump about 5 years ago. But it turns out my RV has an external high pressure pump.
It is possible this pump is failing. I will be installing a fuel pressure gauge soon.
But I believe what is happening is that with modern ethanol-blended gasoline, which has a lower vapor temperature than pure gasoline that this engine was designed for back in 1990, that at high ambient temperatures, combined with the heat load of the AC condenser, that it gets hot enough to start boiling the fuel in the fuel rail.
And when that vapor gets to the Fuel Pressure Regulator mounted on the rail, which controls the flow of fuel back to the gas tank (that is how it controls the pressure), it causes the regulator to shut off the flow of fuel back to the tank, which makes the fuel in the rail get even hotter and boil even more.
After the engine cools off 20 minutes, it starts up and runs fine. We went back and picked up the RV on Friday night after temps dropped into the 80s, and I drove the RV the whole way home with the AC off and no issues at all.
Plugged into ODB1 code reader and no codes.
Sadly temps are now finally starting to dip for fall so I may not have a chance to run this at high temperatures again to confirm until Spring.
But I am going to install a GlowShift fuel pressure gauge and see where my PSI stands right now, and then I'm going to replace the fuel filter (85K miles on it) and the high pressure fuel pump and see what the effect is on fuel pressure readings from the get-go.
I am also considering installing some louvered vents in the hood to help reduce under-hood temperatures.
Steve
Engine just sputters and dies. Backfires through the intake. Any attempt to give gas makes it worse. Eventually it dies trying to idle.
Saw this video:
https://www.youtube.com/watch?v=g6rf9oPDq1I
Exact same symptoms and motor.
I have already replaced the in-tank pump about 5 years ago. But it turns out my RV has an external high pressure pump.
It is possible this pump is failing. I will be installing a fuel pressure gauge soon.
But I believe what is happening is that with modern ethanol-blended gasoline, which has a lower vapor temperature than pure gasoline that this engine was designed for back in 1990, that at high ambient temperatures, combined with the heat load of the AC condenser, that it gets hot enough to start boiling the fuel in the fuel rail.
And when that vapor gets to the Fuel Pressure Regulator mounted on the rail, which controls the flow of fuel back to the gas tank (that is how it controls the pressure), it causes the regulator to shut off the flow of fuel back to the tank, which makes the fuel in the rail get even hotter and boil even more.
After the engine cools off 20 minutes, it starts up and runs fine. We went back and picked up the RV on Friday night after temps dropped into the 80s, and I drove the RV the whole way home with the AC off and no issues at all.
Plugged into ODB1 code reader and no codes.
Sadly temps are now finally starting to dip for fall so I may not have a chance to run this at high temperatures again to confirm until Spring.
But I am going to install a GlowShift fuel pressure gauge and see where my PSI stands right now, and then I'm going to replace the fuel filter (85K miles on it) and the high pressure fuel pump and see what the effect is on fuel pressure readings from the get-go.
I am also considering installing some louvered vents in the hood to help reduce under-hood temperatures.
Steve
