Vapor lock prevention

[jupoa]

Just completed a long road trip with my 97 F53 gasser (460) through some seriously hot weather. Twice, after driving long distances at highway speeds then slowing to a stop, the motor began starving for gas at idle or when trying to accelerate from idle. Both times, things returned to normal after letting it cool down a half hour or so.

I'm told that these symptoms are caused by "vapor lock", a condition where the fuel line gets so hot that the gasoline vaporizes in the line causing the flow to cease. It does not happen at speed because ambient air flow and fresh fuel flow keep the lines cool enough, but when stopped, the heat just soaks in.

Fortunately for me, it happened both times when I was in a safe, convenient place to become disabled. Does anyone know a way to prevent this? Where along the fuel line does it occur? Would additional heat shielding or insulation help? I don't want this to happen when I'm in traffic.

Any and all thoughts appreciated.

[450Donn]

Heat shields are a big help. Another thing to check is fuel pump pressure. Several years ago we had a Ford van and I lost one of the in tank fuel pumps. Needless to say i was not going to spend 500 dollars for a fuel pump, so I dropped the tank, axed the in tank pump and added an inline pump and filter. No more problems.

[Topflite51]

Highly unlikely it is vapor lock. Fuel pump may be getting weak. Was tank below half, if it was pump could have been overheating, the pump is cooled by fuel in the tank. If your build date of chassis was before Oct 96, you have old style pump, this is according to Ford.

[JimM68]

While I've heard of this claim, it seems extremely unlikely that a high pressure fuel system with a rear mounted pump could vapor lock.

[YC1]

This is a very common problem. The in tank fuel pumps get weak and die. Symptoms seem to be worse on hot days, less than a full tank. I would definitely find all the fuel filters and change them too.

[jupoa]

Perhaps I should have supplied more information.

My fuel pump has been replaced at least once already by a previous owner. I know because of the hole cut in floor above the pump location to access it without dropping the tank. I don't know if it was replaced with the old style or new style.

The first time vapor lock occurred there was a ton of vacuum released when I pulled the gas cap leading me to believe the fuel pump was working. The tank was less than half full and the engine coolant temperature was normal. I replaced the gas cap and fuel filter and everything was OK for the next three days of driving.

The second time there was little to no vacuum on the tank, which was a little over half full, but the symptoms were the same. After it set for a few minutes, I was able to start it and, although it was missing badly at first, get it above about 15 - 20mph where the symptoms gradually disappeared with speed. A short time later when I stopped at my destination, the symptoms returned.

The high temperatures were well over a 100 degrees for each of the last 6 days of my trip and there was ample opportunity for this to occur at every stop after a long pull on the highway but it only happened twice. Go figure.

Thanks for all the replies thus far.

[YC1]

My bet is on a sick fuel pump even if it is the second time. I ran with my fuel cap loose to try and duplicate the issue but that didn't help. Hot days, less than 1/2 tank, running hard, often the generator going to keep it cool. At least you can get to eat easy.

[subford]

Those are the same symptoms you get with the the PIP sensor also as it is inside the distributor and the distributor is on the front of the engine right behind the radiator.

You have a loop fuel system to keep it from vapor locking and also runs at 32-40psi while the engine is running that raises the boiling point of the fuel to a higher temperature. Higher the pressure the higher the boiling point of any liquid.

The ICM of the TFI type is mounted in front of the radiator and to the drivers side so it is an unlikely candidate also. But they do some times have those symptoms also but the Black ICM like you have does not seem to go out as much. But never let some place try to sell you a Gray ICM and they will and a Gray one is the wrong one for the 1994-1998 F-53.
Also the Gray one will give poorer MPG and performance in the 1994-1998 F53.

The new fuel pump will pump about 95-100psi into a dead head so a week pump not putting out that much can still put out enough to meet the fuel pressure requirements of the engine but there will be a lot less fuel being returned to the tank by the Fuel Pressure Regulator (FPR) so the fuel can heat up more at the engine fuel rail.