You can see the whole issue here:
https://www.ford-trucks.com/forums/1089626-vapor-lock-in-an-efi-engine-2.html#post18890425
You could install a Hobbs switch to a small led light, but not cheap $80 bucks my last one. Imo probably liquid fuel in till over engine, then liquid into vapor because of engine heat. So your pump might be working good, but fuel vaporizes before getting to where the fuel needs to be liquid at ie injected into cylindar.
Just you or is this common problem with your make and model.
Evidently this is a common problem with Ford 460 engines. If you google "Ford 460 Vapor Lock" you will see tons of people with this issue - when driving at speed, in hot weather, especially with the AC on, the engine will stumble and die, and backfire through the intake. After the engine cools for some 20-40 minutes, it fires up and runs fine.
I have been fighting this issue for about a year. At first I replaced the ICM, and thought I had it licked as it went all winter long without issue. But that was just because the weather was cold. Problem came back in the summer. I have replaced:
Radiator
Catalytic Converter
Distributor (and thus PIP sensor)
Spark Plugs and Wires
Engine Temperature Sensor
Idle Air Valve
In-Tank fuel pump
RV died again last week 2 hours into an 11-hour trip. Up until that point I had assumed I had a heat-related component failure, but now I am not so sure. I believe I probably have fuel boiling in the fuel rail. In the above link, there is another link to a guy who describes the same problem:
Yes. In fact, after I replaced the tank pump (low-pressure), we had the problem again, and a shop replaced the high pressure pump on the frame rail below the driver's door because they said it was running a little low. They subsequently tested all the pressures, and they were fine.
I kept a FP gauge attached to the Schrader valve on the fuel rail during one trip after that. It ran at the correct pressure (I think it was 50 psi, but that was a couple of months ago, so that may not be exact); however, as soon as I climbed a long hill in heat over 85 degrees F, the pressure dropped to zero and stayed that way through multiple attempts to restart. When I pressed the release valve on the gauge, I got nothing more than a few spurts and drips of fuel; I was halfway expecting to get a high-pressure burst of boiled fuel, but got nothing like that.
After about 45 minutes, though, I was able to start it just fine, the pressure went immediately back up to 50, and we were on our way again. That happened three or four times in one trip, and it was always the same: a drop to zero FP in a hot climb, a 45-minute wait, and a no-problem start with FP at specs until the next big climb. It has never happened except when very hot, and then only when climbing long hills. No engine overheat, though.
So this guy has the exact same issue that others and myself have reported, and he captured zero pressure on the fuel rail at the time it was happening. He had already replaced his in-tank and hi-pressure fuel pumps.
There is a video on YouTube of a guy who claims he fixed his problem by replacing the Fuel Pressure Regulator.
So, we can be pretty certain that the problem is heat-related, and we can be pretty certain that it involves zero fuel pressure.
The question is, is it due to vapor lock, or is it due to a fuel pump overheating and shutting down somehow.
This weekend I am going to install a new fuel filter, and a GlowShift digital pressure gauge to the schrader valve on the fuel rail, so I can monitor the fuel pressure at the rail. But, even if I can capture the problem again (temps seem to have broken for the fall, so I may not see this problem again until summer), zero fuel pressure does not necessarily mean fuel boiling.
My suspicion is that these engines were designed and manufactured prior to the common adoption of ethanol-based fuels. Ethanol blended fuels have a lower vapor pressure than regular gasoline. It may be that the design was marginal with pure gasoline, but with ethanol when the temps get high enough, combined with the AC dumping more heat into the engine bay, that it is sufficient to boil the fuel in the fuel rail.
Evidently when the fuel vaporizes in the fuel rail, the pressure regulator interprets this as low pressure in the rail and stops sending fuel back to the tank (this is how it regulates the pressure), and this in turn would stagnate the flow of fuel in the line and let it get even hotter.
But anyway, there is the possibility that the pump(s) are failing.
I would like to monitor the status of the pumps electrically, if there is a circuit that could be devised to do so and drive an activator light on the dash installed somewhere. Just detecting power to the pump is insufficient, as the pump could be receiving power but not running. So I'm looking for an electrical way to determine the status of the pump.
Obviously I can install pressure gauges or Hobbes switches, but I was hoping there was a way to directly monitor power to the pump and be able to infer if it is operating or not based on current draw. Note I do not want to use a Fluke meter or similar current meter - I want a permanent gauge-driving setup.
I am also considering installing vent louvers in the hood on either side of the hood. I considered putting louvers along the entire rear edge of the hood but the cabin air intake is in front of the windshield and I do not want to drive hot engine air directly into the cabin air intake. So, if I install the louvers they will be on the outboard rear edges of the hood.
I am also considering insulating the fuel rail in the engine compartment.
But, all of this is for nothing if the true problem is the fuel pumps themselves. Hence I would like to come up with an electrical way to monitor if they are running or not.
I'm probably just going to go ahead and replace the high pressure pump as well. The low-pressure in-tank pump burned up about 5 years ago, and I replaced it with an AirTex E2060S turbine pump. But when the OEM pump burned up it took out the inertial switch and the fuel pump relays - it is possible that it damaged the high pressure pump also. I did not even know this van had 2 fuel pumps until a couple of weeks ago.
So, there's the long and short of the story.
