If your fuel pressure goes to zero, I am trying to think of other scenario's that would cause this besides the pump failing to pump. I guess bad wiring? If you could tap into the wiring plug right at the pump, I guess you could monitor the voltage there when your pressure goes to zero. I was going to make a monitor system for a Ford efi, but I really need a break-out box. I don't know if I could make a break-out box using some old computers. I was then going to harbor freight and buy a few of those cheap digital meters they have and use them all lined up to monitor voltages on the fly.

I am thinking about it more, a simple incandescent bulb wired to the pump plug would probably work in your case. You could see the brightness of the bulb when things were ok, and if the bulb dimmed out you would know you are losing voltage somewhere before the pump.

 

The theory is that when the fuel boils in the line, it registers as zero pressure. I don't know if this is true or not. I would expect it to cause an increase in pressure. But maybe gauges and devices (like the fuel pressure regulator) that are designed to monitor liquid pressure cannot accurately measure vapor pressure?

Or maybe the pump has just quit.

If the problem is the pump, I don't think it is a voltage problem. I suspect that the fuel being returned to the tank is very hot, and the pump is overheating. So what I would need is some mechanism to tell if the pump is actually running or not.

Another thing is I'm considering installing a fuel line cooler on the return line to the tank.

Steve

 

I could see the fuel in the tank getting hotter if the tank was low on fuel. But when the tank is at least 1/2 full or more, I think there is too much fuel volume for it to get too hot. It has too much opportunity to sit in the tank and shed some heat before it's sent back to the front again.

I don't know of any "fix" or design on newer vehicles to avoid a fuel boiling problem, except the fuel re circulation system. I think you can count on your problem being a component failure somewhere, it's just going to be difficult to find it. If a garage was working on it, it would be cheaper for them to just replace one or more pumps and see what happens. Time is money and they get a lot per hour. And your problem is intermittent, making it even harder to figure out. If it would go ahead and fail all the time it would be much easier to figure out.

 

Yup, all true.

I'm still leaning towards fuel boiling in the fuel rail, personally.

But, I'm going to replace the fuel pressure regulator, fuel filter, and high pressure pump anyway.

There are a ton of people on the internet having this problem with Ford 460s.

Steve

 

Been following this conversation with interest. I tend to support the hot fuel theory, too, but that is just a hunch on my part with no real experience.

It would be very easy to monitor the heat. On my carbureted 351W I was having some problems due to underhood heat affecting the fuel. I made some modifications to minimize the heat factor, and added an inexpensive remote thermometer (AcuRite 00888A3) to keep an eye on things. It has a min/max memory feature so I can see peak temperatures without having to watch the display constantly:



I attached the remote sensor to the outside of the carb fuel bowl. Although it wouldn't give me a direct reading of the fuel temperature, I figured it was close enough and it has worked well for my purposes.

You could easily use such a thermometer to monitor the temperature of the injection rail. Put the display in the cab and run the sensor out to the engine. Attach the sensor to the rail in a safe spot. I think it came with double-sided foam tape for installation, but that would act as an insulator. Remove that foam tape so the sensor is right on the fuel rail. Wrap it with self-fusing silicone tape (or similar) to secure it. Go for a test drive and see if the hot fuel theory holds up. Even though you won't be reading fuel temperature directly, I think the temperature of the rail itself should give you a reasonable estimate.

 

I thought of installing a temperature gauge on the fuel rail. Yours looks like a cheap option. What is the min/max temperature of the product you linked to? I did not see it in the specs.

Steve

 

I suspect the indoor/outdoor temp gauges as above won't go high enough for measuring engine-related temps.

But that got me thinking about grill/oven thermometers. Here's one that will talk to your cell phone for $30:


Works up to 572F.

Steve

 

According to the manufacturer:

https://www.acurite.com/digital-ther...obe-00888.html


Click on the specifications tab. It says -58 to +158F for the remote sensor. (The 32 to 122 on the first line is for the internal sensor)

Now that I think about it, 158F may not be high enough for your normal underhood environment. On my pickup, I've built a cooling shroud around the carb and even tapped into cold air from the AC, so I'm reading inside that "cooled" area, not ambient. I'm not sure what normal temps might be in the tight confines of an E-series. You might be able to find a similar product rated for higher temps, such as for an oven or something like that.

 

Here is one that will run up to 230F for $6:


I ordered one. Gasoline starts to boil at 95F so this should be good enough for catching an over-temp condition on the fuel rail.

Steve

 

One disadvantage we have is not knowing what temperature range at the fuel rail is considered normal. And with the fuel pressurized, the boiling point rises, so we don't really know what temperature is too much, other than to drive and take notes. I suggest a labcoat and clipboard so you look official.

Don't forget that most gasoline today has some ethanol in it, which also alters the boiling point. Also pure speculation on my part, but I think most modern fuels don't have nearly as much protection against heat issues as they did back in the day. Years ago, when nearly all vehicles had a carb, this factor was very important, but not so much today with most fuel-injection systems on the road, present company excluded.

(Cue ethanol complaints, 3, 2, 1...)

 

Yes, I noted this back in my original comment, and I believe it is probably the root of the problem. Assuming this is vapor lock, and not component failure, then probably the issue is that the engine was designed for standard gasoline which has a higher vapor pressure than ethanol blended gasoline.

You are right that I have no idea what is a valid temperature, and in fact there is no set boiling point for gasoline (or ethanol blends) - there is a boiling range where it begins to boil and where it is completely vaporized. I'm sure there is probably data out there for the effects of pressure on the boiling range of 10% ethanol gas.

But mostly, if the problem happens again, I want to be able to have as much data concerning the conditions that trigger it as possible. If nothing else, it will serve as a predictive warning should I start approaching such temperatures again in the future, assuming I can't mitigate the problem in other ways.

Steve

 

I guess you know also, they re-formulate the fuel every fall and every spring, I suppose to help combat these types of problems. It comes back to bite us when we have a unusually warm day in the winter.

 

On a similar note, some research on octane and heat-related issues:

https://www.ford-trucks.com/forums/1...g-and-you.html

Please see post #10 here for my hunch about differing fuel blends and how some locales get the short end of the stick:

https://www.ford-trucks.com/forums/1...l#post16089673

Both topics were primarily intended for carbureted vehicles, but some info applies to fuel injection, too.


Got to thinking more about the theory of the fuel tank heating up, whether from the fuel return, an adjacent exhaust pipe, or both. Carry an inexpensive infrared thermometer with you and record the temperature of the tank under varying conditions, including ambient air temperature. Use the same spot on the tank each time for the best results. Could be interesting.

 

I highly doubt that the fuel is boiling in the fuel rail. At 35 PSI (let alone 50psi the boiling point of gasoline is well above the boiling point of water. The ONLY situation in which the fuel could boil in the rail is if the regulator was faulty an allowing the pressure in the rail to drop below the vapour, point. The regulator maintains fuel pressure by bleeding off excess volume/pressure back to the fuel tank to keep the fuel circulating and the temp below the vapour point.

If you are getting fuel rail vapour lock there are 3 culprits the high-pressure pump failing to deliver adequate pressure or volume, a restricted fuel filter preventing proper fuel volume delivery (no fuel filter is lifetime regardless what Ford says) or a faulty pressure regulator.

With proper functioning components, there are no situations in which the fuel could be boiling or vapour locking in the high-pressure rail.

 

I am with you on the fuel boiling when under psi. This is why a cooling system is under psi to up the boiling point of the water.
If the low psi lift pump was bad and not feeding the high psi pump I would think that could be a cause also?
That is why I said he needs to tap into the system after each pump and the fuel rail to see what the psi is when this happens to know for sure.
Dave ----