2011 4.0 SOHC no crank no start only after the engine has warmed up

[sgtsandman]

I'm in a bit of a conundrum here being the issue is technically intermittent. When cold, the truck starts and runs fine. But if I drive it or let it idle for a bit and then shut it off, it will crank and pulse like it is trying to start, with an occasional stumble. It will stay that way until whatever is wrong cools down enough and then it will start, run, and drive just fine.

What I've done so far:

Fuel pressure is good static or running. The service manual calls for 60-65 psi and it sits right in the middle on the gauge. The fuel pumps seems to prime just fine, hot or cold engine. The fuse looks and test fine for continuity across the pins. Since the pump primes and will run the engine, I'm assuming the relay and the kill switch behind the passenger kick panel is fine.

The EDIS block tests fine for resistance across the primary pin and all the secondary pins as well as across the the paired sockets for the plug wires.

Since the IAC can cause start problems, I checked power to the valve as well as operation. 12 V to the valve and the valve opens when it has 12 V applied to the solenoid.

What I plan to do:

Check spark at each wire to make sure the wires are good and pull the plugs to make sure there isn't anything odd with them.

Check the crank sensor

Check the fuel injector resistance and use a noid light.

It would help if I had a PC/ED manual but I do not. Hopefully, the CD version of the manual I ordered will have it like the 2019 CD version does. The workshop manuals keep referring to that for troubleshooting, which is annoying since Helm claimed the manual set I got from them was a complete set and never offered any other options. It is not. I had to find and order the wiring diagram book separately, which I did a while ago. And apparently, the PC/ED book is separate as well.

 

[lil_Blue_Ford]

So, aside from the fuel pressure readings… that sounds almost exactly like my green Ranger when the fuel pump started dying. I think the “returnless” system is dumb since what happens is if the pressure drops low enough on a warm engine, it essentially vapor locks. With a return style system, you can prime it a couple times to push the vapors back to the tank and go.

At any rate, do you have the ability to run Forscan? There some tests and stuff it can do that may help locate the problem.

 

[sgtsandman]

So, aside from the fuel pressure readings… that sounds almost exactly like my green Ranger when the fuel pump started dying. I think the “returnless” system is dumb since what happens is if the pressure drops low enough on a warm engine, it essentially vapor locks. With a return style system, you can prime it a couple times to push the vapors back to the tank and go.

At any rate, do you have the ability to run Forscan? There some tests and stuff it can do that may help locate the problem.

I do have forscan both on my tablet and my windows computer. Since there hasn't been any DTCs, I had not thought to even look at them. I also have an old Actron Scanner that has some live data ability.

 

[sgtsandman]

So, aside from the fuel pressure readings… that sounds almost exactly like my green Ranger when the fuel pump started dying. I think the “returnless” system is dumb since what happens is if the pressure drops low enough on a warm engine, it essentially vapor locks. With a return style system, you can prime it a couple times to push the vapors back to the tank and go.

At any rate, do you have the ability to run Forscan? There some tests and stuff it can do that may help locate the problem.

Come to think of it, The last time it failed to start on me while I was on the way home from work, I did test fuel pressure by depressing the schrader valve and it did start soon after that. It could be a vapor lock issue.

 

[lil_Blue_Ford]

I do have forscan both on my tablet and my windows computer. Since there hasn't been any DTCs, I had not thought to even look at them. I also have an old Actron Scanner that has some live data ability.

Yeah, live data and tests can bring up things beyond actual codes. Also some codes don’t set a CEL

 

[lil_Blue_Ford]

Come to think of it, The last time it failed to start on me while I was on the way home from work, I did test fuel pressure by depressing the schrader valve and it did start soon after that. It could be a vapor lock issue.

Vapor lock is usually one of three things:

Fuel line leak
Fuel pump fail (or the pressure regulator)
Injector leak down

I’m not sure about the 2011, but my 00 has a return off the fuel filter. The regulator is part of the fuel pump assembly. That can potentially bleed pressure off the system. My dad’s 99 and Paul’s 98 both have a completely returnless system, no return anywhere. So your results may vary.

When you have a loss of fuel pressure in the rail, and a warm motor, it can vaporize the fuel in the rail causing the old issue of vapor lock.

 

[sgtsandman]

Vapor lock is usually one of three things:

Fuel line leak
Fuel pump fail (or the pressure regulator)
Injector leak down

I’m not sure about the 2011, but my 00 has a return off the fuel filter. The regulator is part of the fuel pump assembly. That can potentially bleed pressure off the system. My dad’s 99 and Paul’s 98 both have a completely returnless system, no return anywhere. So your results may vary.

When you have a loss of fuel pressure in the rail, and a warm motor, it can vaporize the fuel in the rail causing the old issue of vapor lock.

The 2011 does have the return off of the filter. I did notice that the pressure did not hold steady with key on, engine off. It dropped down to about 50 psi, if I remember correctly, and stayed.

 

[lil_Blue_Ford]

The 2011 does have the return off of the filter. I did notice that the pressure did not hold steady with key on, engine off. It dropped down to about 50 psi, if I remember correctly, and stayed.

50 psi should still be enough to keep from vapor locking I’d think…

If it was an old 2.9 truck I’d say the TFI might be dying, lol.

I don’t know if you can get a replacement fuel pressure regulator or not. On my 00 it’s just attached to the fuel pump sender assembly so technically replaceable without replacing the entire assembly but I haven’t looked for one for years.