2000 4.0 SOHC just quit while driving on the highway

[aveteam]

Hello all, this actually happened a few months ago but due to a house renovation I'm just now able to do some troubleshooting.
Like the title says, we were going down the highway when out of the blue, it just died like someone cut the ignition. No noise, no warning, and it had been running like a champ up till this. When I tried to start it, it would fire a couple times, but wouldn't completely start. We had just gassed up about an hour earlier. Had to have it trailered home. My first thought and fear was that the timing chain(s) had finally let go. After thinking about it, that seemed less likely because there was no noise or anything, it just quit. I checked the inertia switch, and that wasn't it, it wasn't tripped. I tripped it, and then it wouldn't even try to start at all.
As part of troubleshooting, I unplugged the MAF sensor and it would actually start and run for a few seconds, slow down, lope and then die. This is repeatable, and when reconnected, it goes back to not starting. It does have some fuel pressure because I bled off some from the Schrader valve in the fuel line into a rag. Unknown how much pressure, but a fuel pressure test kit is on the way. I've checked the crank position sensor per another thread that suggested using an OBD scanner to check for engine RPM while cranking- it does register some RPM while cranking and when it's running, so while I guess it doesn't rule it out completely, it does make it less likely.
At this point I'm suspecting either a faulty fuel pump or a clogged filter, but none of the threads I've read here are close enough to what happened to it to give me a decent idea of how to proceed. So I figured I'd come here and lean on the expertise in the forum.

 

[EB4X]

Sounds to me you're on the right track, fuel pressure test. While waiting for the fuel pressure kit to arrive you could spray some carb cleaner / starting fluid inside intake and that would confirm/reinforce suspected fuel issue - pump etc... A bad or poor MAF usually will not kill an engine / stop it from starting.....seems like a coincidence it started those times....a failing fuel pump will usually give a few starts / runs before it gives up the ghost.

 

[aveteam]

Sounds to me you're on the right track, fuel pressure test. While waiting for the fuel pressure kit to arrive you could spray some carb cleaner / starting fluid inside intake and that would confirm/reinforce suspected fuel issue - pump etc... A bad or poor MAF usually will not kill an engine / stop it from starting.....seems like a coincidence it started those times....a failing fuel pump will usually give a few starts / runs before it gives up the ghost.

Good to know, thanks! I read the thread on dropping the tank & changing the fuel pump; it still has 3/4 of a tank in it so I'll have to siphon for a while!
How loud is the fuel pump supposed to be? Most of the other ones I've heard are pretty obvious, but either this is really quiet or just barely running.

I did find a small piece of a feather or something on the element in the MAF- I very gently cleaned it off but it didn't make a difference. I;ve read that foreign matter on it can cause problems. I didn't figure it'd be that easy!

 

[C420sailor]

They’re pretty quiet…at least the stock 4.0 ones are. You can hear em if you pop the fuel cap and listen down the filler neck while a friend turns the key from off to on.

My 5.0 you can hear sitting in the damn car. Doubt it’s stock though…I think PO out an aftermarket in

 

[EB4X]

"it still has 3/4 of a tank in it so I'll have to siphon for a while!"
I'm guessing your 2000 will have a check valve midway down the filler tube prohibiting you from siphoning....as a anti gas theft measure.

 

[Fix4Dirt]

They’re pretty quiet…at least the stock 4.0 ones are. You can hear em if you pop the fuel cap and listen down the filler neck while a friend turns the key from off to on.

My 5.0 you can hear sitting in the damn car. Doubt it’s stock though…I think PO out an aftermarket in

really? this one you can hesr sitting in the rig, its pretty loud for a fuel pump

 

[ChrisMntr]

Hello all, this actually happened a few months ago but due to a house renovation I'm just now able to do some troubleshooting.
Like the title says, we were going down the highway when out of the blue, it just died like someone cut the ignition. No noise, no warning, and it had been running like a champ up till this. When I tried to start it, it would fire a couple times, but wouldn't completely start. We had just gassed up about an hour earlier. Had to have it trailered home. My first thought and fear was that the timing chain(s) had finally let go. After thinking about it, that seemed less likely because there was no noise or anything, it just quit. I checked the inertia switch, and that wasn't it, it wasn't tripped. I tripped it, and then it wouldn't even try to start at all.
As part of troubleshooting, I unplugged the MAF sensor and it would actually start and run for a few seconds, slow down, lope and then die. This is repeatable, and when reconnected, it goes back to not starting. It does have some fuel pressure because I bled off some from the Schrader valve in the fuel line into a rag. Unknown how much pressure, but a fuel pressure test kit is on the way. I've checked the crank position sensor per another thread that suggested using an OBD scanner to check for engine RPM while cranking- it does register some RPM while cranking and when it's running, so while I guess it doesn't rule it out completely, it does make it less likely.
At this point I'm suspecting either a faulty fuel pump or a clogged filter, but none of the threads I've read here are close enough to what happened to it to give me a decent idea of how to proceed. So I figured I'd come here and lean on the expertise in the forum.

I just had this exact problem with my mountaineer. the problem i had was power to the fuel pump.
After changing a few parts including the fuel pump (ignition switch, ignition lock, disconnection remote start). it was a relay pin that dropped into the power distribution box that caused the shutdown.
take a look and see if the fuel pump relay pins is making contact in the power distribution box under the hood.

 

[aveteam]

I just had this exact problem with my mountaineer. the problem i had was power to the fuel pump.
After changing a few parts including the fuel pump (ignition switch, ignition lock, disconnection remote start). it was a relay pin that dropped into the power distribution box that caused the shutdown.
take a look and see if the fuel pump relay pins is making contact in the power distribution box under the hood.

I'm assuming it would be OK to swap it with one of the other relays then? I did wiggle all of them to make sure they were seated. Or in your case, did the connector just push out the bottom of the distribution box? Cause they're kind of hard to get out without breaking them.

 

[410Fortune]

Yes can swap the fuel pump relay with the one next to it for testing

You can also jumper the two large pins which will send battery power directly to the pump

Sounds like a classic fuel pump
Failure to me

Fuel pressure on this should be 68 psi so you would know it when you bleed at the schrader

The v6 and v8 trucks use the same fuel pumps so…. A noisy one is basically old no matter what engine you have

 

[ChrisMntr]

I'm assuming it would be OK to swap it with one of the other relays then? I did wiggle all of them to make sure they were seated. Or in your case, did the connector just push out the bottom of the distribution box? Cause they're kind of hard to get out without breaking them.

The connector has to be pushed out the bottom of the box to try to fix for replace with one from the junk yard. you will be cutting wires and reconnecting a few. if you can push the relay pin connector back up then it'll be good. but yea you will need to open the box either way. i did the same thing. cut and solder wires. I took oout the section with the pump, horn without breaking it. just take your time.

 

[410Fortune]

Why cutting wires? I remove pjb without cutting anything and it all comes apart, can be worked on under the hood

 

[ChrisMntr]

Why cutting wires? I remove pjb without cutting anything and it all comes apart, can be worked on under the hood

If you are trying to replace the section of the box, without bothering other sections. you'll need to cut and splice. some wire run between section within the box.

 

[aveteam]

OK, I looked at the pins for the fuel pump relay and the others, and they all looked intact and where they should be. I had my wife turn the key 4 - 5 times while I listened and I could hear the fuel pump run for a couple or 3 seconds each time, so at least it's running. Doesn't mean the filters aren't plugged though.
I guess now the best thing is just hold off till the fuel pressure gauge gets here.

 

[410Fortune]

You can rent one at auto parts store for free typically
You can also use a dial type $2 tire pressure gauge it will work one time and give you a pressure reading, but the fuel will destroy it
Good tips in a pinch

 

[Nctruckman]

Had a similar issue, fuel pump relay was just worn out. Idk on these but on our 94, theres a EEC relay that feeds the fuel pump relay and that was the culprit.

 

[410Fortune]

Yes the 96-01 also use a pcm relay which the ignition switch powers, then the pcm relay energizes the fuel pump relay. The pcm then controls the fuel pump relay with a signal wire

Before we drop the fuel tank we always do two things:
One check for power baxk at the fuel pump connector. This eliminates the fuel pump fuse, relay and inertia switch as the issue

Two send battery power directly to the fuel pump see if it comes on and fails
To Build pressure. If it does not come on or it does and is weak, now you have confirmed the pump is the issue
Doing these two things have saved me from dropping the tank and replacing a good pump more then once

 

[aveteam]

Yes the 96-01 also use a pcm relay which the ignition switch powers, then the pcm relay energizes the fuel pump relay. The pcm then controls the fuel pump relay with a signal wire

Before we drop the fuel tank we always do two things:
One check for power baxk at the fuel pump connector. This eliminates the fuel pump fuse, relay and inertia switch as the issue

Two send battery power directly to the fuel pump see if it comes on and fails
To Build pressure. If it does not come on or it does and is weak, now you have confirmed the pump is the issue
Doing these two things have saved me from dropping the tank and replacing a good pump more then once

Really good tips there, thanks! The good news is that the gauge should be here tomorrow. Then I should be getting some answers.
I've confirmed that the fuel pump is running when the ignition switch is turned on, then it shuts off after it pressurizes, presumably. What's unknown is what the pressure is. By the way it's acting, there's enough pressure to sometimes start the engine and let it idle for a couple or three seconds, then it slows down and lopes, then dies. I'll have to enlist the help of my wife to try to start it while I watch the gauge to see if it drops quickly.
If I do get the desired 68 psi fuel pressure then I guess I'll have to start looking for a different issue, but we're not there just yet.

 

[410Fortune]

They will run and idle with as little as 42-45 psi! I have seen it. But put it under load and it cannot keep up.
The pump can supply good pressure until it gets hot and then start to drop off
That is why these issues can be hard to diagnose
The gauge does not lie!
Best time to test rail pressure is when the truck is acting up, if course

The older trucks with return style fuel rails, the pumps seemed to either work or not. Pressure on those is 36-42 psi

The returnless rail trucks (98+) the pumps seem to run forever, but when they get to 120-160k likes they begin to get weak
Truck will still start idle run most places
And then it slowly gets worse until the poor thing completely quits

 

[gatzdon]

Don't know if you got your pressure gauge set yet, but with Forscan and an OBDII reader, you can view the fuel pressure value from the PCM. Good Luck.

 

[aveteam]

Don't know if you got your pressure gauge set yet, but with Forscan and an OBDII reader, you can view the fuel pressure value from the PCM. Good Luck.

I do have Forscan and an OBDLink EX so I'll definitely give that a try.