Engine randomly dies - no one can diagnose it.

[blacklimited]

I've had this problem on and off for months and it's driving me nuts. I haven't had to drive much the last couple months due to some medical stuff so it hasn't been as much of a problem, but I know it will be when I'm driving again.

My engine randomly dies. It only has 85k miles on it. What happens is the ignition works fine, everything power works fine when this happens (windows, headlights, radio, etc) but the engine will just quietly die off over the course of a few seconds, and I won't be able to start it back up until my car sits for hours. It's not overheating at all, and you would think that's the fuel pump dying but the engine doesn't rev at all when this happens, which I've read always happens if it's the fuel pump. It's a very controlled dying off of the engine. It just quietly dies. I've wasted $$$$ trying to get this diagnosed and fix and no one is any help. Recently one of the rubber elbows had to be replaced and I was told another wasn't looking too good by someone, but I was told they were fine by someone else. Any idea what this could possibly be? Since it doesn't record it on the computer, diagnostic checks don't tell anything. Thanks

 

[410Fortune]

fuel pump or fuel pump relay / fuse

Very common issue, sounds exactly like your problem IMO

 

[aldive]

Is the CEL illuminated?

Have you checked the fuel pressure?

 

[Turdle]

fuel pump or fuel pump relay / fuse

Very common issue, sounds exactly like your problem IMO

I second this

When the truck is in the "no start" condition, look for a few things--

When the key is turned on, you should immediately see the "check engine" light illuminate. At this time you should also hear the fuel pump run for about 2-3 seconds ( prime cycle). Listen near the fuel filler door for this. It should prime every time the key is switched to the "on" position.

Check the fuel pump fuse for a corrosion buildup in the connection pins-
check the fuel pump and PCM relays for the same.

But I will almost bet you need a new pump.

this may help

http://www.explorerforum.com/forums/showthread.php?t=180814&highlight=power+layout

 

[410Fortune]

even new pumps can do this, I have also found after a truck sits for a long period of time once you get it running again the fuel pump will last or die within a few weeks.

I would do like Aldive and check fuel pressure
I would "wiggle" test the fuel pump relays and fuse
LOOK at the relay and fuse connections down inside the power dist box
check the connections at the fuel pump for corrosion as well..

Aldive he said a computer diagnosis shows up nothing

If you determine the pump is weak, replacing the entire in tank assembly can cost $150-200, I like Napa, Carquest, or Ford for this part, not Autozone or Checker (just my opinion based on my experience)
You can swap the pump out in less then an hour if you are good from start to finish.
A weak pump will also make some nice noises, gurguling, whining, sound like its sucking air, etc

What are these rubber elbows you had replaced?

 

[Cobraguy]

You are very fortunate in that this won't start for hours. That will make it much easier to find. It's when it starts right back up that drives you nuts. My parents had a Suburban that would die about once every 3 months like you flipped a switch. But it started right back up. I finally put a new ECM in it and fixed it. Sent the old one off to our lab where they determined it had a bad driver.

Anyway, I digress. I think Fortune has you on the right track. This is easy to determine. Hook up a manual fuel pressure gauge to the Schrader valve fitting and use duct tape to tape it to the outside of the windshield. Bring the hose up from the cowl and tape it low and out of the line of site, but where you can read it. Do NOT bring the gauge and line into the cab! Then just monitor your fuel pressures.

Another option may be to monitor your fuel pressures with a scan tool if you can get someone to do that for you. I need to go look at my 99 software and see if that's available. I can't remember. But this shouldn't be that hard to determine the problem.