1998 Explorer Limited 5.0 Vapor Lock

[bilug]

Hi,

I've been experiencing what I believe to be vapor lock when the car is hot and only on the hottest summer days.
After parking and trying to restart after about 30 minutes, the motor tries to fire but barely runs and stumbles, almost like the timing has jumped. Lots of misfires.

I've replaced the coil packs thinking that they were getting hot and causing the issue, replaced the MAF thinking airflow was an issue, and found my started was coming apart and felt that maybe the motor was not turning over correctly due to the failing starter. None of those have fixed my problem so now it has to be something fuel related.

Once the car cools down (a few hours minimum), it fires right up and drives fine. My guess is I'm getting vapor lock somewhere in the fuel system.

Any advice on troubleshooting this issue? If replaing the fuel pump was easy, I'd just do that but it requires dropping the tank. I really want to verify the pump is the issue before taking it to the shop.

 

[410Fortune]

Vapor lock pretty much impossible on a efi system like this

You need to check fuel rail pressure

What you have sounds like a weak fuel pump… it gets hot, cannot deliver enough fuel, things start running lean, everything gets hot, eventually runs out of gas… won’t restart until pump cools down and can supply needed pressure again

So when cold you should have 36 psi at the fuel rail. When the truck warms up and fuel pump gets hot I bet it drops way off

So you need to rent or buy a simple fuel pressure tester

I would probably
Plan to replace the pump strainer and filter
We prefer Bosch pumps here

You can drop the tank or cut an access panel from above
It’s not a terrible job
To drop these tanks, but not the most fun you can have either

 

[Squirrelmaster]

Check your fuel pressure regulator, as a hard start when hot is often a symptom of a failed regulator. When a regulator goes bad, it can allow pressure to bleed off too quickly in the fuel rail, and then the fuel in the rail will begin to vaporize due to the engine heat and you end up with a hard start condition as the fuel cannot atomize correctly as it goes through the injector. Pull off the vacuum line and inspect if it is wet, as that is typically a sign that the diaphragm within the regulator has failed.

 

[Turdle]

This also sounds like it could be a faulty ECT sensor. But definitely check fuel pressure when it's acting up.

 

[C420sailor]

Could also be crank sensor going out, but less likely than the suggestions above. Start with them.