80 hard starting when hot - turns over but have to pump the gas

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This is a relatively new situation that has just started in the past year to year and a half.

I have no issues starting the 80 when it's cold or been sitting. Generally I have no issues starting the 80.

However, the last few times I've been on the beach, driving, when I get to an area where we want to park, turn off the truck and then maybe decide a few minutes later to reposition, the truck turns over but doesn't fire up. I have to pump the gas while turning the truck over to get it to start; then it stumbles and starts up. Happened last weekend too..... we were driving up in the mountains with the AC on, got to our camping area and found a spot to park, turned the truck off and then about 5 minutes later we decided to move the truck to a "flatter" spot. Went to start it, it turns over but doesn't fire; I pump the gas a little and it starts.

What is causing this issue?

I did a quick search and didn't find anything.
 
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FPR VSV?
 

doc_random

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Could be vapor lock where gasoline vaporizes in the fuel lines. Heat in the engine compartment rises rapidly after shutting down.
This gets worse with a low fuel tank. The gas recirculates through the engine compartment getting warmer with each trip.
Beach driving, driving up a mountain could certainly make this worse with the engine working harder.
 
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Check the gas tank for pressure the next time it does it? Just slowly open the gas tank cap and listen for pressure to equalize?
 
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Fuel pump relay or possibly a bad connection at the alternator lug or alternator brush kit needs to be changed

The truck turns over just fine, checked fusible link and it was fine. I have not looked to see what happens if I remove the gas cap. There doesn't seem to be any issue with power.

It seems like either spark or fuel issue.

I did have someone else say the same thing about vapor lock. If that's what is happening then what should I do? Let the truck idle for a while before turning it off?
 

landtank

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Also fuel pumps will lock up when hot sometimes. Then run when they cool down. It’s the fuel that cools them so when you shut down the engine the pump heat soaks

Then there is the open circuit relay that might be lazy when it’s hot.

This isn’t going to be simple.
 

baldilocks

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If the engine starts when the throttle is opened allowing greater air flow into the combustion chambers there may be a problem with the idle air controller or possibly a faulty engine coolant temp sensor fooling the ecu into cold start mode.
 

doc_random

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Vapor lock: Rather than letting it idle I would suggest going easy on the throttle for the last 5-10 minutes of driving. You'll have better airflow to cool things if you are moving.
And then popping the hood when you park to let the heat out. Do you have a digital temperature gauge running off the OBDII? The stock gauge is misleading. The needle doesn't move between 185'F to 220'F (or something like that) so you can be in trouble before it moves.

I had a slightly different problem solved by replacing the fusible links. If I was doing short stops in the summer, sometimes it would not start after the third or fourth stop. Replacing the fusible links should be a 5 year maintenance service, IMHO. Pretty easy and maybe $20 in parts.
You checked the fusible links but they can be "walking wounded" with higher resistance and higher voltage drop when they are hot.
 

baldilocks

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Vapor lock of a fuel injected engine, especially one (1fz) that has no known chronic history of vapor lock, is unlikely. The OP stated that the engine starts with throttle opening.
 

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