Difficulty starting when environmental temp is hot?

[skyehunter]

1989 Toyota X-cab 4X4
120 K Miles
3.0 engine

Problem:
I have noticed for the second summer in Arizona that I have had the truck that when the outside (environmental) temperature gets above approximately 90 degrees my truck becomes difficult to start. This issue goes away once temp drops. The truck cycles well and stumbles for approximately 5 to 10 seconds after starting. then rund strong. Did a tune up recently during winter time and no issues after tune up (plugs, wires, cap, oil, majority of smog components replaced) until summer heat..

What could this be???

Symptoms:
Strong battery, Starter continues to cycle w/o hesitation.
No sluggish delay of Starter while attempting to start.
No smell of fumes
Fuel pump has been replaced, unknown when..
Does not matter if truck is hot or cold.
Less common when starting immediately after shutdown of engine.

I did do a search, and checked out some suggestions for similar starting issues. If I missed a solution, sorry, please point me in that direction.

Thanks for any constructive ideas.

 

[inkpot]

Howdy! Maybe a fuel line too close to the exhaust, which is boiling off the fuel, or creating enough pressure to send it back towards the tank? Fuel pump doesn't move air near as good as fuel. Vapor lock is not very common in newer rigs, but not impossible. John

 

[skyehunter]

I'll check it out...