1998 GMC Sierra

I have a 1998 gmc Sierra 5.7 vortec with 84,000 miles. Whenever the outside temp gets around 90 degrees and I drive my truck for awhile, it won't start for about 20 min. after I turn it off, I must allow it to
cool. Had a new fuel pump installed twice, changed the fuel pump relay and still having the same problem. Can someone please help me. Thanks in advance. Rob
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When won't start do you have spark, will it start with starting fluid, basic diagnostics.

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I had the same problem on my 2000 and that did it. I don't know why heat affects it but it did on mine.
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