Buick 3800 difficulty in restarting/cranking hot engine.

[emmett442]

Check for fuel pressure regulator leaking into the intake manifold.

 

[goofy]

So it won't rotate when hot?

 

[Lubener]

Check for fuel pressure regulator leaking into the intake manifold.

Fuel mix would be overly rich, engine would run poorly and likely set a code.

 

[GW.]

Check for fuel pressure regulator leaking into the intake manifold.

Yes the fuel pressure regulator is a common problem on these. All sorts of strange symptoms. I use to replace them all the time at the dealer, even under warranty. Yes I’m old….

 

[Carlostrece]

So it won't rotate when hot?

Sometimes it will not rotate. Other times it rotates with great difficulty. It only happens after a long drive on hot days when using 87 octane gas. I use Shell, Chevron, or U76 gas. Brand of gas doesn't affect it.

When using 89 octane gas there is no problem, even on hot days.

After starting it... It runs smooth, has good power, and gets 34 mpg highway. It functions perfectly after starting it.

 

[Bud_One]

I had a 1991 Chevy S-10 do the exact same thing .
2.8 V6 , TBI - Hard to start when hot only.
Found out it was the coolant temp sensor for the ECM.
It was giving a false reading and showing that it was still cold.
It was flooding the engine when hot.
And to clarify , the temp sensor for the gauges was a separate sensor.
Don't know if the 3800 are the same or share a sensor .

 

[Carlostrece]

I had a 1991 Chevy S-10 do the exact same thing .
2.8 V6 , TBI - Hard to start when hot only.
Found out it was the coolant temp sensor for the ECM.
It was giving a false reading and showing that it was still cold.
It was flooding the engine when hot.
And to clarify , the temp sensor for the gauges was a separate sensor.
Don't know if the 3800 are the same or share a sensor .

Was your S10 having a hard time cranking/turning at hot startup, or was it cranking/turning freely, but not easily igniting/firing up?

My engine struggles to turn over/crank when engine is hot, but only with 87 octane gas. Not a problem with 89 octane gas.

 

[Bud_One]

Was your S10 having a hard time cranking/turning at hot startup, or was it cranking/turning freely, but not easily igniting/firing up?

My engine struggles to turn over/crank when engine is hot, but only with 87 octane gas. Not a problem with 89 octane gas.

It was having a hard time turning over and sometimes backfiring.
I'd let it set a few hours , come back and it'd fire right off.
But I never changed octane. Always ran 87.

 

[PontiacHO]

Marvel Mystery Oil mixed with water drawn into the engine via a vacuum port will clean the pistons and combustion chambers. To be clear, the starter doesn’t want to spin the engine over with 87 octane? Timing advanced too much can cause that but not sure how that can happen with your ECM etc. Have you had a heat sensor gun on the engine? Wondering what your operating temperature is.