# Hard to start when hot 98 5.7 L Suburban



## imanager (Feb 23, 2012)

I have seen a lot of posts on a lot of sites that do not deal with this specific problem but are close. My 1998 GMC 5.7 L Vortec SFI motor starts fine when cold or it has been sitting over night but after I drive it for a while, until engine is hot, it starts as though the timing is far advanced. It hestitates during initial crank and continues for a little while and then it will catch and run fine. It acts like the timing that we used to super advance timing in our street hot rods with heavy cams and compression attributes. Help.

Earl, lost in Suburbia???????


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## Corday (Mar 3, 2010)

Sounds like vapor lock due to fuel pressure regulator failure. This is common in 5.7L of that era.


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## Midnight Tech (Dec 31, 2001)

Starter could also be "heat soaking" and not willing to turn the engine while hot.


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## imanager (Feb 23, 2012)

Corday,

That sounds very plausible except for one thing. Dosen't vapor lock just preclude the starting and does not affect the advanced timing indicator symptom?

Midnight Tech,

That sounds very close to what may be happening. It is much easier to change the starter that the Fuel Pressure Sensor under the intake manifold. I think I may try that remedy first.

TTFN,

Earl


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## Wrench97 (May 10, 2008)

If you have access to a amp draw meter check the starter draw it sure sounds like starter drag from failing armature bushings.

You should see less then 350 amp draw and the battery should stay above 9.6v while cranking.


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## imanager (Feb 23, 2012)

Wrench 97,

That would be a plausible symptom if an advance timing problem would not be part of the problem because the advance timing would also show an increase in amp draw during the initial stages of the starting problem I am having.

Earl


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## Wrench97 (May 10, 2008)

How do you know the timing is advanced?

Check it with a high end scan tool that reports the timing or 98 should still have a distributor use a timing light while cranking but sound alone is a poor indicator.


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## imanager (Feb 23, 2012)

Wrench 97,

I do not know for sure that the timing is advanced. I am just using my 40 some years of experience to describe what I hear and know about my problem.

Earl


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## royce gibbs (Jun 4, 2015)

disable ignition, then crank to isolate timing as a factor... some earlier starters used heatshields to fight heat soak


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## royce gibbs (Jun 4, 2015)

checked the knock sensor and circuit yet ?


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## imanager (Feb 23, 2012)

Thanks Gang,

You all were a great help. I changed the starter and it fixed my problem.

Earl


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