crank but no start w/o jump when hot out

[Farrar]

OK, y’all, this is a weird one – for me, anyway.

Background:
– 2006 PT turbo, 106k miles
– no trouble lights or codes
– water pump, timing belt, and alternator less than 2 years old
– battery and main/accessory belts less than 1 year old
– spark plugs changed 36,000 miles ago
– all fluids up to date except ATF & brake

Symptoms:
When it’s 89°F or cooler outside, I can turn the key and start the engine.
When it’s 92°F or hotter outside, I can turn the key and it will crank but not start — UNLESS it gets a jump.

So it looks like something badly magical is happening somewhere around 90°F ambient temperature. I really don’t like carrying around the extra battery to jump my car most of the time (it’s already hot here in Louisiana), so I need to fix this so I can get on to my other problem, which is fixing the air conditioning! 🙁

I’m stumped.

Thoughts?

Thanks in advance for any help or advice!

Topic

[college man]

It sounds like your battery is having issues. Check the cables are tight and clean.
Have the battery load tested either at an auto part store or do it yourself. More
in this link.

http://www.ericthecarguy.com/faq/solving-automotive-no-start-problems

[James P Grosso]

Heat has the effect of increasing electrical resistance in the wiring.
Bad electrical connections or resistance, especially in the battery cables, can cause ground loop electrical problems that can interfere with the ECU detecting the signals from the various sensors on the car.
Make sure the battery cables are in good condition, with clean connections at the battery, engine and body for the ground. The positive side may be harder to check, It usually goes to a bus bar in the fuse box under the hood, but a “ground loop” issue would be on the ground side anyhow.

[Farrar]

Update:

I gave up trying to figure this problem out myself and took it to the dealer. A new ignition switch fixed the problem.

Thanks!

[college man]

[quote=”Farrar” post=177711]Update:

I gave up trying to figure this problem out myself and took it to the dealer. A new ignition switch fixed the problem.

Thanks![/quote]

Thanks for the update and fix.

[Author]

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