hot start problem

[blackvelvet]

I have an annoying problem with my Chevy Camper.
When it is cold the starter turns nicely. When it is hot, the starter turns very very slowly and occasionally it will fire up. otherwise I have to leave it for ten minutes or so.
I fitted a new starter and a new heavy duty battery and new battery leads. something I would probably do anyway with a used vehicle, but the problem continues.
I have checked for mechanical causes, it is fine no problems.
because the battery is new I assumed it was good.
However. In the morning battery shows a reading of only 12.5 volts, but the van starts easily.
When the engine is running I get a charging reading at the batt terminals of 14 -14.2 volts.
When the engine gets hot I switch off the engine and the reading at the terminals drops to12.4 attempt a hot start the reading drops to 8.6 volts with the starter turning.... turn the ignition off... check the battery
immediately, it only shows 11.9 volts and builds up to 12.04 after a few minutes. It appears the battery no matter how it is charged the voltage it holds is only 12.5.
Because the problem was there before I changed all the components and I still get the same symptoms after, doubt has set in and I can,t reason it out. Any advice before I buy another battery.

 

[Wilko]

Hi - immediate slow cranking is normally caused by insufficient battery. It sounds like the battery is charging (14V is ok) but is failing under load when it's hot. I'd hope to see 10V while cranking (8 is too low I reckon) so I'm thinking battery has a weak cell. Dumb question but can you see if it's got water in all the cells? If battery is new, any chance the shop can test it or swop it?

 

[Deleted member 26818]

Check there is an earth cable from the engine to the chassis.
Check that it is tight and making good contact.

 

[blackvelvet]

Thanks for the reply's.
I suspect the battery, but because I had renewed it, It threw me off the scent. After testing everything out over and over, all logic left me and I started thinking it was something magic.
The main earth lead from the battery was originally connected to the alternator bracket. I moved it and connected it directly to a starter bolt. The volt readings to the ends of the cables is the same as the battery voltage, no loss.
It also threw me when the van starts so easily when cold and only 12.5 volts.
I think a battery condition test is now essential.

 

[Barry White]

Not familiar with the chevy at all but had the very problem you had on a xr3i, new starter still the same, new battery still the same, alternater checked ok.
An old mechanic said fit a heat shield between the exaust manifold and the starter. So I fabricated one from an aluminium exaust heat shield and it worked.

 

[blackvelvet]

Thanks mykey
I have heard about this with Chevs, but heat soak would not explain the low voltage after a good charge,
I think it mainly effects vehicles with headers fitted, but it may be worth a try.