Engine Slow To Start When Hot

[Tazzzzman1]

Hmmm may need some help on this one now.

First thing was to swap starter motor with a spare one I have. Took the car on a run. Stopped and switched off car. Volt meter showing 12.3v. But engine barely cranked...just like a flat battery. So tried to start via the start stop button...same thing.

Ok so final thing fit another battery (fully charged via jump leads) and try again....nothing the same.

 

Now what?

I'm stumped. Its not the battery, its not the starter, its not the Ignition switch.

 

Any ideas? I need to get this sorted by the end of this weekend as Scotland looming (either that or there will be a lot of bump starts) So if anyone has further ideas or can lend a hand to diagnose I'd appreciate the input

[Guest 2b cruising]

If you have got an amp guage you can beg borrow or steal, see what amps you are drawing on cold cranking and on hot cranking. If lots more when hot, it is still pointing to starter fault. That is of course unless your engine itself is tightening up.f you were closer I would defo come. Can't wait to see your and steamers masterpiece.

[richardm6994]

I hope not but could the charger be overheating and getting tightf on the bearings? just a thought as it is directly above the exhaust.....but it does have air rushing through it that should keep it cool.

eliminate it by taking the belt off when it struggles?

 

Maybe too much ignition advance at cranking speed.....ie it's fine when cold but when hot it just takes it over the limit into pinking territory?

[sj-bradley]

Wild guess here.

 

Can you get a torque wrench on the crankshaft nut and set it so it "just clicks" on max compression when cold and then try again when hot and hard to start?

 

You will also get a feel for the cranking resistance that the starter would feel in that way. A crude method, but might show a tight engine when hot.

 

As I mentioned before, electricity in house wiring is rated up to 70 degrees C in normal maximum load ratings so I don't think heat will be affecting the electrics side of things.

 

This you have already confirmed by changing the starter for another one and it does the same. If you have decent heavy duty jump leads, they should be ok to start the car and you have tried a second battery jumping it too.

 

Does the battery in the car feel hot though? if yes, then it's internal resistance is causing current squared heating which will eventually shorten the battery life.

 

Also, if it gets hot, it could be overcharging which will increase its internal resistance too which will affect cranking amps.

 

Simon.

Edited April 6, 2015 by Simon B

[sj-bradley]

You could always build in the old fashioned "starting handle" ...

 

Be the first one ... !

 

Simon.

[theduck]

Could it be that some configuration in the ecu is adding advance when the engine is up to temp and that is resulting in too much advance when starting?

[Tazzzzman1]

That's what I'm starting to think as well. I've emailed CANEMs to see if this could be the case

[steve in stockport]

As Duck said there may be an ignition advance/temperature compensation table in the map that is written wrong but probably not.

The engine is your unknown spare, was it fully rebuilt? Was the crank checked for oval it, bearing clearances checked with plastigauge or similar? A bearing running tight when hot? Excess under bonnet temp or heat soak from the charger and intercooler?

[speedtripledan]

If you suspect the ecu disconnect the temp sensor when hot and see what happens. You could also mark the crank pulley and use a timing light to see the timing hot and cold

[stevedohc2b]

Terry can you plug in a laptop in to the ecu to see what is going on or running data login.

Could you try disconnecting the temp sensor for ecu when hot and prob happens or connect a spare sensor in to a cool water / air

To fool ecu thinking engine is cooler,

 

Stephen

[theduck]

http://www.canems.co.uk/pdf/injection_manual.pdf

 

Pages 34 and 36 (or 36 and 38 if you use the pdf page numbers).

Edited April 6, 2015 by theduck

[sj-bradley]

I think you're all looking up the electrics tree and not the mechanical one.

 

If it turns over slowly when hot, then it has to be that the engine is physically harder to turn when hot. I.e. it's binding somewhere. Have you checked oil pressure etc and is it harder to turn by hand when hot?

 

I had a starting problem with fuelling early on which happened when cold and it was the amount of fuel injected when cold that was the problem and was a simple map fix.

 

However, when I had later starting problems, it turned out that the battery was dying and needed replacing.

 

You have however ruled that out with the replacement starter and jump starting with a known good battery. I would really check to see if the engine is harder to turn over when hot. If you have one of those laser thermometers, you could also see if there are any hot spots too.

 

Simon.

[sj-bradley]

As you have supercharged this, you are physically generating more heat that needs to be dumped somewhere and aluminium has a higher thermal expansion than steel, so the pistons will be slightly larger than normal causing binding problems.

 

An engine should normally be harder to turn when cold and easier when at normal operating temperatures when oil has circulated too. An excessively hot engine will be harder to turn resulting in a sluggish starter motor.

 

It's a simple check with a long torque wrench or breaker bar to see if this is true or not.

 

Simon.

[Guest 2b cruising]

Follow Steamers lead. Just take the drive belt off charger and illuminate that from the problem first mate.

[jaimo]

I agree got to be supercharger or ecu really do as prev recommended remove belt and then temp sender and try