Car won't start when its in operating temperature

[AlbertoUSB]

Our car have been having trouble starting when its heated up. The car starts just fine when its cold, but when it reaches about 190 Fahrenheit(About 90 Celsius)we turn it off and then try to start it again and it wont start.
We have reach to many conclusions about the problem and did lots of stuff.
1) We change Starter Engine and Alternator, and still the problem occurred
2) We found out that a Fuse in the Starter Relay melted (but we guesse it was still working fine), changed it and we still couldn't start the engine.
3) We tried a different Rectifier (TO change from AC to DC). Nothing.

After trying all this we decided it has to be the Crank Wheel Sensor. We are not 100% sure but we haven't try changing it.

Any suggestions? We would really appreciate it!!

PD: Sorry about the english. And the Engine its a Honda CBR 600 F4i

[AlbertoUSB]

Our car have been having trouble starting when its heated up. The car starts just fine when its cold, but when it reaches about 190 Fahrenheit(About 90 Celsius)we turn it off and then try to start it again and it wont start.
We have reach to many conclusions about the problem and did lots of stuff.
1) We change Starter Engine and Alternator, and still the problem occurred
2) We found out that a Fuse in the Starter Relay melted (but we guesse it was still working fine), changed it and we still couldn't start the engine.
3) We tried a different Rectifier (TO change from AC to DC). Nothing.

After trying all this we decided it has to be the Crank Wheel Sensor. We are not 100% sure but we haven't try changing it.

Any suggestions? We would really appreciate it!!

PD: Sorry about the english. And the Engine its a Honda CBR 600 F4i

[Pete Marsh]

Is the engine turning and wont start? Or wont turn?

If it is turning, check and post us the voltage measured at the fuel pump, coils supply and ECU supply.

Pete

[AlbertoUSB]

The starter its turning... but if we push it it starts... It might be that when the Stater soaks power from the battery, the battery its not capable of suplying fuel pump, sensors and coils.

We will also change the battery for a new one tomorrow... Thanks Pete...
If you have any other sugestions

[VT_Electrical]

Alberto,

I used to have this same exact problem with our F4i in 2007. It wouldn't start once it was up to temp, even though the starter cranked over fine, but it would always push start. It turned out that the fix was a new cam sensor (we were running fully sequential), so I suspect it could be that or potentially your crank sensor. If you're looking for a quick fix, try replacing each of those and see what happens.

If you want to satisfy yourself as far as knowing for sure if it's the problem, check the crank and cam signals with an oscilloscope (or your ECU software if it is kind enough to provide this). Also check if you are getting sync errors with the ECU, as that is an indication that your cam sensor potentially isn't being read (if you're running sequential). In my experience, during a hot start problem, I would see sync errors and no cam signal with a scope. I never managed to satisfy myself 100% with an answer as to why and spent a long time trying to work it out, but I have basically deduced that for some reason our sensor's output voltage was reduced once it got hot, and so at say 300 RPM when you're cranking the starter, you don't have enough output. However, when you push start it, your crank rotates much faster (say 600 RPM or so), and since the F4i sensors are variable reluctance (i.e. output is proportional to rate of change of the magnetic field and hence proportional to engine speed) you end up getting a voltage that is higher than before, which the ECU can then read. I have never figured out why heat would cause the sensor voltage to be reduced, but I definitely saw the signals change, and with a brand new sensor, the voltage output was never a problem.

Hopefully that will work for you. If it doesn't and you need more suggestions, just post again and I'll do my best to help.

- Jim

[Landreneau]

Pitt had hot starting issues a few years ago. Our solution was new spark plugs (we pretty much changed them every event), a new higher current load battery, and lots of ground wires. We have switched to the RR since

[Wesley]

Could also be an engine issue - if the engine was rebuilt incorrectly, the hot clearances could be a bit low, making it tight and harder to start. Happened to us two years ago, we just couldn't hot start it. The fuse issue makes me think something like this may be the culprit.

I would say that the heat was changing magnetic properties, but the curie temperature for steel is an order of magnitude or so greater than you're running. It doesn't sound like a sensor issue if you can push start it.

[Yellow Ranger]

yea- when that happened, we could barely push start it! the motor just wouldn't turn, but that will happen when you don't put in all the bolts and mismatch bearings...

[B Lewis @ PE Engine Management]

Are you using any starting compenstaion for the fuel when then engine gets warm?. As the fuel heats and the engine heat soaks it will sometimes need a little extra to get started. We have seen this problem many times during the driver change for endurance.

[VFR750R]

As aluminum expands more then steel, your bearing clearances open up with temperature. All major racing series pre-heat their engines before starting them for this very reason, especially all-aluminum engines. Once they're warm they're fine.
Your valve clearance should do the same, so you shouldn't be holding valves open or something once it gets hot, but it wouldn't be a bad idea to check your valve clearance. Tight clearance do make engines hard to start.

I suspect a sensor/pickup getting hot and not functioning at the speed the starter turns the engine over. When you push start it, the rpm is probably much higher, which may allow a weak pickup to get a high enough amplitude signal for the ECM. When starters get hot, they typically don't spin as fast (as resistance goes up with heat) meaning the start rpm is even lower which just adds to the problem.

[Ben Stockman]

We have had this problem in the past with the older Honda RR. This year we ran 4 gauge welding wire to the starter and a ground directly to the starter this year and didn’t have any starting problems. Something else that we hadn’t been doing in the past was putting a relay on the rectifier, so it was constantly on and draining the battery this wasn’t helping our staring issue, the simple way to fix this is to unplug the regulator when you’re not using the car. This year our car has always started without any problems.

[AlbertoUSB]

Well I forgot to post our results after troubleshooting the problem.
We didn't finish endurance because our car did not start, not when the pilots changed positions, but afterwards during lap 15. It had issues starting when it was a it operating temperature, and we first thought it was something simple, but we were wrong.
So we came back to our country and did lots of testing, measuring current in pretty much every sensor and lots other stuff.
We had an event that we do at our college, and testing the car before the "showdown" the engine broke. Once we open up the engine to see what had happened, there were bearing pieces all over the carter. So afterwards when we took the crankshaft out and checked out the other bearings, they had some kind of red marks and we figured it was because there was lot of friction going on between bearings and crankshaft. It was like a living hell in there. We concluded it was a lubrication problem (that is kind of obvious) but we could not figured why it happened. (we have some theories)
Afterwards we put another engine on the 09 car and it worked perfectly so it wasnt an electronic problem.
Thank you all for your help.