Technical Hot engine start problem

[MXPunto]

Hello, I own a Fiat Punto MK2 188 Sporting 1.2 16v 2001 81hp. I bought the car in 2006 and I still have a problem with it even to this day. When I hop in the car and the engine is cold, the car starts well, but if I travel for a bit and I stop the engine when it's hot, the engine doesn't start. Now, the engine cranks slowly and the dashboard lights seem to fade off when this happens. I changed the starter and, the cables that are connected to the battery are in good condition! A few weeks ago I was at a gas station and after i pumped gas i couldn't start the car, i had to push it. Also when it starts after a push the engine works well!! Can this be a ECU problem? I don't know if it's the battery because the car starts when the engine is cold, what difference would it be if it was hot? The alternator is new.

Thanks! Looking for a tip

 

[varesecrazy]

Have you put a jumper cable on when it has failed to start..?

It turning slowly is a poor electrical circuit... and the battery to chassis cable is a common failure

 

[MXPunto]

I will try that next time, it's the only thing left to do The battery is 5 years old, but when I bought the car it had the same problem but with a different battery. So i changed it and it lasted for a while but the problems reappeared.

 

[jackwhoo]

I will try that next time, it's the only thing left to do The battery is 5 years old, but when I bought the car it had the same problem but with a different battery. So i changed it and it lasted for a while but the problems reappeared.

Is the alternator failing to charge battery properly?
This could be related to faulty battery cables.

 

[varesecrazy]

I will try that next time, it's the only thing left to do The battery is 5 years old, but when I bought the car it had the same problem but with a different battery. So i changed it and it lasted for a while but the problems reappeared.

You would have disturbed the cable getting the battery swapped ;

 

[MXPunto]

The alternator is good, the battery is measuring 13,8v with all headlights on, i checked the negative cable from the battery and there is no corrosion. The positive one that goes to the starter is also in good condition

 

[jackwhoo]

The alternator is good, the battery is measuring 13,8v with all headlights on, i checked the negative cable from the battery and there is no corrosion. The positive one that goes to the starter is also in good condition

Sorry you can't always check by looking.
Do jump lead test.

 

[jackwhoo]

The cables disintegrate under insulation.
Sometimes where the terminals / battery clamps are crimped on

 

[MXPunto]

Will do next, thanks for the replies

 

[MXPunto]

Hello, turns out the battery is fine, the car does the same stuff even with a different battery and another starter... anything else to look for? Also all the cables are in good condition, checked everything..

 

[jackwhoo]

Get a volt meter .

Measure the voltage at battery terminal posts(not the clamps) while engine hot turning on starter.

Post result on forum.

Then measure voltage between battery negative post(not the clamp) and and good clean metal part of engine while turning engine with starter motor.

Post result on forum

 

[Iggy86]

I had this happening in the past with my old Alfa Romeos.
Esactly what you are describing, turned out to be a faulty cam sensor in one and faulty cranck sensor on the other.
I'm not sure if your Punto has either of them but worth checking ?

 

[MXPunto]

Hello, did the errors appeared when you checked with the obd diagnose? The errors I have are P1135 (lambda sensor), P0105(MAP sensor) and U1602(unknown) but i don't think these errors are the problem here since they are not responsible for turning the crankshaft, if you can understand the phenomenon. I also put the jump starter on the car, no matter how much energy it would need, the car should start if it drains energy... but not my case. It is a pretty complicated thing, a guy that worked at Fiat said he doesn't know what to do anymore

 

[jackwhoo]

Hello, did the errors appeared when you checked with the obd diagnose? The errors I have are P1135 (lambda sensor), P0105(MAP sensor) and U1602(unknown) but i don't think these errors are the problem here since they are not responsible for turning the crankshaft, if you can understand the phenomenon. I also put the jump starter on the car, no matter how much energy it would need, the car should start if it drains energy... but not my case. It is a pretty complicated thing, a guy that worked at Fiat said he doesn't know what to do anymore

Do the volt checks .

The energy is obviously not getting from battery to starter motor.

There are only two big wires carrying the energy to starter motor just replace both wires. Replace the big +ve wire going straight to starter motor and replace the big - ve wire going into engine/gearbox.

 

[MXPunto]

I gave energy straight to the starter and didn't work

 

[jackwhoo]

I gave energy straight to the starter and didn't work

Did you use two brand new wires to give energy straight to starter

 

[Iggy86]

Hello, did the errors appeared when you checked with the obd diagnose? The errors I have are P1135 (lambda sensor), P0105(MAP sensor) and U1602(unknown) but i don't think these errors are the problem here since they are not responsible for turning the crankshaft, if you can understand the phenomenon. I also put the jump starter on the car, no matter how much energy it would need, the car should start if it drains energy... but not my case. It is a pretty complicated thing, a guy that worked at Fiat said he doesn't know what to do anymore

There was an error code, can't remember as it was many years ago but it was totally unrelated to the fault.
What I couldn't understand that if the battery or power from the battery was the problem the car would not start no matter if cold or warm.
Replacing the cam sensor was easy as just bolted on top side of engine.

 

[jackwhoo]

Do voltage checks

 

[jackwhoo]

There was an error code, can't remember as it was many years ago but it was totally unrelated to the fault.
What I couldn't understand that if the battery or power from the battery was the problem the car would not start no matter if cold or warm.
Replacing the cam sensor was easy as just bolted on top side of engine.

His problem is slow or no cranking when hot.

 

[jackwhoo]

Why would that matter?

Why would what matter?