Q Why does my engine not start when hot?
I have a La Strada Avanti EB, based on the Fiat Ducato with the 150hp engine. Although registered in 2018, I think it was produced at Fiat in late 2016 from the data plate under the bonnet.
I have a problem with starting when the engine is hot after a run. I arrive at a campsite and book in. Back in the ’van, say, after five mins, and it can take 12 or more goes to start the engine.
It fires up immediately and then stops straight away. If I hold the key in the start position I can hear the engine fire and stop repeatedly and the starter motor ‘fighting’ with the engine. Not good!
Also, this can happen if I stall the engine on the road; it won’t restart straight away. There are no warning lights on the dashboard and the garage says there are no fault codes showing.
The problem started a year or so ago and has got steadily worse. Now I worry about driving it and stalling in traffic.
Cold starting is perfect. As soon as I touch the key, it’s away. When it’s going it runs fine, with lots of power hot or cold. The tacho always works OK and no misfiring.
I’ve added additional earthing straps, which made no difference. Also, injector cleaner in the fuel made no difference.
The battery is good with plenty of power, while the starter always engages and cranks the engine enthusiastically. The Fiat Professional garage can’t find the cause.
Steve Carpenter
A This kind of thing can be infuriating. Because the EOBD system (on board diagnostics) is geared towards detecting faults that could affect the emissions of the engine, there are often no clues.
We must consider anything that has changed between the condition when things work, and when they don’t. Here, it is a thermal matter.
I have seen similar, but not exactly the same problems a couple of times and in each case, it was the crankshaft sensor that was faulty. The contacts in the sensor are sensitive to heat. While they may work when cold, once they have warmed up, and the contacts have moved apart a little, there will be a signal to the ECU that the timing of the cam and crank sensors is incorrect. That will cause the engine to shut down very quickly. It should be recorded by the ECU as ‘crank/cam sensor implausible’ but it often does not.
The sensor is to the rear of the engine and attached to the gearbox, because it gets its signal from the flywheel. These are not expensive, and not time-consuming to replace, so I would do this first.
The other possibility is that the starter motor is working well but, due to a wiring fault, it appears to the ECU that it is drawing too much current, or that the solenoid is not disengaging. The engine will shut down to prevent a fire. The problem could be in the starter motor or the wiring. This would be the next thing to check and repair or replace.
Always start with the simple (and inexpensive) items and eliminate them. Remember, sometimes there can be more than one fault and that the process can be one of looking for improvements, however small, and keeping a record of what helped and why that might be.
I hope this helps!
Nick Fisher