Problems that come into the workshop are pretty steady and straightforward most of the time, but every so often, things can go a bit pear-shaped.
I had one such occurrence recently, concerning an A-class motorhome which the owner had brought in for its MOT and service.
It should really have been nothing to get too stressed about – other than the poor engine bay access you’d expect in an A-class vehicle.
Everything seemed to go perfectly well, with no MOT problems and a straightforward service, followed by a successful road test that revealed no apparent motorhome faults.
The customer collected the vehicle that same afternoon, but only got a couple of miles away before it suddenly lost power – luckily, not far from a layby. I went out to it, but no relevant fault codes were present, so we got it recovered back to my workshop.
With no fault codes showing, it’s a case of going back to basics. The first question was, what might I have done on the service that could possibly affect the engine like this?
The air and fuel filters had been changed and I’ve been caught out before (by a dead mouse falling through when I took the filter out!), so I removed the filter and checked with an endoscope for little critters – but found nothing. I replaced the fuel filter with a new one, but that made no difference, either.
Now with common rail diesels, a variety of sensors could cause the issue. However, testing them involves the use of specialist equipment, as well as knowing what readings to expect.
I don’t own the necessary equipment or have the specific knowledge, so I called in a friend, who is brilliant at this kind of diagnostic work.
After a couple of hours, we narrowed it down to a failed EGR valve. This electronically controlled valve recirculates exhaust gas into the inlet manifold, to reduce cylinder temperatures and nitrous oxides in the exhaust. If it sticks open, the intake air has an excessive amount of exhaust gas in it, which smothers the combustion process, causing a loss
of power and difficult starting from cold.
The valve for the 2.3 Ducato is at the right-hand end of the head as you look at the engine and has a cooler attached, to reduce the temperature of the recirculated gas. It is also connected to the exhaust manifold at the rear of the engine.
In an A-class, access is limited, and in this case, the manifold flange nuts were corroded in place, so it was quite challenging. The good news is that after replacement, the motorhome ran fine and the customer drove it home with no issues.
If you’re considering buying one, see what I had to say about the importance of investing in a good fault code reader – it’s a gadget that can provide plenty of functionality.
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