Should it be so difficult?

[Suff]

My car is back in the garage again. 5th time I think now. They asked me to come in and show them the problem. Basically they clear the fault with the computer then they can't make it happen again. I can make it happen in 10km.

So I drove with the cable fixed into the dash under my legs and the mechanic sitting with the laptop on his knees as we drove out of town. He was explaining to me that the high pressure diesel in the injection system was showing slightly low pressure (about 200 bar). So I drove it to the next town, pushing the engine then slowing the engine. Then we turned around, I waited for a truck to pass and get down the road as I was going to really give the engine some revs in each gear then slow down whilst going up a hill.

Off I pulled, pushing the car hard up to 4th gear then just backed off the throttle. Immediately the mechanic said "whoah" as the engine dropped 500 bar of pressure. I then went to accelerate away, up hill, from 35mph in fith gear and the light came on again and he told me the engine management had taken over.

However, once we got back into town the car was totally back to normal with full pressure, but the engine management had a fault and there was no way it was letting go.

I left it with the garage on Monday and they've asked me to come back in today to talk to me as they didn't know what the problem was.

A classic case of "to err is human but to screw things up entirely requires a computer"... In the meantime I've been doing some searching on the problem. It would appear that this is almost always one switch which disables part of the high pressure pump. £40 to buy. Depending on what they say I'm going to ask them to replace this switch first and then we'll see if it's fixed.

This used to be easier. I could tell what the engine was doing and what the computer was doing just by driving it. But working out why the damned thing was doing it? That's a different issue. The car has had this fault since May last year. Very irritating especially as I'll need it for work very shortly.

[Workingman]

Ahh... long gone the good old days of strobe lights, a vacuum gauge in this line, a pressure gauge in the other, a strain gauge on the governor....

There is the upside, though, that when things work they do go on for a lot longer and with a lot less human interference. It's when they go wrong.......

[cruiser2]

Suff,
I once broke down coming home from Scunthorpe. I had a Peugot 405 at the time and it kept cutting out. I was on the M18 at the time.
Got towed home by the RAC. Like you it was a small part in the engine management system which kept failing. It was a company car so I did not have to pay. Evidently it took longer to dismantle parts to get at it than fir the new one.
Hope you soon get it fixed and doesn't cost too much.
Had an uncle who was a motor mechanic. He could tune a twin carb jaguar better than the local main Jaguar dealer workshop

[Suff]

I spent two hours getting to the garage and to talk to them today. I asked if they could replace the potential failing switch and learned the PSA only offer the pump, complete. The garage offered to send me to a Bosch fuel system specialist where they could check the entire system and, if required, replace the switch. More time lost.

I've seen the switch and connection. One of the advices is to unplug the cable and ensure everything is very clean. As I've had issues with oil inside the cable runs I'll try that on Sunday before talking to the garage about going to the specialist...

Frustrating. Although they have cleared the error and the car is driving normally again. Well for the next 30 miles anyway.

[TheOstrich]

Sorry to read of your travails, Suff ...

A near-neighbour of ours, self-employed, uses a good-sized van for his gardening work, carting his mowers around. A couple of weeks back, some strange glitches developed in the electronics; the engine kept switching off, the lights kept switching on, and the doors wouldn't lock or something - the upshot is that its had to be referred back to a specialist dealer for remedial work and/or a new SIM card or whatever; he has no idea when he's going to get it back, or more crucially what the repair bill is likely to be, and in the meantime he's got the expense of hiring a replacement van ....

[Suff]

Yep, the moment you mate a computer with a chunk of hardware, problems may occur.

The main issue, as I'm well aware, is that when hardware starts sending signals (or not sending them), which are not anticipated by the software, then the software either shuts down (likely in the case you are talking about) and reboots, continuously, or it goes in a complete sulk and virtually shuts the hardware down.

This is not only in cars, it's common across the whole computer/machine landscape. But is a tad annoying when it's your only means of transport either personally or for your business.

Because I'm aware of what the physical mechanics can do and also how brain dead the software can be (having written software and maintained vehicles), I can usually work out what is going on fairly quickly. But you do need to know the systems and it's long, long, since I studied any fuel injection systems or ECU implementations.