Thread: Common rail explained

I'm sure some backup could be built into it but it always seems that designers don't think that way.

I was driving an EFI diesel LandCruiser a few years ago that was struck by lightning, but nothing happened to the car as it was raining and it seems that gave a Faraday cage effect. But I wonder what would have happened to the computer, (assuming we weren't fried), otherwise.

Honestly we left the field repairs behind a long long time ago. Yes I have towed my EFI diesel work car (not commonrail) home when a circuit board on the fuel pump died.
But even if it were a fully mechanical diesel, I'd have towed it home to fix anyway. The rest of the time it performs far better and runs cleaner/quieter than an equivalent mechanical so it's a tradeoff I've happily and knowingly made.

In very remote areas, it basically comes down to having another mode of transportation as backup (mountainbike on the back?). There are always a huge number of things not engine related which can disable a vehicle beyond field repair.

Originally Posted by Davo

I was driving an EFI diesel LandCruiser a few years ago that was struck by lightning, but nothing happened to the car as it was raining and it seems that gave a Faraday cage effect. But I wonder what would have happened to the computer, (assuming we weren't fried), otherwise.

I had a lightning touchdown 3 ft from my RRS two years ago - blew things in the house and blew up the Scangauge I had fitted to the RRS. Initially the car went berserk when I started it but it was due to the Scan gauge still being connected. When the scanguage was removed there were no issues.

So while the strike was strong enough to blow the scangauge it did nothing to the multitude of electronics in the RRS.

In reality in all circumstances the actual ECUs etc are very robust - the issue is really the peripheral sensors and connectors etc.

Garry

Originally Posted by Dougal

Honestly we left the field repairs behind a long long time ago. Yes I have towed my EFI diesel work car (not commonrail) home when a circuit board on the fuel pump died.
But even if it were a fully mechanical diesel, I'd have towed it home to fix anyway. The rest of the time it performs far better and runs cleaner/quieter than an equivalent mechanical so it's a tradeoff I've happily and knowingly made.

In very remote areas, it basically comes down to having another mode of transportation as backup (mountainbike on the back?). There are always a huge number of things not engine related which can disable a vehicle beyond field repair.

When you say it's a trade-off, you've hit the nail on the head, but if I was doing a report card on modern design my notes would read: "Could do better." I would love to see some real effort put into this, and in the 4wd world it would probably be groundbreaking, meaning that once somebody finally did it, then the rest would follow. But in the meantime any big trouble means a recovery, which means expensive. It just tickles me that in some ways we're worse off than in the 70s or 80s.

And I haven't left field repairs behind by any means. I never do them because I haven't needed to, but I carry the gear anyway so at least I have a chance.

I do know of people with Holden V6 conversions to HiLuxes etc that have mounted a second ECU adjacent the original and have it all sealed up. If their primary ECU fails, they simply swap the harness over to the spare.

It really depends upon where and how often you go to remote places.

Originally Posted by Davo

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And I haven't left field repairs behind by any means. I never do them because I haven't needed to, but I carry the gear anyway so at least I have a chance.

I think Dougal is saying that diesel technology has left field repairs behind some time ago.

Originally Posted by isuzurover

I think Dougal is saying that diesel technology has left field repairs behind some time ago.

Indeed. It's one thing to have enough tools to replace hoses, bypass a dead turbo etc. But a lunched injector pump on any diesel can't be fixed outside a fully equipped specialists workshop.

How common is ECU failure? I met one guy who had his early 90's nissan one die (road car). Another workmate had the one on his Pathfinder drowned and damaged, but it still got him home.

It seems they are quite robust. The wiring is more vulnerable.

Originally Posted by Dougal

Indeed. It's one thing to have enough tools to replace hoses, bypass a dead turbo etc. But a lunched injector pump on any diesel can't be fixed outside a fully equipped specialists workshop.

How common is ECU failure? I met one guy who had his early 90's nissan one die (road car). Another workmate had the one on his Pathfinder drowned and damaged, but it still got him home.

It seems they are quite robust. The wiring is more vulnerable.

Agreed, however a commonrail diesel has an extra level of complexity over an old mechanical diesel.

For a fully mechanical diesel, you could carry a spare lift pump, injector pump and injectors. That and some hoses and filters is the entire fuel system. All of which can be easily replaced in the field. Those bits would probably cost you $2-5k new all up.

For a commonrail diesel you need all the above - except that the equivalent parts are bigger, heavier and much more expensive, plus you need at least a couple of critical sensors and pressure valves for the fuel rail, etc... Easily $10k plus in parts and probably lots of special tools...