Sorry to bother you but I need help figuring out how to fix a fault with my 2007 man TGM 15.240 tow truck. As I am blessed with a totally useless MAN dealer here in my area, I typically need to try figure it out on my own.
The truck has “always” been a bit reluctant to start, if it sits ten minutes or over night it’s almost as the diesel leaks out and it has to turn over for a few seconds to build fuel pressure. Of course there is no external leak.
Some times, typically when it’s wet and a few degrees about freezing, I get an error code edc 03779-01. This code relates to loss of common rail pressure. Now this is the clue, the code always come if I’m on engine brake or just rolling in gear, and rpm reaches 800-1000. If I let it all the way down to idle (pressing the clutch pedal) or blips the throttle a bit, I can avoid the code completely. But when conditions are right for the code to come, its takes a bit longer to start. Like it takes longer to build rail pressure. With the code active I loose a bit of power. But shutting the engine off for a few seconds clear it, and it’s ok until next time. Which can be five minutes or a month.
The code never comes as long as I use the throttle, only on engine brake or no load.
From what I read online it could be one or more injectors, or the pressure control valve leaking.
Could be any of the items you’ve stated. You need to do a leak off test from the banjo union on the front of the head to see if there’s a fault with the injectors. If that is OK you need to isolate the limiting valve leak off return from the rail and pipe it into a container. Carry out a loaded roadtest, get the fault to come on and see if the plv has been allowing fuel to escape, replace the plv if there’s any fuel in the container. If you want to check fuel pump delivery, pipe the injector return from the head and the plv return from the rail into a measuring jug and run the engine with the m prop disconnected, that will give you total delivery volume. your dealer should be able to give you the figures you’re looking for.
Get someone to sit in the cab whilst just raising the revs very slightly and then back to idle, check to see if theres any puffs of black smoke. Whats most likely happening here is an injector is sticking open slightly which will lower the pressure in the rail causing the error code.It could also be a slightly blocked fuel filter.
Cheapest options first- change the fuel filters and give the tank a good dose of injector cleaner. Run it for a while and if that doesnt cure it next cheapest thing, change the fuel rail pressure sensor.
It could also be a faulty centrifugal pump but probably unlikely, do the above first before going further…
Hope this helps.
Main dealer will do a leak off test and replace all the injectors which will fix it for a while but the errors will come up again in no time. The problem is more than likely with the fuel pump. Problem happens on D20, D26.
Took a closer look today, drained fuel filter and checked the connectors on the rail sensor and the pressure valve on the pump. Didn’t find anything out of the ordinary. But need to crank for several seconds to start.
I have tried some different injector cleaners over the last year without any result. Some kind of diesel additive I have used from time to time makes it a little bit easier to start, but it might be all in my head.
I am thinking that the next thing is trying to change the pressure control valve. Not overly expensive on eBay and easy to access. If not I’ll probably have to go back to the MAN workshop again.
Btw there is no smoke or stumble in any way, runs fine and fuel consumption is good. Does not use oil or water. Also checked wires inside the looms, as the problem gets worse in real wet conditions, but nothing wrong.
I wouldn’t normally recommend the usual list of filters, additives etc. It’s usually better to put the money towards the injectors rather than throwing it at cheaper bits and pieces in the hope it’s not injectors.
It can be a failing pump murdering the injectors but a truck of that age it might just be the injectors have had it.
As time wears on it often goes from just a fault to the engine shutting down, until you switch it on and off, on the key, whenever you lift off the accelerator or are on overrun.
Spoke with the dealership the other day, the injector test they did turned out ok. Injectors was fairly good, so the next step was replacing two valves on the pump. So waiting to have that done now. I bought them through MAN but use a local shop to change them.
The MAN shop said that if it was hard to start it usually was one valve, in if it threw trouble code is was the other.
Changed both valves on the high pressure pump, starts easier, sometimes almost right away, and sometimes it needs a few turns to get going. But a lot better than it was.
