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+--- Thread: Vacuum leak = internal injection pump shutoff? (/showthread.php?tid=8470)
Vacuum leak = internal injection pump shutoff? - vica153 - 08-20-2021
I have a OM603 pump on a OM606. Been running it for a while, but I've have always noticed a shutoff issue that I want to see if it is a known feature.
I have noticed that if I introduce a large leak to the vacuum system such that the system isn't holding any vacuum, then in 5-10 seconds the engine will shut off. I have tested it many times and it perfectly repeatable even with the hose removed from the actual vacuum shutoff valve. The only Mercedes parts I'm using are the OM606 engine and OM603 injection pump, so there is no way its some other external electronic/vacuum shutoff.
In the OEM Mercedes setup, vacuum gets used everywhere so it would make sense for them to build in a safety shutoff if the vacuum system isn't working.
Is this a feature of the OM603 injection pump? Or is this an indication that something is installed incorrectly?
My setup takes a couple revolutions to start and I'm wondering if that all may be due to this internal auto shutoff needing to see a little vacuum before it allows for fueling. I guess I could test that hypothesis by pulling some vacuum with an external source and seeing if it starts quicker.
RE: Vacuum leak = internal injection pump shutoff? - Eric78 - 08-21-2021
I've had similar issues that I traced to the actual connection to the vacuum actuator on the pump, a 30mm long piece of rubber that connected a hard plastic vac line to the actuator had expanded. There is a manual shutoff on the side of injection pump(between the intake runners of cylinder 2 & 3 on an OM602), but you're screwed when you snap your bonnet(hood) cable. I have to fix my vac line & my bonnet release, thinking of running a cable from the manual shut off into the footwell.
RE: Vacuum leak = internal injection pump shutoff? - vica153 - 08-22-2021
Normal vacuum and manual shutoffs are functioning fine.
RE: Vacuum leak = internal injection pump shutoff? - barrote - 08-23-2021
Vica173,
A mechanical pump as many some other electronics kill the engine by stopping fuel delivery, almost all. Newer devices have IMObilizer feature wich may call for acessories to avoid fuel being delivered for start... thats why some vehicles take time to stop when this is being done by IMO.
In the M pumps with RSF governor, fuel delivery is stopped by pulling rack to 0 delivery by means of a pneumatic actuator.
This actuator uses vac (neg press) and is kept open by a spring, once pressure is gone it returns to fuel delivery... if u have a leak big enough engine will not stop, and if leak is small it may take a wile to stop.
Just that... plain and simple. Using pneumatic valves to do the job requires 2 of them as vac need to excape in 1 sec after key is on. Otherwise rack take time to recover to start delivery...
RE: Vacuum leak = internal injection pump shutoff? - vica153 - 08-24-2021
huh? A single 3 port valve works fine for shutoff. Energized=blocks vacuum and vents the line to the pump shutoff. De-energized=applies vacuum to pump shutoff and plugs vent.
Anyway my issues doesn't have anything to do with external pressures.
RE: Vacuum leak = internal injection pump shutoff? - barrote - 08-26-2021
Well as u say, now u're in possession of all info u need about M RSF shut of mechanism.
What u describe is not common.
RE: Vacuum leak = internal injection pump shutoff? - Petar - 08-26-2021
I've never seen the behaviour that you describe. But what could happen is that your crankase breather is partially clogged. The vacuum pump exhausts into the crankase, and when there is a vacuum leak it exhausts more air.
I know for a fact that crankcase pressure will shut off the engine. You can try it by yourself by blocking the breather with your finger. The reason why is that the vacuum actuator on the injection pump works on the pressure difference, the crankcase pressure pushes it from the other side.
RE: Vacuum leak = internal injection pump shutoff? - vica153 - 08-31-2021
Yes it is quite the odd phenomenon. Erik @ Dieselmeken had the same suggestion about the possibility of crankcase pressure buildup. I'll test that hypothesis as soon as I get a chance.