JHZR2
Staff member
My 1991 MB350SD. Still sorting this car.
The fuel systems in these cars are pretty simple. Tank, strainer, prefilter, lift pump, filter with loop to and from the injection pump, and a return from the injectors.
On all these cars, I own a few, I can open the fuel system, change filters or whatnot, bolt it back together, purge air, and move on.
On this 1991, even though the tank has no pressure, and even if the tank is more or less empty, the diesel won’t stop flowing.
I made a huge mess a few weeks back doing my fuel filter because of that.
Now I’m trying to remove an injection pump. A much more involved job, in my garage. It’s not a five minute swap, it’s a hours long reseal.
This is the only car with this type fuel system that does that. There isn’t an electric pump, not much of anything.
Usually this is a great thing. Kind of lets filters prime if they’re open. But when you open the system… not so good…
Any ideas or thoughts on this?
I can somehow block off one of the rubber lines to stop the flow. But it’s just so strange. It won’t stop.
It’s not like I have an identical second vehicle, same model, year, everything, and it doesn’t do this.
I’d think the lift pump would be the “gate keeper” here. It seems to work fine, but maybe it implies that the seals in the pump are leaky/failed?
Any ideas?
The fuel systems in these cars are pretty simple. Tank, strainer, prefilter, lift pump, filter with loop to and from the injection pump, and a return from the injectors.
On all these cars, I own a few, I can open the fuel system, change filters or whatnot, bolt it back together, purge air, and move on.
On this 1991, even though the tank has no pressure, and even if the tank is more or less empty, the diesel won’t stop flowing.
I made a huge mess a few weeks back doing my fuel filter because of that.
Now I’m trying to remove an injection pump. A much more involved job, in my garage. It’s not a five minute swap, it’s a hours long reseal.
This is the only car with this type fuel system that does that. There isn’t an electric pump, not much of anything.
Usually this is a great thing. Kind of lets filters prime if they’re open. But when you open the system… not so good…
Any ideas or thoughts on this?
I can somehow block off one of the rubber lines to stop the flow. But it’s just so strange. It won’t stop.
It’s not like I have an identical second vehicle, same model, year, everything, and it doesn’t do this.
I’d think the lift pump would be the “gate keeper” here. It seems to work fine, but maybe it implies that the seals in the pump are leaky/failed?
Any ideas?
