Diesel knocking

I'm sticking with my suggested feed it a can or two of straight diesel purge and go from there plan. You can buy it at Autozone.

Start with the cheapest recommendation you've gotten so far. Especially if it's good for maintenance. That way, you'll be solving the puzzle and getting something beneficial out of it too.

So, I am confused with this problem. What I figured out last evening though was this. I drove it about 40 minutes to my son's doctor appointment. It ran flawlessly after starting a little poorly due to the temperature. After the appointment we were waiting in the parking lot for my wife who was picking up my son as I had another place to be. I had the car idling while waiting. It was running fine while idling, but as I went to leave the engine was down on power and smoking pretty good. Could it be a bad injector that rears it's head when idling for a while, but otherwise works? After about a 1/4 mile the engine ran fine, and the whole trip home was fine as well a few hours after I finished what I was doing. It was quite cold for the trip home, and everything was fine.

Chris

Hello all,

A little update on my problem with the Delica. I haven't driven the van in quite sometime due to the salted roads around here. Yesterday afternoon/evening though I had it out as it was a nice day, and the roads are pretty clear. I drove the van about 30 minutes each way to go pick up a gift for my mother, and it performed excellently. We went home briefly, and then headed out to a local restaurant about a 15 minute drive away. Again it ran fine. We were in the restaurant about 1.5 hours. It was cooler after dinner than when we went in, but not cold. The van fired right up, but then started falling on its face, and smoking badly with the weird knocking noises pretty much the whole way home. There seems to be no rhyme or reason to this issue. When it last did this it was after driving for a while, shutting it down, and then restarting it about an hour later with it idling in the driveway to warm up for about 10 minutes or less. The weather was much warmer then though. Any help is greatly appreciated.

Chris

I agree with other's input on the injectors. Get them cleaned. Also, how often do you run the tank down to almost empty and how long does the diesel sit in the tank? Water is the enemy here. If you don't drive it often, consider investing in a diesel/water separator filter inline between engine and tank.

Have you done any of the mentioned above? (diesel purge? injectors cleaned? new fuel filters) My Mercedes was doing this, I got rebuilt injectors from this guy on a forum and it ran even better than before.

Okay, so I changed the oil, filter and fuel filter on Sunday. I also disconnected the egr valve vacuum line. Took the van out this evening to play volleyball. It ran flawlessly for the 30 minutes to and from. Not sure if it's fixed or not, or what fixed it if it is.

This sure sounds like an injector problem to me. Is it fuel smoke? Dark smoke? To me it seems like an injector is intermittently failing to seal up which means that as the injection pump is building up fluid pressure to that injector but before it is reaching its intended pop-open pressure, it's spraying diesel into the cylinder. The cylinder will at some point near the end of its compression stroke, reach the magic mixture of intake temp and temp rise from compression and hit the auto-ignition point of the diesel and start to burn, making that one cylinder 'fire' way early and in an inconsistent manner. The equivalent of 'pre-ignition' on a gas engine. If the injector doesn't seal up then it also wouldn't STOP spraying when pressure behind the injector fell below the pop-open pressure, so it would end up spraying more fuel than normal and make that cylinder run rich and cause smoking (although if it was only one cylinder, you may see it as rythmic puffs of smoke rather than a continuous stream). That's my guess, anyway.

If the injection system is purely mechanical, I would look into how the system works to adjust injection timing under load. My guess is it is likely a combination of vacuum for load related increases and centrifugal for engine speed.

If the car is fairly old, I'd consider replacing all of the vacuum hoses. There could be a crack in one that is causing a sporadic leak. Sometimes the crack is closed and the engine runs fine. Sometimes it opens and things go pear shaped.

Similar to fiddling with a carburetor to fix an ignition problem, it sounds like you have a timing issue more than a fueling issue, so I'd check the fuel pump timing before yanking the injectors.

Can't say i'm very familiar with this engine, but in general diesels don't have much vacuum equipment because they don't have throttle plates in the intake that cause vacuum. Many newer ones have electric vacuum pumps for certain things, but not controlling injection timing AFAIK.

This van is super simple with an all mechanical injection system. It does have a vacuum pump and uses vacuum for certain things. The van runs so smooth otherwise I really don't think it's timing related.

Still running flawlessly since the egr disconnect.