12 valve MisFire
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Well there are only two things that can happen IN the combustion chamber that would cause this; 1. No fuel 2. Not enough pressure to ignite the fuel.
So, if you crack the line to check for the miss, and no fuel comes out, look toward the injection pump. otherwise, look the other way.
If the compression is low, it will not ignite the fuel, and I would say look towards a burnt valve, as rings would have to be HORRIBLY smoked to not make enough compression. check your valves, they are supposed to be adjusted regularly on a 12 valve. If they get too tight, the valve never seats, and cannot dissipate heat to the seat, only through the stem. This causes the valve to warp/burn.
If the fuel makes it to the line and your valves have some lash, I would assume the valves are ok, and perhaps you have a stuck injector. A compression test might be helpful if you are taking the injector out, but beware, you MUST use a diesel comp tester as the pressures FAR exceed normal testers. And don't do a "wet" test. The oil will be ignited and could hydrolock your engine (break big stuff).
So, if you crack the line to check for the miss, and no fuel comes out, look toward the injection pump. otherwise, look the other way.
If the compression is low, it will not ignite the fuel, and I would say look towards a burnt valve, as rings would have to be HORRIBLY smoked to not make enough compression. check your valves, they are supposed to be adjusted regularly on a 12 valve. If they get too tight, the valve never seats, and cannot dissipate heat to the seat, only through the stem. This causes the valve to warp/burn.
If the fuel makes it to the line and your valves have some lash, I would assume the valves are ok, and perhaps you have a stuck injector. A compression test might be helpful if you are taking the injector out, but beware, you MUST use a diesel comp tester as the pressures FAR exceed normal testers. And don't do a "wet" test. The oil will be ignited and could hydrolock your engine (break big stuff).
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I crack the fuel line at the injector on number 1 and the motor calmed right on down purred like a kitten. I tighten it back up its starts missisng again. The compression check came at 300 i put in brand new injectors (370's) and had the injection pump gone through just to make sure nothing was going on with it. They put in hi flow DV's and 3GSK and now it still misses on number 1 and it wont get over 2000 RPM's. Could it be a lift pump that is the only thing that I havent replaced.
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I am really thinking it's your injection pump. +1 a lift pump would affect all cylinders.
My knee jerk reaction is who "went through" it? Fooling with injection pumps is not for your average mechanic. Not even a highly experienced mechanic. That type of work is usually done by a shop specializing in injection pumps. Well other than exterior work anyhow. Also, this type of work is VITAL to be kept surgical room clean. The tiniest microscopic specs of grit will wreak havoc on the swiss watch/sewing machine looking little parts, and can also readily plug up the orifices in the injectors.
Unless gotten dirty, run dry/low lubricity these things pretty much run forever. They don't wear out, they "break".
I hope I'm wrong.
BTW isn't there some dowel pin issue on these things? (referred to as KDP killer dowel pin) I would consider doing a search on that. I have zero experience with the 12valve, just general knowledge from working on heavy equipment.
My knee jerk reaction is who "went through" it? Fooling with injection pumps is not for your average mechanic. Not even a highly experienced mechanic. That type of work is usually done by a shop specializing in injection pumps. Well other than exterior work anyhow. Also, this type of work is VITAL to be kept surgical room clean. The tiniest microscopic specs of grit will wreak havoc on the swiss watch/sewing machine looking little parts, and can also readily plug up the orifices in the injectors.
Unless gotten dirty, run dry/low lubricity these things pretty much run forever. They don't wear out, they "break".
I hope I'm wrong.
BTW isn't there some dowel pin issue on these things? (referred to as KDP killer dowel pin) I would consider doing a search on that. I have zero experience with the 12valve, just general knowledge from working on heavy equipment.
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hey total thanks for the reply I sent my injection pump to a place called Hoffman Injection Service and thats all they do and they have been in buisness for 25 years but I talked to em today and they said they can throw it up on the bench tester (again)!! and see what it is doing therefore I have to take the pump off again:CRY: Hopefully by the weekend they should have it tested I will keep you posted. Sometimes i wonder why i even work on stuff it never seems to work out the easy way Thanks again bud:thumbsup:beer
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naw the KDP will pretty much destroy your engine, or do nothing. there isn't a whole lot of in-between and it certainly would not cause backfiring
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