broken injector pump timing arm
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Senior User
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From: ny
broken injector pump timing arm
When i bought the engine for this truck a few weeks ago i believed that someone had broke to ip timing arm by prying on it with some thing .Well after getting everything running and replacing the arm with one from my parts pile lol.the engine has been running great .So after leaving a local water hole last night the engine was power joke rattling and i could smell raw diesel .This morning i checked it out and the arm was broken just like it was when i first bought the engine .what would cause the arm to break ?It must be hanging up and when the throttle is opened then the cam slide must be pushing it enough to break it .Any ideas everyone
Last edited by 40dog; Jul 27, 2012 at 11:34 AM. Reason: fte needs more info
Lead Driver
Joined: Nov 2003
Posts: 6,900
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From: Campbell River, B.C.
Dog, we're going to need some more pictures of that tilt front end. Looks like a sweet setup
I think the automatice timing advance/retard piston in your injector pump may be jammed. I would also mean the timing map of the injection pump is also not as dynamic as it should be. I would not try to free it unless in the process of a rebuild. Any metal that scrapes loose inside the pump can damage other parts in there, before being sent off to the injectors.
I think the automatice timing advance/retard piston in your injector pump may be jammed. I would also mean the timing map of the injection pump is also not as dynamic as it should be. I would not try to free it unless in the process of a rebuild. Any metal that scrapes loose inside the pump can damage other parts in there, before being sent off to the injectors.
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David, what the cam arm interfaces is the servo piston, which is inside of the advance piston. Its not shown in that picture.
Anyways, you have things hanging up that shouldn't be, so your pump is basically a core at this point. You should start shopping for a new pump.
Anyways, you have things hanging up that shouldn't be, so your pump is basically a core at this point. You should start shopping for a new pump.
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From: ny
Is the advance/retard piston the small piston the timing arm depresses?if so its laying in the valley pan with about a 1/4 inch of diesel covering it it kinda reminds me of a Brigg's and stratton needle valve ..there is a small spring that the piston stacks on when installing and then the arm holds everything in.i put a new arm on since the original was broken when i got it. . Really cant understand why there would be enough Resistance on it to snap the arm.unless its hanging up on something in the hole.?? I'm hoping i don't need a ip soon . Dose some thing actually contact the piston or dose the spring lay pressure on to deeper internal parts to adjust timing.I hoping that there is just a cleaning needed of the orifice in the large cap hex nut the piston enters thru.Ive had the nut off before but the engine was on the stand. well more Pict's coming of the hood and front for everyone.
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the small piston is called the servo piston.
It slides inside of the advance piston and controls your light load/speed advance by bypassing diesel.
If there was enough force to break that arm, and the servo is out, the advance piston is seized... You need a new pump.
It slides inside of the advance piston and controls your light load/speed advance by bypassing diesel.
If there was enough force to break that arm, and the servo is out, the advance piston is seized... You need a new pump.
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Senior User
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From: ny
i went out to the shop and opened up a spare pump to get a idea of whats going on .so when i get the one on the truck opened at the hex nut i will see if the main sliding piston is seized. ip wasn't what i wanted to be getting into . my pump has remanufactured printed on the main steel tag .was hoping it was swapped at about 100k and had only 25k on it now .125k was on the donor truck odometer and was lowest mileage i could find in the jy's
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Lead Driver
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From: Campbell River, B.C.
Thanks, that makes more sense.
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From: ny
the interior piston is free moving.so the issue must be deeper in the pump.would a issue with the cold advance sticking on create a loss of moove mentand binding in the piston?It appears the piston and slide action is realy just hydraulicly activated with the flow of diesel thru it .The piston being free moving has me wondering why its hanging up.
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its all hydraulic. The only other thing I can think of is that the calibration is so far off, and the mechanical adjustments are out of wack, that you bottom out the servo piston before the face cam is done rising.
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From: ny
well here are some more picts of the hood and truck for all you one piece tilt front lovers/dreamers.2 guys can remove the front nose in about 3 mins couple wire connections and off it comes. rather light to. i don't know much about the nose it was on it when i got it about 5 years ago .i love my truck!! 
what would be the basic setup for the cam/ramp ?I'm thinking someone may have replaced the IP and never set or maladjusted the cam/ramp .Maybe I'm to much of a optimist.
what would be the basic setup for the cam/ramp ?I'm thinking someone may have replaced the IP and never set or maladjusted the cam/ramp .Maybe I'm to much of a optimist.
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there is no basic.
There are many different variables in the calibration of a pump, and every single one of them affects the rest. Its a "team effort" so to speak.
You have roller to roller, run out, transfer pump pressures, idle/light load advance, speed advance, gov advance, timing arm gap, fuel return flow...... to name a few.
There are many different variables in the calibration of a pump, and every single one of them affects the rest. Its a "team effort" so to speak.
You have roller to roller, run out, transfer pump pressures, idle/light load advance, speed advance, gov advance, timing arm gap, fuel return flow...... to name a few.
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