Archived 12 Valve pump Problem????

[Hammer]

Ok where to start...

My 98 12 valve has developed a problem during acceleration & deceleration. When you lift off the throttle,no matter how you do it fast or slow,it sounds like the motor is mixing up the cylinders.

The truck has only minor mods to the pump(cam plate,afc housing work)and the timing has been advanced. My pump man was here today and went over the timing and checked it-same as where its been for the last 30,000 miles,valve adjustment has been checked-ok,fuel lines were looked at for leaks-none found,fuel filter was changed today-no difference.



This problem started on my way to work last week and along with it the motor has a almost uncontrolable low end throttle response. What I mean here is,when you try to pull out the low end fuel comes on so hard you better be ready(just touching the throttle will cause you to stall the truck if your not fast enough with clutch). Truck makes power and runs and idles fine(no showing of blue smoke) except for trying to pull out and during deceleration when it does the noises. Motor has had no governor spring work done and pump side is still sealed and has the stock injectors.



I thought maybe a bad load of fuel so I did add some biocide and Power Service to fuel. I am at a loss and need some other opinions before it gets sent out to have the pump checked. Any help is greatly appreciated... ... ... . Andy



P. S. the truck has only 72,000 miles on it.

 

[bighammer]

So the only time it really acts up is sort of a stumbling on decelleration and a very touchy throttle on acceleration? I wonder if it isn't something wrong with the governor. (something working loose or broken? maybe not the spinning weights but the connection to the rack?)



Sorry I can't give you more than just guesses It sounds odd to me.

 

[Hammer]

Touchy on the throttle application is a understatement. If or when you let off the throttle it sounds like a fueler mixing the cylinders up on the big end. Its hard to explain and has me baffled. One call I made to a good friend today had him suggest to me either a bad diaphram in the afc housing or a broken or bad governor springs. Now,with me running the AFC spring adjustment loose and not much pressure on it I do not feel it could be a problem,but,I will tear it apart tommorrow and insatll a stock one I got today off a wrecked truck a buddy of mine has sitting. From there if its not that its off to a place that can pull it down and go thru it. Thanks for some insight BH... ... ... Andy

 

[Deezul1]

Sure sounds like governor trouble. Pull the plate out and look at the Governor springs and make sure they are still in place and my next guess would be a broken spring. When installing a 4K GSK the tension on the retainers can make for a touchy throttle. and the addition of the noise makes the spring integrity suspect.

Good Luck

 

[98rammer]

have you tried playing around with the governor springs? pull them out and see if one has broken. look at the rod that the springs go around. is it bent? mine is. either a weld broke or a pin broke and is pushing against the weights which bent the rod.



make sure you at least pull the retainers off, they wont tell a story if you just push and play on/with the springs with the retainers on (to see if there's any extra non-normal tension).



Tom