Fuel pin operation

[MMeier]

Guide pin operation

Does the pin move in proportion to throttle input by mechanical means or ... . ? Playing with the pump again today and noticed the pin would not move till about 60% throttle then it would 'snap" out of its little hiding spot. Could explain why I feel the truck was down on power during "normal" driving perhaps? Tried to clean it up a bit with cleaner, now it does not seem to want to come out at all! I take it I have to remove throttle linkage from pump and remove the plug on front side of pump to remove the lil' bugger. Is that a 5/16 allen on top off the linkage or metric? Which aftermarket pins do you guys like most... and where can I get one NOW?

 

[CSchafer]

I don't think the pin is in direct relashonship with the throttle lever when not running. I think the pump has to be spinnin for full operation.

 

[dpuckett]

The pin moves in relation to LOAD, i. e. relative to the sweep of your boost gauge needle. I would refer you to the sticky on VE performance, and all should read it if you dont know it already, but I will give a brief synopsis here.



As boost increases, the diaprhagm moves downard, allowing the internal pump pressure to push the guide pin out of its hole, allowing, by means of a few levers, the governor flywheights to come farther forward on the shaft, allowing more fuel to be pumped per stroke, and more power produced.



The fact the pin didnt come out immediately, as opposed to creeping out with throttle position, isnt bad, as long as it eventually comes out. WHen it wont come out at WOT position, then you have some sticking, which will lead to lower power. I have had the bright notion to stick the pin back in the bore farther than needed, then it wont flow enough fuel to pop the injectors.



I believe the allen screw on the throttle shaft nut is a 8 or 10mm. There is also an allen screw (metric, in the neighborhood of 5mm) on the front side of the neck of the AFC housing. Remove that plug, and push the lever rearward (toward the back of the engine bay) to move the guide pin out into the well. Make sure you have a new gasket/ metal seal, and put the plug back in. I had to put some anaerobic sealant on the threads to get it to seal up tight and not leak.



Daniel