When there is approx 3/4 throttle or more, the engine will climb to max rpm, without actually moving the pedal.
This happens unloaded (in neutral) or in gear.
The fuel screw is only in 1.5 turns.
What else could be causing this???

 

could be something as simple as a spring oncable close to pumps that has not enough tension on it and lets throttle go further without u pressing pedal more

 

I would have said full fuel screw but highly doubt it if its only 1.5 turns. im not even sure what else could do it

 

These pumps are so fickle...1.5 turns on your full fuel screw could be 3 turns on another pump. I think Monty called it RPM flare in a post many months ago. For the heck of it, back the screw out .5 turns and see of the problem persists. I'll go look for that thread....

 

The fuel screw is in too far.

If there's one thing I've learned about these trucks, it's that no two are set up the same from the factory.

Back the screw out 1/4 turn and you will probably be OK.

edit: Dang, Greg! You are Mr. Speedy tonight!

 

I've already backed the screw out far enough that I can't come close to 1200 degrees.
Before, it would easily get to 1500, empty.
I don't want to go any further.....that takes the fun out of it

 

If only my truck were as quick on the draw as I am

 

I always test for pump runaway by losening the lock bolt on the full fuel screw and then running the rpms up slowly by hand with the linkage and if it doesn't run off i turn it in more until it does and then i back it out about half a turn i think and test it again its pretty easy and its not very time consuming either.

 

Wanna is right. Not all pumps are the same nor react the same to mods/tweaks. Can have one run away with one turn from stock, another won't run away at all with the fuel screw ALL the way in. RPM flare is exactly what it is.

MrHappy, do you have a ground afc cone- fuel pin as some call it? What about governor spring, or afc lever grind? These are mods that can be done to give more fuel without turning the fuel screw in. Once you've maxed it out with stock internals/setup, you need to modify them and you will get more fuel out of the pump with less or the same fuel screw position.

 

Bill, the gov. spring and afc level grind are on the near horizon, just haven't got to that yet.
Thanks.

Does this mean the my pump doesn't have the "potential" of one that does not experience RPM flare?

 

I wouldn't say so. If you had your pump and a different one on a stand I bet they would 'flow' the same amount of fuel at different full fuel settings. Could your pump been turned up by a previous owner? Just because the tamper cover was/is in place, doesn't mean its been tampered with LOL.

Back it off to where its safe. Then do the afc lever grind, gov spring, and fuel pin grind. That will give you more fuel.

AIR + FUEL = POWER. More air will equate to more power, so don't forget about that part of it .

 

I know the previous(original) owner, and am absolutley certain that the pump has not been touched.
At one time, however, the fuel pump was replaced under warranty. Seems the dealer was having trouble diagnosing a problem and replaced the pump and turbo, among other items. It actually turned out to be something simple and unrelated; although the exact details escape me.

Kris.

 

THAT RIGHT THERE IS WHY I WILL NEVER LET THE DEALER TOUCH MY TRUCKS AGAIN. I learned to work on these truck for that exact reason!

 

Yep.
Considering that the engine is a 1990, and the warranty claims came in THAT year and the next.
AND.
This is a small town in BC, Canada.
AND every soccer mom and dad were not driving them in the early 90's....

Maybe my pump is installed upside down.

I'll do the gov spring and afc lever grind and report the results.

Kris.

 

What small town and were in BC.......Maple Ridge here...

pb..