Our Cummins C8.3-325 engine has a throttle bracket that is pulled in one way by King Control cable to increase RPM and two springs in the other way when the accelerator pedal is not being pressed.
Last year the throttle bracket broke into two pieces while driving up a hill. We previously posted on Foreforums how we made a replacement bracket in a hardware store parking lot using a spare piece of aluminum we carried. Broken throttle bracket repaired Cummins C8.3 (http://www.foreforums.com/index.php?topic=17104.msg112762#msg112762)
This is a follow up posting explaining a design problem with the original OEM bracket that may affect others.
The two springs, hooked into two small separate holes in the bracket, are at all times exerting a pull on the bracket to return and keep the throttle at idle position. Springs pulling on the original steel bracket for 15 years wore away both holes and may have eventually released the springs, maybe preventing throttle from returning to idle. We found the worn holes when our bracket broke in another place.
We had a concern that the springs would wear the new bracket and maybe much sooner because the replacement was made from aluminum, which is softer than steel. Today we took the aluminum bracket off and found some minimal wear and decided to modify our throttle bracket by using eye-bolts to attach the springs. Eye-bolts are made of steel and are round where the springs attach. Maybe because the springs can move in the 'eye' they will not cause a wear point.
Photos show the worn original bracket and our new modifications.
How did the bracket at the other end of the springs look? How about the springs themselves, or did you just replace them?
Gayland, you can see springs and the other brkt in the last 2 photo's
John H
Gayland, funny you should ask about the other end of the springs. As I wrote up the posting last night, I realized that I have never looked at the spring's bottom bracket for wear. It is on our list to check out soon. I think I can only see it from leaning over the bed and it may be hard to get a good view. I will see if this is job for our new boroscope.
The springs looked ok so I did not replace them. We are now using a hardware store spring that we cut down and make a new hook on the cut-off end. We have several spares springs made up.
Gayland asked about the bottom bracket spring hole wear.
We have significant wear that shows its 16 years of usage. Not sure what I am going to do about it yet. There is a lot of metal left before the spring pops through.
I did use our borescope Borescope - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Borescope) , but our camera worked better.
Thanks Barry. My SOP Engineering degree (seat of the pants) says that since it is now worn to fit the curvature of the spring, wear rate will be lessened and should easily last another 16 years ;D If it ever warms up above freezing here in ND I'll try to check mine.
Looks like a great fix... Just curious,How many hours on the engine??
The 8.3 mechanical cummins is a great engine but they dance like a train off the track running out of control down a mountain and at a idol it's like a box full of rocks.... Lot of shaking going on.
I have no ware on the brackets but I have lost the springs more than once "I carry spares''..
and if I remember right it breaks at the hook where yours holed the bracket..
Makes me wonder if some brackets go faster than others.
Anyways I'll take the old school spring set up over the new TPS anyday