CJLennon
Well-Known Member
Hey Folks,
I just jumped off a previous post on how to diagnose a Cummins 855 engine miss and I got some great answers. Thanks. Now I am looking at understanding how to set injection travel. I have done a lot of reading on this forum and others but I did not find a clear explanation on how to set up the injector travel. I found a lot of bits and peices but nothing from begining to end. So, if you folks have a moment, I would like to paint this picture using my situation.
I have a Cummins 855 NTC-400 with a manufacture date of 6/87 that is in a 1987 Ford 9000 tractor. The tag on the side of the engine identifying the valve lash is crystal clear (.011 intake, .024 exhaust) but the injector travel data states "T.S. Zero" which I have learned means Top Stop injector. I also learned that Top Stop injectors have a flat washer inside the injector (shake out the center part so you can see it) that holds the spring in place. I also learned that you can't use the travel (dial indicator) method to set these injectors up. You must use the torque method.
What method you have to use (I must use the torque method), you might as well set/check the valves also at the same time as long as you have the Jake (if equipted) off. BUT, there is a difference and the difference has to do with what injector you are setting. If you use the travel method (non-top stop injectors), you want to set the injector on the cylinder that is one BEHIND the cylinder on which you are adjusting the valves. For example, if you are adjusting the valves on cylinder #5 because the pointer is pointing to the "A" on the pulley and both valves on #5 are loose (i.e., #5 on TDC compression stroke), then you need to be setting the travel on injector #3 (i.e., 1-5-3-6-2-4). If you are using the torque method, then you need to be setting the SAME injector as the valves you are setting/checking.
With the travel method, they have you setting the travel on the injector just before it starts to go into its travel (if you are setting valves on #5, then the engine is TDC at #5 on the compression stroke and #3 is right behind it but just before the injector starts its travel). With the torque method, the idea behind it is to bottom out the injector on the cylinder that is TDC on the compression stroke so you are actually making sure that the injector is in the proper position (closed tight against the seat) for TDC. When you think about it this way, you are taking any wear on the cam out of the equation because the push rod assembly is sitting on the high lobe of the cam giving you the actual lift you will see once the engine is running. From what I understand, Cummins indicates through a service bulliten from years back that this is a more accuarate method. Besdies, with top stops, you don't have a choice. You have to use the torque method.
So, the reason I typed all this in is to get you Cummins experts to verify that I got it right and for the next poor slob that used to be a gas engine guy like me and thinks he's a diesel mechanic, so that he doesn't spend a good part of his life trying to figure out why one of these Cummins REALLY smokes or has a miss. So, any takers to verify that I finally got it right? I owe you folks BIG time. Thanks!
Chris
I just jumped off a previous post on how to diagnose a Cummins 855 engine miss and I got some great answers. Thanks. Now I am looking at understanding how to set injection travel. I have done a lot of reading on this forum and others but I did not find a clear explanation on how to set up the injector travel. I found a lot of bits and peices but nothing from begining to end. So, if you folks have a moment, I would like to paint this picture using my situation.
I have a Cummins 855 NTC-400 with a manufacture date of 6/87 that is in a 1987 Ford 9000 tractor. The tag on the side of the engine identifying the valve lash is crystal clear (.011 intake, .024 exhaust) but the injector travel data states "T.S. Zero" which I have learned means Top Stop injector. I also learned that Top Stop injectors have a flat washer inside the injector (shake out the center part so you can see it) that holds the spring in place. I also learned that you can't use the travel (dial indicator) method to set these injectors up. You must use the torque method.
What method you have to use (I must use the torque method), you might as well set/check the valves also at the same time as long as you have the Jake (if equipted) off. BUT, there is a difference and the difference has to do with what injector you are setting. If you use the travel method (non-top stop injectors), you want to set the injector on the cylinder that is one BEHIND the cylinder on which you are adjusting the valves. For example, if you are adjusting the valves on cylinder #5 because the pointer is pointing to the "A" on the pulley and both valves on #5 are loose (i.e., #5 on TDC compression stroke), then you need to be setting the travel on injector #3 (i.e., 1-5-3-6-2-4). If you are using the torque method, then you need to be setting the SAME injector as the valves you are setting/checking.
With the travel method, they have you setting the travel on the injector just before it starts to go into its travel (if you are setting valves on #5, then the engine is TDC at #5 on the compression stroke and #3 is right behind it but just before the injector starts its travel). With the torque method, the idea behind it is to bottom out the injector on the cylinder that is TDC on the compression stroke so you are actually making sure that the injector is in the proper position (closed tight against the seat) for TDC. When you think about it this way, you are taking any wear on the cam out of the equation because the push rod assembly is sitting on the high lobe of the cam giving you the actual lift you will see once the engine is running. From what I understand, Cummins indicates through a service bulliten from years back that this is a more accuarate method. Besdies, with top stops, you don't have a choice. You have to use the torque method.
So, the reason I typed all this in is to get you Cummins experts to verify that I got it right and for the next poor slob that used to be a gas engine guy like me and thinks he's a diesel mechanic, so that he doesn't spend a good part of his life trying to figure out why one of these Cummins REALLY smokes or has a miss. So, any takers to verify that I finally got it right? I owe you folks BIG time. Thanks!
Chris