cat 3116 cylinder 1 "misfiring"

[Eliteweapons]

I have been having really rough idle issues in my A3 and a little loss of power so I took my truck in to get a checkup last week and check the adjustment of the top end. I have never worked on a diesel engine and don't have the tools for the top end adjustment so that's why I took it to a shop. I just got this truck in June and I don't have a detailed history on maintenance. Thru all the reading I have been doing I didn't see anything specifically referencing this issue. There were more than normal bubbles in the return line, and cylinder 1 is running much colder than the others. I am trying to determine the best course of action. They think it may just be a dirty or defective injector for #1 but have not torn into it that far to know for sure. They said the valve adjustments looked normal without getting any further into it money wise and fully checking them. The injector seals are also suspect due to the excessive bubbles. This engine has just over 17000 miles on it and 1000 hours of runtime. Any thoughts on what direction I should go? This is going to get very expensive very fast so I am looking for experienced input to keep from wasting money.

Thanks

 

[cattlerepairman]

I am not sure what the shop actually did. Hook up diagnostics? They did not actually disassemble anything. The valves can be adjusted with a basic tool kit (and should be checked/adjusted. One hears of dropped exhaust valves on these engines). You do need the CAT tool set (or equivalent) to adjust injector timing, synch the fuel rack and set the full fuel setting.
So, while you can remove an injector without too much fuss (even if you do not have CAT tools), the new/repaired injector needs to be adjusted before startup, otherwise damage can ensue.

Here is a pic:



Air bubbles could come from bad injector seal; actually be gas forced into the fuel line from inside the cylinder. Maybe a check valve further down the line that's leaking also. CAT knowledgeable people will chime in with better diagnostics.

 

[rustystud]

Cattlerepairman your picture does not come up. Remember your suppose to post all picture here just for those reasons.

As far as the air bubbles go, where did the shop find these bubbles at ? At the injector ? At the pump ? It could be as simple as a loose line or as complex as cattlerepairman said with the compression blowing back in. If it is on this one line only (number 1 cylinder) I would replace the number 1 injector and see what happens. As this is not an electronically controlled engine it should not be hard to "run the rack" and make sure all the injectors and valves are OK. You won't have to get the proper injector "codes" from CAT. Though I still have about 30 CD's with 100 codes each on them so I could help you there if you had a more modern engine.

 

[Eliteweapons]

Cattlerepairman your picture does not come up. Remember your suppose to post all picture here just for those reasons.

As far as the air bubbles go, where did the shop find these bubbles at ? At the injector ? At the pump ? It could be as simple as a loose line or as complex as cattlerepairman said with the compression blowing back in. If it is on this one line only (number 1 cylinder) I would replace the number 1 injector and see what happens. As this is not an electronically controlled engine it should not be hard to "run the rack" and make sure all the injectors and valves are OK. You won't have to get the proper injector "codes" from CAT. Though I still have about 30 CD's with 100 codes each on them so I could help you there if you had a more modern engine.

They checked the return line for bubbles. I had considered having them replace that injector as well but I don't have any experience on this engine, and didn't want to just start swapping parts. Is there a screen at the pump inlet on these that could be clogged? I cleaned the tank and changed the filter but I saw something recently that suggested there may be a screen at the inlet of the pump. Would it cause any problems running it as is and see if injector cleaner would help? It just has a rough idle and is a little low on power. I am going to ask them to run the rack today and test that part of it to get more information for a better decision.

Thanks

 

[rustystud]

The injector pump doesn't have a screen, but there is a filter just before the pump. The injectors can sometimes have a small screen on them though. If you have some small particles at the pump now then you should take the fuel lines off and blow them out. Cleaner won't really help much once the crap gets past the filter. Oh, change that filter after cleaning out the lines !

 

[Monkeyboyarmy]

Actually the pump is before the filter. The order of flow is tank,pump,filter,head (from the back),pressure regulator (front of the head), return line to tank. I've seen the small check valve in the pump get a piece of cap in it and it wouldn't pump. My A3 has a water separating filter that I installed just above the tank for that reason.

 

[Eliteweapons]

Actually the pump is before the filter. The order of flow is tank,pump,filter,head (from the back),pressure regulator (front of the head), return line to tank. I've seen the small check valve in the pump get a piece of cap in it and it wouldn't pump. My A3 has a water separating filter that I installed just above the tank for that reason.

A water separator may be a good idea. What type did you use? I found a Dahl 100 that looks like a good option with a 30 micron as a prefilter. I keep finding a reference to a screen at the inlet of the pump but I am not sure if its for the newer electronic 3116.

 

[rustystud]

Actually the pump is before the filter. The order of flow is tank,pump,filter,head (from the back),pressure regulator (front of the head), return line to tank. I've seen the small check valve in the pump get a piece of cap in it and it wouldn't pump. My A3 has a water separating filter that I installed just above the tank for that reason.

OK I see what you mean. I didn't realize this unit had this style of injection system. This is not a high pressure injection pump system. I thought it was a newer engine. If you have crude past the filters and it is lodged in the cylinder head then you will have to remove the fuel inlet lines and blow out the crude. I would use some brake cleaner or carb cleaner after blowing out the lines, then after replacing all the filters try and start it up and see what is going on. If you still have the miss and the injector rockers are all properly adjusted then you do have a bad injector. I'm sorry to say but in this style of injection system you are suppose to replace those injectors every 60,000 miles or by hours ( I don't remember the amount though) . They are not like the injectors in a regular high pressure external pump system. They get "hammered" by those rockers and wear much faster. If one is starting to cause problems then it is just a matter of time before they all cause trouble. At work we would replace the Cummins M11 injectors every 50,000 miles like clock-work . Thankfully they can easily be rebuilt.