Engine/Transmission (1994 - 1998) Marine Cummins Diesel TDC issue

[madmanmanick]

I feel embarrassed asking this, but we are having problems with a 12 valve 6BT5. 9M2 CTD. The engine would not start. We ended up finding a bunch of water in the fuel and ended up stripping the tank, draining the filter and changing the filter. The engine would not start. We then replaced the entire fuel filter housing. After that we bled off the entire fuel system. When bleeding the lines at the injectors the fuel was oozing out instead of spraying. Based on this we determined the injection pump was bad. We have to replace the fuel injection pump. We could not get the TDC pin to push in. The pin would spins, but not push in. We rotated the engine very slowly and still could not get it to push in. We tried tapping it in to no avail. In the end we made our best guess based on the operation of the intake and exhaust valves. We then removed the pump the grove on the gear was off by a butt hair from the position of the key on the new fuel pump. Based on that we turned the engine the tiny amount necessary to line up the key and the grove. We replaced every fuel line on the engine also. We have not op tested it yet as we are still putting it back together. Now that I have bored you all I will ask the questions:



1. Besides taking the head off or using the pin was the way we determined TDC correct?



2. Will the engine blow up when we try to start it?



3. The engine has a mechanical lift pump, has anybody had these fail?



Thanks in advance.

 

[Bob4x4]

In the trucks you must use a barring tool to turn the engine slow enough to be able to push the pin into it's hole in the gear. It is plastic so it will shear off the tip very easily.

Since it was running before the water incident,timing should not have been an issue. The pump will not spray a ton of fuel out when turninh at cranking speed.

No it will not blow up if the fuel timing is off a bit just less power or no start.

Yes the lift pump can fail but more common that the overflow valve is weak not allowing the correct pressure. easy enough to test lift pump pressure with a gauge as long as you have the appropriate adapter. .

 

[Joseph Donnelly]

You can also check timing with the blade in the side of the injection pump. It is behind a round-headed cap, with about a 7/8" hex iirc.

 

[madmanmanick]

Alright, am having more problems, I took the front cover off the engine and have run into something I didn't think was possible, the timing between the Crankshaft and the Cam shaft is off by 2-3 teeth. This would not seem unusual if the teeth had extensive damage, but there is no damage to any of the teeth on any of the gears. Has anybody seen this happen before, and is it possible for the engine to jump gears like that?

 

[DWeaver]

I would say that the teeth did not jump, the engine is not on TDC.



Reason: I was testing my timing skills on a core engine with the cover off. The marks were close but not dead on. I turned the engine another revolution and the marks lined up.



If you have not taken off the injection pump yet, I would go with J. Donnelly's suggestion and take my mark off the inj. pump timing tab.



OR if you can get to it, take the timing pin out and look for the dimple on the cam gear with a mirror and flashlight.



Grain of salt: I am still learning on these 12 valves also.

 

[Bob4x4]

I would say that the teeth did not jump, the engine is not on TDC.



Reason: I was testing my timing skills on a core engine with the cover off. The marks were close but not dead on. I turned the engine another revolution and the marks lined up.



If you have not taken off the injection pump yet, I would go with J. Donnelly's suggestion and take my mark off the inj. pump timing tab.



OR if you can get to it, take the timing pin out and look for the dimple on the cam gear with a mirror and flashlight.



Grain of salt: I am still learning on these 12 valves also.

It is not a dimple it is a hole that the plastic pin goes into

 

[hsmith]

As DWeaver said, you are probably on the exhaust stroke. Make another revolution and recheck the marks.