Timing belt questions

Jay ne Ohio · **Joined:** Sun Dec 12, 2010 5:49 pm **Posts:** 216

I decided that today is the day to replace the timing belt. Everything is going smoothly so far, but I have a couple of questions. After I removed the front cover, I instantly noticed the paint marks on the three gears. I turned the crank to 3 o'clock and the paint marks lined up on TWO gears, but is one tooth off on the exhaust cam. Here are the questions:

1) Are the paint marks from the factory or has my Jeep been opened up already (I bought it with 93k miles and it now has 109k miles,,, no history available)?

2) Do you think the exhaust jumped a tooth, or are the paint marks just a reference to get it in the general area for final adjustment?

3) I removed the cam plugs for the cam lock. I put a pin into the hole to "feel" for a flat spot, hole, or a dimple, but I did not feel anything that told me to stop when rotating the crankshaft at the same time. Is there a flat spot, hole or dimple OR does the bolt simply grab the cam and hold it???

4) I have two CRD's. This is an 05 and has always got less MPG than my wife's 06 which I bought at the same time. Could the exhaust cam timing be the cause of the poor fuel economy?

I am attaching a picture of the white paint marks that I found on the cam gears.

Here is a picture of the pump gear:

Sir Sam · **Posted:** Mon Sep 05, 2011 6:34 pm

1) The white paint is not factory, that is someone adding their own timing marks.

2) I can't say for certain if it jumped a tooth based off of the pictures alone.

3) There is a small hole in the cam that it goes into, keep turning the engine slowly while trying to screw in the pin, eventually you will find the spot and will be able to screw them in.

4) Lets first make sure that the cams are timing correctly before speculating about anything else.

papaindigo · **Posted:** Tue Sep 06, 2011 8:59 am

Sir Sam has done timing belts so he knows a lot more than me but based on his write up and GDE's (http://www.greendieselengineering.com/f ... st/72.page) I'd agree that these are someone's marks but not factory. As I understand it there are 6 meaningful "points" related to timing in the engine's rotation cycle and ideally, but not necessarily, they should all be lined up to make sure everything is "right" before installing a timing belt. I say "not necessarily" because if the belt you are replacing is "right" then you in theory can mark everything in the current position and as long as nothing is moved during the belt install all should be good. I would not recommend nor will I use that approach.

To be sure everything is right I'm pretty sure 1) per GDE the flywheel timing hole should line up and allow insertion of a 6mm hex key; 2) both the intake and exhaust cams should line up with the cam pins so that the pins go into the holes in the respective cam shafts; 3) both the intake and exhaust toothed cam pulleys have a small indentation stamped in 1 tooth and those indentations should both be oriented vertical (NOTE it's not clear to me if there is a corresponding mark on the inner cover behind those gears but there should be although I cannot clearly see one on any picture); and 4) per GDE the fuel pump timing dimple should align with the timing mark on the housing. The fuel pump timing has been the subject of some discussion. As I understand it the fuel pump does not run an "even" number of cycles with respect to the engine cycles such that the fuel pump timing marks don't necessarily line up when items 1-3 line up on any given engine rotation cycle in which case rotate the engine 360 and check again, may have to do this check twice. Unless someone tells me otherwise this is what I intend to do to be absolutely sure everything is lined up before doing my TB.

I toss this out there for consideration because when I enlarged your picture of the 2 cam pulleys you can see the marks on the teeth mentioned in item 3 above at about the 4:30 position. I'm about 100 percent sure that those marks are 1 tooth apart which strongly suggests 1) something is 1 tooth off and 2) whatever it is you are one lucky person not to suffer the bad TB engine failure although that 1 tooth off may explain your mpg difference. Unfortunately, as Sir Sam indicates, I don't think you can rely on the white marks to decide which cam is 1 tooth off in which direction. Hence I think I'd recommend ignoring those marks entirely and aligning everything per the above outline (Sir Sam - comments please). Once that's done you can remove all these apparently somewhat incorrect marks, make correct marks, and install the TB.

My personal bet is 1) you are about 120 degress off being able to insert the cam pins based on where the cam gear marks are and 2) someone did a TB job and installed the TB 1 tooth off on one cam gear something that's not too hard to mess up and do.

Ajamant · **Posted:** Tue Sep 06, 2011 11:04 am

I had similar issues of finding the "holes" to line up the cams. They are not holes that a hex key can slide threw like the flywheel, but about 1/4 inch detents that the key sits in. The proper cam locking pins really pay themselves off at this step and I would highly recommend using them instead of hex keys.

As far as the white timing marks I'd have to agree those are definitely not stock. Fixing your timing in reference to the apparent 1 tooth off is above my expertise and will leave that to the experts.

Those are some great picture of the proper cam pins locked in place!!!!!

Jay ne Ohio · **Joined:** Sun Dec 12, 2010 5:49 pm **Posts:** 216

Thanks for the advice guys! I am 99% certain that the exhaust cam was one tooth off. I was going to make my own pins, but I could not find any 10 mm metric bolts with the fine thread (1.0 thread pitch) today. So I tried some drill bits and found one that fit pretty good. I turned the crank and could feel the dimple. When I found the dimple, the white marks lined up on the exhaust cam. Based on this, I decided to use the white marks that were already present.

I removed the old belt and old pulleys. I then installed the new tensioner, one idler and then the belt. After I aligned everything, then I installed the other idler. I then used a couple 3 mm hex keys to tighten the tensioner. I rotated the crank clockwise (by hand) until the cams had made one full revolution. The crank mark and cam marks were still in line, but the fuel pump marks do not line up (need to do 2 more revolutions for them to line up). I then had to readjust the tensioner to the proper setting. I put everything back together and fired up the engine. It is purring perfectly. Hopefully I will gain a couple mpg's now with the exhaust cam in the proper position.!!!!!!

Ajamant · **Posted:** Tue Sep 06, 2011 4:30 pm

Strong work, glad it's running good for you!!!

Timing belt questions

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