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How to check timing belt marks with TB cover on?

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XC92

Proven Member
1,573
358
Jul 22, 2020
Queens, New_York
So I did a complete timing belt job, new TB & BSB, pulleys, seals, tensioner, WP, etc. All the marks aligned perfectly, after turning the crank 6, 12 and 18 times. Tension looked fine, used a DIY pulley tool to get the torque right, etc.

Only possible issue is that the tensioner-arm gap MIGHT have been just a hair under 3.80mm, but probably not. I understand that if it's below 3.80mm the arm could his the tensioner under acceleration and lead to a tooth skipping.

I've run the car several times and I didn't hear or feel anything that seemed like a tooth skipping or anything worrisome from the engine. But I want to make sure. Is there a way to check alignment with the lower TB cover on?

I see timing marks on the lower TB cover around the crank pulley, and I can easily remove the upper cover to check the cam sprocket timing marks. But does that allow me to check alignment? I can't find a mark or notch on the crank pulley. Is there one?
 
So when that top mark on the lower cover and the pulley notch align, the 2 cam sprockets should align like they do when doing a TB job, and if they al align then you're good?
 
Just to ease your mind, when I got my White 90 GSX, the tensioner was KNOWN to be an issue and it was pretty sloppy up top. When I did the timing job, and ANY TIMING JOB, I always double/triple check like you did and then button it up and call it good so you can move on to the next (its a DSM) project.
I think you are worried about nothing. You checked numerous times before you buttoned it up. If it all checked out like we've talked about, you're fine. Pat yourself on ththe back and jump into the next problem (hopefully coming to the end) :thumb:
Marty
 
Well like I said I'm pretty sure that it's at least 3.80mm. A 5/32" or 3.95mm drill bit wouldn't fit flat, but at a slight angle, around 5-10 degrees tops, it did fit. Doing basic trig math that means that the gap is at least 3.89mm.

The angle would have to be greater than 16 degrees for the gap to be less than 3.80mm, and there's no way it was this great.

I even confirmed it with a digital angle gauge I just bought (not for this but because it was on sale and seemed like a good tool to have).

Plus I'm guessing that 3.80mm is a "soft" lower limit and the engineers who designed this allowed for a lower "hard" lower limit, as any decent engineer would. The fact that the rod extends way beyond the upper limit of 4.30mm all the way to 12mm indicates that they've built in some leeway at either end of the range.

In any case, I think I'm good. I haven't driven the car yet as I'm still finishing up cleaning up the cooling system from the rust that developed during the extended time the water pump was off, but I've run the engine many times without incident.

As for next projects, most likely they'll wait till spring, between the colder weather and me being a bit burnt out on all this work. Nothing critical, just some relatively minor fixes, adjustments, upgrades, maintenance, etc., like replacing rear bushings, BJ's and links, cleaning up some rust, unjamming a power window, getting the radio fully operational again, fine tuning the idle, scratches and dings, etc. Old car, lots of small problems, checking them off one at a time. I'm shooting for having everything done by late spring.
 
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