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Strange compression numbers..

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Old 06-12-2008, 03:10 PM
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Strange compression numbers..

VQ35 swap.. JWT S1 cams.. The engine has been sitting for a year or so.. but, was a good running motor, out of a 30K mile car..

Cylinder 1- 120psi
Cylinder 2- 170psi
Cylinder 3- 140psi
Cylinder 4- 155psi
Cylinder 5- 155psi
Cylinder 6- 160psi

I checked the cam timing.. at #1 TDC, cam lobes on the number 1 cylinder are pointing up and towards each other.. Cylinder 4's lobes are point down, and towards each other.. Which is how it should be.. So, I don't think it's a cam timing issue..

Could it just be stuck rings, from sitting for so long? The engine has not run, yet.. so, it hasn't had any combustion to push the rings out again.

Travis
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Old 06-12-2008, 05:57 PM
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did you try a wet test? if so what were those numbers?
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Old 06-12-2008, 06:26 PM
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I didn't.. I'm fighting another issue right now.. I'm not getting any spark.. This is a car that's powered by a 2002 Maxima harness, ECU, transponder key, etc.. etc.. I have the key programmed, and I'm getting fuel, but, no spark. I have voltage going to the coils, and the ground is good.. No codes pertaining to cam or crank position sensors.. so, timing is good.. I'm thinking that I may have a bad ECU.

Travis
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Old 06-12-2008, 10:47 PM
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have you checked the flywheel? if there is a ding in the reluctor ring you will get no spark and also you wont necessarily get a code
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Old 06-13-2008, 07:28 AM
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yeah.. I checked it over with a flashlight and hand-turning the crank while I had the plugs out. This one isn't as succeptable to damage as the A32/early A33 reluctor. It's got way less teeth.. but, I did check it, nonetheless.

No cam phase codes.. so, the cam timing has to be correct. I also pulled the valve covers and verified the lobes were facing the right way.

I have another computer ordered.. it'll be here on Monday..
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Old 06-13-2008, 10:36 AM
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I got the car to start.. Turns out.. there's more than one hall effect sensor that will bolt in for the Crank position sensor.. I figured that they were all the same.. but, they're not. If you rotate the sensor.. it gives a different reading, or none at all. I had a cam position sensor installed, and it was sideways.. It didn't throw a code, but, it didn't give the correct signal to the ECU. I noticed that while cranking.. my timing was -7 degrees.. I went to Nissan and grabbed a maxima crank sensor, and installed it.. and it fired right up.

So.. long story made short.. a cam position sensor will bolt in, but, will not read properly. Also, it will not throw a code, for some reason..

My compression figures are all around 170-180psi, now.. so, I guess the rings were just stuck from sitting for a while. You should hear this thing with the equal length header/y-pipe setup that we put together.. Sounds badass!

Travis
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