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RB20DET Down 1 Cylinder - Why?

MM2death

By MM2death,
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MM2death Grand Master

MM2death

Posted
Posted

My brother has just done his timing belt. It was done the correct way by aligning number 1 cylinder to TDC. The CAS is in the same position as before. Checked timing and it was in the correct range.

Now when the car's started, it's only running on 5 cylinders. Number 1 cylinder is down (figured out by pulling the connector on #1 coilpack while it was running).

So the sparkplug was checked and it's making spark. #1 coilpack was swapped with another one and yet #1 cylinder still doesn't fire.

The car was running fine before the timing belt change. It has aftermarket turbo and powerfc.

What else could the problem be and how could i go about diagnosing it?

Any help appreciated.

Scott

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Revhead Grand Master

Revhead

Posted
Posted

An engine needs three things to run - air, fuel and spark. You've ruled out spark, and we can safely assume it's getting air unless you have a sock or something jammed into the intake runners :P So I'd assume it's a fuel issue. Check that the injector is firing, perhaps swap #1 with one of the others and see if the problem follows the injector, or whether it's in the wiring or ECU (unlikely) somewhere.

If it were a cam timing problem I expect the problem would be consistent across all six cylinders, or at least move between them erratically. The same goes for CAS, TPS and just about any of the other sensors.

Cubes Grand Master

Cubes

Posted
Posted

When I did mine I pulled everything off and lined all the marks up (crank, cam gears)

Pulled the belt off and slipped the new one on (was a nissan one so it had the markings on the belt) I also discovered it was one tooth out on the crank.)

Easy peazy japanezy.

On the dyno it lost a tinny bit of top end but picked up some much needed bottom end.

So your definately getting spark to cyl 1 then?

Stuffed ignition module or wiring to cyl 1?

MM2death Grand Master

MM2death

Posted
  • Author
Posted

Thanks Marc & Joel. All comments taken on board.

Marc, the last time it was running (before timing belt), there were no problems. So i'd have to think that the injectors are fine. FYI, they are 550cc RX7 ones and have been tested and only been in the car about a month.

Joel, i was maybe thinking the ignitor module myself. As you know, you have to take the module off to get to the coilpacks, so in doing this the associated wiring to the module was moved around as well. I notice that the wiring is a bit stiff...prolly from years of heat. I'll pass this info on to him.

Regards,

Scott

blind_elk Grand Master

blind_elk

Posted
Posted

Did you test for spark using the plug in #1? Or did you use a spare plug? Try moving #1 plug to a different cyl and see if the problem follows it. Also, do a compression test (you might have done something nasty like bend a valve while re-aligning the cams and crank).

4door_Sleeper Veteran

4door_Sleeper

Posted
Posted

Did you get wet and a dry compression test results?

This may help determine if the problem is in the top or bottom end.

Whilst I have never looked at the rings on a skyline, I have seen other cars suddenly develop huge drops in compression when the rings turn on the piston and all of the ring gaps line up (nearly all pressure blows past the rings) but this can come good again as the rings move back around.

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