Jump to content
SAU Community

Recommended Posts

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

Link to comment
https://www.sau.com.au/forums/topic/50728-rb20det-down-1-cylinder-why/
Share on other sites

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.

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?

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

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).

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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • No, your formula is arse backwards. Mine is totally different to yours, and is the one I said was bang on at 50 and 150. I'll put your data into Excel (actually it already is, chart it and fit a linear fit to it, aiming to make it evenly wrong across the whole span. But not now. Other things to do first.
    • God damnit. The only option I actually have in the software is the one that is screenshotted. I am glad that I at least got it right... for those two points. Would it actually change anything if I chose/used 80C and 120C as the two points instead? My brain wants to imagine the formula put into HPtuners would be the same equation, otherwise none of this makes sense to me, unless: 1) The formula you put into VCM Scanner/HPTuners is always linear 2) The two points/input pairs are only arbitrary to choose (as the documentation implies) IF the actual scaling of the sensor is linear. then 3) If the scaling is not linear, the two points you choose matter a great deal, because the formula will draw a line between those two points only.
    • Nah, that is hella wrong. If I do a simple linear between 150°C (0.407v) and 50°C (2.98v) I get the formula Temperature = -38.8651*voltage + 165.8181 It is perfectly correct at 50 and 150, but it is as much as 20° out in the region of 110°C, because the actual data is significantly non-linear there. It is no more than 4° out down at the lowest temperatures, but is is seriously shit almost everywhere. I cannot believe that the instruction is to do a 2 point linear fit. I would say the method I used previously would have to be better.
    • When I said "wiring diagram", I meant the car's wiring diagram. You need to understand how and when 12V appears on certain wires/terminals, when 0V is allowed to appear on certain wires/terminals (which is the difference between supply side switching, and earth side switching), for the way that the car is supposed to work without the immobiliser. Then you start looking for those voltages in the appropriate places at the appropriate times (ie, relay terminals, ECU terminals, fuel pump terminals, at different ignition switch positions, and at times such as "immediately after switching to ON" and "say, 5-10s after switching to ON". You will find that you are not getting what you need when and where you need it, and because you understand what you need and when, from working through the wiring diagram, you can then likely work out why you're not getting it. And that will lead you to the mess that has been made of the associated wires around the immobiliser. But seriously, there is no way that we will be able to find or lead you to the fault from here. You will have to do it at the car, because it will be something f**ked up, and there are a near infinite number of ways for it to be f**ked up. The wiring diagram will give you wire colours and pin numbers and so you can do continuity testing and voltage/time probing and start to work out what is right and what is wrong. I can only close my eyes and imagine a rat's nest of wiring under the dash. You can actually see and touch it.
×
×
  • Create New...