Really_wierd_ignition_system

Gemi_King · rice boy Joined: 15 Jan 2002 Posts: 15

I was putting a new engine in my brothers tg gem the other day and we had some dramas getting it to run due to some idiot (not me, just a pain in the arse friend) deciding to pull all the leads off the distributor. Out comes the trusty gemini manual to find the firing order which was 1342! easy, put the leads on and away we went. I then got home and wandered into the shed and popped my head under the hood of my gemi. Turned the engine to top dead centre, pulled a spark plug to make sure it was TDC. It was!! I popped the dizzy cap off and the rotor button was facing forward (normal for the other 4 gemis i checked). The other gemi's number one lead was just after where the rotor button was facing which is normal as you want the spark just as the pistons starting to go down. Well imagine my shock when i realised that my number one lead is at the rear (exact opposite of rotor button) and they continue in the correct firing order from there. I changed them around to the way they are supposed to be and it wouldnt start. I put them back the wrong way and it fired.
I have a small misfire low in the rev range but once the tacho hits about 2500rpm, it screams all the way to 6500-7000rpm????
somebody please explain and solve my confusion. Thanks

Cyas, Gemi_King!!

IMDGEM · tinkerer Joined: 16 Oct 2001 Posts: 103

all i have 2 say is weird very weird but if it goes harder who cares?

Benjamin · backyard mechanic Joined: 05 Oct 2001 Posts: 525

When (if) the engine was rebuilt it is likely that the dizzy drive from the oil pump was shifted, which will have rotated the location of TDC #1. My TX engine is arse about on the dizzy as well, but once you have it nutted it is fine Smile

bantex · rice boy Joined: 14 Jan 2002 Posts: 10

you have to rotate the dizy so's that it is in the right spot with out making it ping!!!

Fastgem · tinkerer Joined: 04 Oct 2001 Posts: 166

The distributor shaft is probably 180 deg the wrong way. Just pull the dissy out, rotate the shaft half a turn and put it back then connect the leads to the correct cylinders.

Gemi_King · rice boy Joined: 15 Jan 2002 Posts: 15

The dizzy is in the right way. The rotor button is throwing the top dead centre spark for cylinder one toward the front of the car and the number one lead is at the rear of the dizzy. We turned the engine till the rotor button lined up with number 1 lead and the number one piston was almost at the lowest point of its stroke!!!

Its freakin wierd and my mate who is a mechanic for holdens cant figure it out!! When you think about it, the stupid thing shouldnt even be running?????

Keith · rice boy Joined: 05 Oct 2001 Posts: 36

Sounds like someone has had the head off before and has timed the cam 180 degress out. That would explain why your number one leads is firing number four.

Tooleeda · tinkerer Joined: 04 Oct 2001 Posts: 93

No, its just what the first guy said. The oil pump drive gear has been shifted, and it doesnt really matter a rats. You cant rotate the dizzy shaft 180degrees either and re install it as the shaft will only go in one way. As for the guy at holden with NFI, remind me not to go there.

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

I'm pretty sure I know what you are doing wrong.

The dsitributor drives from an offset keyway, so it can only go in one way, so that rules that out.

When you checked for TDC by pulling the plug, yes the pistons was up, but it must have been at the top of the exhaust stroke, not the top of the compression stroke when you want it to fire.

Cylinder no. 4 would have been at the top of its compression stroke at that time, which is why the rotor would have been pointing in that direction.

If you want to do the check again, just spin the engine over another revolution, and everything will check out. The only real way to check if you didn't have a 'one way in' distributor would be to pull the rocker cover off and see what the camshaft was doing. You would have found that the exhasut valve was just closing and the inlet valve was just openning on cylinder one, whereas on cylinder 4, both valves would be shut as combustion is about to occur.

Ben Wight

Gemi_King · rice boy Joined: 15 Jan 2002 Posts: 15

Thanks ben, i just checked it all out and you were dead right.
Thanks again, gemi-king.