75 cos cold cylinder

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75 cos cold cylinder

Postby Lytesp33d » Sat Feb 16, 2013 11:41 pm

I'm trying to figure out why one cylinder isn't getting any fire. I've got spark and I know the injector works because I've swapped them around and the same cylinder is dead. All have good compression. All seems to be in relatively decent order, other than the valves clacking like crazy. Need lifter shims if anyone knows a source for those.

Only thing I could think to try was hook a multimeter to the harness for that injector and it seemed to read constant voltage while running unlike the others that appeared to be pulsing. Was a bit hard to tell with a standard meter though.

Only thing I can think of is the computer. Not sure what else to check at this point. Any ideas?
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Re: 75 cos cold cylinder

Postby NVEGAR8D » Sun Feb 17, 2013 1:20 am

Hi,
Try exchanging the wire to that cold cylinder for the one beside it and run it to see if the other cylinder gets cold. it could be a wire problem.I assume you have looked at the plugs, and the cap for defects.
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Re: 75 cos cold cylinder

Postby Lytesp33d » Sun Feb 17, 2013 1:32 am

I was actually thinking that but didn't try. Started raining on me so I stopped but didn't get back to it. I'll try it tomorrow. It does backfire some and actually the one header is just warm, barely. Don't remember it backfiring before but the header was the same so it may be unrelated.

I'll post a reply tomorrow to let you know.

Thanks
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Re: 75 cos cold cylinder

Postby Lytesp33d » Sun Feb 17, 2013 4:08 pm

Sure enough, when I switched the injector wires the other cylinder went cold/warm. It does somewhat fire because if I unplug that injector it changes the idle. I tried my multimeter again and that one injector wire gets a constant ~12.5 books while the others flicker around the mv range.
With the ignition off they all have about .006 mv. Sounds to me it may be the computer but that's where I lack a little knowledge. Anything else it could be besides the comp?
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Re: 75 cos cold cylinder

Postby cosvega76 » Mon Feb 18, 2013 11:40 am

You might want to check the wiring harness between the injectors and the computer. Cosworths fire the injectors in pairs, 1 & 4 and 2 & 3, if I remember correctly.

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Re: 75 cos cold cylinder

Postby NVEGAR8D » Mon Feb 18, 2013 12:39 pm

Hi,
Did you try swapping the plug wire on the dead cylinder for its neighbor to check for spark?
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Re: 75 cos cold cylinder

Postby Lytesp33d » Mon Feb 25, 2013 11:42 pm

I tried testing the wires all the way back to the cpu and visually inspecting them they seemed perfect. They are untouched, no damage. While testing voltage to the bad injector wire while it's running the bad injector wire shows about 2 volts steady. All the others were in the 100ths or 10ths of a volt range and pulses. Now I can't remember exactly what the volts were. If the bad injector write was unhooked it measured around full battery voltage. While hooked up to the injector about 2 volts.

Since I switched the injector wires and the symptom switches cylinders and the spark is fine on all cylinders then im out if ideas other than the problem being the cpu.

If anyone has any other ideas I'll try it, but I think I might be looking for another computer. If I need a computer does anyone have one for a decent price? I don't exactly have a lot of money to put into this but I want to get it running right. I had regular 74 vega for my first car and got rid of it because I didn't know how to work on anything. Now I have a fair amount of knowledge on cars and can manage to keep them all running and fix a few friends cars, so I kind of wasn't to redeem myself and keep this thing alive. Also need the timing belt and dizzy belt.

I love this car no matter how much of an outcast it is.
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Re: 75 cos cold cylinder

Postby cosvega76 » Tue Feb 26, 2013 10:12 am

See my previous post. Check your injector harness wiring.

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Re: 75 cos cold cylinder

Postby Lytesp33d » Tue Feb 26, 2013 3:53 pm

I did, everything is solid as far as condition and how the plugs fit. I didn't check ohms on each wire though. I might do that today if I have enough light after work. Not sure how else to check it.
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