Interesting- missing on every other cylinder

R

rbone

Member
Need a little help here. Motor is 59ab, new Skip coil and distributor, new FA54 condenser. New plugs.

Motor is running very rough, especially at idle. Compression is between 85 and 90 pounds on all 8 cylinders. Getting ready to do a cylinder leak down test.

With the motor running, I pulled the plug wires off one at a time. This is where it gets interesting. Cylinders 1, 4, 6, and 7 are not firing. When I put my spark tester between those particular plug wires and the plugs, it has a big spark and I can hear the spark jumping as I lower the plug wire back on the plug. Interesting that is is every other cylinder in the firing order.

Thoughts?
 
rbone said:
Need a little help here. Motor is 59ab, new Skip coil and distributor, new FA54 condenser. New plugs.

Motor is running very rough, especially at idle. Compression is between 85 and 90 pounds on all 8 cylinders. Getting ready to do a cylinder leak down test.

With the motor running, I pulled the plug wires off one at a time. This is where it gets interesting. Cylinders 1, 4, 6, and 7 are not firing. When I put my spark tester between those particular plug wires and the plugs, it has a big spark and I can hear the spark jumping as I lower the plug wire back on the plug. Interesting that is is every other cylinder in the firing order.

Thoughts?
Click to expand...

Jets/idle passages are clogged on one side of carb. One side of carb feeds the end two cylinders of one bank and the middle two cylinders on the other bank. Learned this the hard way almost 60 years ago. Thought I had cleaned the carb but had to take it back apart and run tag wire through the passages. Then it ran great.
 
No way I could be that lucky. I will take it apart tomorrow and give her a good cleaning. Carb is a Holley/Ford 94.
 
Or intake heater has corroded and leaks exhaust gas into that runner...been there done that...almost drove me nuts since it ran open throttle but not with exhaust mix on idle...
 
Glad you found the issue. It's always worth remembering how the cylinders are arranged and what can affect what.

For what it is worth, I had a similar problem once when starting after sitting idle for quite a while. In my case, it was the distributor having the identical effect. What? you say? That's impossible! Not if it is a Lucas industrial unit. If one set of points goes down, the other set work but with a screwed up dwell, and four cylinders (1,4,6,7 or 2,3,5,8) get nothing.

I also had it happen on my coupe but when trying to drive along. It was the carb, but this time some shred of sediment had lodged in one of the main jets. It idled ok.

Mart.
 
You must log in or register to reply here.
Back
Top