I have an old 84 AMC 150 4cyl Cherokee that wont start. I rebuilt the engine several years ago. I drove it for about 25 miles and wanted to make an adjustment to the downshift linkage. Ya know, trying to get every ounce of power out of a 150. It would'nt start after that. I could get it semi running, but only enough to move it out of the garage.
Tested the electronic control module, coil, fuel, all checked out ok. It has been sitting for serveral years, and I decided I forgot enough of what I tried, so try again. I could get it to start, but seemed like it was running on about two cylinders. Had to slowly give it fuel, any faster and it felt like there was not enough fuel.
Put a new fuel pump on it today, and it wants to start, but just doesnt. Check timing serveral times, even moved it 180 and that was worse, so put it back. Fuel does squirt when pushing the accelerator. I checked the coil again, and it seems to be within spec, but the spark is yellow not a blue spark. The cap and rotor were new when I put the engine together and I dont detect any cracks.
So, any ideas?:banghead:

I found the problem. It was Split Fire Spark Plugs. I put them in new when I put the engine together. They only had 12 miles on 'em. They would spark when cranking, like I indicated in my earlier post, so I thought nothing much of it. I found my old Autolite 985 plugs in the garage and swapped one out. Still would not start and keep running, but it would try and catch. I pulled each plug wire off, one at a time, to see if I could find where it made no difference in trying to start. It made no difference in each one that I tried, except for the one I put in the old Autolite plug. It would'nt start at all when I took that one off. Swapped out the remainding Split Fires out for the old Autolites and it started.
Just thought I'd post the results for others.

That is why also the professionals I know use the factory Champions (or Champion Truck plugs).