Engine '89 GT Won't run unless base timing is 30deg

Hey everyone, this is a stumper for me. My 89 GT will not fire up or stay running unless the base timing is set to ~30 degrees. With the timing light reading 12 degrees the car will crank but not start. While someone is cranking I turn the distributor to 30 degrees it will fire up and run alright but definitely has some hesitation. I am definitely hooked up to #1. I replaced the balancer thinking that it spun, but no difference. I swapped in a different distributor, cap, and rotor that I had laying around but no difference. What could it be? My theory is that the timing chain skipped a tooth and now the valves aren't closed until later in the rotation of the crank. Could this be right? Would a compression test let me figure that out?

Oh! and to throw a wrench in the whole thing, I tested for slop in the chain. I rotated the engine to TDC by hand, and then back the other way. Within 3-4 degrees the distributor rotor was turning, so is seems like the chain is tight.

Mustang5L5 said:

Did this combo ever run? Did you do any recent work?

Check the balancer for slip. It's very common for older balancers where the rubber breaks down and the outer ring actually moves. If you suspect this, replace the balancer.

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Yeah, it ran for a while. The start of the season had no problem. Later on it started to act up and I messed around with things trying to diagnose. I replaced the balancer because the timing marks were hard to see and I thought it could have slipped. But this new balancer reads the same.