Volvo: 1984 240 volvo, throttle position sensor, electrical problem

Question
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Followup To
Question -
My husband has been working on this car for our teenage sons girlfriend.  He has replaced the throttle position sensor, new plugs, new timing belt,new fuel pump and the car still has a mind of its own.  It did crank if you held the throttle to the floor to crank then pat to keep it running.  Then sometimes it would idle on its own but very rough backfiring and the whole motor shaking.  Now however it wont crank at all.  He also cleaned the fuel injectors.  So do you have any ideas that we might could try?    She cant afford to take it to a mechanic.

Answer -
I'll have to clarify some information before I can give you a good answer.  When you say that the car won't crank at all, do you mean that when you turn the key, the engine doesn't even turn over or make any sound, or do you mean the engine turns over but doesn't "catch" and be able to run on its own?

It turns over but doesnt catch.  

Answer
I think that you might be dealing with an electrical problem, like spark not getting to all the cylinders all the time.  If you've already replaced the plugs, check the distributor itself, and the coil, make sure you're getting good spark from both systems.