Ihave 91 buick that all of a sudden would,nt start one day. I took it to the local mechanic and he found a bad crank sensor, It starts perfectly even in cold weather but when it warms up about to the point where the fans kick on It will shut he motor down and will not start until it is cooled down. I got a complete wiring diagram off of the internet and of course the computer is wired into the control module that fires those 3 coils on the front side of the block. I am about to try a used computer but I can,t find one that matches up exactly as far as numbers go. I have put a new base plate under those 3 coils, that is what fires them. Anybody have any ideas as to which way to turn next? thanks in advance.
Whoa whoa. Before you go for the computer, I am willing to bet you dollars to doughnuts that the problem is the ignition module that lives underneath the coils. It hugs the block, gets plenty of heat, and it is rather prone to failure. I’d start there before replacing the computer.
He said he replaced the “base plate” under the coils. I assummed he meant the module but if not would agree that could be the problem. The thing is that you really need to test for fuel pressure and spark when it shuts down. If you have no spark but have fuel pressure, that would lead you in the direction of the module or other ignition components. If you have no fuel pressure, you may have a bad fuel relay that is right up on the fire wall and susceptible to heat. You really need to see if spark or fuel is the problem though first. Computer? I dunno, I have a spare one to swap to rule out the computer but never had a bad one.
I agree that checking for spark and fuel is the thing to do when this problem happens. You could use some starter fluid as an easy fuel test, and spark. If the engine still doesn’t try to run with some starter fluid sprayed into the intake then the ignition probably isn’t working. Whatever the problem is I suspect it is under the hood since you say it is heat related. There may be a faulty ignition relay causing this or bad wire connection also.
thanks to all that replied! I will try the ether test next time it shuts down and go from there I did replace ignition module . I will try and check out both ignition relay and fuel relay to see if either shuts down when motoer warms up thanks John