I have a 2002 4 door 4.3 that was running perfect until I hit a bump, it was a realty good jolt. Blazer died instantly, cranks but no spark. also I have noticed the gas gauge is reading empty even though has over half a tank. I have replaced the coil, distributer cap and rotor. No change. Is there some kind of sensor that kills the ignition system? I know the fuel system has a inertia sensor.

 

 

I found a bad fuse in the cluster under the hood replaced and now the gas gauge is working and it is getting gas you can smell at the throttle body. Still no spark.

 

This 4.3 was running perfect before bump, I have noticed that the wire harness going to the ox sensor has gotten melted under the exhaust manifold but this is old damage and I have been getting check engine light, I checked the codes way back when and they were all for the ox sensor so I replaced both, last year but I did not see the melted and exposed wires then. After replacing ox sensors I still had the light and the codes. I just found the bad wires a few minutes ago while climbing around he engine. Can a short in these wires cause the computer to shut off ignition. Wish I would have been more diligent back then and found these wires been looking at a check engine for awhile now but it still ran like a champ. I am stuck way out of town, wish I had a code reader for this one.

 

There are 2 fuses ecm1 ecm2 I believe under the hood. Same thing happened to me. Wires going over the passenger side exhaust manifold melted and were shorting out on the manifold blowing the fuse. Ecm1. Pink wire is the power wire. I would replace the fuse, drive hit a bump and it would die. Maybe this is it for you also. Good luck

 

I'm not at a proper computer to send you links but the next thing I would do is find out if you are getting the signal pulses to the ICM when you have the crank but no start condition. Report back and we will go from there. There are some you tube videos or maybe Les or someone can send you a thread link.

George

 

Got a code reader on it comes back with --No Codes Stored on Your Computer. Replaced the ICM because I was not getting signal to the coil has power though. Still no spark, my question is can a crankshaft position sensor or oil pressure sensor cause a no spark condition? The only fuse that blew was the ECMB it is for the fuel pump, module, oil switch. It makes sense because the second the engine died after bump fuel gauge dropped out. I have replaced the fuse and the gauge is working and has pressure, no spark. I have been told it could be the computer.

 

My last post I should have said it has fuel pressure. The oil pressure gauge will start to move up to 40 when cranking. No spark.

 

Yes a crank sensor can prevent ignition signals. We need to determine if the ECM is sending the pulse signals to the ignition module. If the answer is yes then the problem is down strean towards the plugs. New parts does not rule that possibility out completely. If the answer is no then its upstream: ECM, wiring, plugs, grounds, sensors, power. The reason for the diagnosis is to determine the failure point and only fix that problem. If you prefer to replace parts until you get it then next up is the crank sensor, check all engine fuses, locate and examine all relevant grounds, wiring and connectors.

George