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1990 gmc truck won't start 4.3

detailer67

By detailer67
in Ask A GM Technician

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detailer67 New Member

detailer67

Posted
Posted

Hi, I have a 1990 GMC 1500 truck automatic, 4.3 litre V6 (Vin-Z), that will not start. It got really cold here a couple of days ago, Freezing actually. and i went out the next morning to start my truck to let it warm up. It would not start. It would turn over and fire a couple of times. But would not fully start. I let it rest, and then tried to start it about 10 minutes later. This time I heard a very loud POP, Like a shotgun. And white smoke came barreling out from underneath my hood. I popped the hood open,nothing was on fire. It was just white smoke and it looked like it was coming from the TBI carb, and the Ehaust manifold. And i noticed that the right side valve cover gasket was completely blown out. I have never seen anything like this. I checked my fuel pump, its working. I installed new distributor cap, rotor, wires, coil, and a new EGR valve, but The truck Still will not start. it was running excellent before this happened. Any advise would be greatly appreciated.

Thanks.........Patrick.........

 

There was plenty of antifreeze in the truck. Normal maintnance was done on the truck like clockwork (oil changes,tunups). This one has really got me baffled....

citydriver Enthusiast

citydriver

Posted
Posted

The Coolant Temperature Sensor may be bad, causing the computer to flood the engine. I'm guessing that the extra fuel bled past the rings into the crank case and the fumes ignited causing the valve cover gasket to blow out. Pull the dipstick and take a sniff, if it smells like gas, then I would change the oil. I would also change the Coolant Temp. Sensor for around $15. If it still won't start, I would do a compression check on the cylinders to make sure the timing chain didn't jump.

And if the back-fire happened AFTER you changed the ignition parts(cap,rotor,etc.) double check the firing order to make sure you didn't cross any ign. wires, also a possible cause of the back-fire....just a thought....Good Luck :confused:

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