I loaned my sister my old '94 Blazer (VIN W) from October of last year to just a few weeks ago until she got another Voyager van. She loves Chryslers. Before she turned the Blazer back over to me she told me that it wasn't running well and didn't have much power.

Today I had the chance to spend some time diagnosing the problem. I test drove it and I noticed that it was definitely lacking power and had a very loud exhaust. The back of the muffler is blown out. There's a crack in the right exhaust manifold on the runner going to #2.

I did a compression test. #6 was 90psi. #4 and #2 both got up to 90psi but the compression bled off to nothing in less than a minute. It's losing compression somewhere. My guess is bad exhaust valves. Am I correct? Can I know that for sure without pulling the head?

A friend wants to buy the Blazer from me but only if I can fix the power/compression problem. Can I remove the cylinder head while the engine is still in the truck?

 

There is a tester that uses smoke to tell where the compression leak is. They Get the smoke to fill the cylinder then it either stays, comes out the oil cap/dipstick or the exhaust. If there was a violent missfire that cracked the exhaust manifold and blew the muffler chances are something in the cylinder got damaged. I would check the fuel system, do a pressure and leakdown test. Cylinder 2 and 4 are the ones the excess fuel leaks into when there is a fuel leak in the intake. The power loss could just be the leaking spider injector.

 

If it's a leaking spider then I'll be sorely disappointed. The spider injectors were just replaced in December 2011. I bought a rebuilt set from Dr. Injector. If they're leaking after only fifteen months I won't be the least bit happy about it.

 

I pulled the head today. Before I took anything apart I checked the fuel pressure and leakdown just to be sure. It went to 58psi and held for ten minutes so it would appear that there's no fuel problem. I found a complete, disassembled engine from another '94 Blazer for $100 on Craigslist so I'm going to buy it and use the head and manifold to fix up my '94. Then I'm selling it to a friend for his teenage son to drive.

 

The job is all done. I found a completely disassembled 4.3 from a '94 Blazer on Craigslist for $100. I used the cylinder head and exhaust manifold from that donor motor and put my Blazer back together. It runs perfectly now.

Another Blazer is back on the road.

This one is going to my friend for his son.