2003 4 door, 4WD.

This blazer has been vapor locking recently. The engine is not overheating (tops out at just above 210), but apparently the ambient temperature is high enough to cause the fuel to boil in the lines. Is there anything that can be done to prevent this?

 

Vapor lock is extremely rare in fuel injected engines due to pressurized fuel lines with the pump in the gas tank. I cannot imagine the ambient temperature being hot enough to boil the fuel. Can you describe the exact symptoms your truck is showing?

 

This Blazer belongs to my son. The first time it died he was following an RV slowly up a mountain grade. Next was after he had topped out on a 1,000 foot climb in very hot weather. Third was while he was backed up on the freeway due to an accident, again in hot temps. Since I was not with him, I did not know exactly what it was doing. We got the fuel pump and filter replaced, and then I was driving it last weekend. Climbed from 6,000 to 10,000 feet up the mountain. I watched the temperature very closely. Didn't have the AC on. It got just above 210 degrees. Just about the time I topped out at 10k feet, it shut off. The classic sputtering, running out of fuel symptom. I sat on the roadside for about 10 minutes. It started and I got to a parking area, where I let it sit for another 10 minutes. I started it, let it run to circulate water, and the temp came down a bit. I went to get on the road, and it died again. I let it sit for awhile, and then I started again. I drove about a mile, and it quit again. This time I let it sit for about 20 minutes and I sprinkled a little water on the fuel line to cool it. When it started, I let it idle til the temp was below 210, and then drove slowly for awhile until I started downhill. The temp dropped considerably, and I had no more trouble. Subsequently, my son drove it 100 miles, taking care on the hills to slow down and not run the AC. He had no problems.

Anyway, the stalling is clearly from fuel starvation. I'm certain it is vapor locking, even though I know it's rare. I live at 6,000 feet, so I'm sure that's not helping.

I'm wondering if the fuel line can be re-routed farther away from hot engine parts.

 

Let's start by looking into the fuel system possibilities. Get a fuel pressure gauge and work through the diagnostic steps in 96+ Fuel System Diagnosis. Get back with your results.

 

I extremely doubt you are experiencing vapor lock. As Rich stated, it is really difficult for this to happen with a return style fuel system. Fuel is continuously flowing through the lines and back into the tank.

From your symptoms, I would suspect a problem with the ICM and/or coil overheating.

 

Okay. So how do I determine if the coil is overheating? Is there a diagnostic for that?

 

Both the coil and the ignition control module (ICM) can be tested at AutoZone and some other similar stores.

 

The Chilton manual shows a separate coil for each cylinder? Is that correct? The Blazer is away from home this week, so I can't look for myself.

 

No, not correct in the slightest.

 

Just follow the coil wire backward from the distributor. It should be sitting on the top right side of the engine.