Diesel Engine Troubleshooting GM 6.5

When it comes to diesel engine troubleshooting you're opening up a really big can of worms. There are so many models and designs that you would need several years of study to know everything about them.

However I have seen so many of the same failures in non-fuel injected areas of a diesel engine that it's always a good practice to check the simple things first. If you start at the fuel tank (The Source) think about the problem and if lack of fuel is related to the symptoms.

Is the engine hunting and sounding like Grandma's old wringer washer? If the flow of fuel is interrupted by a restriction or a gaping hole in the suction line then you will get this type of symptom.

If you're getting plumes of black smoke then there's too much fuel that could be caused by a bad injector. With today's electronic engines if you don't have a laptop, all I can say is Good Luck. If you have a bad sensor somewhere you gotta have a computer hooked up to find it.

I know it's tougher and more expensive to run a diesel these days but it's all for the good of helping sustain a healthy environment, I'm all for that but the frustration is accelerated sometimes when a problem isn't poking you in the eye telling you directly what's going on with a diesel engine performance problem.

Troubleshooting: GM 6.5 Diesel Engine. 
We had a 2001 GM One Ton Van with our 6.5 diesel engine making a strange noise. It was very loud right after start-up but would quiet down a fair bit 3 minutes or so into the morning warm up.

It was a thumping sound coming out of the intake side through the air cleaner. That made it obvious we were looking at a possible intake valve problem. A couple of us put our inquisitive minds together and guessed it could be a valve lifter. The lifters are hydraulic and can be noisy at first start up.

The only drag about changing lifters on a 6.5 is you have to pull the heads. You can add some time since we're working on a van body. You can see the defective lifter below. It got misaligned somehow and caused the intake valve it was operating to not close properly and turn that cylinder into a compressor.

It's highly advisable to send the heads out for a magniflux treatment which checks the head for cracks. Both of these heads had hairline cracks around the combustion chamber so the only option was to get 2 new ones. One of our local machine shops Valley Speed supplied the heads and did the testing. This isn't the first time we've had trouble with the 6.5 models.

They tend to crack in the block as well from high heat and loads. We've had a couple of long blocks and a rebuild go out the door in the past year. We bought half a dozen of these 1 ton vans in early 2000. They gave us ten years of service so it's worth the time and money to fix'em up.
Modern Diesel Technology: Diesel Engines