Injector Cleaning Question

A few months back, I had the injectors flushed on my 2000 Blazer. My buddy at Ford used the IV type setup and flushed through the shrader valve. He couldn't get at the fuel pump connection by the tank to shut down the pump, so he pulled the breaker to disable the pump, and was able to run the vehicle fine with the injector flush. On my brother's 2001 Jimmy, he went to do the same thing, but when he pulled the breaker, he got a no start condition, so that breaker must also control some part of the ignition. My question is, how do they disable the fuel pump on the 2001 when doing the injection flush? I suspect it must be through the diagnostics, but just curious.

Of course it won't start with no fuel pump!

If you unplug the relay for the pump, and also the oil pressure sender it will work. The reason I say the oil pressure sender because there is a secondary circuit that energizes the pump in the event of a relay failure, and its the oil pressure sender/sensor. This will disable the pump totally.

Of course it won't start with no fuel pump!

We are doing a fuel injection flush. A typical flush (professional flush) involves shutting down the pump so the vehicle runs completely on the injection solution. I'm not referring to a fuel additive for the gas tank. The setup involves hanging the injector cleaner can from the top of the hood similar to an IV setup in a hospital. A pressure regulator is attached to the flush solution can and the other is connected to the shrader valve and the vehicle is run until the can is empty, at which time the vehicle will stall. The setup worked fine on the 2000 blazer by removing the fuel pump relay and the truck died when the bottle ran out. On the 2001, removing that relay kills more than just the fuel pump, (likely ignition) so my question really is how do the GM's techs perform a professional flush of this nature?

So you unpluged the relay and not the fuse and it didn't work. I am not sure on the '01's. Could it be uplugged at the tank?

Yep, unplugged the relay. Problem with getting to the connector for the pump is that I think it is up above the tank and not easily accessible on the Blazer. Thought it was strange that it would work on the 2000 and not the 2001. When I flush my grand am, I just disconnect the pump connection in the back and it is a piece of cake.