Hi guys, I have a 2000 chevy blazer with an intermittent no start problem. After a little investigation I learned that when it doesn't want to start there is no power to the fuel pump. It seems like the ignition switch has something to do with it. Can a bad ignition switch cause no power to the fuel pump? Or is it just a coincidence and I need to look elsewhere? Thanks

 

*Moving into a post of your own* - I am sorry to have to scold you so soon after the first time, but you really should create your own thread on a topic instead of interjecting your question into someone else's unrelated thread.

Now, yes, the ignition switch can cause the symptoms you are experiencing, but there are other things that typically happen when the ignition switch goes bad as mentioned in the ignition switch link in my signature.

With as common as fuel pump problems are in these vehicles, I would be inclined to think your problem is with the pump itself, but some diagnosis must be done first. You can jumper the fuel pump to +12V power at the relay location. I have detailed this in other threads and some day (hopefully in the not too distant future when I have more time ) I will have to create a how-to on that. You can also test for +12V at the relay location. With the key in the RUN position, the fuel pump should be energized for 3-5 seconds before being de-energized. A multimeter or test light will let you know if it is getting the proper voltage. There should be two pins at the relay that have +12V, one constant with the key on and another switched. Then there is a ground. The other cavity is the lead to the pump.

 

Sorry about that. I didn't know.
I have replaced the fuel pump relay and I replaced the pump with a used pump, which is why I was sure it was the pump. But since it is an intermittent problem I thought before I started I should Hook up a test light. Sure enough, no power to pump. I left the test light hooked up. This was the series of events the next time it would not start. Turn key to ON, light should come on fro 2 seconds, no light. I turned key to start, no light and of course no start. I released the key back to start, no light. I turned the key to the OFF position, the light came on for 2 seconds, just as it is suppose to. I turned the key to ON position, light came on for 2 seconds. Turn key to start position and truck starts. I know other things can cause no power to the pump but doesn't that sound like a switch?
Thanks for all your help. This forum is a great resource!

 

The fuel pump relay is triggered by the PCM. The wire runs between the underhood fuse box and the PCM. It is a dark green w/ white tracer wire that is on connector 4, pin 1. If this wire isn't energizing, then the problem could be in the power supply to the PCM from the ignition switch.

 

OK, I replaced the ignition switch. In the process, I also removed the remote starter module that I didn't know it had. I took it out for a drive and it died after 5 minutes. I managed to make it home and probed the green wire with the white stripe, the one that goes from the VCM to the Fuel pump relay. Next time it died I had a volt meter attached to the green wire and when it died there was no voltage at that wire. So now I'm thinking its the VCM but I'm wondering if there are any other sensors that would go bad and make the VCM turn off power to the relay. Like the crank sensor. If the crank sensor was bad and stopped sending a signal to the VCM, the VCM would then stop sending power to the fuel pump. Does this make sense? Would a scanner tell me if the crank sensor stopped sending a signal? Or if any other sensors weren't functioning when the car dies?
Thanks for any and all help.