I need feedback or suggestions, please. I have a 2006 MC, 3.5 L, 6cyl, LT. Earlier this year the car wouldn't start. Replaced the ignition switch, ran for about three weeks, died again. Had it towed to Firestone and they repaired the fuel circuit to the fuse box under the hood. Eight months later, won't start. I was told that if the connections they repaired again went bad I would need to replace the fuse box. Installed a new fuse box today. Won't start. We now have power to the circuits..didn't have that yesterday, but after a second or two the power to the circuit goes out. This was checked with a meter. Turn the key, have power for a couple seconds and then none. In reading it says the ECM can turn the pump off two seconds after the key is turned, seems to be what is happening. Visual inspection of ECM and TCM all looks good. We are not sure how to test these modules or what else to look for. Anyone seen this? Any suggestions would really be appreciated. I love this car...have always wanted one but at this point and explosion is looking good. Please help if you can. Thanks!

 

electric fuel pumps go through a pressure up cycle when the key is turned on. it runs for about 2 seconds, then shuts off, and awaits the pcm to tell it the engine is trying to crank and to start pumping. it does this to get the pressure built up in the lines. most cars you can hear this by sitting in them with the radio off, and just turning the key to run (right before it will crank). visual inspection isnt any good with a module, u normally wont see anything. most of the times, a module problem is from a shorting out inside of it, and the whole module is replaced. there are prob pinpoint tests to follow with your condition, and although firestone makes good tires (im guessing...) i wouldnt take this kind of drivability prob to them. it could be a crank signal not getting received by the pcm, which i would think would be what would tell the computer the car was cranking and therefore to energize the fuel pump. your pump will come on for the 2 seconds no matter if the crank signal is there or not, just not run for start up. you prob had this prob all along and the previous repairs werent needed. you need a tech to examine your car. there could be other things causing this as well, and a good drivability mechanic would be able to test these componets.

 

Thanks for your response. The mechanic working on it now is very good. Just isn't Chevy specific. He will be talking to someone tomorrow who is. I will suggest the PCM. If that doesn't work it may need a tow to someone who knows more about it.

 

scary that the customer has to suggest what the tech should inspect. pcm would be much more expensive than a crank sensor, but you shouldnt just throw parts at it until u get lucky. thats what separates a tech from a parts changer. being chevy specific doesnt really matter. i dont work for dealerships, and in the independant shops you see all diff kinds of vehicles. this is just general knowledge that all techs should possess.

 

Agreed.

 

turned out to be a security issue. locked my key out