deja Posted July 4, 2007 Share Posted July 4, 2007 I added my push button start today and decided to test it of course. When I tuned on the ignition I did not hear the fuel pump start, not good. The push button start kicks the starter but I have no fuel. I figure I must have left out a wire but I checked and everything is hooked up. If I hit the fuel pump purge the pump runs. The purge wire is hooked to the same wire that is the output of the relay. I have +12v from the ignition in run position on the pink wire (switched contact) at the fuel pump relay and ground on the coil. The hot side of the coil is a green/white wire which has +12v when I first turn the ignition on, but it goes away very quickly and you can hear the relay click off. That green/white wire comes the PCM 7A (fuel pump relay control). Obviously this is my problem. I tried another computer, same result. I even rewired in that EBay VATS bypass module to the PCM input, no help there either. I have another relay I am going to try and am charging the battery. I've been doing a lot of headlight/dimmer testing and maybe the battery is low. The voltage is dropping quite a lot when I hit the starter and the volt meter in the gauge cluster is reading less than 12V. Keeping my fingers crossed, I would hate to waste these 5 days off chasing this problem. Quote Link to comment Share on other sites More sharing options...
deja Posted July 5, 2007 Author Share Posted July 5, 2007 I changed the relay and charged the battery for 3 hours. The fuel pump ran as soon as I turned the ignition. OK was it the relay or the low battery? I swapped in the old relay and no fuel pump. Strange that the relay would just decide to die, then again it is probably the original and that makes it 14 years old. Quote Link to comment Share on other sites More sharing options...
bodie Posted July 5, 2007 Share Posted July 5, 2007 relay are like that they work good than all of a sudden they dont btw did you mount the button in the cig lighter hole? do you have and pic of the finished install Quote Link to comment Share on other sites More sharing options...
deja Posted July 5, 2007 Author Share Posted July 5, 2007 relay are like that they work good than all of a sudden they dont btw did you mount the button in the cig lighter hole? do you have and pic of the finished install Finished? ROTFLMAO. I am no where near finished. I am redesigning the dash using TransAm gauges and a new center panel that will house the lights switch, wiper switch, ignition and this push button, fuel pressure gauge AC and my stereo and a few other things. I will post some picts when I get further along. right now the dash isn't even in the car. BTW the push button I'm using is out of a Viper. Quote Link to comment Share on other sites More sharing options...
naviathan Posted July 5, 2007 Share Posted July 5, 2007 I changed the relay and charged the battery for 3 hours. The fuel pump ran as soon as I turned the ignition. OK was it the relay or the low battery? I swapped in the old relay and no fuel pump. Strange that the relay would just decide to die, then again it is probably the original and that makes it 14 years old. More than likely the low battery voltage burned up the relay. Quote Link to comment Share on other sites More sharing options...
deja Posted July 5, 2007 Author Share Posted July 5, 2007 More than likely the low battery voltage burned up the relay. Hmmm, that's a possibility. I plan on taking it to work for analysis. Quote Link to comment Share on other sites More sharing options...
naviathan Posted July 5, 2007 Share Posted July 5, 2007 What happens in a relay (just in case you don't know not saying anything) is the switched voltage energizes a coil which creates a magnetic field and pulls two contacts together. If the voltage is low then the magnetic field isn't as strong and the contacts won't make a good connection which creates small arcs and burns the contacts so they can't make a connection. EDIT: The low voltage can also cause the coil to burn up, but that's less common. Quote Link to comment Share on other sites More sharing options...
deja Posted July 5, 2007 Author Share Posted July 5, 2007 What happens in a relay (just in case you don't know not saying anything) is the switched voltage energizes a coil which creates a magnetic field and pulls two contacts together. If the voltage is low then the magnetic field isn't as strong and the contacts won't make a good connection which creates small arcs and burns the contacts so they can't make a connection. EDIT: The low voltage can also cause the coil to burn up, but that's less common. I'm an electronic tech so I know relays, even though our industry doesn't use them much these days. But it is the input to the relay switch from the computer that was dropping 12v. Some how the computer knew the pump wasn't working and shut the votage off to the relay. I am still learning the workings of the GM PCM. I started the car this morning....WHEW that was a nice sound, LOL. Quote Link to comment Share on other sites More sharing options...
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