No power to fuel pump relay

[gatorcountry]

I'm new to the forum so hello to everyone from Florida! I recently aquired a 1990 firebird formula, 5 liter 305 TBI. the previous owner told me it was not getting power to the fuel. After double checking the fuel pump and ensuring it runs with 12 volts hooked to it I then replaced the fuel pump relay only to realize im not getting power to the fuel pump relay. I then replaced the oil pressure switch which supplies power to the fuel pump after the engine has 30psi of oil pressure, still no power to the pump relay and obviously then to the pump itself. Am I correct in thinking the relay gets power via a wire from the ECM? I know the line has a fuse for the fuel pump in it which I checked and the 20 amo fuse is fine, does this sound like the symptoms of a bad ECM or possibly the security system shutting power off to the fuel pump? As far as the security system goes I think it is fine because when the key is turned to the on position the security light on the dashboard lights up and then goes off after 3 or 4 seconds, which i've read means it is working properly, any help would be greatly appreciated. Bad ECM or any other leads? Thanks in advance eveybody!

 

[Zimgxp]

The relay uses low amp power to control a high amperage circut, You need to find out which side of the relay has no power.

 

[gatorcountry]

Ok so quick update, if i run 12v to the pump and prime the lines while turning the engine over she fires right up abd will stay running even after i disconnect the hot wire to the pump, meaning that the pump is recieving proper power supply from the oil pressure switch, if i turn it off it fails to give power to the pump again, this pretty much points directly to the ecm being bad and failing to give power to the pump relay on initial start correct?

 

[melsg5]

Not sure if you have TBI but if you do read this about crank signal during starting
http://www.gmceast.com/technical/Swartzendruber_Generic_TBI_SlidesNotes.pdf

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[gatorcountry]

Well that article says the crank signal is from a fused tap into the starter wire, i thought the 3rd gen firebirds get the crank signal from the distributor control module in the distributor?

 

[melsg5]

found another link for slightly older model but you say you have no power at the relay, there are two power wires, one to energize the relay, wire C, and the other to power the pump, wire E. Are they both without power?
http://www.thirdgen.org/forums/electronics/619864-maf-system-fuel-pump.html

 

[gatorcountry]

Ya I have no power going into the relay at all, the relay should have a constant hot going into it from the better though right? The wire going into the relay from the ECM should just be a small amperage wire to send the signal for the relay to trigger the 12v power source to the pump correct?

 

[melsg5]

since you have no power at either wire the problem is not the ECM.

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[gatorcountry]

Maybe a break in the constant hot to the relay than?

 

[melsg5]

yes that is what I suspect based on that wiring diagram

 

[gatorcountry]

O

 

[gatorcountry]

Ok so the newest development is that my injectors arent pulsing, i verified they are getting power but not pulsing by a test light and my noid lights. I know they were working yesterday because after i jumped the fuel pump it fired up and ran fine. I have noticed that the little black security box by the drivers side kick panel used to have a red light lit up on it but its no longer lit up. My security light on the dashboard still functions like it always has though, lights up for 3 or 4 seconds then goes out like its supposed to...now im really at a loss lol

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[melsg5]

what box, an aftermarket device?

 

[gatorcountry]

It looks like factory to me but im no expert by any means

 

[Zimgxp]

Looks more like aftermarket to me.

 

[melsg5]

I agree does not look factory to me and would not be surprised if that may be related to your problem. Is there a name on it that you could google to find out more about it?

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[gatorcountry]

Nothing at all except a sticker saying "GM security system" but its wired into the passkey box.

 

[Zimgxp]

A remote starter security bypass module?

 

[gatorcountry]

Problem solved!!! The wiring going into the fuse socket for the fuel pump fuse was bad and also the constant hot from the battery to the little hot junction next to the battery was cut, thanks to a previous owner using it to splice in a frickin amp wire. Problem solved and she runs like a top now! Thanks for the help man, hope this thread helps other people also lol

 

[melsg5]

that was quite an adventure tracking that down, glad to hear you got it running