No power to the fuel pump - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**mongocanfly** · 08-23-2022, 09:04 PM

yeah , i took one look at building my own harness...then i clicked buy it now..!!
who unlocked your ecm?

**kev2809** · 08-23-2022, 09:06 PM

ya I don't think I want to do it again. lol it wasn't too bad but I really hate wiring and trouble shooting it.

Brendan at lt1swap flashed the ecm for me

ls1nova71 · 08-23-2022, 10:39 PM

If you pulled the relay and the fuses still have power, then it's a wiring issue of some sort. Try pulling the ignition relay and all the fuses and see if the buss bars have power. Looking at your pics, I don't see how they could, but its hard to tell in a pic. If they don't have power, then put the relay back in and turn the key on, check the buss bars for power, they should have power. If they do, then put the fuses back in one at a time with the key off and see when the power comes back to them, then you will know what wire is the culprit that is supplying power to it.

**kev2809** · 08-24-2022, 08:13 AM

got it will head outside in a bit and get to testing

**kev2809** · 08-24-2022, 02:55 PM

ok no relay in, there is no power. with the relay in and key forward, all the fuse terminals have power. I then turned the key off and I probed them all with no fuses and only 1 pink has power... according to my crappy paper drawing it is the pcm wire (top corner opposite of the fuel pump relay)

according to lt1swap that would be pin 19 and 75 on the blue connector which is labeled..

"Pin 19 and 75 - Pink - 12v+ KEY Power Source to PCM. Hot when Key is in the ON and CRANK positions."

mine seems to be hot all the time, even with the key off

ls1nova71 · 08-24-2022, 10:01 PM

That's going to be your problem. There shouldn't be any power on that wire with no fuse in it, so it was back feeding the whole fuse block. The only thing you can do now is un-loom the harness and start following that wire to see where it's getting that power. Fix that and it should be good to go!

**kev2809** · 08-25-2022, 07:56 AM

dang, that's what I was afraid of! I just don't know where I could've possible tied it in to constant power. I remember soldering the 2 wires together but that's it. I'll unwrap it today and check.

i emailed Brenden about the fuel pump green wire and he said it should be on for 2 seconds then turn off with the key on... but I don't even get that. I I'll trace that constant pink wire problem first and see what it fixes. but, if I'm still having problems with the fuel pump kick on, couldn't I tie the green fuel pump wire in with a 12 volts key source and it work correctly?

**kev2809** · 08-25-2022, 10:20 AM

ok, were getting some where now. i pulled back the harness a bit and traced that pink pcm wire. i have it tied into my accessory plug and branches to the 12 volt key in that plug (for the check engine light). i posted a picture of my diagram i made a few months back. plug 2 and 5 are getting 12 volt hot all the time. 5 is wired to the TCC for the brake switch. plug 2 is "suppossed" to be my 12 volt key tap in. i traced it back to my 12 volt key strip i made inside the truck and terminal feeding it is 12 volt constant. im guessing not all "Accessory" fuses are keyed 12 volt? i moved it another "Accessory" fuse and that one is keyed. so everything is working right now..even the fuel pump kick on. is there a better way to plug into this fuse spot? i used a male blade and plugged it in, but if you barely tug it, it will come out...very annoying.

but thanks for all yalls help, hopefully i can get it to start before the weekend for the first time!

LeesTruk · 08-25-2022, 04:30 PM

Get one of these. Dorman #642-291

**kev2809** · 08-27-2022, 06:13 PM

thank you! that dorman number looks out of date but i did find something similar on amazon

Pico 0951pt Gm Fuse Tap Batt Cavity(Blk)
https://www.amazon.com/dp/B00030CPSM...roduct_details

LeesTruk · 08-28-2022, 06:39 AM

Sorry about that. The package has been in my wiring supply box for a while. Don't know if you purchased the tap from Amazon already, but you can get the same thing from Summit for $5.00. Also, Std Electrical parts lists this as ET461, which you could possibly find locally

**kev2809** · 08-28-2022, 07:53 AM

I did not try summit but I did see it at speedway motors for 1.99 I believe. problem is they wanted $21 to ship it I think!

08-23-2022, 09:04 PM	#26
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: No power to the fuel pump yeah , i took one look at building my own harness...then i clicked buy it now..!! who unlocked your ecm? __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

08-23-2022, 09:06 PM	#27
kev2809 low n' slo Join Date: Mar 2009 Location: rosenberg, texas Posts: 5,175	Re: No power to the fuel pump ya I don't think I want to do it again. lol it wasn't too bad but I really hate wiring and trouble shooting it. Brendan at lt1swap flashed the ecm for me __________________ 67 1/2 ton Suburban - Project DRGNWGN. Build thread -_--_--_ _________ _--_-_ -/____\|__\|__\__ ,.,,,.,.,,.,\|_O _______ O_]

08-23-2022, 10:39 PM	#28
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: No power to the fuel pump If you pulled the relay and the fuses still have power, then it's a wiring issue of some sort. Try pulling the ignition relay and all the fuses and see if the buss bars have power. Looking at your pics, I don't see how they could, but its hard to tell in a pic. If they don't have power, then put the relay back in and turn the key on, check the buss bars for power, they should have power. If they do, then put the fuses back in one at a time with the key off and see when the power comes back to them, then you will know what wire is the culprit that is supplying power to it. __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

08-24-2022, 08:13 AM	#29
kev2809 low n' slo Join Date: Mar 2009 Location: rosenberg, texas Posts: 5,175	Re: No power to the fuel pump got it will head outside in a bit and get to testing __________________ 67 1/2 ton Suburban - Project DRGNWGN. Build thread -_--_--_ _________ _--_-_ -/____\|__\|__\__ ,.,,,.,.,,.,\|_O _______ O_]

08-24-2022, 02:55 PM	#30
kev2809 low n' slo Join Date: Mar 2009 Location: rosenberg, texas Posts: 5,175	Re: No power to the fuel pump ok no relay in, there is no power. with the relay in and key forward, all the fuse terminals have power. I then turned the key off and I probed them all with no fuses and only 1 pink has power... according to my crappy paper drawing it is the pcm wire (top corner opposite of the fuel pump relay) according to lt1swap that would be pin 19 and 75 on the blue connector which is labeled.. "Pin 19 and 75 - Pink - 12v+ KEY Power Source to PCM. Hot when Key is in the ON and CRANK positions." mine seems to be hot all the time, even with the key off __________________ 67 1/2 ton Suburban - Project DRGNWGN. Build thread -_--_--_ _________ _--_-_ -/____\|__\|__\__ ,.,,,.,.,,.,\|_O _______ O_]

08-24-2022, 10:01 PM	#31
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: No power to the fuel pump That's going to be your problem. There shouldn't be any power on that wire with no fuse in it, so it was back feeding the whole fuse block. The only thing you can do now is un-loom the harness and start following that wire to see where it's getting that power. Fix that and it should be good to go! __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

08-25-2022, 07:56 AM	#32
kev2809 low n' slo Join Date: Mar 2009 Location: rosenberg, texas Posts: 5,175	Re: No power to the fuel pump dang, that's what I was afraid of! I just don't know where I could've possible tied it in to constant power. I remember soldering the 2 wires together but that's it. I'll unwrap it today and check. i emailed Brenden about the fuel pump green wire and he said it should be on for 2 seconds then turn off with the key on... but I don't even get that. I I'll trace that constant pink wire problem first and see what it fixes. but, if I'm still having problems with the fuel pump kick on, couldn't I tie the green fuel pump wire in with a 12 volts key source and it work correctly? __________________ 67 1/2 ton Suburban - Project DRGNWGN. Build thread -_--_--_ _________ _--_-_ -/____\|__\|__\__ ,.,,,.,.,,.,\|_O _______ O_]

08-25-2022, 10:20 AM	#33
kev2809 low n' slo Join Date: Mar 2009 Location: rosenberg, texas Posts: 5,175	Re: No power to the fuel pump ok, were getting some where now. i pulled back the harness a bit and traced that pink pcm wire. i have it tied into my accessory plug and branches to the 12 volt key in that plug (for the check engine light). i posted a picture of my diagram i made a few months back. plug 2 and 5 are getting 12 volt hot all the time. 5 is wired to the TCC for the brake switch. plug 2 is "suppossed" to be my 12 volt key tap in. i traced it back to my 12 volt key strip i made inside the truck and terminal feeding it is 12 volt constant. im guessing not all "Accessory" fuses are keyed 12 volt? i moved it another "Accessory" fuse and that one is keyed. so everything is working right now..even the fuel pump kick on. is there a better way to plug into this fuse spot? i used a male blade and plugged it in, but if you barely tug it, it will come out...very annoying. but thanks for all yalls help, hopefully i can get it to start before the weekend for the first time! Attached Images __________________ 67 1/2 ton Suburban - Project DRGNWGN. Build thread -_--_--_ _________ _--_-_ -/____\|__\|__\__ ,.,,,.,.,,.,\|_O _______ O_]

08-25-2022, 04:30 PM	#34
LeesTruk Registered User Join Date: Mar 2015 Location: Manchester, CT Posts: 433	Re: No power to the fuel pump Get one of these. Dorman #642-291 Attached Images

08-27-2022, 06:13 PM	#35
kev2809 low n' slo Join Date: Mar 2009 Location: rosenberg, texas Posts: 5,175	Re: No power to the fuel pump thank you! that dorman number looks out of date but i did find something similar on amazon Pico 0951pt Gm Fuse Tap Batt Cavity(Blk) https://www.amazon.com/dp/B00030CPSM...roduct_details Attached Images __________________ 67 1/2 ton Suburban - Project DRGNWGN. Build thread -_--_--_ _________ _--_-_ -/____\|__\|__\__ ,.,,,.,.,,.,\|_O _______ O_]

08-28-2022, 06:39 AM	#36
LeesTruk Registered User Join Date: Mar 2015 Location: Manchester, CT Posts: 433	Re: No power to the fuel pump Sorry about that. The package has been in my wiring supply box for a while. Don't know if you purchased the tap from Amazon already, but you can get the same thing from Summit for $5.00. Also, Std Electrical parts lists this as ET461, which you could possibly find locally

08-28-2022, 07:53 AM	#37
kev2809 low n' slo Join Date: Mar 2009 Location: rosenberg, texas Posts: 5,175	Re: No power to the fuel pump I did not try summit but I did see it at speedway motors for 1.99 I believe. problem is they wanted $21 to ship it I think! __________________ 67 1/2 ton Suburban - Project DRGNWGN. Build thread -_--_--_ _________ _--_-_ -/____\|__\|__\__ ,.,,,.,.,,.,\|_O _______ O_]



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