5.3 factory harness with carburetor? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Derek.Matirne · 05-06-2019, 09:23 AM

Hi guys... Starting to get frustrated with the factory injection... I have been having nothing but problems after i took the motor off the test stand and put it in the truck, the injectors don't seem to be getting enough volts to make them engage, that being said i want to switch to carburetor... My question is, can i still use the factory harness and computer to save me some money? Thanks

ls1nova71 · 05-06-2019, 09:28 AM

No. You will have to buy an aftermarket controller for the coils. Add in the cost of an intake and carb and a new low pressure fuel pump, it would be cheaper to fix your problem

Derek.Matirne · 05-06-2019, 09:42 AM

The problem is I don't know what the problem is... I have been racking my brain for quite some time now, starting to get frustrated with the whole thing... One guy i talked to seems to think i dont have a good enough ground, unless its a ground in the wiring harness ( i cut a lot of them out). I bough one of those light noid's hooked it up, seems like the light is very low, I dont know if that is the way its suppose to be or not... I can spray some carb cleaner in it, and it pops right off, fuel pressure is right around 50lbs...

JMac11 · 05-06-2019, 10:00 AM

It ran on the test stand? I had clogged injectors in mine, made a bench tester to find 8 that worked.

**mongocanfly** · 05-06-2019, 10:07 AM

Exactly what ls1nova said....carbing a LS is not cheap and defeats the purpose...fix what ya got..
A LS has to be grounded to death...frame to motor to cab...even the injectors have a ground

ls1nova71 · 05-06-2019, 10:15 AM

Well, you cant test injectors by how bright or dim a noid light is. Like the other guy said, if it ran on a stand, and has been sitting for a while, it's possible that some or all of the injectors are stuck. Also, 50psi is a touch on the low side for fuel pressure, it should be around 58 or so.

Derek.Matirne · 05-06-2019, 10:20 AM

do you guys recommend a good pump to get me up to the 58 psi?

**mongocanfly** · 05-06-2019, 11:03 AM

My bad eyes thought you had 60 in your earlier post..now I see you said 50...
How do you have you fuel system setup?

**First c10** · 05-06-2019, 01:24 PM

The grounds for the injectors come from the ECM. You may need to make sure the ground is good that feeds the ECM.

if was running good on the stand then it has to be something simple. Like a loose or smashed wire or wires, lack of or loose grounds, etc.

Just a question but where did you get your 12+ volt power for injectors, coils, ecm etc? are you using the old coil wire for power???

Custom 68 · 05-06-2019, 01:29 PM

Yep when in doubt add more grounds. There are several in the original wiring harness.

Derek.Matirne · 05-06-2019, 01:44 PM

When i transferred the motor from the stand to the truck, i cut a bunch of wires back at the ECM according to a wiring diagram that i found... That was the only thing i did that was different than what i had set up...

Derek.Matirne · 05-06-2019, 01:47 PM

Quote:

Originally Posted by First c10

Just a question but where did you get your 12+ volt power for injectors, coils, ecm etc? are you using the old coil wire for power???

I added a fuse block with relays according to a wiring diagram that i found on line, it goes straight to the battery...

**mongocanfly** · 05-06-2019, 02:48 PM

Sounds like you just sorta identified your problems....so it's not exactly the same as it was when you cranked it on the stand...its gonna be something to do with all the wiring you cut loose sounds like...
Whose wiring diagram did you use?..have you rechecked all the wiring and connections?....I'm still thinking grounding issue

Derek.Matirne · 05-06-2019, 04:52 PM

Here is the sheet i used.. http://www.lt1swap.com/99-02_vortec_pcm.htm I just kept the blue ones like it stated... After looking at it again, i see #1 pin is PCM ground, im sure i cut this one, and pin's for the injector 1-8 control are also cut, should they be connected? it stated that they weren't needed...

Custom 68 · 05-06-2019, 05:25 PM

Yes, you will need that ground and all the wires marked for the injectors.
I am not sure where you saw the information that they are not needed. I dont see that in that link. I have done a couple of these and probably used that chart as well.
The injector plugs are spread all thru the blue harness.
it states all those not highlighted stay but they are part of the harness so they go to a sensor, the others you will need to hook up to an "external" like ground or positive or brake switch ect...
I always unpin mine rather than cut them.
Good luck
Dave

nobox351y · 05-06-2019, 11:35 PM

After chasing down somethings for quite sometime, a fresh set of qualified eyes really helped sort a couple of small things that I looked over. If you have a friend that knows their way around cars that may help.

See if you can locate another harness, and start over, with that if youre not too comfortable tracking down issues. My second harness sure turned out much better than the first.

I really like carbs, but if you plan on putting any miles on this swap, efi is the way to go. You would spend less to buy the new holley ecu and harness than swapping to a carb.

Derek.Matirne · 05-07-2019, 07:34 AM

Thanks for all the great info guys, i could be wrong with which wire's i have cut, its been a while since i have looked at it, been working out of town, it is hard getting a few hours here and there then jumping back on a project that you haven't put eyes on for weeks at a time...

**First c10** · 05-07-2019, 10:47 AM

Best thing will be to start from the beginning I think! Take it 1 wire at a time and verify its connections. A few hours and you should be able to complete that and possible fix what you find wrong.

Angryman117 · 05-11-2019, 06:45 PM

Quote:

Originally Posted by First c10

Best thing will be to start from the beginning I think! Take it 1 wire at a time and verify its connections. A few hours and you should be able to complete that and possible fix what you find wrong.

Good advise, I had to do the same thing when re-working my harness. I thought I had everything good. But when double checking I found a couple of misplaced wires. I printed the info off and crossed off each pin after verifying. Long and PITA but worth it.

swissarmychainsaw · 05-11-2019, 08:22 PM

To answer your original question:
https://www.jegs.com/i/Holley/510/30...SABEgKgu_D_BwE

This is what you need to run a carb. It's about $700 and you need a carb.
I bought a Holley 670 Street Avenger $250? Plus jet and tune kit $200, and Mine does not run right either.

Once you get your FI dialed in, you'll like it.
Or we can trade.

05-06-2019, 09:28 AM	#2
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: 5.3 factory harness with carburetor? No. You will have to buy an aftermarket controller for the coils. Add in the cost of an intake and carb and a new low pressure fuel pump, it would be cheaper to fix your problem __________________ 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 Last edited by ls1nova71; 05-06-2019 at 10:16 AM.

05-06-2019, 09:42 AM	#3
Derek.Matirne Registered User Join Date: Sep 2015 Location: Haughton LA Posts: 75	Re: 5.3 factory harness with carburetor? The problem is I don't know what the problem is... I have been racking my brain for quite some time now, starting to get frustrated with the whole thing... One guy i talked to seems to think i dont have a good enough ground, unless its a ground in the wiring harness ( i cut a lot of them out). I bough one of those light noid's hooked it up, seems like the light is very low, I dont know if that is the way its suppose to be or not... I can spray some carb cleaner in it, and it pops right off, fuel pressure is right around 50lbs...

05-06-2019, 10:00 AM	#4
JMac11 Registered User Join Date: May 2005 Location: Tallahassee Fl Posts: 773	Re: 5.3 factory harness with carburetor? It ran on the test stand? I had clogged injectors in mine, made a bench tester to find 8 that worked.

05-06-2019, 10:07 AM	#5
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: 5.3 factory harness with carburetor? Exactly what ls1nova said....carbing a LS is not cheap and defeats the purpose...fix what ya got.. A LS has to be grounded to death...frame to motor to cab...even the injectors have a ground __________________ 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

05-06-2019, 10:15 AM	#6
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: 5.3 factory harness with carburetor? Well, you cant test injectors by how bright or dim a noid light is. Like the other guy said, if it ran on a stand, and has been sitting for a while, it's possible that some or all of the injectors are stuck. Also, 50psi is a touch on the low side for fuel pressure, it should be around 58 or so. __________________ 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

05-06-2019, 09:23 AM	#1
Derek.Matirne Registered User Join Date: Sep 2015 Location: Haughton LA Posts: 75	5.3 factory harness with carburetor? Hi guys... Starting to get frustrated with the factory injection... I have been having nothing but problems after i took the motor off the test stand and put it in the truck, the injectors don't seem to be getting enough volts to make them engage, that being said i want to switch to carburetor... My question is, can i still use the factory harness and computer to save me some money? Thanks Attached Images

05-06-2019, 10:20 AM	#7
Derek.Matirne Registered User Join Date: Sep 2015 Location: Haughton LA Posts: 75	Re: 5.3 factory harness with carburetor? do you guys recommend a good pump to get me up to the 58 psi?

05-06-2019, 11:03 AM	#8
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: 5.3 factory harness with carburetor? My bad eyes thought you had 60 in your earlier post..now I see you said 50... How do you have you fuel system setup? __________________ 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

05-06-2019, 01:24 PM	#9
First c10 Registered User Join Date: Dec 2012 Location: Los Banos CA Posts: 2,705	Re: 5.3 factory harness with carburetor? The grounds for the injectors come from the ECM. You may need to make sure the ground is good that feeds the ECM. if was running good on the stand then it has to be something simple. Like a loose or smashed wire or wires, lack of or loose grounds, etc. Just a question but where did you get your 12+ volt power for injectors, coils, ecm etc? are you using the old coil wire for power??? __________________ 1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR SOLD GO GO!!!

05-06-2019, 01:29 PM	#10
Custom 68 Registered User Join Date: Nov 2001 Location: Springfield, MO Posts: 2,939	Re: 5.3 factory harness with carburetor? Yep when in doubt add more grounds. There are several in the original wiring harness. __________________ Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!"

05-06-2019, 01:44 PM	#11
Derek.Matirne Registered User Join Date: Sep 2015 Location: Haughton LA Posts: 75	Re: 5.3 factory harness with carburetor? When i transferred the motor from the stand to the truck, i cut a bunch of wires back at the ECM according to a wiring diagram that i found... That was the only thing i did that was different than what i had set up...

05-06-2019, 02:48 PM	#13
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,670	Re: 5.3 factory harness with carburetor? Sounds like you just sorta identified your problems....so it's not exactly the same as it was when you cranked it on the stand...its gonna be something to do with all the wiring you cut loose sounds like... Whose wiring diagram did you use?..have you rechecked all the wiring and connections?....I'm still thinking grounding issue __________________ 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

05-06-2019, 04:52 PM	#14
Derek.Matirne Registered User Join Date: Sep 2015 Location: Haughton LA Posts: 75	Re: 5.3 factory harness with carburetor? Here is the sheet i used.. http://www.lt1swap.com/99-02_vortec_pcm.htm I just kept the blue ones like it stated... After looking at it again, i see #1 pin is PCM ground, im sure i cut this one, and pin's for the injector 1-8 control are also cut, should they be connected? it stated that they weren't needed...

05-06-2019, 05:25 PM	#15
Custom 68 Registered User Join Date: Nov 2001 Location: Springfield, MO Posts: 2,939	Re: 5.3 factory harness with carburetor? Yes, you will need that ground and all the wires marked for the injectors. I am not sure where you saw the information that they are not needed. I dont see that in that link. I have done a couple of these and probably used that chart as well. The injector plugs are spread all thru the blue harness. it states all those not highlighted stay but they are part of the harness so they go to a sensor, the others you will need to hook up to an "external" like ground or positive or brake switch ect... I always unpin mine rather than cut them. Good luck Dave __________________ Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!"

05-06-2019, 11:35 PM	#16
nobox351y Registered User Join Date: May 2016 Location: LeRoy Posts: 69	Re: 5.3 factory harness with carburetor? After chasing down somethings for quite sometime, a fresh set of qualified eyes really helped sort a couple of small things that I looked over. If you have a friend that knows their way around cars that may help. See if you can locate another harness, and start over, with that if youre not too comfortable tracking down issues. My second harness sure turned out much better than the first. I really like carbs, but if you plan on putting any miles on this swap, efi is the way to go. You would spend less to buy the new holley ecu and harness than swapping to a carb.



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05-07-2019, 07:34 AM	#17
Derek.Matirne Registered User Join Date: Sep 2015 Location: Haughton LA Posts: 75	Re: 5.3 factory harness with carburetor? Thanks for all the great info guys, i could be wrong with which wire's i have cut, its been a while since i have looked at it, been working out of town, it is hard getting a few hours here and there then jumping back on a project that you haven't put eyes on for weeks at a time...

05-07-2019, 10:47 AM	#18
First c10 Registered User Join Date: Dec 2012 Location: Los Banos CA Posts: 2,705	Re: 5.3 factory harness with carburetor? Best thing will be to start from the beginning I think! Take it 1 wire at a time and verify its connections. A few hours and you should be able to complete that and possible fix what you find wrong. __________________ 1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR SOLD GO GO!!!

05-11-2019, 08:22 PM	#20
swissarmychainsaw Registered User Join Date: Jun 2009 Location: san francisco, ca (east bay) Posts: 674	Re: 5.3 factory harness with carburetor? To answer your original question: https://www.jegs.com/i/Holley/510/30...SABEgKgu_D_BwE This is what you need to run a carb. It's about $700 and you need a carb. I bought a Holley 670 Street Avenger $250? Plus jet and tune kit $200, and Mine does not run right either. Once you get your FI dialed in, you'll like it. Or we can trade.

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