5.3 factory harness with carburetor?

[Derek.Matirne]

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]

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]

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]

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

[mongocanfly]

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]

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]

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

[mongocanfly]

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]

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]

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

[Derek.Matirne]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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.