I've been looking for weeks for what needs to go and stay far as the engine harness from a computer controlled carb to a holley everything I see is for tpi to carb. Has anyone done this? What can I just remove from engine harness and what do I need to modify to make work? Thanks for ur help.

 

 

Orangebird sorry to upset u man, to be honest I completely forgot about my last post and I apologize, and I didn't ignore your last reply I was researching ways to do what I gotta do to make it work, thank you for your help btw, and no I'm hoping for a different answer from someone else or an "ECM fairy" as u put it just simply forgot my bad, I was just trying to be more specific also. Now I have an electric cooling fan that also runs through the passenger side harness correct?

 

Cool , you have my apology as well , I wasn't in a great mood this AM and really shouldn't have posted in anger .

So with that out of the way , I'll help you as best I can . Like I said earlier , the biggest thing will be setting up the lockup . Next up will be controlling the fuel pump , provided you have an electric in the tank in the car now . Thing is , even if both your old and new engines have a mechanical pump bolted on , I'm fairly sure some CC Carb cars had an in tank pump also and the in tank pump will need to either be ;

#1 , run with a pressure regulator to drop it's output down to carb PSI levels , or ;

#2 eliminated with a straight pipe and pickup "sock" in the tank and go with the mechanical one on the new engine only

I mention the pump only because I have read here of early CC carb cars having both an electric in tank and a mechanical on the engine . if your car is this way , you'll need to decide which you'd rather do , pump wise . A peek into your fusebox will tell you if a fuel pump fuse is present and if so an electric in tank is likely and will need addressing .

And that's really the project here when eliminating the ECM , the fact that you'll now take manual control of the (needed) functions of the ECM . Sure you need something pumping fuel and control of the lockup , and that's the way you'll wire things , so that every needed function is under your control . EGR and EVAP and all the rest are nice to keep the EPA happy , but as you know they really aren't required to run the engine and to most are seen as excess . I can surely understand the desire for a clean looking engine bay , with nothing extra under the hood except a big thumpin 350 , which is why I don't mind helping you , having done a few swaps in my younger days myself .

I'll close by telling you to search out the site www.austinthirdgen.org When you find that site , look around it and you will find a page there where they have convienently hosted ALL of our third gen wiring diagrams , which will be mad valuable to you in this project .

Feel free to ask anything else you think I can help you with

 

Cool thanks for the info!

 

The 87 lg4 has an in tank electric pump that assists the mech pump. It is a low pressure pump and should be retained with any carb swap. Ensure that it works (many fail with time and the motor will still run) while you're there. You can jump the relay and observe the flow. It is run thru a two wire oil pressure switch at the China wall tee'd off of the single wire opsu.

The electric fan is NOT controlled by the ecm. The fan relay is engaged by a temp switch in the right head and a fan switch within the ac control head (runs the fan with ac compressor on). Removing the ecm harness will not affect fan operation. Again a good idea to ensure it works properly prior.

The harness can be carefully removed through the pass fender in its entirety. Once the carb AND distributor are replaced with mechanical units.

Recommend that an alternate method of converter lock is installed, either a specific kit or a home made solution. A search will reveal some options. The lockup helps prevent excessive heat buildup from slippage at cruise.

 

And this is where the wiring diagrams hosted at austinthirdgen will be most helpful , since for instance on my car the ecm most certainly does control the fan , as well as the temp switch in the head does . With the year by year and engine differences it's nice to have a definitive diagram for the actual car in question before any wiring changes are contemplated .....

 

Always best to use the wiring diagram has a baseline but always temper it with reality. I've been through several 87 lg4s and all were controlled by a temp switch. Had to rebuild a completely hacked ecm harness once even.

Although a sample does not prove a universal truth, I think most would agree that it is extremely unlikely for gm to have made such a significant change to the ecm program for only a portion of the population of that year's production.

I admit that I cannot recall whether the ecm controls the fuel pump. Lost to time I guess.

 

Well, looks like I need to drop the tank I bought the car in rough shape and the guy put some loud @$$ pump inline and hacked into the distributor wiring for key on power with a hacked up extension cord to power the pump

 

Hi Naf ,

For sure I agree 100% on the oddity of the "running changes" GM made year to year on our cars . That's why when I found the ECM in control of the cooling fan relay on mine , I made the mistake of assuming that cause mine was , all must be . In my admittedly limited third gen ownerships (on my second one now) I have learned that there were changes to things like wiper motors , headlight motors , and engine harnesses such that it's all but impossible to give blanket "one fits all" generalizations when it comes to our cars as to things like wiring functionality and parts interchanges . I've seen at least a couple of folks tripped up by the "early vs late" versions of the wipers and headlight motors and I truly thank God for having a resource like the diagrams at austinthirdgen . With them, I can look at every year and engine configuration and see the major differences in the way things were done .

 

This is where the project gets good , you'll find all the previous owner's hacks and by the time your done you'll have a car that your not only proud of , but also one that you know every inch of . It's kinda like "forensic mechanics" , you figure out what in God's name they were thinking , you find the real problem they were trying to hack around , and when you fix both the original problem and the hack your car is all the better for it , and then you move on to the next repair . As words of encouragement go , it took me almost 3 years to get my car back to somewhat resembling a properly set up thirdgen , and admittedly I loved every minute of it , as I now know every nut and bolt on it . Just think of it as a giant jigsaw puzzle that needs a couple of the pieces prettied up before it's all put together .

 

Yeah just looking at the wiring harness I've looked at it and just said why lol