TBI to Carb Wiring?

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  #1  
Old 10-19-03, 05:36 AM
LeeWay
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TBI to Carb Wiring?

Hi Ya'll. First post.
I just completed an engine swap in my 87' chevy pick-up. It had a TBI in it and I installed a motor with a new Edelbrock manual choke carb on it.
This engine isn't computer controlled now, so I have a lot of wiring harness not being used now. I removed all the computer controls and installed a manual fuel pump system.
Anyway, to the point.
I can't get my charging guage to operate. The alternater has a two wire plug and then a small wire and a large wire from the battery on the large stud.
Did I remove some relay or computer part that controlled the ammeter? Do ya'll know of a typical wiring diagram available online. I have the Haynes book, but it stops at the computer chip. How would I get the guage to work, short of running a separate wire?
Thanks in advance for your help.
Lee
 
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  #2  
Old 10-19-03, 06:52 AM
Joe_F
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Why on God's green earth you went from a TBI to a carburetor is beyond me as the TBI is much more reliable, gives better fuel economy and nets a better running truck.

There are plenty of kits to hop up a TBI equipped vehicle and it will outrun and outperform a carburetor on a daily basis day in and out.

You might check Painless Wiring for kits to help you straighten out the spaghetti mess of wiring you have. They have lots of kits for modified and swapped vehicles. There's a lot tied into a computer controlled vehicle and you cannot just bypass everything.
 
  #3  
Old 10-19-03, 08:25 AM
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Talking Hey, Joe_F has a point but no sense of adventure. LOL

Lee:

Did a similar project and it worked out great.
Replaced a computer 6.2 diesel with a carb'd 350 in an '89 Chev van.
I used a Chilton's wiring diagram and sorted out a lot of the wiring then cut out what I didn't need. I wound up with a shopping bag full.

As far as I know and correct me if I'm wrong, the "charging" guage on that vehicle is just a voltmeter and needs only a live wire from anywhere in the system, unlike an ammeter which needs a pair of wires directly connected to the alternator.

The answer lies in your wiring diagram.
If you find the guage in the instrument cluster diagram, follow the wire in the diagram, making note of the color coding to see where it connects. The colors should work out.
The diagram in my Chilton's for GM was right on. Unlike a Dodge 4x4 I'm working on now where the colors don't match.
(Might be posting on this later today.)
 
  #4  
Old 10-19-03, 11:25 AM
mike from nj
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ask away--greg H, i just hope i didn't forget too much stuff about the old iron.


you are correct though, a voltmeter is a voltmeter, it can be wired to the cig. lighter for a voltage referance, or anywhere to get the voltage.

if the guage is reading low volts(like 11-12)----chances are the alt is not charging, put a handheld voltmeter on the battery to confirm this.

if it's reading 0 volts, something isn't hooked up somewhere.

i'm curious, how is the distributor wired up, is this still HEI, and not computer controlled yet?

i don't know about L.A. (lower alabama as they call it in nascar) but most librarys i've been to have excellant wiring diagrams, what i do is photocopy the pages i need and use that as my guide, what you need to look for is the huge mitchell manuals.

unfortunately, most alternators have the computer tied in somehow to it's charging system(not sure about yours), it wouldn't be too hard to get creative and hook up an external voltage regulator or even a 'race' one-wire alternator, just remember to make sure the one-wire has a switch on it, it will drain the battery as it is always 'live'
 
  #5  
Old 10-19-03, 12:08 PM
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I'm not sure how carefull Lee was when he removed the wiring from the original set-up.
When I took everything apart on my '89 I was carefull to mark all the wires that went to things I would hook-up later. Water temp, oil pressure, alternator, low coolant warning light, etc. I then split the looms and started carefully separating and cutting. I then located a hot in start and run wire from the left over computer wiring to power my HEI.
Re-loomed everthing and with carefull fastening it looks oem.
One thing that Lee may have to do and would make his rig perform better is to hook up his torque converter lock-up if he has a computer controlled one.
I have some info on this if he needs it with a part number for a low vacuum disconnect that he will need to shut off the lock up under hard acceleration.

This "old iron" is new iron for me and is somewhat baffling. Oxygen sensors, throttle position sensors, sensor sensors???
I've never had to fix anything automotive that is computer operated as they have never failed me.
Now that my project vehicles are getting into the late '80's I'll be doing a little head scratching but can kinda follow a wiring diagram, have a few books and you guys as back-up.

The problems with my '88 Dodge 3/4 ton 4x4 have to do with the fuel pump and power to it. The cut-off relay is not energized and have to find out why, also when I manually depress it the terminal at the pump energizes but the pump doesn't run.
The previous owner gave up and installed an electric in-line pump and it worked fine for him.
I've removed the box to clean-up the frame which is 10x easier that laying on your back and dropping the tank.
I'm nursing a flue and so I work an hour and rest an hour and will be at it soon.
I'll start a new thread if I come up against a brick wall on this thing.


Edit: I forgot to mention that the diesel didn't have a distributor to worry about and the alternator was not computer controlled.
I doubt that Lee's dist and alt are are computer though.
 
  #6  
Old 10-19-03, 03:08 PM
LeeWay
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Thanks for all the info Guys. This actally started out as a simple head gasket replacement. My Dad had bought the truck new, then I bought it from him. He said the motor that was in it was just rebuilt by some salvage yard. Yeah Right! This engine was in terrible condition inside and had never seen daylight since the factory. Hadn't seen much new oil either.
Anyway, I had a 94' Ford pickup that was the same way. I spent over $1000 on that Ford after the rebuild was done. It had 3 different computers put on it and lots of other parts too. Never did run right because of the computer system.
I had been having problems with this Chevy in the computer area also and I was not gonna go through that again. I put in a known good rebuilt 305 out of a 83 camaro. I put a new oil pump and timng chain on and this motor was spotless inside.
I put headers and carb on this as well as a blueprited HEI distributor. Only needed one hot wire from the ignition to this dist.
My old distributor had computer controlled advance, so it had to go.
I got lucky on the transmission. They went to computer controll the next year in 88 so I've been told.
Thanks for the input about the Library. I had forgotten how helpful it can be.
As far as the TBI outperforming this setup I have now, I have never seen this truck scoot like it can now. Plenty of power, nice sound and dependable enough to fix anything that goes wrong with just a couple of tools. No computer or Mechanic needed.
The engine only needed about 4 or 5 wires out of about 70 in the bundle of harness.
Sorry for the long story and all, but I thought it might help to give more of the story.
The guage does indeed register voltage and not amps. Sorry about that.
Anyway, thanks again and ya'll have a great Forum going here.
 
  #7  
Old 10-19-03, 10:48 PM
mike from nj
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lee--good to hear it, i always enjoy a 'happy ending'


greg--old for me is anything older than 10 years, except for what i'm driving!

sounds like you have two problems---first, you need to verify ground at the fuel pump connector, if it's hot on one side and a good ground, it can only be a pump, try banging hard with a rubber mallet on the bottom of the tank WHILE the connector is energized.
second, check all your fusible links right on top of the harness right behind the battery, probably one is blown/melted. there might also be a fuse under dash, wouldn't hurt to check all them with a testlight.

ps. keep a spare dist. 'pick-up' in the glove box, you don't even need tools for this job
 
  #8  
Old 10-20-03, 12:46 AM
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mike:

Here's what I have so far.
I've located the auto shut down relay and have found it does not energize when the key is on.
I have a wiring diagram and found that there is power at the 12v+ term from the charging system and when I move the contacts the terminal at the pump energizes. Pump won't run but I'll worry about that later.
The diagram then shows 12v+ from the ign sw to energize the relay which it does. The problem is the other side of the coil that comes from the 'puter won't pull in the coil. If I probe this term with a test light it will pull in telling me that the controller supplies a ground to complete the cct.
I guess I will now have to check the wire from the relay to the controller. I'm not sure if anything else will cause the computer to not want the pump to run.
In the wiring diagram the terminal on the controller is labeled ASD. Not sure what the D stands for.

Kind of funny but my discovery of DIY.com and my first post was about a fuel cut-off switch on an Escort.
Too bad I didn't check here before replacing the fuel pump!
 
  #9  
Old 10-20-03, 04:11 AM
Joe_F
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Arrow

Bear in mind swapping in a carbed motor from something older may cause you to not pass emission regulations for the state as well.

If you don't have emission laws yet, it's a-comin soon to your area. That is unless the state doesn't want federal money .
 
  #10  
Old 10-20-03, 05:59 PM
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Greg

Every GM fuel pump relay I've seen in those years uses the ECM to apply trigger ground to energize the relay. Key on will give you approx 3-4 seconds and then when it picks up a tach signal, it will give you constant ground. You could ground the relay permanently and run a "key on" B+ for the trigger side of the relay (that you may already have). Just remember not to ever leave the key on without the engine running.
With a carbed engine and electric fuel pump, you'll have to install a low pressure regulator and return line but it should work OK if you do all that.
 
  #11  
Old 10-20-03, 06:14 PM
KurtDixon
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I wonder if we will ever get emissions laws here? Probably not in the future I will see. But it is quite gross to see cars with bad engines spewing clouds of grey smoke and watching diesel trucks pump jet black clouds of smoke after every stop.
 
  #12  
Old 10-20-03, 06:37 PM
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We had them here in Florida and they repealed them. We have no inspections at all now.
 
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Old 10-20-03, 08:04 PM
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mike and Desi, thanks for your help, problem is solved.

On checking the ecm plug for the wire to the relay I found small bits of white stuff on the tips of the pins making the connection suspect. A cleaning with a lubricating contact cleaner and a fine brush made the asd relay cut in.
Checked at the pump + terminal and when key is turned on it energizes for three seconds and then goes off. On cranking it then energizes continuously.
Pump still doesn't run and after I double check for a bad pump ground, a new pump will be feeding my engine.

So, front end is done, frame is painted, fuel problem just about wrapped up, on to the next thing.............rear shocks and brakes.
 
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Old 10-20-03, 09:08 PM
mike from nj
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this got confusing fast

desi--i think he was talking about his own dodge truck, halfway through the thread.

greg--glad to hear it's almost fixed


joe----emissions is only checked in very populated areas, i think half of pennsy doesn't have it. most of the real country areas don't or will never have it.


i would love to have no inspections to worry about
 
  #15  
Old 10-21-03, 04:02 AM
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Originally posted by mike from nj

i would love to have no inspections to worry about
Are you kidding? That's how we make our living. they drive some real junk down here because of no inspection.
 
  #16  
Old 10-21-03, 04:15 AM
Joe_F
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I guess I'll open up that incinerator in Central NJ in your backyard, Mike. LOL.

Again, if it's not there, it's a-comin. Ya, I know about PA. See a ton of their cars in the U-pull it yards too. Older and older ones. Getting off the road. Some look pretty decent. Me thinks they couldn't pass the smog tests coming their way as many had some recently expired stickers on 'em .

Besides, a clean running engine means a well performing one. If you know what's coming out the back, good chance it's running well. The two go hand in hand.

Anyone can slap a Chevy V8 into a truck or car. No brainer. The trick is to make it run 100% and be in compliance/run clean AS WELL as fast. What good is a vehicle that stinks, overpollutes and gets single digit fuel mileage (especially with gas going up 40% soon so I've read).

With this in mind, you don't want to be just cobbling anything together. A TBI equipped motor is miles ahead in all ways in this situation.

I'm with Desi. Not only do you clean the air, you line your pockets---in a legit way because you are doing the right thing.
 
  #17  
Old 10-21-03, 05:34 AM
LeeWay
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To ease your mind a little, Joe, I won't be using the truck everyday. I have an 02 PT Woody Cruiser that gets the bulk of miles put on it. When it gets paid off, I will probably buy a new Dodge Dakota or even a bigger un.
In South Alabama, we are always the last to do everything.
We just got seat belt Laws a few years back and Mandatory Liability insurance only last year.
You might say we just don't jump into a new fad without thorough testing. By the time that we get emmissions testing mandated, my truck might fall under the antique clause and not need to be covered under the emmisions law or at least a different standard for antiques. I can also assure you that this truck is not a cobbled up smoker. It runs very well with no smoke. The body is fine with no rust and with a paint job, would make some teenagers drool. It's a short wheel base model.
I spent a lot of time in Germany and they have the strictest laws anywhere regarding inspections and emmisions testing. I know that it is possible to put a carburated engine through and pass the test. You may need different jets and have it running so lean that it barely goes, but there are ways around it.

The 87' Chevy truck I have also came with carbs that year, or so the Haynes manual says. I will only be using this truck for trips to town or to the hardware or lumber yard anyway. No Harn. no foul-ed plugs I say.
 
  #18  
Old 10-21-03, 07:00 AM
Joe_F
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Sure whatever floats ya boat . Pound for pound the TBI is superior all the way around. Proven. GM wouldn't have done it if they didn't think so .

I make 'em run clean and mean. I do my maintenance so I get in and drive. Blasting the A/C in 100 degree heat, starting it up and having it idle great in 0 degree weather, whatever. I build 'em for the long haul. Make 'em look stock to the naked eye and perform twice as great.

You could say that whenever I decide to sell one of my cars (rare) I never have to advertise, they sell themselves, they come with a bit of a legacy. LOL
 
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