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Topic Review (Newest First)
01-12-2010 11:27 PM
lowandloud91
Quote:
Originally Posted by Pre-Tuner
The blinkers sound like there is an intermittent short or the load is too great/fuse too small. Does the case of the fuse look like it's been hot or is the center of the fuse simply popped?

You're fuel system problem sounds like nothing more than a bad relay. The jumper simply jumps 12 volts from the battery (at the relay connector) to the positive side of the fuel pump instead of that connection happening internally. I'm sure if you replace the relay the pump will work as designed.

OR!!!

If the ECM is gone, there is nothing to tell the relay to turn on, and that might be why there is a jumper. The fuel pump relay was one of the few things that needed to be wired differently to work. If I remember correctly, both of the relay coil wires needed to be cut, one side grounded, and the other to a switched 12 volt source (so it would only turn on when the ignition was on). The way it is from the factory is the 12 volt side always had 12 volts and the ECM switched the ground to control the pump.

I believe the only things that I had to "wire" was the fuel pump relay wiring (which we just covered), the torque converter lockup (which I still haven't got around to actually installing), the choke, and the A/C clutch.

I've read that you need to lockup if you have a lockup converter or you can burn up the transmission. I really haven't driven mine much since the swap, and right now I'm building another engine for it (406).

The choke is wired to a switched 12 volt source. I used a relay, and it definitely needs to be fused. DO NOT run the choke to the ignition coil lead (pink wire). Both are high current and pulls away from the other resulting in problems, or so I've been told.

I can't remember right now what I had to do for the A/C for sure. I think I had to ground one of the wires at the pressure cycling switch, but don't take that as gospel.

As for wire diagrams, the absolute best thing you could do is to go to www.alldatadiy.com and purchase a subscription for your truck. It's only like $15 a year and it's worth every penny. It is the same information that independant shops use and it all comes from factory service manuals. It's very handy, and is where I found all of my diagrams. The most helpful diagrams were the pin out diagrams that labeled every wire at the ECM so you know exactly what wire does what. I have had subscriptions for all of my vehicles for years.
The blinker fuse is popped. And cool the fuel problem sounds like an easy fix.
The ECM is still in the truck. I do have the correct fuse for the blinkers too, it just constantly blows. I'm not sure how to go about fixing that.

I'll for sure check into that site, sounds like a good deal, and i think I remember hearing about from someone before
01-12-2010 10:31 PM
Pre-Tuner The blinkers sound like there is an intermittent short or the load is too great/fuse too small. Does the case of the fuse look like it's been hot or is the center of the fuse simply popped?

You're fuel system problem sounds like nothing more than a bad relay. The jumper simply jumps 12 volts from the battery (at the relay connector) to the positive side of the fuel pump instead of that connection happening internally. I'm sure if you replace the relay the pump will work as designed.

OR!!!

If the ECM is gone, there is nothing to tell the relay to turn on, and that might be why there is a jumper. The fuel pump relay was one of the few things that needed to be wired differently to work. If I remember correctly, both of the relay coil wires needed to be cut, one side grounded, and the other to a switched 12 volt source (so it would only turn on when the ignition was on). The way it is from the factory is the 12 volt side always had 12 volts and the ECM switched the ground to control the pump.

I believe the only things that I had to "wire" was the fuel pump relay wiring (which we just covered), the torque converter lockup (which I still haven't got around to actually installing), the choke, and the A/C clutch.

I've read that you need to lockup if you have a lockup converter or you can burn up the transmission. I really haven't driven mine much since the swap, and right now I'm building another engine for it (406).

The choke is wired to a switched 12 volt source. I used a relay, and it definitely needs to be fused. DO NOT run the choke to the ignition coil lead (pink wire). Both are high current and pulls away from the other resulting in problems, or so I've been told.

I can't remember right now what I had to do for the A/C for sure. I think I had to ground one of the wires at the pressure cycling switch, but don't take that as gospel.

As for wire diagrams, the absolute best thing you could do is to go to www.alldatadiy.com and purchase a subscription for your truck. It's only like $15 a year and it's worth every penny. It is the same information that independant shops use and it all comes from factory service manuals. It's very handy, and is where I found all of my diagrams. The most helpful diagrams were the pin out diagrams that labeled every wire at the ECM so you know exactly what wire does what. I have had subscriptions for all of my vehicles for years.
01-12-2010 05:16 PM
cobalt327
Quote:
Originally Posted by lowandloud91
Ok, I'll look into a Haynes. Can I go to a GM dealer to get a factory manual?
There's a publisher that I don't have contact info for at the moment that handles all the manuals for Chevy. Prolly someone here will have it...

There are a couple guys on fleabay that deal in old car and truck factory manuals- you might look there, too.

THIS is what you need- about to the bottom of the page but itís almost $125.00!

1991 CHEVROLET C/K TRUCK Body, Chassis & Electrical Shop Manual
01-12-2010 04:52 PM
lowandloud91
Quote:
Originally Posted by cobalt327
Haynes maybe, Chilton prob. not, Motors prob. not, unless they're the pro series.

Factory will, but you will have to get the right one (there are Overhaul Manuals, Repair Manuals, etc.), and they're high priced- but good.
Ok, I'll look into a Haynes. Can I go to a GM dealer to get a factory manual?
01-12-2010 04:43 PM
cobalt327
Quote:
Originally Posted by lowandloud91
Also, anyone know where to get any wiring diagrams??? Would a Haynes book(think thats what its called) have one?...Thanks
Haynes maybe, Chilton prob. not, Motors prob. not, unless they're the pro series.

Factory will, but you will have to get the right one (there are Overhaul Manuals, Repair Manuals, etc.), and they're high priced- but good.
01-12-2010 04:34 PM
lowandloud91 Also, anyone know where to get any wiring diagrams??? Would a Haynes book(think thats what its called) have one?...Thanks
01-12-2010 04:02 PM
lowandloud91
Quote:
Originally Posted by red65mustang
I mis-read your post,,,I thought you still had the tbi unit and tbi intake available

learn just the basics of electrical troubleshooting and you can correctly fix your problems....

Oh ok I see, not a problem, and I'll work on that, thanks
01-12-2010 03:47 PM
red65mustang I mis-read your post,,,I thought you still had the tbi unit and tbi intake available

learn just the basics of electrical troubleshooting and you can correctly fix your problems....
01-12-2010 02:59 PM
lowandloud91
Quote:
Originally Posted by Pre-Tuner
I did this exact thing on my '91 truck, so I know what problems you are facing.

First of all, the transmission is not electronically controlled, so the only thing the computer is used for is torque converter lockup. You will need to buy a lock up kit to control this.

The ECM is also not used for any of the gauges in your truck. They will all work perfectly provided they work now and you have all of the sensors (oil, water, fuel) installed. The idiot lights also work, except for the check engine light (obviously).

I removed the whole harness and basically disassembled it and removed the wires that I did not need (injectors, TPS, MAP, etc.). It's not very difficult to do this right, just start at the inside and remove the ECM, and untape the harness so you can see that nothing is holding it in the truck anymore. Then unscrew the grommet that holds the hole thing in the vehicle from under the hood and pull it out. I used wire diagrams that listed what each wire did to decipher what I still needed, and in the end, it wasn't much. In the end, both connectors that went to the ECM were no longer needed.

You're problem's sound like they may be ground related, and this will not fix those problems. Get some wire diagrams and start tracing down the grounds. I honestly wouldn't waste the time or money in a new harness.

What specifically is going on with your electrical problems? What happens with the blinkers, fuel system, etc?

TBI is nice if it's your daily driver and having a carb on a TBI vehicle is illegal. I tried tuning my TBI for years and spent thousands of bucks trying to make it run good. I finally threw in the towel when I couldn't tune it enough to make it pass emissions. I installed a carb setup and it now passes emissions with flying colors and also hauls ***.

Awesome, good to know there's someone that has gone through this before. I've had a carbed engine in there for a couple years now, but just had a different one built for more power. The blinker problems I've had for a year or so, the fuel problem is new. The blinkers will work for 2 seconds or even 2 hours, then it blows a fuse. The fuel system problem is that the fuel pump is not turning on. A guy I know intsalled a jumper wire in a little plug connecter thing under the hood by the a/c that makes the fuel pump turn on; however the fuel pump stays on at all times. It never shuts off unless I pull the jumper wire out. I didn't know the gauges would still work, thats good, but i would still like to get aftermarket gauges...is that possible? And yes I too love the carbed engine, it really moves
01-12-2010 02:46 PM
lowandloud91
Quote:
Originally Posted by red65mustang
honestly,
there is no real big difference between a carb or TBI functionally...
(one sucks fuel the other squirts fuel)

there is a HUGE difference and advantage when you can simply plug in a diagnostic scanner to tell you exactly what a problem is on a stock harness!!!

I picked this (nightmare) thread example at random just to give you a "clue" for what it takes to just get a tranny shift controller to work....

http://www.fullsizechevy.com/forums/...00r4-swap.html

the smart plan is put the tbi back on the motor and hook up all the wiring factory correct....
(or take all the courses needed to truly understand what you are doing)

enough time and $$$$ you can do anything but the actual results will be not as good as when you started (and endless hours of trouble shooting debug and tuning to gain nothing)....

actually read the instructions first when swapping or adding guages does make that job relatively simple


Well I'm keeping this motor, I'm not changing back. That guy had a different tranny than I did as well. I don't want a stock truck or I would have kept that motor. Maybe its not the smartest route to go but I can't just get rid of my motor, I just had it built the way I wanted it.
01-12-2010 02:22 PM
Pre-Tuner I did this exact thing on my '91 truck, so I know what problems you are facing.

First of all, the transmission is not electronically controlled, so the only thing the computer is used for is torque converter lockup. You will need to buy a lock up kit to control this.

The ECM is also not used for any of the gauges in your truck. They will all work perfectly provided they work now and you have all of the sensors (oil, water, fuel) installed. The idiot lights also work, except for the check engine light (obviously).

I removed the whole harness and basically disassembled it and removed the wires that I did not need (injectors, TPS, MAP, etc.). It's not very difficult to do this right, just start at the inside and remove the ECM, and untape the harness so you can see that nothing is holding it in the truck anymore. Then unscrew the grommet that holds the hole thing in the vehicle from under the hood and pull it out. I used wire diagrams that listed what each wire did to decipher what I still needed, and in the end, it wasn't much. In the end, both connectors that went to the ECM were no longer needed.

You're problem's sound like they may be ground related, and this will not fix those problems. Get some wire diagrams and start tracing down the grounds. I honestly wouldn't waste the time or money in a new harness.

What specifically is going on with your electrical problems? What happens with the blinkers, fuel system, etc?

TBI is nice if it's your daily driver and having a carb on a TBI vehicle is illegal. I tried tuning my TBI for years and spent thousands of bucks trying to make it run good. I finally threw in the towel when I couldn't tune it enough to make it pass emissions. I installed a carb setup and it now passes emissions with flying colors and also hauls ***.
01-12-2010 12:40 PM
red65mustang honestly,
there is no real big difference between a carb or TBI functionally...
(one sucks fuel the other squirts fuel)

there is a HUGE difference and advantage when you can simply plug in a diagnostic scanner to tell you exactly what a problem is on a stock harness!!!

I picked this (nightmare) thread example at random just to give you a "clue" for what it takes to just get a tranny shift controller to work....

http://www.fullsizechevy.com/forums/...00r4-swap.html

the smart plan is put the tbi back on the motor and hook up all the wiring factory correct....
(or take all the courses needed to truly understand what you are doing)

enough time and $$$$ you can do anything but the actual results will be not as good as when you started (and endless hours of trouble shooting debug and tuning to gain nothing)....

actually read the instructions first when swapping or adding guages does make that job relatively simple
01-12-2010 12:00 PM
cobalt327 Painless makes a harness for 1973-'87 Chevy trucks that might fit the bill, P/N 10205.

They have a 12 circuit pick up harness w/GM column, P/N 10103.

They also make a 'universal' 12 or 18 circuit street rod-type harness for a GM column that could be adapted. P/N 10101/10201.
01-12-2010 11:21 AM
lowandloud91 ok thanks, I'll definitely read into that. I realize that finding a kit like mine is not likely, unless i did what you said and called a body shop or junk yard to get a replacement, but thats the thing, I don't want a replacement. I would like to set this up as if it was an older vehicle without a computer, and so I can get some aftermarket gauges. I know it probably would not be to hard to track down these common problems, but there is also a lot of wires that have been messed with, along with a lot of wires that are not in use anymore as I've already stated. I'm basically redoing the whole truck and figured if I fixed those problems, who's to say there wont be more electrical issues later? I just thought it might be better to start over new. Maybe not?...I'm not trying to argue, I'm just trying to figure out what's best. I'm making everything else new so why not that?

Thanks again for the replies.
01-12-2010 10:47 AM
red65mustang Andy,
your ride has so many special termination connectors designs it's not likely available in the general aftermarket....

you can contact some local body shops to see what harnesses are available for collision repairs (and gasp when the tell you the price!)

it's not rocket science to trouble shoot / diagnos and correct the very very common problems you listed....

on this link, scroll down and read the "electrical trouble shooting" article(s)

http://www.aa1car.com/carleyware/library.htm

it is just a step by step testing and eliminating procedure starting from one end or the other of any problem curcuit to pin down the problem souce...

in a sense it is the same as Sherlock Holmes solving a murder for (in this case) "what" is the guilty party...

I prefer and use a volt meter for everything but for very many common problems just a cheap probe test lamp is all you do need...

suggestion,,,keep this "picture" in your head:
on a car 12V neg ground system,,,, the energy flow is from the neg batt terminal thru the car body (electrical conductor) and ground wire at the device where "work" is done by the device with on/off control from a switch and what energy is left after the work is sucked to the positive terminal...
that explains why you disconnect the neg batt cable to work on the electrics in a car to truly kill the "energy source" (and why by far lost ground curcuit side energy "supply" is the most common problem source)...
so most often I do start troubleshooting from the "supply" end of the curcuit...

it is SO worthwhile to learn how to do the troubleshooting basics because it is the same procedure for correcting anything electrical in your life.... (appliance/outboard/house/whatever)
to save service call bucks for the rest of your life....
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