86 Silverado Father and Son project

[mcbassin]

Which one of the senders is for "idiot" light and which one goes to the pressure gage?

[rfmaster]

Mike

1) Fuel Pump relay wiring

Fuel pump relay socket on a 91 B- Body should have the following wires:

1) black-white (16AWG) | coil ground
2) dark green-white (16AWG) | coil hot - pulled by ECM to +12 V to activate FP relay.
3) Orange (10AWG) (NO - 87)| Battery hot (there should be 20 Amp inline fuse)
4) Red (16AWG) (NC - 87a)| Fuel pump test (4" pig tail with a blade connector)
5) Gray (10AWG) (COM - 30)| Switched Fuel Pump line - this should be connected to FP + terminal.

2) Ignition On Power
I end up wiring a simple relay circuit (see Painless Wiring switched fuse box #70107 for electrically challenged) that gets energized when ignition is on or in start position. For this you'll have to probe your fuse box and find a spare tap port (there should be several ) that remain hot when ignition key is in run and start. This is very important to make sure that this port STAYS hot during cranking!!! Otherwise your ECM will never get a chance to fire injectors during cranking.


3) AC control circuit

Will have to dig into it since B-Body ECM compensates idle RPM when AC is commended to ON. It makes for better idling setup.

//RF

[mcbassin]

Originally Posted by rfmaster

Mike

1) Fuel Pump relay wiring

Fuel pump relay socket on a 91 B- Body should have the following wires:

1) black-white (16AWG) | coil ground
2) dark green-white (16AWG) | coil hot - pulled by ECM to +12 V to activate FP relay.
3) Orange (10AWG) (NO - 87)| Battery hot (there should be 20 Amp inline fuse)
4) Red (16AWG) (NC - 87a)| Fuel pump test (4" pig tail with a blade connector)
5) Gray (10AWG) (COM - 30)| Switched Fuel Pump line - this should be connected to FP + terminal.

2) Ignition On Power
I end up wiring a simple relay circuit (see Painless Wiring switched fuse box #70107 for electrically challenged) that gets energized when ignition is on or in start position. For this you'll have to probe your fuse box and find a spare tap port (there should be several ) that remain hot when ignition key is in run and start. This is very important to make sure that this port STAYS hot during cranking!!! Otherwise your ECM will never get a chance to fire injectors during cranking.


3) AC control circuit

Will have to dig into it since B-Body ECM compensates idle RPM when AC is commended to ON. It makes for better idling setup.

//RF

Thanks RF for you patients with this novice on this wiring subject. I was able to figure out a few things about the truck wire harness but still have a long way to go.

While your on here, which one of the oil sending units was the one for the idiot light? I need to get rid of it and put the original one for the ecm back on there.

right now, I am searching ebay to find some fuel line inline pump filter clamps etc. BTW, how did you tie into the tank? this truck has dual tanks and I assume there is a switching valve under there....so I guess that is where I cut the 5/16 line and tie into with the inline pump?

[mcbassin]

Update:
I had a few hours to spare over the long weekend. I did a mock up of the wiring that will be perminant once I get this harness figured out. I hooked up everything I thought was necessary to make it run including the fuel tank and lines from the donor car. (with the tank sitting on the ground).I was able to get fuel to the TB but never made the injectors fire. I can pour gas in and it will run until it runs out. I was glad to hear it run but dissappointed I can't figure the injectors out. I looked all over CJ's thread and can't find what would cause this problem. Any suggestions?

[cableguy0]

the ignition module times the injector firing on these motors. theres also a fuse for the injectors showing as fuse #11 i cant save these wiring diagrams out of mitchell and send them to you. have you checked to make sure you have voltage to the injectors?

[mcbassin]

Originally Posted by cableguy0

the ignition module times the injector firing on these motors. theres also a fuse for the injectors showing as fuse #11 i cant save these wiring diagrams out of mitchell and send them to you. have you checked to make sure you have voltage to the injectors?

Haven't checked for voltage yet. Does the ignition module signal to the ecm? then tell the injectors to fire in time? I will check for 12 volts at the injectors tonight hopefully. I was thinking I read on one of these threads where one of the guys had the same problem but I couldn't find the solution anywhere.

[cableguy0]

there should be a ride wire that runs to both injectors thats the power wire. one injector wire is dark blue the other dark green these are the trigger wires from the computer.

[mcbassin]

Originally Posted by rfmaster

Mike

1) Fuel Pump relay wiring

Fuel pump relay socket on a 91 B- Body should have the following wires:

1) black-white (16AWG) | coil ground
2) dark green-white (16AWG) | coil hot - pulled by ECM to +12 V to activate FP relay.
3) Orange (10AWG) (NO - 87)| Battery hot (there should be 20 Amp inline fuse)
4) Red (16AWG) (NC - 87a)| Fuel pump test (4" pig tail with a blade connector)
5) Gray (10AWG) (COM - 30)| Switched Fuel Pump line - this should be connected to FP + terminal.

2) Ignition On Power
I end up wiring a simple relay circuit (see Painless Wiring switched fuse box #70107 for electrically challenged) that gets energized when ignition is on or in start position. For this you'll have to probe your fuse box and find a spare tap port (there should be several ) that remain hot when ignition key is in run and start. This is very important to make sure that this port STAYS hot during cranking!!! Otherwise your ECM will never get a chance to fire injectors during cranking.


3) AC control circuit

Will have to dig into it since B-Body ECM compensates idle RPM when AC is commended to ON. It makes for better idling setup.

//RF

RF,
I'm a little confused about the pink/black wire in your diagram? Where does it go? I have it tied into the power on during start and run from the fuse box terminal. You show it going to gauge/fuse? I feel like I don't have power hooked up on the ecm somewhere. I can hear the fuel pump relay kick on and pressure up the fuel system. But it won't squirt gas at the injectors.
I think we need to see that we are getting power to them first and then go from there.

Mike

[rfmaster]

Originally Posted by mcbassin

RF,
I'm a little confused about the pink/black wire in your diagram? Where does it go? I have it tied into the power on during start and run from the fuse box terminal. You show it going to gauge/fuse? I feel like I don't have power hooked up on the ecm somewhere. I can hear the fuel pump relay kick on and pressure up the fuel system. But it won't squirt gas at the injectors.
I think we need to see that we are getting power to them first and then go from there.

Mike

Mike

Attached circuit diagram is my circuit implementation that I have built for my '75 conversion. The pink-black wire is used to power up auxiliary gauges (WBO, Tach, etc). You can omit it if not needed for your build.

Since you can get engine to run by dumping fuel into TB it indicates that you have ignition, but ECM is not firing injectors. Two possibilities - ECM is not getting power during cranking or injectors do not get 12 volts during cranking.

Got to run - will continue.

//RF

[mcbassin]

Thanks RF,
Your right I wasn't getting power to the injectors but I think I found the reason. One red wire from the donor I suspected needed hooked up while the key is on was unhooked. When I put power to it the injectors started squirting. It now kinda runs under it's own power (still has to be wired permanantly).

I was trying to figure the fuel lines and I may be wrong but it sure looks like the original fuel line is 3/8" The return looks like 1/4". I guess I still need to run a 5/16 return? I picked some 3/8 steel line from Autozone and it is the same dia. as the original. Also there was a lot of discussion about the use of dual tanks. I don't understand why we can't just tie into the main line and use one pump? I guess if your driving down the road under a heavy load it may stumble the engine? Maybe a little? If it's unsafe then I may need to consider the small pump to move the fuel from one tank to the other.

Things to do still:
Finish the wiring
Install the new fuel pump
fix all the vacuum leaks
change the starter? it sounds like the gear is hanging on the flexplate
install speedo gear and vss
make it driveable

[rfmaster]

Originally Posted by mcbassin

Thanks RF,
Your right I wasn't getting power to the injectors but I think I found the reason. One red wire from the donor I suspected needed hooked up while the key is on was unhooked. When I put power to it the injectors started squirting. It now kinda runs under it's own power (still has to be wired permanantly).

I was trying to figure the fuel lines and I may be wrong but it sure looks like the original fuel line is 3/8" The return looks like 1/4". I guess I still need to run a 5/16 return? I picked some 3/8 steel line from Autozone and it is the same dia. as the original. Also there was a lot of discussion about the use of dual tanks. I don't understand why we can't just tie into the main line and use one pump? I guess if your driving down the road under a heavy load it may stumble the engine? Maybe a little? If it's unsafe then I may need to consider the small pump to move the fuel from one tank to the other.

Things to do still:
Finish the wiring
Install the new fuel pump
fix all the vacuum leaks
change the starter? it sounds like the gear is hanging on the flexplate
install speedo gear and vss
make it driveable

On electrical
Looks like you are getting close to a working solution. Just be aware that you are dealing with 20+ year old OE wiring harness. Use of auxiliary relay block removes current from old harness (including ignition key) making the overall installation robust. It is extra work, but it provides long term reliability.

On Fuel Lines
I used both 3/8" lines for supply and return. You can go with 5/16" return, but why bother. Do not use 1/4" vapor line for fuel return line. The back pressure will screw up fuel pressure regulator in the TB. This will create fuel delivery havoc!

On dual tanks
I have fully functioning dual tank system. This system revivals the one found on B-737 - no kidding:



The fuel system took me about four month to fabricate (I was not in a hurry) which included a lot of 3/8" fuel line cutting and bending (soft steel).

Tank select valves and low pressure lift pump:


Low pressure pump lifts fuel out of selected main tank and feeds it into surge tank which provides un-interrupted fuel supply to high pressure EFI pump. Surge is needed since I have non baffled (pre EFI) main 20 G tanks:


//RF

[mcbassin]

I really like what you did with your fuel system! That is really nice! I could fab up a tank like that. I'm not sure we need to worry about the fuel supply since this will be a road only 2wd truck. I totally understand why you did yours like that. As far as the lines I am using, I am really thinking about using the original car fuel lines since they are the correct size and they have the correct fittings and have an inline filter setup already. I just have to make fittings to adapt to the truck lines or use the quick connect fittings from the tank.

On the power,
I have thought about the relay setup. I want to build a setup like that and I'm sure with your diagram I can. Right now I'm wanting to get past the mess that I have of the harness. It really looks like a rat got under the hood. I need to have the best reliability possible (it will be driven by a kid). This project when done will move us toward finishing the 69 project we started. I would really like to install a 5.3 or 6.0 in it with matching late model tranny.
thanks for all the help!
Mike