4.3 chevy guys??

BTW...how's that projcet going mike??

 

I need some wiring help...not sure whether to start a new thread or not but here goes...

I have an '88 4.3 out of an astro van with an automatic. I'm sorting out the wiring and today I began putting the engine harness back. I have most of the wires plugged where they belong except for a few that I don't know where they connect to and what they do.

1) Fuel Pump Assembly plug - what is a fuel pump assembly?

2) TCC solenoid - what is this? there are three wires coming out of the plug:
*Purple --->diode--->TCC Switch...what is this tcc switch?
*Tan/Blk ---> ECM ,also to the DL connector
*Lt. Blue---> ECM

3) EST, what is this? two wires coming straight from the ECM

4) Neutral Switch - the wires are orange and black I have two of those wires. The donor was an automatic and I have an SM465...what do I do with these wires?

 

1) Computer turns on the fuel pump for a given amount of time when ignition switch is turned on. That's what that plug is for, to turn on the fuel pump.

2) Torque converter clutch solenoid. Basically locks up the torque converter in an auto trans. You won't need it, but may turn on the check engine light. not sure what to do on that one without researching it.

3) EST, Electronic Spark Timing. Controls ignition timing. You need that. Make sure it's hooked up as per wiring diagram or the vehicle may not start or even get spark.

4) Won't allow the ignition circuit to operate the starter unless in park or neutral. Also used as a clutch safety device so won't start in gear on manual transmission equipped vehicles. Also sends a signal to the ecm letting it know you are in neutral/park and not in gear to control torque converter and idle air control (idle speed).

 

thanks nick,

ok, the EST is connected through a plug into the distributor. I've mistaken the two wires, of the same color, as the ones for EST. so no problems with EST...

is my haynes manual calling the fuel pump and sender combination a fuel pump assembly?. I was thinking it was a separate component from the pump and sender. I'm looking at the diagram and now I see a symbol for a motor and zizag lines (resistor?) for the sender, inside a rectangle symbol that the manual is calling the assembly...nice. i think i'm starting to get this one. I'm seeing that there are 3 wires coming out of this connector: probably one for the sender, one for ground, and the other to power the motor...

I gotta look into how to deal with the TCC...

ahhh...so the neutral safety switch will require me to put some kind of switch (like a brake light switch) at the clutch pedal?

 

can the neutral switched be somehow wired/tricked so that the computer will always allow the ignition circuit to operate?

 

Yup. a simple toggle switch will do it, but it will allow the vehicle to start in gear.... (safety).

 

IIRC the fuel pump and sending unit were wired through the same plug as the wiring was located in the same place at the tank. These vehicles had an in tank pump attached to the pickup tube in the same assembly as the sending unit. Should be easy to separate, just need to check the wire colors.

Manual transmission equipped vehicles with this system had a switch on the clutch pedal to keep it from starting when the clutch wasn't depressed, safety item. You could wire in a toggle switch, or better yet a momentary contact button that has to be pushed before operating the ignition switch. That would be an easy safety item. Or a toggle switch with one of the red covers that turn off the switch (open) when the cover is closed. That way you would have to open the cover and close the switch before it would crank over. Could work as an antitheft device too......

 

The 4.3L is a great engine. I would never separate the factory GM injection system from the motor. They are easily modified by a programmer, if necessary. If anyone is not getting the results they were hoping with fuel injection, there may be one of four sensors not working right:
- O2, the most important
- MAF or MAP sensor
- Throttle Position
- Vehicle Speed Sensor

The latter is one that gets missed a lot. It starts to become a bigger deal on the ~1992 motors/computers. There is a bolt on, cable pass-through (for your original speedo) VSS for your Dana 18 that will bump up the fuel economy and power, esp. at higher speeds.

The neutral safety start switch can be permanently closed to allow starting in any gear. Then your Jeep will by like it always was... unsafe to start if you're not thinking. I think a programmer can shut this requirement off while they are doing the other mods.

When the computer is being programmed, it will have its auto tranny features removed and you won't have to worry a bit about the the TCC circuit.

Here is a list of companies that can mod your harness and computer for you:
http://www.novak-adapt.com/knowledge/wiring_pcm_sources.htm

Doing your own harness can be fun, but you may be better getting a day or two of overtime and then paying a pro to do in three hours what may take a beginner a day or two, IMO. I have done harnesses, and once the technical fascination wears off, it just feels like slow movin'.

The 4.3 is a strong motor. It is the only Gen I GM engine that is still able to achieve Gen III performance and compliance without the really fundamental redesign that the Gen III V8's have. I drove a heavy CJ8 with one, and it was a real kick.

Eric

 

I'm currently doing the wiring on my 4.3 and need help...

I'm not sure how to connect the ppl/wht wire, aka pin c9, from the computer. The engine control diagram is showing that wire is suppose to connect from the computer to the 'charging system'. When I look at the charging system diagram, it shows that wire goes from the starter terminal to a 'crank fuse'. What happens in between?

I've read somewhere that it connects directly to the starter terminal with a fusible link, which makes me a bit cautious since It seems like a recipe for frying the computer...I was looking at the donor's fuse block and there is a dedicated fuse labeled 'crank fuse'...

 

What year is your 4.3 and what did it come out of? I may have a diagram and can try to decode it. It may be the constant 12v power wire to the computer...

 

BTT from farr ago.

I decided to try and stay original and rebuild the 225, which then became a 225 rotating assembly in a 231 block, and ended up with an hour glass of an oil pressure sensor (think 14lbs at idle when hot trying to pull 34's on 3.73's... i know the gearing is my fault, but the oil pressure is not.) To add on to problems I opened everything up today to finally find out what is wrong only to find a 10 thousandths gap between the piston and wall (both sides - 20 thousandths total, and that wasn't even hard to slide in). Awesome machine work huh??

So, I'm right back at square 1. I need a complete overhaul on a 225 or I can swap in a 4.3. The local pull-a-parts both have multiple 4.3s that are much cheaper than a rebuild. I can pull 2 right now that seem to be complete, but is it worth it when comparing costs?

I haven't been able to find an in depth write-up, and I plan on looking some more. Could someone forward a link with specifics in it? i.e. do you need to switch to hanging pedals, will the 71 cj radiator work, what exhaust problems are there, etc...

 

Oh man, I completely missed your response by a month or so. It's from an '88 Astro Van.

So I ended up connecting the ppl/wht wire directly to the starter terminal but I installed a fusible link and an inline fuse to replicate the diagram. I was looking at the donor's fuse box and found the "crank fuse". I checked the two wires going into the fuse and one is a ppl/wht wire that I suppose is the one that comes from the computer pin c9 and the other is a 12 gauge purple wire that I'm supposing is the one that goes directly to the starter...I also traced the purple wire and found the fusible link that was being referred to in the diagram. I think I got it right but would like to get a confirmation before I actually try to start the motor (btw, I haven't done so yet...day job is holding me back)

I've read somewhere that the ppl/wht wire lets the computer know that the engine is cranking...

Does this sound familiar and did I hook it up correctly?

ps.
I have the constant 12v power to the computer hooked up...there's actually two wires on mine: one sends 12v at all times (accessories/start/run)) and the other during run/start.

The design of safety in the fuel system, I think, is pretty cool...Unlike a mechanical fuel pump where the fuel delivery stops if the motor stops. In an electric fuel pump, it has the potential to continue pumping gasoline to the engine even if the motor has stopped (in the case of a wreck) as long as there's power. I've read that fires usually resulted in these types of accidents/wrecks. Since the fuel relay is connected to the oil pressure sending unit, the computer stops the operation of the fuel pump if the oil pressure drops significantly. I guess that's standard nowadays. I've found out too that the Astro Van harness has a thing called "tailgate switch" that connects directly to the computer. This, apparently, is another disabling switch so that you can't start the motor if the tailgate is open...someone must've gotten mistakenly ran over taking groceries from the back of the van...or someone fell out