Can a caveman do DIY EFI? Nothing ventured, nothing gained...

[Cyclone03]

I'll take a stab at the shielded wire question.
First you need to ground only one end of the shield. I would say to ground it to the same gang ground you have the sensors grounded to,aviod ground offsets.

We have "solder sleeves" we use here at work to terminate shielded wires but you can do pretty close to the same by stripping the insulation over just the shield back about 1 1/4" then trim the shield to about 3/8 and roll it back over the outer insulation then soldering a wire to the shield and coving it with heat shrink.The ground the added wire. A piece of 22 gauge wire is all you need.

The other end is the "float" end just trim the outer insulation back 1 1/4" and trim the shield near flush and heat shrink over the shield.

[TheSilverBuick]

Tinned the wire ends eh? Don't think the wire length will change when it gets in the car? Though it's not tough to do better than me

I don't recall what size I used for the power and ground to the battery, but it was definitely too big. Didn't fit in the power holes at all, but I soldered them in anyways. I'd figure out what fits nicely there and use that.

As for question 2, the tach wire that came in my kit only had one wire and shielding. Congrats, you got twins! Actually depending on the type of sensor out are going to use for the tach signal would tell me. If you are using a VR sensor (or pickup coil in an HEI) I'd use just one wire and ground the other side locally next to the VR sensor. If you are using a hall sensor you may want to run the power and signal through that wire and ground locally. As for the shielding, I personally have never done any thing special with it except to make sure the shielding wire isn't contacting the signal wire. IF I had a noise issue in the tach signal I'd ground one side of it to the engine somewhere. Or more likely inside the distributor. Currently my Hall sensor doesn't have any shielding on it and it has a pretty clean signal. My advice is from my experience, so your mileage may vary.

[STINEY]

Tin both ends? Not me, just the end that terminates at the relay board.

Although it appears this will be a neat clean harness, 11 out of 17 wires go to the TBI, 2 to O2 sensor, 1 to fuel pump, 2 to coolant temp sensor and 1 to ignition hot.

That's only 4 groups to loom, and the tbi and coolant sensor can be loomed together part of the way, same with the O2 and fuel pump.

I'll hold off cutting them to length until I actually get the harness laid out on the engine compartment, THEN I'll solder the pigtails on. Hopefully AFTER I slip on the heat shrink tubing.... maybe I should go ahead and slip that stuff on now while I'm thinking of it....

[TheSilverBuick]

I'll hold off cutting them to length until I actually get the harness laid out on the engine compartment, THEN I'll solder the pigtails on. Hopefully AFTER I slip on the heat shrink tubing.... maybe I should go ahead and slip that stuff on now while I'm thinking of it....

I did it the other way. Hardwired the pigtails to the wire in the house, plugged in all the sensors, ran the wires through the engine bay appropriately, ending at the relay board. Then cut them to fit at the relay board where they all terminated. Never worried about tinning the end of the wires. With all the engine pulling I've done, there have been a couple of occassions where I clipped the end off and stripped the wire again for a clean unmangled wire end, thus shortening my wires by an 1/8th inch at a time.

[TheSilverBuick]

I'd be more inclined to tin all the wires at the relay board under the hood (one location) than to solder then heat shrink the group of wires all over the place.

[TheSilverBuick]

And where is the best place to ground it on the relay? Just jump into one of the other sensor grounds?

Here is what my pickup coil with tach wire looks like.

[milner351]

Here's some additional motivation- this one has me thinking - I did pick up that cheap dual quad intake....

[STINEY]

I'd be more inclined to tin all the wires at the relay board under the hood (one location) than to solder then heat shrink the group of wires all over the place.

Didn't you solder and heat shrink the pigtail connections?




^^^^^THAT looks cool John! Having evil thoughts on overcomplicating the falcon and putting a closer squeeze on the deadline?

[TheSilverBuick]

Didn't you solder and heat shrink the pigtail connections?

I did, on the table in the house, not under the hood of the car.

[milner351]

That set up is running in a falcon wagon - guy claims 23mpg highway - it's running megasquirt, found it on tffn.net

that would be stage two or three for the falcon....

[STINEY]

Ahhhh........I see now..... very good.

I can be a little slow somedays. Maybe that's why my boss had me in the field with him this morning picking up rocks. And no Randall, rocks are not a typical part of my day.

[milner351]

I'll figure out a way to rope you into helping on the megasquirt project when I get there - you're the closest expert and you do drive right by relatively often....

[STINEY]

- you're the closest expert and you do drive right by relatively often....

Expert..... ....... Grandpa always said I just never knew to quit while I was ahead.

I'm learning lots though. Have already used this MS education to troubleshoot 3 other newer EFI cars, and I nailed them, so its definitely been worthwhile.

Be glad to help when you're ready. We still have a campfire to attend to someday! You ready to try that overweight Ford truck out in the sand?

[TheSilverBuick]

Picking up rocks is making him smarter

[STINEY]

I wanted to include this exchange in this thread, just to further illustrate the stumbling blocks and solutions of this project.



QUESTION:
"The tach signal shielded wire has me a little unsure.
Should I ground it at the relay board, or at the distibutor end? The manual says not both, and implies the relay board............ but is not specific as where to ground it - battery ground or on of the sensor return "grounds"?
The harness wire bundle supplied by DIYautotune has a 2 wire + shielding that I'm thinking is for the tach signal although it is labeled IGN. Is it okay to just leave the 2nd wire cut short and heat shrink tube over it? Can't think of anything else to do with it.
Last question. What guage wire is best to run for the battery + & - to the relay board? It looks like a 12 guage might fit in the hole.....is that severe overkill? I'm thinking that larger wire would be desired for the load the board distributes?"


ANSWER:
"The Megamanual says "ground the shield with the other Megasquirt grounds" but the OEMs do it differently, almost all of them ground the shield to the block out under the hood. I do the same, to keep transient noise spikes from being drawn INTO the ground plane on the MS. Other "expert" opinions will differ. Try one or the other and see how it goes! You can always move it later. If it were me I'd ground it to the block.
You are correct, the IGN wire is for "Tach Input" to the megasquirt. If you use a VR pickup, you'd use two of the wires (ground the shield same theme as above). If doing a hall pickup, you'll use only one wire. Leave the unhooked wire "floating" i.e. do nothing with it.

On the wire gauge, I'd run the largest that will fit - 12 gauge perhaps? It's been a long time since I have used a relay board but they're good for your application and great for first timers.
I'm hoping you plan on "fuel only" at first, then switch to ignition control later? This REALLY makes the process simple. Trying to do ignition AND fuel on the first try is really hard to do IMO."


QUESTION:
"The Tach terminal on the relay board is a input, correct? I was hoping I could use this to input the tach signal from the factory GM HEI tach terminal, and let the GM HEI complete distributor do the ignition for starters.

Then by just gutting the HEI and locking out the advance use it for a crank position sensor when letting MS do the ignition. But that leads to a question I'll have at that time..... how do I input that crank position information? Simply move the "tach" wire from the shielded wire to the pickup, and add the second wire to the other side of the pickup? Where does the second wire go on the relay board?"


ANSWER:
"Yep, tach terminal maps right to pin 24 on the main harness into the megasquirt - "Tach In." You should be able to use the HEI's "tach" pin which is what would normally drive a dashboard tachometer in the car (you can share them), as the initial Tach Input to the megasquirt for your Fuel Only setup.
Then when you switch over, you can technically still use the HEI module to provide the tach signal, or you can ditch the unreliable module and read straight off your coil pickup inside the HEI distributor - just like the HEI module does now. There are two wires, a positive and a negative, one gets grounded and the other goes into your MS Tach In. So this answers your question "what to do with the other wire coming off the coil pickup" - it gets grounded where the megasquirt is grounded. NOTE - at that point you will need to reconfigure the MS for "VR" input which is two easy jumpers and a VR potentiometer adjustment. That's if you are initially going to use the Hall/Opto configuration since the HEI module's tach pin is putting out a square wave.
To further confuse things, you could be like Randal and use the VR input to read the square wave of the HEI module, it also requires a couple special turns of the potentiometers but isn't difficult. How did you jumper your MS already - for Hall/Opto input?"


QUESTION:
"I'm with you so far.
I jumpered my MS for VR, with the intent of never using the HEI module except as a standalone ignition while doing only fuel.
My intent upon taking over ignition is at that time to gut the HEI including module and use only the VR sensor to input to MS. MS would then either control a coil directly, or control a MSD box. I understood that it could do either with the version I bought, I liked the idea of direct control and ditching the HEI module.
Now, if I understand you correctly, my tach input may be screwed up because of that? At least as far as being configured correctly for use as a tach input for fuel only?"


ANSWER:

"It's OK, you just need to make sure your "Zero Crossing" pot has 2 turns clockwise from zero. This will detect a square incoming waveform, which is what your HEI module puts out. Then when you switch over to reading from the coil pickup directly, take out those two turns and zero out both pots. Piece of cake.
So your tach input won't be screwed up, just need to know about the Potentiometer differences required between the two. No sweat."



Awesome stuff........so now I have a solid set of steps to take when it is time to take over ignition.

Stopped by this morning and ordered a rebuilt kit for the throttle body. Also my buddy the parts guy set me up with some fuel inlets and outlets for the TBI from his goody box. I love that parts store, its like stepping back in time, same creaky wooden floors I remember from going there as a kid. Now my kids are smiling from the creaks when I take them with me.