Certainly sounds like the harness. Most likely culprit is the pins in the connector at the ECU. Those connectors are a major PITA to assemble. I'd suspect the serial connection wires themselves first.

Will find out tonight. If I can get a connection with it my plan is to take it to Tonys tomorrow and put it back in the car. Go connector by connector until it fails to try and isolate the problem.

Zach

how many pins is the connector?
Have you considered buying a more rugged cable with the correct number of wires, and redo the connectors at each end to match the new wire?

Something that may be easier to assemble and more reliable??

I am watching with loads of curiosity because I am about to go down this road....

Rich

Rich it's an amp-seal connector. Stop by my room at the Inn tonight it tomorrow night, I'll have it there. It's pretty rugged, and weatherproof.

Can't wait.

Pretty sure this is your problem. Need a new hampster.

bring a gas mask...

Well, not the harness.

I did find a fault in the fuse block, but that is fixed easy enough.

I connected the harness to my laptop via my little tester setup and had a connection instantly.

I am at a total loss as to what I need to do next.

Its got to be something in my car, which makes ZERO sense to me. I'm totally stumped.

Zach

I now have full confidence in the harness.

When I did my test at Hershey I only used one ground point. It occured to me when I got sober the next day that there are 8 ground points. I married all the ground together when I got home on Sunday and retested.

ECU connected right away on the test bench.

So, its something in my car. YAY! ;-|

I dont wantto tow the car back home, but I dont see it making sense to work on it at Tony's as I have to take off work. I also dont want to pay tony to chase wires. I want to pay him to tune...

So I guess I have to tow the car home and start digging into it old school style. Which will have to be Friday, and then work on it while I still have my post Hershey 914 buzz going on.

I will admit I was pricing buying IDFs again to get the car moving under its own power. But I'm not giving up yet.

Zach

Bad relay board? Test the power supply pin. It's the one in the white connector on the right/passenger side. Make sure it's getting 12v, maybe even try jumpering it straight to the battery.

Relay board is first of the things I have to check.
The fuel pump also does not turn on when the key is turned, so I think there has to be some wierdness going on there.

When I had carbs it was not much of an issue.

Zach

Hot wire. Eliminate everything and then add back one by one. Do you need to borrow my trailer?

Zach,

Have faith, look what Wally did....

https://www.youtube.com/watch?v=5ufjeBe0PYo

Herb, I'll just flat tow it. Thanks for the offer though!

Main power relay on the board may not be tripping. That would cause both issues.

relay board fuse, could be a switching transistor on the main board also.

What do you mean?
Specifically the "switching transistor on the main board" part. Something in the cabin?

Zach

Since he's got Megasquirt I listed in his signature I suspect he's talking about the MS board. Another reason I only use MicroSquirt.

Since I will be doing some rewiring, I made something big.
All the 914 wire diagrams in one wall poster.
Big one is the engine side, since that will be my main target.
Little copy of the firewall forward.
Detail of the relay board - my likely nemesis.
And the ledgend for all three charts.
Calipers are in there for scale reference. It's 48x36 inches.
Click to view attachment

That should help a bit.
Zach

my 914 is back in my garage.
Work starts tonight...
Zach

Are you using the ms relay board? I only use my original one for the voltage relay.

Using the stock board for a few things. Some of the wires come out, some stay in.

Zach

The main MS board has switching transistors on it. There is in for the FP. The are small and could fail with a voltage overload.

Of you go to the megamanual It will show you where it is in the assembly instructions.

As usual, life got in the way. But work started at home again on this today.

An old wire harness I got from Joe a longtime ago paid off. I needed to make a new 12 pin harness, and that got made today and is in the car. For the first time in YEARS my car will have reverse lights... assuming the switch at the transmission works.

I still need to test the main board, which will happen this evening after the kids go to bed. After that, I need to attach the plug to the crank fire wires I had to cut. Good times. This is what I want to get done tonight after the kids are in bed - assuming I can keep my eyes open.

Zach

Fingers crossed

Good Luck, If it works are you going to the Import Show next weekend in Carlisle? It sure would be nice to meet you after being so close a couple of weeks ago. I just broke something in my shifter yesterday. I got carried away and shifted to hard or fast I guess. Paul in Harrisburg is going to get it fixed for me so I can attend the show next weekend.
John

Nah, going to a different, non-porsche show next weekend.

Though I may drive up Sunday for the AX.... in my WRX.

Zach

Good luck, keep on it.

Work complete.







Got a lot done today, in my own slow way. Both Molex plug ends are in and the crankfire wires are connected again. So tired I can barely see straight. Goodnight.

Zach

I love your poster board! My schematic pages are all taped together and rolled up like the Dead Sea Scrolls. Good luck on this

Keep at it, even an hour a week and you will conquer your demon....
You should rename the car demon btw.

progress is progress. It all ads up and soon you will be driving.

And then sell it and buy a Miata

On the other side is a poster of Elle Macpherson.

The other side is the hole I've been digging to freedom.


Zach

With any luck, tonight I put the harness back in the car, unhooked aside from power and ground, and see if it connects.

Zach

Booya!
We have a connection in the car. repeat! We have a connection in the car!

I had a really good feeling when I turned on the key and suddenly I heard the fuel pump turn on for a few seconds. I had not been getting that.

Loaded tuner studio, and the MS connected!

Slightly scary part is that I have NO CLUE what I did to make it start working. But it is WORKING!

Tomorrow, if I get released from mothers day duty, I'll start replacing the harness in the car. Right now its just the power and ground plugs installed.

The only thing that is not connected now which had been connected earlier is the crankfire sender. Easy enough to see if that kills it, but not tonight.

Zach

Send Mom to the spa, instruct kids to clean their rooms in 15 minute segments broken up by Pokemon episodes on Netflix. Attend to car.

Great news!!!

Great news Zach!! If you are using a VR sensor, remember that it will only work with the wires in the right order. So if you get nothing when you crank it, flip the wires around and try again.

In MicroSquirt, maybe others, you can switch this in software by switching the triggering from Going High to Going Low, or visa-versa.

Well, found the issue!
Something is wrong with either the throttle position sensor or the wires for the throttle position sensor.

I thought I'd have an easy night hooking back up all the leads. Some of them are not easy to get to.

Turn the key, and no fuel pump. Dammit! I am now using the fuel pump as my dowsing rod. If it turns on foe a few seconds, I'm confident that the brain is working.

Take off a lead and try the pump. One by one. I got the point where I thought I had all the leads off and was starting to get really angry when I noticed the TPS tucked deep in there. Took that lead off and the fuel pump came back.

So, I'm going to replace the sensor, as I really doubt its the wires. I also happen to have another TPS on hand. But not tonight. Its 11:30 on a work night. I gotta get my ass in bed.

Frustrating, but at least I found the issue. I wish I had found it a month ago while the car was at Tony's shop.

Zach

Are you saying the fuel pump turns on because of the TPS?

They should have noting to do with eachother

shorted wires in the TPS, drawing down the operating voltage, fuel pump relay won't kick in for the short prime cycle.

fuel pump is a good test to see if the cpu is functioning correctly as it has full voltage...

Just like D.jet. No fuel pump no tickee.

Replaced the TPS after work today. Tested it and and the fuel pump kicked over! We are in business.

Before I had to start being Dad, I was able to get the rest of the harness plugged back in, and turned the key for a quick test. The fuel pump kicked on just like it should.

I'm close to first start. Stuff left to do:
1) Calibrate sensors (TPS, AIT, CHT... I have a feeling I should have done this earlier, but I think I can do this with the sensors in the car.)
2) add fuel
3) put the air filter in
4) pressurize the fuel system and look for leaks
5) try to start it.

Would be totally awesome to be able to drive the car back to Tony's for final tuning.
Zach

Sweet

Sensors are calibrated and seem to be working correctly.

Click to view attachment


I did run into a hiccup trying to update the ECU to the latest firmware. The installer would not install the firmware. More investigation is required, but I followed the printed firmware updater instructions to the letter.

Push comes to shove, I just run with the current installed firmware, which is 1 rev behind (for now).

Next step is fuel, and make sure my fuel system does not leak when pressurized.

You will note there is a "coolant temp" gauge. That is actually the head temp at the stock location (as opposed to under a spark plug). I have an under the spark plug CHT for the gauge in the car, giving reading for Cyl 3. Eventually I will install the 4 way. But first things first....

I also learned today that my throttle sticks open a little. There is something it grabs on before it gets fully closed. Thats why in the screen shot its reading at 10% open instead of fully closed.

I still have a few mysteries to work out with the spark tables. I set the offset to 295 degrees per Mark's instructions, but did not see where to set the initial cranking advance to 12 degrees. Still in the steep part of the learning curve for this software.
Zach

C'mon Hershey 2020! You can make it! Probably!