Finished Z31 ECU swap... but now problem...
 

Hey guys. So I finally got a nice day to finish the Z31 swap, installed the disty with the Z31 Chopper Wheel, plugged in the ECU, and she fired up first try. Timed the engine and got her idling well, let her idle for about 5 minutes then revved great, revved a few times just to make sure, and she revved great with no bog, then settled back down to 800 rpms and sat nice. So I decided to hop in and take her around the complex to see how she'd react, hopped in, put her in gear, pressed the gas to rev, shift, and take-off, and she bogged down and died. Now she won't start. She'll crank all day long, but nothing more than that. I pulled the ECU back out and checked all the wires and everything still seems tight, and none of the connectors popped out or anything. Checked the MAF and it's all connected, so what could cause this?

I don't have time to check anything else today as I have to be at work in an hour, so I am posting this to get suggestions so I can try stuff tomorrow morning. I am not hearing the Fuel Pump prime when I turn to accessory now, so I guess that could be a problem... Going to test spark tomorrow just to make sure it's not anything on the disty...

It's flooded. Clamp off the fuel line right after the fuel filter (or unplug the fuel pump wiring) and crank @ full throttle till it starts, or for 10 second intervals, waiting about 20 sec between tries.

hmm ok... what would cause that, cause the car has been sitting for about 2 months unstarted... and would the fuel pump not prime if it was flooded?

on the subject of the fuel pump, the only wiring difference I did differently than the excel spreadsheet what that my 82 280zx didn't have a wire 20 for the analyzer, and so when the wire #20 on the Z31 ECU said it was used for the fuel pump relay, I attached that wire to #108 so it would still be linked to the relay. Would this be a possible problem?

um... you don't do anything w/ pin20... you need to learn how to follow instructions. :D Disconnect it. Pin16 & 108 are swapped.... not pin20.

I know but on the chart is shows that on the 280 pin 20 is for the analyzer and pin20 for Z31 is fuel pump relay... thought that if that wasn't connected it wouldn't run...

That's what pin 108 does. Notice how it says "Fuel Pump" under Z31 for pin 108? That's the one that controls the fuel pump. You can trace it on the Z31 wiring diagram too.

The way you have it wired... the air regulator isn't working properly.

I don't have an air regulator... I have a 240sx throttle body and deleted the air regulator...

Welp... I would swap the wires back to how they should be, then disconnect the fuel pump & crank @ full throttle.

alright, will try that tomorrow after work then come back and tell the result...

Bump.... how'd it turn out?

Inquiring minds want to know!

man I am so lost on this. It sat for a week because I had constant work scheduling, and I came out and went to start it last night and she fired right up, no messing with the fuel pump relay or anything. Turned it off and then got up this morning with the intent of doing more to it. With the ECU sitting in the floorboard she fired right up, idled perfectly fine, great revvs, no bogging, and then I turned the car off to unplug the ECU and bolt it to the car and then plugged it all in, turned the car on, she fired up, ran for about a minute, then fizzled out and won't start again. Let her sit for about 20 minutes and then pulled the Fuel Pump Relay and tried cranking but to no avail. Did it for about 15 minutes intermitently and nothing happened...

Too much fuel or not enough.... pull the plugs & check the tips.

I am really leaning toward too much fuel. If you look at the facts, the last time it bogged down, I did nothing to it aside from just letting it sit, and then it fired up perfectly fine, idled and revved for a while then died again and wouldn't start.

If it was starved for fuel it wouldn't start up after the initial, would it?

How can I turn the fuel down?

Eh, that sounds like a grounding problem. If it works with the ECU on the floor, but not with it bolted in where it's getting grounded properly then you have a wiring issue. I'd say pull that #20 wire off as it's probably grounding something out. I've never had any experience with this swap but given the above comments and the reaction I'd say that's grounding the fuel pump circuit out and causing it to kill the pump when the casing gets a ground.

yea #20 wire was already ripped off... I am thinking that it's either too much fuel for the system or that there is a break in a crimp in the wiring... gonna let it sit overnight with the ECU still bolted to the car and gonna try it and see if it starts

what are the differences in fuel pressure between the 83 280zx turbo and the 84 300zx turbo?

None. :paranoid:

Shouldn't be any difference. Have you checked the fuel pressure yet?

no not yet... what should it be at?

so I am pretty sure it's a fuel problem now. After it died yesterday I figured I'd leave the ECU bolted to the wall just to see how it would react today. went to work last, came home and slept, woke up about an hour ago and went out and she fired right up. Idled perfectly for about 25 minutes, went to hop in, drove her for about 15 feet and then she died. Won't start back up. All gauges are reading normal...

so I just double-checked the wiring harness, and everything is connected how it should be except the #20 wire. It shows on the diagram that for the Z31 ECU it goes to the Fuel Pump Relay, but the 280zx wiring harness does not have a wire there. What am I supposed to do there?

Also, it shows on the diagram taht wire #114 goes to the fuse box, but on the 280zx wiring harness it isn't used. I have an 82, so the wire is there, but does it still go to the fuse box or do I need to hardwire it somewhere?

These two wires are the only ones I know of that could be to blame. The car ran fine before the swap, so somewhere in here lies the problem.

Please help, need the car running by the end of the weekend...

You don't have an 82, I have an 82, it's just at your place...:075:

But yes people, please help, we need this thing running before Monday!

please someone give us some info, time is almost up!

What happens on Monday?