zlaxbro

So i fished up the swap yesterday on my '81 280zx and i cant get it started. I swap out the oil pump and distributor from an '83 280zxt. i put the z31 chopper wheel in the correct way and checked it again. i checked all the wiring and cant seem to find the problem. I hear the fuel pump turn on when i go to start the car and the pressure stays. Im also getting a spark so i dont think its a fuel problem. The only way i can get it started is to step on the gas and even with that is runs terrible and wont stay running. I just dont know what to do next, Any thoughts would help!

NismoPick

You installed the dizzy / oil pump shaft 1 tooth off (maybe 2?).

Did you align the dots correctly? Check the position of the rotor at TDC cyl#1?

zlaxbro

damn. yeah i just checked and its a bit far behind where the 1st park plug should be. I guess its a start..

sonethirty

How bout now?
(I really need to do this swap.)

FricFrac

The main part of the swap is the MAF - are you sure it's hooked up properly? There is a cleaning cycle as well for the MAF. NismoPick had a good thread on the swap with a nice spread sheet, etc. Also the early and late ECUs and injectors are different.

zlaxbro

So my timing was off with the oil pump shaft and so i fixed that but it still doesnt want to run, ill spend tomorrow trouble shooting the wiring again along with the MAF.
And Fric Frac i was under the impression only the 81 has a resistor pack for the injectors so i was told that i need to cut them off. If any one could shed some light on things that would be great!

FricFrac

All the 280ZX injectors are low impedance. Make sure your Z31 ECU is compatible with low impedance injectors.

XenonZ31

You are correct - just the '81 turbo had the resistor pack (which unplugs - no need to cut it off!) whereas the 82-83 ECU was capable of running low impedance injectors without the resistor pack.

NismoPick

^^^ Whoa... never knew about this part (I guess I never read it anyway)...

zlaxbro

I have a '84 z31 turbo manual California emissions ecu and it looked to fall under the right category.
Im gonna see if all the injectors are getting a signal since i may have cut off the resistors when i was doing the swap....

NismoPick

I'm hoping you read this before doing the swap:

Z31/300zx ECU/MAF to 280ZXT swap guide: 1981 supplement - HybridZ

zlaxbro

turns out i was a tooth off still on the oil pump shaft so fixed that. Finally got it to idle but stumbles when you press on the gas. just about to adjust the fuel air mixture with the maf. and ill go from there.

zlaxbro

hah Yeah i referred to that as i was doing the swap and connected all the wires since the resistors were in a series.

zlaxbro

Well we were hoping it was a bad ecu but we just swap in another and its still having a stumbling problem. Timings if fine, getting standing fuel pressure and everything else seems to be in order, but once you step on the gas it stumbles down and then revs up. if you stay on the gas it just loops through doing that. Rising then falling , rising then falling.

zlaxbro

ok, back to working on the car. after cleaning the connections, fixing a huge vac leak, adjusting the TPS and adjusting the fuel pressure we were able to get it running, timing is set at 20 BTDC, it idles great (700rpm), throttle is responsive..only issue is that it seems to be in limp mode, but there are no codes. I picked up a used maf from the junkyard, but no joy, still only revs to 2.5k or so then dies off, the only codes which display are for the speed sensor (14) which makes sense as we have not driven any where since clearing mem, and for the ignition signal (21), fyi pin 3 is not connected and 5 does go to the transistor I ohm'd out the connection from the transistor to pin 5 of the ECU.. Do I need pin 3 for this swap to get rid of the 21 code? Oh, we also swapped out a different ecu same codes.

Any ideas on the limp mode, Im about to go drop 200 on a MAF at oreillys would rather not if there are other options, based on the reading Ive done it seems like the most likely part..but havn't convinced myself yet.

Testing the two MAF's I have the voltages measure the same at the ECU as at the MAF, at least what I can see using a DVM. using the tests from xenon z31 site to test the MAF I get comparable measurements with the old MAF the new one has different electronics in it and dont match his results.

Thanks.

FricFrac

Is self cleaning mode working on the MAF?

Is your O2 working and do you have the correct one for the ECU?

NismoPick

Also try wiggling the ecu wires right at the plugs. The lowest plug has several common faulty connections (I've discussed it in detail before).

zlaxbro

thanks for the suggestions,..

I checked on the Self cleaning mode and it didn't seem to be working, I revved it over 1500, turned the key off while measuring the voltage output from pin 12, I expected to see it go to +12 for a second about 5 seconds after turning off the key, but it did not, I'll admit it was just a quick test, when I have more time I will verify.

As for the O2 sensor it is the zirconia type which seems to match ok with the 84 ECU, it is the single wire type so there is no heater for it, that dosn't seem to me that it would make a difference, I have not checked to see if there was a voltage off of it or not, I will do that tomorrow.

I'll give the wires a wiggle also, at the connector and see if that makes a difference, The MAF signal wire is not shielded currently, We may pursue getting a shielded wire for that this weekend.

I think the current plan will be to recheck for vac leaks on the intake, replace a few vac lines which are suspect and then work on getting the MAF signal wire shielded.

Thanks.

zlaxbro

Once I get to about 2000rpm its seems the injectors stop firing and its runs really lean. but once you back off the gas, everythings golden and she will idle like a champ. anything?

zlaxbro

Ok, looks like the coil was wired in backwards - seems odd since we have not touched it but once I swapped it to match the wiring in the FSM it revs fine while in park. I took it for a drive but now seem to have a TPS issue we are getting code 23. we tried adjusting the TPS as well as swapping a new one in still seeing the code 23 and unable to get past 2krpm while driving. I checked out the wiring at the connector and I see there seems to be an extra wire. There are 4 total - based on the schematic I expected 3 wires with only two of them being connected.

I opened it up and I see that it is wired as follows:

pin 1 - Blue/Black to pin 18 of ECU
pin 2 - Green/Blue + a ground wire - to pin 25 of ECU
pin 3 - N/C

I don't see the ground wire mentioned in the schematic -- should it be there?


I removed it and still get the same code 23 and behavior.

Also, does anyone know how the signal is interpreted at the ECU? I'm wondering what condition triggers the fault code.

PS - I checked the grounds as nismo suggested they seem pretty solid to the ecu I removed each pin from the connector and cleaned it as best I could, also tried to make sure it had good pressure when pushing it on the ecu pin while it was out of the connector.

while wiggling stuff I did find the CAS harness up by the distributor seems to have an issue, when I wiggle it I the car dies and I get the CAS ecu code.. So now Im thinking of cutting it off and replacing it with the newer style connector like is on the 82 CAS, just need to find the connector for the car side of the harness..

FricFrac

Bypass the CAS connector - it's a pigtail that goes to another connector at the dizzy itself. The square plug at the dizzy is much easier to find....

zlaxbro

ok, so re-read the directions for the tests seems I skipped the part about the AC, TPS and neutral switch codes not being saved in the ECU memory so the way I was testing it was incorrect after driving the car I was turning it off then back on apparently clearing the current results.
So now I'm just down to the code 31 for the AC switch not working, although when I turn on the AC the idle does increase just slightly. - Ill look at that once I get the rest figured out, unless someone thinks it could be related.

Still have what seems like limp mode cant get it past 40mph, when it gets to 2500rpm it just drops down to 1000..it fakes me out every time.. seem to be going good the just shuts off.

I don't get any codes now except the 31.

idle is crappy now too.. seems to be running lean when I measure the voltage on the O2 sensor it bounces between .35 and .25 generally and the idle surges. If I unplug the MAF it idles great steady vacuum reading of just under 20 when I reconnect the MAF and the idle varies up and down and the vac gauge goes up and down between 15 and 20.. I hooked up a smoke tester to check for vac leaks but couldn't find any.

The vac air control stuff is disconnected I have an adjustable AAC valve to adjust the idle it is almost all the way closed, if I close it all the way it dies

I did notice it runs great first thing in the AM, it was pretty cold here today it ran great for about 2 min then got progressively worse - I disconnected the thremo switch thing but no change.

Running out of ideas.. maybe going in circles too

ThaPimpShrimp

This is definitely normal haha. When you turn on the AC the compressor kicks in and it's another thing running on the engine. The idle rises to keep the car going and run the compressor

benny127

Oil pump needed to be swap also? I did not know about this. Instruction did not stated.

zlaxbro

yeah, I guess I said oil pump in my first post.. I really meant just the drive spindle was replaced

FricFrac

You don't need to change the oil pump spindle - it's the CAS optical encoder wheel (or chopper wheel as some people call it) that you swap in from the VG30E or ET