BitchinZ Posted May 29, 2014 Share Posted May 29, 2014 (edited) Ok I need some help. Ive been messing with my L28ET/Z31 swap after work for two months trying to get it to start and run and its getting depressing with summer being here. Today I had a break through and it now starts instantly and idles fine but it will only start with one spark plug removed. Doesnt matter which plug is removed, I tried taking them all out one at a time. Pulling a plug wire wont let it start, a plug has to actually be out, any plug, and itll fire up instantly. With all 6 plugs/wires in it will just crank. My Z is a 77 280Z with a stock 83 L28ET and Z31 ECU/MAF swap. The '83 motor ran and drove perfectly smooth and strong before I swapped it. I have two Z31 turbo ECUs, 84 & 86, its doing the same thing with both. Any ideas on what this is would be appreciated. Heres some info I can give you - Fuel pump primes for about 4 seconds when key is ON. Fuel pressure right before the rail is 36PSI on prime, 29PSI when idling on 5 cylinders. Autometer inline gauge. Fuel pump is new AC Delco rated at 75psi, grounded to the chassis for the Z31 swap. All injector plugs are new, getting 12.68V on both sides, the ECU should ground them. With a Noid light, each injector plug will light the Noid and pulse when cranking but the Noid light is dim. I temporarily double grounded every ground having to do with the motor, ECU and Maf. No difference Firing order is right, Z31 optical disc installed right side up I even tried flipping it, new NGK plugs and wires, every plug has blue/white spark when grounded on the valve cover bolt while cranking, new rotor and cap. Gently installed so not to mess with the timing. Battery was 12.8v today. I tried an spare turbo coil and ignitor I had too. Ive cleaned every contact on the car, top to bottom and used Deoxit on every connection. My CHTS is getting 5.05v. Resistance through it is 1600 ohms, I bought new one just to try and same thing. Both red/green ECU lights light up on both ECUs when key is at ON. I do not have the tach hooked up, dash is out of the car. Tach wire and resistor are in place. I do not have the knock sensor or the oil temp sensor on the oil pan hooked anywhere. Both arent supposed to be needed after the Z31 swap. My friend thinks it could be bad grounding or wire resistance somewhere. Edited May 29, 2014 by BitchinZ Quote Link to comment Share on other sites More sharing options...
TimZ Posted May 31, 2014 Share Posted May 31, 2014 Ok I need some help. Ive been messing with my L28ET/Z31 swap after work for two months trying to get it to start and run and its getting depressing with summer being here. Today I had a break through and it now starts instantly and idles fine but it will only start with one spark plug removed. Doesnt matter which plug is removed, I tried taking them all out one at a time. Pulling a plug wire wont let it start, a plug has to actually be out, any plug, and itll fire up instantly. With all 6 plugs/wires in it will just crank. My Z is a 77 280Z with a stock 83 L28ET and Z31 ECU/MAF swap. The '83 motor ran and drove perfectly smooth and strong before I swapped it. I have two Z31 turbo ECUs, 84 & 86, its doing the same thing with both. Any ideas on what this is would be appreciated. Heres some info I can give you - Fuel pump primes for about 4 seconds when key is ON. Fuel pressure right before the rail is 36PSI on prime, 29PSI when idling on 5 cylinders. Autometer inline gauge. Fuel pump is new AC Delco rated at 75psi, grounded to the chassis for the Z31 swap. All injector plugs are new, getting 12.68V on both sides, the ECU should ground them. With a Noid light, each injector plug will light the Noid and pulse when cranking but the Noid light is dim. I temporarily double grounded every ground having to do with the motor, ECU and Maf. No difference Firing order is right, Z31 optical disc installed right side up I even tried flipping it, new NGK plugs and wires, every plug has blue/white spark when grounded on the valve cover bolt while cranking, new rotor and cap. Gently installed so not to mess with the timing. Battery was 12.8v today. I tried an spare turbo coil and ignitor I had too. Ive cleaned every contact on the car, top to bottom and used Deoxit on every connection. My CHTS is getting 5.05v. Resistance through it is 1600 ohms, I bought new one just to try and same thing. Both red/green ECU lights light up on both ECUs when key is at ON. I do not have the tach hooked up, dash is out of the car. Tach wire and resistor are in place. I do not have the knock sensor or the oil temp sensor on the oil pan hooked anywhere. Both arent supposed to be needed after the Z31 swap. My friend thinks it could be bad grounding or wire resistance somewhere. Have you checked the battery voltage while cranking in both conditions? Could be that you are borderline on operating voltage for the ECU during cranking and one plug removed takes less current (hence higher battery voltage), giving the ECU just enough to operate... Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 31, 2014 Share Posted May 31, 2014 Check voltage condition as stated above . Also need to check what's missing , spark or injector pulse , with all plugs are installed . Quote Link to comment Share on other sites More sharing options...
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