1988 z24i ignition modules overheating - Infamous Nissan

ThunderChicken · 09-14-2021, 04:27 PM

The truck had a bunch of new parts thrown at it, starter, alternator, fuel filter, cap, rotor, plug wires, both coils, both ignition modules. This was all before I bought it. Orileys warrantied me a new set of modules and upon plugging them in and starting the truck it ran for about 40 seconds and quit. I look at the intake side module and it has a crack with smoke pouring out, too hot to touch. Suspecting a bad orileys coil and bad grounds, I ordered new coils and modules from rockauto and grounded the crap out of everything, checked codes on ecu(nothing), and no fuses are blown. They don't get hot if the key is on and they are unplugged from the coil. The truck just cranks if only one is plugged in. The rockauto stuff still heats up, but with aluminium foil behind them as a heat sink it'll run for 3 or so minutes before getting too hot. I had to build my own bracket to mount the coils and modules on, the original location was too rusted, but its all still grounded, I test everything with a voltmeter. I've done a bunch of research and can't really find anything, all that's left to replace is the ecu and wiring harness or convert this to another ignition system. Anyone have this problem or knowledge of how this ignition system is wired up? I'm also curious if the distributor has a stock ground location, and if the ecu is what sends power to these things. This truck is so cool but man these are expensive to replace. They have fins to dissipate heat but not this much heat. Napz is quite the interesting motor. Thanks in advance for any help

ThunderChicken · 09-14-2021, 04:52 PM

I got a morning off of school tomorrow and found a parts truck so I'm going to rob the whole ignition system off of it, plug wires to ecu. The fuel pump went out on this thing so it all should work. I'll test the resistance on those coils vs my new ones and see if I can get any results. Also might measure voltage from the power wire on the modules while the truck is cranking vs the key just being on. I'll keep the thread updated.

ThunderChicken · 09-18-2021, 12:35 AM

Parts truck was a complete bust, wrong year and motor than what the guy said over the phone. This thread https://forums.nicoclub.com/86-5-z24....html#p5833248 and some basic gnition system resarch provided a lot of good information moving forward. Another 120 bucks on a new ignition module and also this jumper harness to bypass the modules from rockauto are my next steps. It appears as though either the ecu or these modules control the dwell time on the coils, this harness thingy should tell me that. If this isint the fix, then I'll probably order a new ecu and inspect the one in the truck very closely for anything weird looking. Still very interesting that this truck won't just run on one coil.

Stinky · 09-18-2021, 04:25 PM

My '86 Z24 ran on 4 plugs. Check your fuses....I was missing one.

ON an HEI in a Chevy, the pick-up coil, if bad, could cause this. I have no idea if this is the same type of system. Is there a star thingy under the rotor, on the dizzy shaft? If so, then magnetic pick-up for the stars is the coil. Also, bad coil(s) might do it.

You are using grease under the module right? It helps conduct heat away from the module.

ThunderChicken · 09-19-2021, 05:24 PM

Holy crap I think it might actually be the pick up coil. When I unplug the plug wire from the distributor and turn the key on they stay cool, and when I plug it back in they get super hot like right away. Thanks for the advice man!! Gotta figure out how to replace that now.

Deerhurst · 09-19-2021, 06:07 PM

Don't use just any grease if you want to use the body as a heatsink. A thermal paste will be what you want.

Sounds like it's probably a funky coil.

ThunderChicken · 09-20-2021, 01:47 AM

Ordered a complete distributor and two new coils just to be safe. I really hope this is the fix, I’ll keep the thread updated with results. If anyone knows of a write up on distributor shaft replacement on these, I’d be very thankful for a link. Seems pretty straightforward as long as I get the timing set right.

Deerhurst · 09-20-2021, 02:19 AM

Got a copy of the FSM?

09-14-2021, 04:27 PM	#1
ThunderChicken Join Date: Aug 2021 Location: PA Posts: 13 Vehicle: 1988 d21 hardbody 4x4 Thanks: 3 Thanked 2 Times in 2 Posts	1988 z24i ignition modules overheating The truck had a bunch of new parts thrown at it, starter, alternator, fuel filter, cap, rotor, plug wires, both coils, both ignition modules. This was all before I bought it. Orileys warrantied me a new set of modules and upon plugging them in and starting the truck it ran for about 40 seconds and quit. I look at the intake side module and it has a crack with smoke pouring out, too hot to touch. Suspecting a bad orileys coil and bad grounds, I ordered new coils and modules from rockauto and grounded the crap out of everything, checked codes on ecu(nothing), and no fuses are blown. They don't get hot if the key is on and they are unplugged from the coil. The truck just cranks if only one is plugged in. The rockauto stuff still heats up, but with aluminium foil behind them as a heat sink it'll run for 3 or so minutes before getting too hot. I had to build my own bracket to mount the coils and modules on, the original location was too rusted, but its all still grounded, I test everything with a voltmeter. I've done a bunch of research and can't really find anything, all that's left to replace is the ecu and wiring harness or convert this to another ignition system. Anyone have this problem or knowledge of how this ignition system is wired up? I'm also curious if the distributor has a stock ground location, and if the ecu is what sends power to these things. This truck is so cool but man these are expensive to replace. They have fins to dissipate heat but not this much heat. Napz is quite the interesting motor. Thanks in advance for any help

09-19-2021, 06:07 PM	#6
Deerhurst 4/86 SE-V6 2 tone 4x4 HB Join Date: Apr 2013 Location: Oregon Posts: 8,039 Vehicle: 1986.5 SE-V6 4WD D21, 2003 Audi A4 Avant 3.0 Quattro Thanks: 917 Thanked 1,080 Times in 976 Posts	Don't use just any grease if you want to use the body as a heatsink. A thermal paste will be what you want. Sounds like it's probably a funky coil. __________________ 1986.5 SE-V6 4X4 D21 Hardbody Pacesetter Long Tube Headers Morimoto Mini D2S HID Projectors and Hella 500s VG33i

09-20-2021, 02:19 AM	#8
Deerhurst 4/86 SE-V6 2 tone 4x4 HB Join Date: Apr 2013 Location: Oregon Posts: 8,039 Vehicle: 1986.5 SE-V6 4WD D21, 2003 Audi A4 Avant 3.0 Quattro Thanks: 917 Thanked 1,080 Times in 976 Posts	Got a copy of the FSM? __________________ 1986.5 SE-V6 4X4 D21 Hardbody Pacesetter Long Tube Headers Morimoto Mini D2S HID Projectors and Hella 500s VG33i

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09-14-2021, 04:52 PM	#2
ThunderChicken Join Date: Aug 2021 Location: PA Posts: 13 Vehicle: 1988 d21 hardbody 4x4 Thanks: 3 Thanked 2 Times in 2 Posts	I got a morning off of school tomorrow and found a parts truck so I'm going to rob the whole ignition system off of it, plug wires to ecu. The fuel pump went out on this thing so it all should work. I'll test the resistance on those coils vs my new ones and see if I can get any results. Also might measure voltage from the power wire on the modules while the truck is cranking vs the key just being on. I'll keep the thread updated.

09-18-2021, 12:35 AM	#3
ThunderChicken Join Date: Aug 2021 Location: PA Posts: 13 Vehicle: 1988 d21 hardbody 4x4 Thanks: 3 Thanked 2 Times in 2 Posts	Parts truck was a complete bust, wrong year and motor than what the guy said over the phone. This thread https://forums.nicoclub.com/86-5-z24....html#p5833248 and some basic gnition system resarch provided a lot of good information moving forward. Another 120 bucks on a new ignition module and also this jumper harness to bypass the modules from rockauto are my next steps. It appears as though either the ecu or these modules control the dwell time on the coils, this harness thingy should tell me that. If this isint the fix, then I'll probably order a new ecu and inspect the one in the truck very closely for anything weird looking. Still very interesting that this truck won't just run on one coil.

09-18-2021, 04:25 PM	#4
Stinky Join Date: Nov 2019 Location: Whitewater, CO Posts: 124 Vehicle: 86 2wd 720, 86 4x4D21 Thanks: 0 Thanked 12 Times in 12 Posts	My '86 Z24 ran on 4 plugs. Check your fuses....I was missing one. ON an HEI in a Chevy, the pick-up coil, if bad, could cause this. I have no idea if this is the same type of system. Is there a star thingy under the rotor, on the dizzy shaft? If so, then magnetic pick-up for the stars is the coil. Also, bad coil(s) might do it. You are using grease under the module right? It helps conduct heat away from the module.

09-19-2021, 05:24 PM	#5
ThunderChicken Join Date: Aug 2021 Location: PA Posts: 13 Vehicle: 1988 d21 hardbody 4x4 Thanks: 3 Thanked 2 Times in 2 Posts	Holy crap I think it might actually be the pick up coil. When I unplug the plug wire from the distributor and turn the key on they stay cool, and when I plug it back in they get super hot like right away. Thanks for the advice man!! Gotta figure out how to replace that now.

09-20-2021, 01:47 AM	#7
ThunderChicken Join Date: Aug 2021 Location: PA Posts: 13 Vehicle: 1988 d21 hardbody 4x4 Thanks: 3 Thanked 2 Times in 2 Posts	Ordered a complete distributor and two new coils just to be safe. I really hope this is the fix, I’ll keep the thread updated with results. If anyone knows of a write up on distributor shaft replacement on these, I’d be very thankful for a link. Seems pretty straightforward as long as I get the timing set right.