84 No Spark - No Power at Coil

Kudzu911 · 04-08-2021, 09:00 AM

Good Morning,
I'm trying to get a rig back on the road after 12 years of sleeping with Kudzu. I've replaced the gas tank, patched up what I hope is the most of the rodent damage, cleaned and tested all of the fuses at the fuse panels as well as cleaning the fuse panel itself.

My current situation is crank no start - Fuel at the rail ( new pump new filter ) have not tested pressure, DME relay clicks when the key is turned and the fuel pump is coming on and the ICV is humming. I have no power to the coil and hence at least the first reason for no spark. I've got a green and black wire to the coil which is the +12v, I was going to try to provide 12V and see where I was, anyone has a diagram of this circuit so I can backtrace the power issue? The circuit seems to go from battery to key igniton to a fuse then the coil ?

mysocal911 · 04-08-2021, 10:58 AM

Quote:

Originally Posted by Kudzu911

My current situation is crank no start - Fuel at the rail ( new pump new filter ) have not tested pressure, DME relay clicks when the key is turned and the fuel pump is coming on and the ICV is humming. I have no power to the coil and hence at least the first reason for no spark.

OK.

Quote:

Originally Posted by Kudzu911

I've got a green and black wire to the coil which is the +12v

So you do have 12V coming to the coil!

Quote:

Originally Posted by Kudzu911

I was going to try to provide 12V and see where I was, anyone has a diagram of this circuit so I can backtrace the power issue? The circuit seems to go from battery to key igniton to a fuse then the coil ?

Why do that, when you have 12V there.

Kudzu911 · 04-08-2021, 11:18 AM

Ok I wasn't clear, I have no power to the coil.. there is one green and one black wire, I was asking which one was the +12V side

mysocal911 · 04-08-2021, 04:15 PM

Quote:

Originally Posted by Kudzu911

Ok I wasn't clear, I have no power to the coil.. there is one green and one black wire, I was asking which one was the +12V side

The black wire goes to fuse #8, and the green wire goes to pin 1 of the DME ECM.

Kudzu911 · 04-08-2021, 04:21 PM

Ok so the top if I'm reading this correctly is that the DME Relay provides +12V on the black wire, the green wire goes to the DME and is a controlled ground. So I need to see if I have power after 87b on the DME Relay and between 87b and+12V at the coil, I should have a connection?

mysocal911 · 04-08-2021, 05:38 PM

Quote:

Originally Posted by Kudzu911

Ok so the top if I'm reading this correctly is that the DME Relay provides +12V on the black wire, the green wire goes to the DME and is a controlled ground. So I need to see if I have power after 87b on the DME Relay and between 87b and+12V at the coil, I should have a connection?

No! The DME relay has nothing to do with the 12V power to the coil. You're misinterpreting the wiring diagram.
The ignition switch provides 12V directly to the coil.

Kudzu911 · 04-08-2021, 07:04 PM

Ok so key switch - Fuse panel - Coil? above diagram showing from the fuse panel on? Is it its own circuit from the key switch as I have key on power for pretty much everything else. I'm trying to get this nailed down before I try to trace down every wire in the loom.

mysocal911 · 04-09-2021, 03:28 AM

Quote:

Originally Posted by Kudzu911

Ok so key switch - Fuse panel - Coil? above diagram showing from the fuse panel on? Is it its own circuit from the key switch as I have key on power for pretty much everything else. I'm trying to get this nailed down before I try to trace down every wire in the loom.

Why do you highlight the wiring shielding? It's not part of the actual 12V power. No electrons flow in the wiring shielding!

Kudzu911 · 04-09-2021, 07:51 AM

ok, I thought I was highlighting the circuit in question? It's a "wire" diagram though the wires run in color-coded shielded casings, I was attempting apparently poorly to point to the area. Does anyone have a better diagram?

Solamar · 04-09-2021, 01:23 PM

I thought I had a '84 schematic, but can't find it...

Heres a few notes/drawings from when I swapped in a '84 motor. Might help?

This is the DME harness laid out. You can see the coil power goes through this harness (through the fuse panel and ignition switch first) -

DME Pin-out for reference -

DME relay for reference -

Best of luck saving it from the Kudzu!

Flat6pac · 04-09-2021, 02:13 PM

The fuel pump relay is a 2 click to start as the starter engages..
Bruce

Kudzu911 · 04-12-2021, 09:58 AM

Update:
I hate reading threads that never have a conclusion so I'm going to try to document this till it runs.

So now have power at the coil, cleaned up the engine ground on the intake manifold, three separate grounds, all polished up and now have power at the black wire +12V at the coil.. still, no spark moving on to DME ECU diag

Kudzu911 · 04-19-2021, 07:53 PM

Ok so still slogging, the ref flywheel sensor isn't showing any ohms, so I need to order a new one of those. I've also opened up the ECU to see if there is any moisture damage, so far looks good, removed the DME relay, and inspected it, it's a Transistor type and all the solder joints look good. The bolts stripped out on the flywheel sensors so removing the shock and seeing if I can get the bolts drilled out. Fun!

ischmitz · ischmitz's Garage

As an easy test get yourself some NOID lights (cheap on evil bay) and check if you have fuel pulses at the injectors when cranking. If spark AND fuel are missing that points to one or both of the FW sensors. If you have fuel pulses the FW sensors are good and it's more likely the DME.

Keep us posted,
Ingo

Kudzu911 · 06-12-2021, 03:26 PM

ok so progress, got my hands on a spare ECU, replaced the speed sensor, and ref sensor senders and whooo hoo, I got spark, I've got run with starting fluid. I've got 40PSI at the rail cranking but no run. can get a start and die from key on if it's cold.

Kudzu911 · 07-07-2021, 08:31 AM

Update, so the there was no power to the Injectors, there was at pin 87 on the DME relay. Long story short something had eaten the cyl head temp sensor ( I assume it's a one wire white wire ) through, I crimped it together and I have power at the Injectors, still crank no start. now I will be doing the Noid lights now to see if I have a pulse which I bet I have, I'm pretty sure all the Injectors will need to come out and be cleaned or replaced.

911obgyn · 911obgyn's Garage

If it has been sitting, yes injectors need to be cleaned/ checked. I did this with a can of carb cleaner a battery with a momentary switch and a 10cc syringe.
Or just send them out.
Get new O rings

Kudzu911 · 07-13-2021, 02:51 PM

911obgyn, you are so right, there are little filters in the top of the injectors that were F*&ked up. So 1 injector rebuild kit with hats, orings and filters, one amazon injector cleaner kit, which consists of a spray nozzle attachment for carb cleaner and a box to pulse the injector.

Note on the noid lights - I did make sure the the injectors were firing with noid lights, I got the HF kit $36 bucks. The light is very dim I think they are incandescent not LED, you can see them fire but boy it's not bright at all. I checked in several places and that seems to be normal and OK for this type / kind of injector.

So as of last night - IT RUNS - Whoo Hoo

Now I have to rebuild the pedal box of ferrous oxide, re install the driver side rear suspension and reassemble the misc engine parts that are in a box under the rear bumper, mount the new seats and hopefully drive the damm car