Hey guys. So I've got a crank no start, and am not too familiar with the ignition system on these puppies. I hook my timing light up, and nothing on either plug wire of the leading or trailing coils.

Fuel pump is direct through a switch ATM.
Coil resistance checks.
Getting voltage at coil terminals (constant and igniter terminals)

Where do I got from here? I don't have an igniter tester, so I'm not sure if it's an ECU problem, or something simple I could be missing. Just got the car, I've never had it running. It was sitting in a field for a few years.

 

The EGI fuse needs to be good and installed in the fuse block(often overlooked so had to say it).
Now when you are using the timing gun,it is a finicky thing.
the spark may not show unless you have it on the wire "just right".
Try the "spark plug up against a ground" trick to see if the spark is getting to the plugs...keep any spark away from the Fuel that will MIST out of the Spark plug holes though!..boom!( a good way to tell if you have fuel)

 

does the tach bounce while cranking? if not then correct, it's not triggering or powering up the coils.

check the 30a EGI fuse in the engine bay nearest the battery
check the 15a engine fuse at the driver kick panel inside the car
check the CAS connection at the front driver side top of the engine

if all the above is ok then you need to test the main power circuit for a fault in the main relay, disconnect the 2 pin connector from the leading coil and use a DMM to check for power at the black/yellow thick wire off the chassis harness lead coil connector with the key to on, it should read 12v.

 

Soooo.....I'm guessing the EGI fuse is that 75A one right beside the ECM? Cause if so...Yeah, it's burnt :p Gotta say, not a big fan of the schematics in the haynes manual I have. Should have known better though, I had only checked the fuses in the engine compartment.

I won't be able to hit up a store to get another one till tomorrow, so I checked my resistances on the plugs, and I'm getting 4.3 to 4.9K ohms, and the cables have roughly 3.2K ohms per foot, so they check out.

 

i don't know what you're looking at but the ECM is nowhere near the fuses boxes and there is no 75a fuse in the FC.

there is a black 80a fuse in the main fuse box near the battery, if that is burnt the car will receive no power to the electrical components inside the car(this fuse powers just about everything so the dead gauges and idiot cluster should give you a hint). main cause for this fuse to blow is a short to ground in the alternator charging wire/circuit inside the alternator. reverse battery cables can also pop that fuse, and the starter may still turn.

 

The main 80A fuse is good, as are all the other ones (engine compartment and kick pannel). I was talking about the fuse by the kick panel beside what my manual says is the CPU (ECU, ECM, ELC. etc.) There were 2 75a fuses in there...but it's quite possible they might not be the right ones. I have no cover or fuse identification diagram, but it was in the slot that's raised, at the top of the panel, smack dab in the middle.

I'm getting 12 Vs at the leading coil and both of the trailing coils.

I'm getting 160 Ohms across G1 G2 and S1 S2 of the crank angle sensor.
Lead coil is getting .6ohms, trailing are getting .8 both.

 

strange, i would like to see this additional fuse panel because i'm not familiar with it on any FC.

 

Hope this isn't against the forum rules.
https://www.facebook.com/photo.php?f...2&l=946e599751

That's the dead pedal at the bottom.

 

That's the interor fusebox located near the CPU and not ECU. The Room fuse is 7.5 amps and not 75 amps and it has nothing to do w/running the engine. The EGI fuses are located in the engine fusebox.

Link to interior box pic: https://www.rx7club.com/2nd-generati...faq-fc-494667/

 

Haha, well then. I cannot for the life of me see the dot between the 7 and the 5, so my bad on that sucker. How many computers are in these cars? And what is the difference between the central processing unit and the electronic control unit on these?

That link looks like it has lots of info, can't wait to get on a computer so I can actually see everything on it.

So having said that, all the fuses for that system are good, I'm getting voltage to the coils, the computer ground (the one from behind the engine to the firewall?) has no resistance, the CAS is good, the plugs and wires are good (even though I'm not getting any power to them).

Kinda missing the ol' distributor systems of the V8s hehe. Is there another ignition lockout? I see something about anti theft in the print, but it looks like the coil pulse is all actuated by the computer from what I'm looking at. I'll also check the inhibitor when I can get the car up, just to make sure.

All my gauges are working fine as well, no fluctuation in the tach or anything.

 

Just pull the plug from the leading coil bore, rest the plug up against the coil bore leaving a fraction of an inch between the two, turn the engine over and try to observe spark. Also, jumper the fuel check connector in case the internal fuel switch inside the AFM is shot. Also, a very important step, check for 5 volts w/key to on at the Brown/White wire found at the TPS or Pressure Sensor as this voltage powers the engine sensors and is required to start the engine.

 

mazda calls the ECU an emissions control unit which doesn't actually have much to do with emissions(it controls idiot factor) and is located behind the driver kick panel.

 

The opening relay works when I jump the check, tried that yesterday. I'm not the one who wired the FP direct, so I'm going to have to trace this back when I get it started to bring it to the garage.
I tried bridging the two leading plugs also, so pretty much the same thing as checking at the coil, with nothing still. Did not know about the TPS though, so I'll check that out as soon as I get back. If there's no voltage there, what is the source I should be checking? And if there is voltage, is there a way to bypass it with a resistor just for the sake of starting it at idle? I'm used to simple potentiometer style TPSes, not sure what kind these are.

Thanks for all the help BTW guys

And as for the ECU part...Guess I better bone up on the RX lingo! Here I am creating some un-due confusion.

 

bridging the lead coils won't give you a result since they fire in tandem and you're just completing the circuit. you'd need to arc a coil wire to ground or off a grounded spark plug.

 

10 4, I'll do it properly then. So hypothetically speaking, if one of the lead plugs wasn't firing, what would be the symptoms I'd encounter?

 

If the Br/W wire did not check out then it would likely be caused by a short to ground which is not too uncommon and the leading cause would be a misbehaving AFM. And there's no need to bypassing things w/a resistor.

 

Ok so I only managed to do 10 mins since my daughter didn't feel like working on the car haha

Anyways, redid all the grounds, sprayed some contact cleaner on all the fuses and plugs/wires, tried cranking with my timing light and voila, now we have coil function. The primary light was firing a little eratically, the secondary very steadily, but I chalk that up to a wonky connection to the battery on the primary.
She still didn't fire up, so Sunday I'm going to drain the tank, check fuel pressure, and hopefully that'll be that.

Thanks for the help, I'll keep you guys posted!

 

normally both fire or neither. a non firing lead coil would be difficult to start, idle poorly and have low power output. if the engine is in bad shape it would flood out on crank or stall instead of idle low and labored. trailing only ignition is retarded by 15 degrees and gives you an idea of the symptoms severe ignition retardation causes. the trailing plugs are also not well exposed in the engine and do not ignite the combustion very well.