xreplicax

So a few days ago I was driving out my 86 NA 13B around when all of a sudden I lost spark (while driving). I've only owned the car a few days at this point and I would love to say that I should be pissed about it, but I don't really feel the guy that sold it to me could have foreseen something like lost spark coming, not to mention I got the car for kind of a steal.

Where should I start with diagnosis? I'm assuming check the ECU and Fuses. Battery isn't bad because it does try to start, I would assume if the battery was bad there would also be some sort of spark whenever it tries to turn over instead of nothing at all. Anybody have any clues on what it could possibly be? I'd hate to start troubleshooting the car already. Whenever we tested for spark, we used brand new spark plugs, so its doubtful those are the cause. And we tested on both leads. So its probably not the wires either.

satch

iTrader: (1)

In the engine fuse box check both EGI fuses. In the interior fuse box check the 15 amp engine fuse.

There is a Green check connector plug near the lead coil w/4 wires. If the Black/White wire has 12 volts w/key to on then the EGI Comp fuse is good. If you pull the 2 wire plug from the lead coil and the Black/Yellow wire has 12 volts w/key to on then the EGI INJ is good. If neither wire checks out then the engine fuse is likely bad. And if the turn signals or wipers don't work w/key to on then the main fuse in the engine fuse box is likely bad.

xreplicax

EGI Fuse is good. Engine comp fuse is good. MAF is good. Ignitor is getting power. Unless both coil packs went bad at the same time they are fine. Doubtful that the plug wires are bad because neither is showing spark and its uncommon for those to go out at the same time. Put new gas in it. Going to double check the fuel pump but according to the previous owner, it was replaced within the past 6 months. So I am thinking there may be a short somewhere that may have caused the fuel pump to go out again. I am just pretty frustrated right now because everything is showing power. We were looking for the orange connector to put it into test mode but we could not find it or where it was for the 86. A good friend of mine has an 87 and its in a completely different spot. I am just running out of options of things to test.

Keep in mind it happened while I was driving.

satch

iTrader: (1)

The Orange connector near the lead coil is for the S5 while you have an 86 so you have the S4. The 4 wire Green check connector mentioned earlier is for diagnostic purposes and would be connected to a pair of LED lights to pull codes but the list of codes on an S4 are very limited and usually not much assistance.

For the engine to run all you need is the lead coil so even if the trailing coil was malfunctioning it would not prevent the car from either running or starting.

One thing you could do is check the Brown/White wire at the boost sensor w/key to on as it should read 5 volts. If it reads much lower then the car will not start. Secondly, you might have an issue w/the fuel switch internal to the AFM. You jumper the fuel check connector to bypass this switch. You could also go to the circuit opening relay which governs voltage to the fuel pump and jumper two wires there to achieve the same thing done at the fuel check connector. And you can also test for voltage at the relay as it pertains to the Blue wire as it powers the fuel pump. The relay is located under the dash and to the right of the steering column. The relay is Yellow and Black. The bottom row which has two wires are the wires to be jumpered. Also, the Blue wire on the top row powers the pump so w/key to start it should have voltage. W/the jumper in place the Blue wire would also have voltage w/key to on.

xreplicax

We are going to check all of it tomorrow morning. Thanks for everything. I am sure it's somewhere in all of that. Definitely appreciate the suggestions.

satch

iTrader: (1)

And you might want to check the compression to rule out the worst case scenario.

xreplicax

I'm really hoping that isn't the case, but I would think that it would still be running, however poorly if that were the case. The moment it is up and running though that will be done.

satch

iTrader: (1)

And just because the EGI Comp fuse is good does not necessarily mean that the Computer/ECU is receiving power. If you check the Brown/White wire as suggested it will tell you if the ECU is powered or not.

xreplicax

We tested the ECU and it got power. My buddy said that the ECU's in the cars tend to not go out so he didn't want to go through the process of trying to test it. I may see if I can find one around town that I could borrow for a little while just to plug it in and see if it works. He has an 87 TII but the connector is different. Shame, that would have been so easy to test the ECU if it were. Just waiting to find time to go through the list of things to check.

Akagis_white_comet

iTrader: (4)

Just to clarify, the ECU connectors are the same on N/A & TII. The difference is that they are pinned differently and certain sensors (such as the Boost sensor, AFM and a couple others) are ranged differently as well. If the ECU is getting power and you've tested the Main Relay (power at the green diagnostic connector as previously mentioned), the next thing I would look at are grounds.

When a circuit behaves kind of funky and falls on its face (like yours did), then comes back up the next day with seemingly no rhyme or reason, a bad ground is usually the culprit. Aaron Cake spells it out better here: Proper RX-7 Grounding Procedures

Something I would like to expand on here is that both leading and trailing coils are grounded to the chassis by their metal cases, they do NOT have a ground wire. If it's got a poor connection to the chassis sheetmetal, it'll have difficulty getting power to the spark plugs. Also, if the ECU ground is questionable, it won't be able to deliver a clean signal to the coils or injectors either. Result is that the car falls on its face.