ericdash

I have been chasing my tail on this for quite a while so I thought someone might have some thoughts. When I turn on the ignition, everything lights up. When I try to start, everything goes dead. Disconnect negative terminal and reconnect. Nothing. Disconnect both positive and negative terminals and everything lights up. Try using a jumper wire from the starter directly to the positive battery terminal, the solenoid clicks, and will continue to do so, but dash lights go out. I have a relatively new starter and it bench tests just fine. I thought that it was a problem with the ignition switch because when I removed it and bench tested it, I got intermittent connectivity in start mode. I bought a new one and replaced it. At the same time, I had rebuilt the carburetor and removed the birds nest solenoids, closed off the shutter valve and all of the vacuum ports, and removed the air pump and fittings. I did the Sterling pump piston mod and locked the secondaries to manual mode. A new fuel pump, filter, and hoses, fresh gas. It cranked up and started right away. I thought I had sorted all of it, but it was running at 4K rpm and I couldn't adjust it down. Removed the carb and found that the weld on the secondaries was interfering and they weren't closing properly. Got that all fixed and reinstalled the carb. Cranked it for a bit getting fuel up into the bowls and the dead short reappeared before it started. I pulled the starter again and bench tested; pulled all of the heavy cables to check continuity (no issue). The fusible links are all fine. I've looked at the wiring diagram for the car (the one that Kevin Wright posted from the wiring manual) to see if the main relay could be the problem. However, there is no wiring description of it for the 12A, only for the 13B. It's a strange relay with a 2-connector and a 4-connector and no printed description on the case. The 2-connector has a BW and a YB. The 4-way has YL, B, LR, and BW. I assume that BW is the power source from the ignition switch and that B is the ground, but I can't find YL, YB, or LR. I don't even know if it's the problem. When the dead short first appeared, I was able to jump start the car in 3rd gear when the dash lights were on. Haven't tried that since the car is in my workshop on the lift. One final thing...I have a double blade connector on the starter motor so that I can have both the standard BY ignition wire and a jumper wire connected. I guess I should try pulling the BY and only use the jumper when trying to crank. Any further thoughts on this would be most welcome.

LongDuck

Having had a similar problem for most of last year, check your ground connections first. Sounds like you have new cables in place, but be sure you have zero drop between the battery terminal and the DS strut tower, and minimal drop to the negative ground at the long Starter Bolt. A loose connection or a rusted bolt or hole is all it takes, and you get weird symptoms as the system tries to ground through any other connection - which is a very bad thing.

Secondly, check your Positive Lead to the Fusible Link Block at the DS Strut Tower and to the Starter. Not sure why Mazda didn't use red cables for the Positive side, but check for continuity.

Lastly, wait for GSLSEforme to show up, as he has the insight into all things electrical and how to troubleshoot them; I'm throwing you some ideas to get you started.

ericdash

Thanks for the thoughts, LongDuck. I'll check them out. Also want to recheck the main fusible link. My heavy cable is grounded to the top bolt on the bell-housing and shows continuity.

spedy7

I'd second this assuming everything else checks out. Worked on a few non-roto cars that ended up having an oil covered starter signal wire. Cleaned it up and starts fine. Poor/loose/corroded grounds are super common causes too.

ericdash

Well, I finally got back to the dead short issue. I've been playing with the carburetor in another thread and finally got it to idle (although more work is needed). So, I pulled the lower harness that goes to the starter and transmission. I did so because there is a 6-way connector around the steering box for the lower harness and I saw that it had 2 slots with a heavy (10gauge) B/Y wire (that's what goes to the starter solenoid). Since there is only 1 B/Y at the bottom, I wanted to find out why there were 2 at the top. Turns out that they are spliced together in the lower harness not far from the connector. There was perfect continuity between the 2 ends of the harness, so that's not where the problem lies. So I went to the upper harness connector to find out where the 2 B/Y connections went. According to the limited wiring diagram in the factory manual, one goes to the ignition switch and another goes to some fuses in the fuse box. The bottom left B/Y connector has continuity with the ignition switch. My logic says that when the switch provides power to the solenoid to start, that power is also then supplied to the other blades in the connector, i.e., the top right B/Y blade. I pulled the fuse box down (2 phillips head screws hold it in place) and found that there were 2 B/Y 10gauge wires going into the box. Okay, is there connectivity for either of them to the top right B/Y connector, fully expecting to find it. Unfortunately, neither showed connectivity. This doesn't make sense to me. When I start the car (with the solenoid jumper wire, not the ignition switch), everything works, so the fuse box must be getting juice. Why are there 2 B/Y wires to the fuse box and is it the same splicing deal that the lower harness has? I was planning on replacing what I presumed to be the bad wire, but now I'm at a bit of a loss as to how to proceed. Any thoughts welcomed.

ericdash

Just a bit more information. I found that there was a 2nd B/Y from the ignition switch bundle of connectors and that one has continuity with the 2 B/Y lines in the fuse box. So apparently that's where it gets the heat (at least for the several fuses that the wires connect). However, I still can't figure out what the B/Y from the main harness connector (X-09 is the manual's label for it), especially since the book shows it connecting to a B/W, not B/Y that I'm seeing on my car. There was some indication that it could go to the hot start assist system and/or the emission system, but I'm not seeing any B/Y wires elsewhere. Since I get a dead short when I connect the B/Y to the solenoid and try using the key, I'm wondering if that strange connection is the culprit. I get good connectivity from the ignition switch to the main harness X-09 connector on the blade that goes to the solenoid. It was also interesting that the dead short continued even if I used a jumper from the solenoid (while the switch connection was still connected), but not when the switch connection was removed (and the car started without issue with the jumper alone).

GSLSEforme

I've read thru your thread and nowhere do i see evidence of a short(s). What damage do you have? Blown fuses,melted fuse links,signs of overheated wires/connections... When a repetitive short condition exists,there is almost always collateral damage from heat in the form of previously mentioned and these can be used as clues to determine a direction to go to begin diagnostics.

ericdash

Okay, then I should clarify the symptoms. First, I have no blown fuses, no burnt wires, no melted fusible links, i.e., no obivous collateral damage. So, what does it do? Assume everything connected as normal, when I turn the key to ignition, dashboard lights up as normal; turn the key to start, and everything goes dead. If I disconnect the negative terminal to the battery and reconnect, still dead. Under the same conditions, if I use the jumper wire that I have dually connected via a double blade connector on the solenoid, I get a couple of clicks from the solenoid and then nothing. If I disconnect both the positive and negative terminals to the battery and reconnect, the dashboard lights come on again when key turned to ignition-on. If I then use the jumper to the battery and not the key, I only get clicks from the solenoid and then nothing. When I disconnect the B/Y connector at the solenoid and leave the jumper wire, I get full dashboard lights and the car starts immediately using the jumper wire and runs just fine. I have checked all of the fusible links, and as described previously tested the transmission harness for continuity (after unwrapping it to understand where the 2nd B/Y line came from). Since I get good continuity from the X-09 bottom left plug all the way to the ignition switch, and continuity from the switch to the fuse box (B/Y) wires, but no clear connection from the 2nd B/Y X-09 slot (upper right slot that is listed in the manual as a B/W wire, but not on my car), my thinking is that this 2nd B/Y slot is the culprit, but since it disappears in the main harness, I have no idea where it goes. The 84 Mazda RX7 wiring manual is not clear about it at all. I should also add that I have replaced the old original ignition switch with a brand new one. The starter tests fine on the bench and is relatively new, and obviously works with the jumper. One last piece of information - while pretty consistent, there has been a time when the key worked for a bit and then went dead earlier in my debugging process. What's that expression....curiouser and curiouser.

ericdash

Did some more studying of the wiring diagrams and it looks like the hot start assist motor/relay and zero degree assist motor/sensor systems are getting juice from the B/Y line, as well as the emission control module. I decided to try disconnecting the 2 systems (not emission control module), reconnect the ignition B/Y to the starter solenoid and see what happens. I poured a little gas in the primaries and tried starting with the key. It worked, but stalled. I tried again with the key, but the car kept trying to start while cranking, but just couldn't catch. I kept at it for a minute or so when all of a sudden, everything went dead. Disconnected the battery at both terminals, reconnected and turned on the key. As in the past, the dashboard lights came on, but gave a solenoid click and then went off when I tried to start with the key. I then disconnected the B/Y connector at the starter solenoid, did the battery terminal thing, and tried again. The dash lights came on, but when I touched the jumper from the solenoid to the + battery terminal, same solenoid click and everything went dead. I'm wondering now if it's the starter/solenoid combination. The fact that I have to disconnect the positive battery terminal in order to get the ignition and lights to seemingly work, and that positive cable goes directly to the starter, would seem to indicate that the starter/solenoid system has an intermittent fault that may or may not crop up when it gets hot. That could explain the positive bench test (not under any load), and initial working until it gets really warm. I don't like parts replacement as a diagnostic tool, but I may be forced to try it. I have an 83 parts car and I may try pulling that starter/solenoid to see if it works. I'll also try again tomorrow to see if cooling overnight makes a difference.

Maxwedge

iTrader: (1)

And you're sure its not the ignition switch? I think you said you replaced it but...

KansasCityREPU

iTrader: (9)

Try adding an additional ground. I like to run one from the alternator bolt to the bat neg terminal. Also make sure the negative connection on the drivers side strut tower is good. As a test you can use a set of jumper cables as a neg from the alt body to the neg battery terminal.

ericdash

I'm sure it's not the switch.

As to the 2nd negative ground, interesting idea, but I'm not sure why it would need it, never having needed it in the past. I'm sort of honing in on the starter or solenoid as the source. In another thread, I believe it was GSLSE.... who said that he rebuilds his starters and alternators himself. I also saw in that thread that explained why my 83 parts car with automatic tranny starter wouldn't work (gear reduction starter to account for the added weight of the torque converter).

GSLSEforme

Without having car present it’s difficult to make a diagnosis...having said that,it seems to have a problem on power distribution side of circuit.
Op may have hit on source of problem with possible faulty connection inside starter/solenoid.
Have all issues occurred with current starter in place? Waiting to see results from starter swapped in from parts car.

ericdash

Thanks for your thoughts. The parts car starter was a no go. It's an automatic and uses the gear reduction starter (the torque converter is heavier than flywheels apparently and needs the extra oomph). I tried bench testing my starter again and that didn't work (I believe the battery I was using didn't have enough juice) so I checked my receipts and found that it wasn't even a year old (obviously I replaced it to solve this on-going problem). So I took it back to Autozone and they were able to successfully bench test it, but were only too happy to replace it for me, which they did. I just installed it today and it ain't the starter. I'm back to square one. I disconnected the B/Y wire and the other wire for the hot start assist motor (that's on the other heavy pole of the starter), and tried using only the jumper wire. No go.

I went back to the wiring diagram to see what that other X-09 BY wire does. It goes 3 places from what I can discern: the subzero motor, the emission control module, and the cruise control unit. For the latter it changes to BW at the X-10 connector. For the emission control, it looks like it splices off under the dashboard (from the diagram) and doesn't have a specific connector. The subzero motor comes off the X-09 connector, but the diagram says that it changes to BW on the receiving side of X-09, but on my car both sides are BY. X-09 also shows a LW coming from the fusible link and going to the hot start motor. I had tried disconnecting both the hot start motor and the subzero motor to no effect. I have tested continuity on all of the fusible links, pulling them from the holder and manipulating them around while testing without issue. I have checked the WR from the battery for continuity to the link body without issue. I may have previously indicated that I removed the bird's nest and solenoids, some of which have connections to the emissions control module, but this dead short issue predates that removal. I don't know how one would test the emission module, with its multiple connections both in and out, nor can I fathom how it would or could cause this dead short on start up. It doesn't make sense that it would be the problem, because when the dashboard idiot lights come on, and I push start the car, it runs perfectly (or at least used to until I started playing with the carburetor). I'm thinking I might try swapping the fusible link from the parts car if it tests out on the bench. What else could cause a complete drop of all current to the harnesses? One further item, while the battery 4 years old, I keep a battery maintainer/trickle charger on it and it's showing 12.6 volts when no draw is on it. Another piece of information - when the short occurs, the solenoid on the starter will continue to click when I use the jumper.

GSLSEforme

Really should stop referring to no start as a short.It essentially is the opposite of that,an open circuit,poor connection.

No blown fuse(s),links,meltdowns,no short.

Very much sounds like a poor connection that opens under heavy load(starter).

Turn headlights on and try to start car. Do they remain on when All dash lights go out?

KansasCityREPU

iTrader: (9)

Do you still have the fusable link on the starter?

ericdash

That's 2 very helpful thoughts. I keep thinking of it as a short, but you've clarified how I should think about it...as a connection failure under load. Also, the idea of checking the headlights adds additional focus for me since they come directly through the fusible links. I'll dig into that tomorrow. Thank you.

ericdash

GSLSEforme, that was the clue that I needed to solve the problem!!! The headlights went out the minute I touched the jumper to the positive terminal. I shook the heavy WR wire to the fusible link and the lights came back on. I wasted a whole bunch of time pulling apart the fusible link to confirm that everything was showing continuity. The positive cable to the starter is aluminum. The WR wire is copper. I took the battery clamp apart and found a large yellow O connector and clamped the copper cable to the fusible link into the electrical connector and then screwed that down to the battery clamp. Voila! All that chasing, and the answer was simple. THANK YOU for your insight and better debugging skills.

GSLSEforme

Glad you got it sorted...you're probably more glad than me,though. So today's a happy day!