theRider28

Here’s a fun one for you guys. I have not found any other posts with exactly this issue, and I’ve never heard of anyone else having issues as seemingly random as these.

Just bought a 1990 manual Miata that was a no crank no start. Guy told me it drove perfectly until one day it just died on him and refused to start again. Being the idiot I am, I figured it would be an easy fix, and bought the car from him for a discounted price. It has been a week and I want to put this thing in a car crusher. Here are the symptoms:

-As I said, the car will not even crank. Some of the lights will turn on in the dash though (air bag light and E-brake light) everything else In the cluster does not turn on, at least not completely. The reason I say that is because if I turn the key to the “on” position, the check engine light will very slowly start to glow if I sit there for a second, but it is extremely weak and hard to see. There is a second light right above it (check battery maybe?) also will slowly begin to glow, but it’s much much weaker, and barely visible. This happens every time I turn the key to the “on” position. Blower, headlights, signals, reverse lights, and everything else seems to work perfectly (now that I think about it, I haven’t checked to see if the radio works, I’ll have to check). There was ONE SINGLE TIME that I went to try and start it, and the entire cluster lit up normally. I thought “great, I must’ve bumped a loose connection back into place while I was working”. I tried to turn the engine over, i heard one “click” (as if the battery were dead) and everything went back to the way it was before. Wtf.

-The second issue (which I originally thought was unrelated, but now am not so sure) is that the fuel pump primes when I turn on the key, but it never stops. Even after I’ve removed the key it continues to run. The only way to shut it off that I’ve found is:
1. Disconnect the battery obviously
2. Remove the fuel pump relay
3. Turn the car off while in reverse. Wtf
Weird right? Or maybe it’s not and I’m just a numbskull, not completely sure. Electronics are not my strong suit.

So. My first thought (after doing basic **** like jumpstarting it, push starting, testing the battery, etc.) was to check the ECU, since idk how else the fuel pump issue and no crank issue could be related. I popped it out, and it looked fine. Nothing looked fried or melted, and nothing smelled burnt, in fact it actually looked fairly new. All fuses are good. Fuel pump relay is good (tested it) jumpered the clutch interlock switch to see if that was my issue (no luck). Jumpered the key ignition cylinder to get the starter to turn, no luck there, so it’s not the key cylinder. Checked my grounds (visually only though, my damn voltmeter broke) They all appear fine. Oh, and clamps on the battery are good too. Clean and no corrosion.

Now, at some point, the car got an after market speaker system (two speakers just sitting behind the seats) I pulled the wires off of them and traced them back to where they go behind the radio. They weren’t touching anything else, and I imagine that the just plug into the back of the radio, but I haven’t gotten a visual on it yet, because I haven’t had the time to pull apart the dash. I know that if done wrong, that could lead to some issues, but I wouldn’t think those issues would be this bad.

So ya, that’s about it. Again, I apologize if anything I’ve tested or not tested seems incompetent, as i am good at working on the mechanical aspect of cars, but definitely not the electronics. I’ve searched through about every YouTube video and forum about this issue, and haven’t been able to find a solution, or a situation quite the same as mine tbh. Any advise would be greatly appreciated! I am completely stumped.

gooflophaze

Check the main ground on the PPF. There's a flag connector that goes to the body about 6 inches from the battery terminal and connects to the body, then runs down a grommet and connects to the PPF via a M6 bolt.

What is the battery voltage? Disconnected and when key is on?

theRider28

Good call, lol. I missed that ground earlier. Went to check it, and the wire pretty much turned to powder in my hands it was so corroded. I’ll replace it and get back to you.

Battery read 12.8 or so with the car off and like 12.2 with the key on.

theRider28

Update- Replaced that ground (checked the resistance to the PPF, its good) Didn't change anything at first until I shifted my weight in the car when I was trying to start it. For some reason, when I sat up straighter in the car and tried again, the check engine and check battery light came on along with the air bag and brake light, just like what I had experienced that one time I mentioned earlier. The only difference between then and now is it is staying this way. Every time I try to turn the engine over, all of the mentioned lights come on, and I hear a click coming from up front, kind of like the starter isn't getting enough juice to actually turn. Also, the fuel pump doesn't turn on immediately when I turn the key on now. It doesn't turn on until I try to turn the engine over, or until I put it into a gear (its completely random every time, sometimes 1st turns the fuel pump on, sometimes it doesn't. Same with all the other gears.) The fuel pump also turns off whenever I turn the key off now, regardless of the gear, which is nice. Every put the car into a gear, the brake light in the cluster comes on for a split second and then disappears. What's next?

SpartanSV

Please describe exactly what you did for this test.

theRider28

Actually followed instruction from a post on this forum. I pulled the large connector out of the socket of the key cylinder, took some spare wire I had and connected the black/blue wire with one of the two white wires present in the connecter. It was said in the thread that it doesn't matter which of the two white wires is used. Obviously this wouldn't start the car, but it should spin the starter motor, which would mean that the key cylinder is bad. In my case, nothing happened, so unless I did something wrong, I assume my key cylinder is fine.

theRider28

Update- Right after I made the last "update" post, I decided to give push starting the car a shot to see if anything had changed after that ground brought up by Gooflophaze was fixed. It started up on the first try. Runs perfectly, no idling issues or anything. Was a little jerky at first taking it around the block, but everything worked perfectly once it had a chance to get warmed up. Only issue I had was that the check battery light was on the entire time, unsurprisingly. I drove around for about 30 mins in my neighborhood, trying to find any issues, but other than the battery light, there was nothing at all. When I got back, I shut it down and tried starting it back up two minutes later to see what would happen. Instead of just clicking once when I try to turn the engine over, it clicks for as long as I hold the key, as if the battery is just dead. Checked the battery again, it was still over 12 volts. There's gotta be a loose connection somewhere which isn't allowing enough power to reach the starter, I'm just not sure where to find it.

gooflophaze

Battery light, while not a traditional "excitor lamp" like in other alternators, does indicate a voltage difference between hot and alternator - so you might want to see if you're getting 14.2v out of the alternator while it's running. Remember, anything below 12.6v on a lead acid battery is undercharged.

x_25

Sounds like the alternator is bad and/or there is a loose ground somewhere. If acttig the switches in the transmission changes things, that means current is flowing through them trying to find a ground. Check the engine ground straps, bet they are toast.

theRider28

Alright, that makes sense. Ill check everything that you guys mentioned once I get home. I appreciate it, Ill keep you guys updated.

Darry

Sorry to revive and old thread but I’ve just encountered the same issues, did you end up fixing your problems or figuring out what it was?