PMRacing SuperDork
April 23, 2016 8:52 p.m.

OK, I'll try and keep this short.

Engine out service on my '97 Miata. Did front and rear main seals, cleaned lifters, timing belt, clutch and flywheel.

Put engine back in, and started fine twice. Then wouldn't restart. Battery was on charger for a couple of weeks before putting it back in. Charged it for a bit and it started again.

Today, didn't start again. Battery was low 12.xxV even after being on the charger. Bought a new battery and put that in. Cranked faster, but still no start. Remembered I had disconnected the rear O2 sensor. Plugged that in and the car started right up. Yahoo! So I let it get up to temperature, check for leaks and shut it off. A while later I go to start it again. Crank, crank, crank,...

I have spark (plugs out, hooked to wires and grounded on valve cover, spark while cranking). I smell fuel when cranking. So I let the cylinders dry out while I did some other stuff. Put everything back together and crank crank crank. Try again and after a half dozen or so cranks it catches and runs fine. Drive it around the storage lot, pull it back into the shop, check for leaks and shut it down. I try to start it again...can you guess yet?

So any suggestions? I've checked all the electrical connections. Timing is set at 14deg TDC. What am I missing?

On top of that, the rear main is still leaking. I'm hoping it just hasn't seated completely yet.

Dusterbd13 PowerDork
April 23, 2016 9:29 p.m.

Sounds like a loose ground.

Doc Brown Dork
April 23, 2016 9:36 p.m.

Could be a failing CAS or as Dusterbird mentioned a loose ground. The Miata engine has two grounds, one on the passenger side of the head near the front of the engine. The other ground is on the drivers side near the firewall.

Edit... Fox Auto U-Pull in Bellville has a 97 Miata in stock. I have no idea if the car still has the CAS on it, however according to the price list they get $4.99 for the CAS.

Keith Tanner MegaDork
April 23, 2016 11:36 p.m.

$4.99 for a CAS? Buy as many as you can carry.

I'd be normally looking at the main relay in this case - sounds like it's dodgy, as they often will stay closed once they close, but may have trouble getting to that point.

But you always go back to what you did before the problem, and that was a motor pull. So check those grounds. The main engine ground is in place (it's cranking), but you may have missed another. Go over the engine slowly and remember just what grounds you disconnected, including any on the powerplant frame. There's an important one there.

PMRacing SuperDork
April 24, 2016 8:20 a.m.

I think I'll definitely try to snag that CAS if I can get down that way. I don't remember there being any ground on the passenger side of the engine. There was the one near the driver's firewall and the small grouped ones under the master cylinder (didn't touch those).

Would a 1.6 CAS work on a 1.8? I think I have one laying around from my old cars.


Zeitgeist Reader
April 24, 2016 9:05 a.m.

I am in a similar situation with my Exocet build. It cranks well but won't start. I have the ground by the rear engine to firewall but where is the one on the front of the engine located? what does it connect to on the engine and where did it connect to on the car? I seem to have no power to the dash,fuel pump and it seems no spark but I am am working alone so hard to check things while cranking. 1 relay does click when key is turned to ON position.

Doc Brown Dork
April 24, 2016 10:06 a.m.

Hi Phil, this is Jim from PTM electronics. I have changed my user ID a few times. Anyway, as you know, I dont have a normal Miata but there should be one or two grounds on the front of the engine near the throttle body. There is also a braided ground strap on the rear of the engine that attaches to the body of the car.

The front grounds effect the ecm and the instruments. As I recall the front location may be split into two ground points requiring two bolts for proper ground. Its also possible that both front grounds use the same bolt.

Random picture from the net showing one of the ground locations.

PMRacing SuperDork
April 24, 2016 12:43 p.m.

In reply to Doc Brown:

I know who you are Jim. that ground is hooked up. I thought there was an engine to body ground that you were talking about. I won't get to the car again until later this week. Hopefully a coworker can find a Mazda cable for his scanner so we can read whats going on.

Zeitgeist Reader
April 24, 2016 4:22 p.m.

I think Doc Brown was helping me with my question for a similar issue posted above his post. Thanks Doc and I just checked. I have that ground tight right next to the throttle body between it and the cam cover.

Keith Tanner MegaDork
April 24, 2016 11:11 p.m.
Zeitgeist wrote: I am in a similar situation with my Exocet build. It cranks well but won't start. I have the ground by the rear engine to firewall but where is the one on the front of the engine located? what does it connect to on the engine and where did it connect to on the car? I seem to have no power to the dash,fuel pump and it seems no spark but I am am working alone so hard to check things while cranking. 1 relay does click when key is turned to ON position.

It's almost impossible to keep a Miata from cranking. Seriously, the starter system is about as complex as a flashlight and completely divorced from anything else.

If you don't have power to a bunch of things, look at the wiring diagram and see what those things have in common. Main relay is a good bet in this case as it lights up both the ECU and the coils, but I don't have the diagrams with me on the road. If it's an NA donor, check for power on any white wire with a red stripe (injector plugs, for example) when you key on. The fuel pump will not have continuous power when you simply have the key on. Spark can be easily checked visually when working alone.

Zeitgeist Reader
April 27, 2016 3:30 p.m.

I got my Exocet running. I had to hotwire it as the ignition switch wasn't sending power to 1 wire. Hotwired and she started right up. Glad that issue is fixed.

PMRacing SuperDork
April 27, 2016 8:47 p.m.

In reply to Zeitgeist:

Congrats! I'll have to check my ignition wiring.

PMRacing SuperDork
April 30, 2016 8:46 p.m.

OK, so I'm kind of an idiot. When I bought the car, the PO told me that there was some parts prototyping done on it. For some reason the ignition switch got a bit screwed, up. If you turned the key fully to start, it would just crank. Turn it 7/8ths, it starts every time. I completely forgot about that over the winter. So, yeah, there is something wrong with it, but it's got a work around. But it's running great and pretty much ready for track time now!


Keith Tanner MegaDork
April 30, 2016 10:41 p.m.

"Parts prototyping". Like a prototype screwdriver used to start the car.

PMRacing SuperDork
May 1, 2016 6:05 p.m.

In reply to Keith Tanner:

HA! No. It had a prototype aluminum exhaust system for autox on it (I melted it at the track, won't take sustained heat), and I think it had a prototype coil on plug system on it for a while. I don't remember why the ignition was messed with though.

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