pbkelley New Reader
Aug. 26, 2013 7:56 p.m.

Need some help from the Miata crowd please!

91 Miata stopped running. Cranks over fine. With a shot of Starting fluid the car will run.

Fuel Pump runs and I have fuel at the injectors. The pump only runs while the motor is turning over. Does not come on to prime the system when I turn the key to on. Jumped it out in the diagnostic connector and it runs.

Check Engine Light gave me a code 1 - Ignition Pulse. (Don't know how long it may have been saved in there.)

I am fortunate that I have 2 of these so I swapped out some of the items that I found when I googled this problem. Coil, Air Sensor, ECM Relay. I also swapped out the ECM.

No wiring problems that I can see. The car is in pretty good shape.

I'm leaning towards a bad Cam Sensor, but the fact that it will crank with starting fluid has me second guessing. What else do I need to check? I thought about timing belt problems (next on list to check).


foxtrapper PowerDork
Aug. 26, 2013 8:26 p.m.

Sounds like the fuel isn't getting into the engine itself. Two things come to mind. One is blockage preventing pressure at the injectors (a quick pressure test would reveal if this is the case). The second is failure of the signal actually getting to the injectors (a noid test would reveal an electrical signal at the injectors).

Jaxmadine Reader
Aug. 26, 2013 8:42 p.m.

What enables the injectors on a miata? Cam or crank? I shall assume u have spark?

Keith Tanner MegaDork
Aug. 26, 2013 9:34 p.m.

Are the plugs getting wet when you crank it?

Kenny_McCormic SuperDork
Aug. 26, 2013 10:26 p.m.

Wait, will it actually start and stay running with a bit of ether, or will it only run on ether?

pbkelley New Reader
Aug. 27, 2013 4:44 a.m.

Plugs are dry. It will only run while I spray ether.

I'm guessing the computer isn't pulsing the injectors. I have power 12v to one side of the injectors. It acts like the computer isn't turning on since the fuel pump doesn't prime for 3 seconds when you turn the key to on.

pbkelley New Reader
Aug. 27, 2013 6:12 a.m.

I'll add a few more things. I have replaced the two ground pins in the ECM plug. All of the fuses are good except the wiper fuse under the dash. (Something is shorted). I don't think it is connected to the problem.

And to top it off - my other Miata refused to crank this morning when I left for work. Engine just spins - no attempt to fire. I didn't do any diagnosis. I just jumped in my truck and came to work.

When it rains - it pours.

tpwalsh Reader
Aug. 27, 2013 6:46 a.m.

Fuel, Air, Spark, Compression. Which one are you missing?

pbkelley New Reader
Aug. 27, 2013 6:49 a.m.

Fuel. It runs with starting fluid.

Keith Tanner MegaDork
Aug. 27, 2013 6:54 a.m.

If you're getting spark, the computer knows the engine is turning over. So it's probably not the CAS. It's definitely not the timing belt.

You said you can jump the FP in the diagnostic connector and "it" runs. Do you mean the car or the fuel pump? If you mean the fuel pump, then your problem is not a lack of prime.

I'd check the fuel pressure. I suspect you have none.

pbkelley New Reader
Aug. 27, 2013 7:21 a.m.

The pump runs when I jump out the diagnostic connector. Not the car. I have not been able to hear the car run (without ether) since buying it. I'll check the fuel pressure tonight and report back.

I wasn't sure about the function of the CAS.

tpwalsh Reader
Aug. 27, 2013 9:11 a.m.
pbkelley wrote: The pump runs when I jump out the diagnostic connector. Not the car. I have not been able to hear the car run (without ether) since buying it. I'll check the fuel pressure tonight and report back. I wasn't sure about the function of the CAS.

It won't run with the FP relay jumped either? If the Noid light shows the ECU is trying to fire the injectors(which it should be if the coils fire) then it might be gummed up injectors. I had a friends miata that did that. Swapped in a junkyard motor, and didn't get any fire at all. Turned out it was 4 gummed up injectors. swapped in the old injectors and it fired right up.

We determined this by sticking a screwdriver on the injectors when cranking. Didn't hear a thing. unpluged an injector and plugged in one from the old one, and it clicked away.

Sofa King Reader
Aug. 27, 2013 9:29 a.m.

fuel filter?

pbkelley New Reader
Aug. 27, 2013 6:11 p.m.

Ok... got home tonight and now it has injector pulse, but no spark. Car will not fire with ether. Noid confirmed that the injector is pulsing. Pulled a plug and sure enough I have fuel on the plugs. Started chasing the lack of spark and found a defective ignition module, good coils,(swapped parts off my driver) and still no spark (with a good module).... Now is it the CAS?

My driver that wouldn't start this morning was simply a loose connector. I like quick fixes.

pbkelley New Reader
Aug. 27, 2013 6:12 p.m.

Fuel filter is new.

tpwalsh Reader
Aug. 27, 2013 6:55 p.m.

Now it's no spark, but you've got fuel, yesterday vice versa? Odd. I'd start with cleaning every ground. I doubt it would fix the issue, but if you went from chasing fuel to chasing spark, I'd start looking hard at the wiring.

Keith Tanner MegaDork
Aug. 27, 2013 10:44 p.m.

The suggestion of clogged injectors is a good one - I've seen a set plug up in 18 months of sitting.

But now you have fuel and no spark. This is a computer problem, and the ground suggestion is a good one. Bad CAS or CAS wiring would mean no fuel OR spark, but you would get a prime squirt so your plugs would be wet.

Or it's a diagnosis problem and we're dealing with bad info. For example, you say it stopped running. But you also say you've never actually heard it run without starter fluid.

pbkelley New Reader
Aug. 30, 2013 6:37 a.m.

Sorry about that. I bought this car from a friend of a friend after it quit running. He threw a whole of parts at it and couldn't get it running.

I installed a new ignition module and a used air meter and the car cranked after a few spins. I let the car warm up and drove it around the neighbor hood several times. Best I can tell the air meter was the original problem and the ignition module went out between my first and second attempts to work on it.

I cleared the codes and I'll let you know what happens.... fingers crossed. Thanks for everyone's input.

tpwalsh Reader
Aug. 30, 2013 10:53 a.m.

Thanks for the followup. It's nice to hear what the actual issue was.

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