Miata Won’t Start

Our 1994 Miata just died. Ran fine last night, but when I went to fire it up today it would try, but not kick over. 
 

If it sits for a second it builds up just in a fuel pressure to to kinda over, but not enough.

Because I am better at replacing parts than I am diagnosing, I did go ahead and replace the fuel pump, but no change.

After that, I tested to make sure the chassis side of the relay was getting power (it is) but I'm at a bit of a loss otherwise.  I do need to confirm that it's getting power at the pump, but my probes on my multimeter are a hair too big  

What should I check next?

In reply to Gimp (Forum Supporter) :

Put a smaller wire in the connector and then test for voltage at the pump. 

Stampie said:

In reply to Gimp (Forum Supporter) :

Put a smaller wire in the connector and then test for voltage at the pump. 

Duh. 
No power on the blue/red wire at the pump. 

IIRC the pump is triggered three ways:

during starting
by the ECU for a prime
by the ECU when the engine fires up

You can also turn it on with the ignition by jumping FP to GND in the diagnostic connector. If this makes it fire up, that tells us something. Or just yank the relay and bench test it :) let me know if you need the diagrams.

In reply to Keith Tanner :

I wouldn't mind diagrams. I have a Haynes  manual, but I'll always take more help. 
I also noticed a nick in the yellow wire to that same connector, so I'll patch that up. 
 

I'll jump back on it tomorrow. Thanks for some direction!

OK, I had to check. Jumping fuel pump to ground in the diagnostic port turns on the fuel pump, so that's good. It is definitely not running without doing that. Car still won't start. Same as the video above.

Got spark?  I love the little Harbor Freight in line spark testers. 

Stampie said:

Got spark?  I love the little Harbor Freight in line spark testers. 

Because I can hear it try to kick over I'm assuming I do. I have not done any testing.

In reply to Gimp (Forum Supporter) :

IIRC those have two coils so you could have spark on two but not the other.  IIRC 94 coil pack is a one year only item.

In reply to Stampie :

All NA/NB Miatas have two coils. The 94 pack is only interesting in how it runs the tach. 

EFI/fuel pump relay made no difference. 

Does anyone have some tried and true methods for checking spark operation?

If you have an extra plug, you can just unplug the boot from the plug that's in the engine, put the extra plug in the boot nice and secure, ground the plug, and watch to see if you get a little spark.  Alternately, you can pull the plug out of the engine and check it.

In reply to Gimp (Forum Supporter) :

There is a tool for that.  Many actually.  This is one

I made one from an old spark plug a section of wire and an alligator clip.  I soldered the wire to the body of the plug and attached the clip.  You hook the alligator clip to to a good ground and plug the plug into a spark plug boot.  Crank and see if you have spark.  It is a useful thing to have.

I use these.  $5 at Harbor Freight.

Am I the only guy who just grounds out the spark plug on the engine? 

Have you confirmed the timing belt is actually still there? :) They generally don't kick at all, though. Another pair of basic questions: do you have lots of battery charge and fuel in the tank? A low battery can cause the ECU to shut down when the system voltage drops due to the starter draw.

Fuel: you could use a noid light to check that the injectors are firing. They should squirt once as a prime and then fire when you crank. Knowing that would tell us a LOT, but if it's firing spark it's almost definitely firing injectors.

In reply to Keith Tanner :

Some of us just learned better after the millionth time of getting tickled by the spark.

...I thought the fuel pump was not working.

You can replace the fuel pump relay with an ATC fuse across the high current terminals to make the pump run all the time the ignition is on.  If it now runs, and I have a feeling it will, then the relay is not being engaged in the first place.  Do these still have the switch in the airflow meter?

In reply to Stampie :

I prefer to think of it as haptic feedback.

Pete. (l33t FS) said:

...I thought the fuel pump was not working.

 

You can replace the fuel pump relay with an ATC fuse across the high current terminals to make the pump run all the time the ignition is on.  If it now runs, and I have a feeling it will, then the relay is not being engaged in the first place.  Do these still have the switch in the airflow meter?

The 1.8 cars don't have the switch in the airflow meter, the ECU commands it on when there's airflow through the MAF. But you can jumper the relay directly using the diagnostic box.

Jumping fuel pump to ground in the diagnostic port turns on the fuel pump, so that's good. It is definitely not running without doing that. Car still won't start.

Normally, the pump will only run when jumped, for priming, when cranking or when the car is running. It can be hard to hear while cranking. But it the pump runs with the jumper in place and the car won't start, it's not the pump.

I'm having trouble coming up with a failure that takes out the entire fuel or entire ignition system and still allows for the occasional cough. Fuel pump is plausible - it could be running but weak, and a fuel pressure test would answer that question. A main relay would take it out completely, the ECU wouldn't wake up so it would never cough. Lose one coil and it'll run on two cylinders. 

My experience at the Challenge this year is that you should make sure there's gas in it.

I'd check the fuel rail pressure.  Maybe the regulator let go and it's not building pressure.

I'd see if it starts with a snoot full of starting fluid.  If it does, great, you just ruled out ignition, compression, and timing.  If not, fuel is probably not the culprit, maybe.

wae said:

My experience at the Challenge this year is that you should make sure there's gas in it.

I have also experienced this failure mode. 

My 1992 had a clogged fuel filter than led to burned out fuel pump relays and a random no start condition. I replaced so many parts before changing the $9 filter.

Don't be like me. Change your fuel filter.