UPDATE: PROBLEM SOLVED!!! Turns out that it was water in the gas tank. After pumping the water out of the bottom of the tank, it fired right up! Original post below:
Hi all,
After my Miata had been sitting for about a month, I went to start it up and it idled rough for about 30 seconds, then died. I tried to start it again and then it idled rough for about 5 seconds, then died. I tried again and it just kept cranking without firing anymore. I unplugged the connector from the pump assembly and used a multimeter to confirm that voltage was being sent to the fuel pump when cranking. Because the car had been sitting for a while in the cold with an old battery, only 9 volts was being sent to the pump during cranking. I then pulled the fuel pump from the tank and connected it to a 12 volt car battery to test it and confirmed that the pump does run.
I am currently charging up the battery, but are there any other things that I should look at? My next suspicion is that the fuel pressure regulator may be bad.
https://youtu.be/oUCZJ4yTBK4
Give this 3 part troubleshooting series a shot. I found some of his other content very useful when I've had issues. Cheers
I'll bet that fresh battery will help. And you do have fuel in the tank? I've been caught by that in the past.
After that, check fuel pressure. The pump running on the bench doesn't tell you if anything else is clogged. It does sound like fuel delivery more than anything else.
Try starting it using ether. My guess is it will fire up and then die. It definitely sounds like lack of fuel.
Thanks for everyone's feedback.
I installed a pressure gauge in the fuel line and after cranking for about 20 seconds, it started idling but then died a few seconds later. The fuel pressure while it was cranking/idling was between 30 and 35 psi. Does this sound about right?
Is there a chance that it could be the cam angle sensor or the air flow sensor?
Try jumping the fuel pump - use a piece of wire or a paper clip to connect FP to GND in the diagnostic box under hood. That'll make the pump run whenever the ignition is on. If the problem is in the AFM wiring, it'll keep running in this case. You didn't just do any work involving the AFM, did you?
That pressure is about right for idle. Spec is 31-38.
If you had a CAS problem, it likely wouldn't start. This sounds like the pump is running for cranking but shuts down afterwards - and not always running when cranking in your original post.
Keith Tanner said:
Try jumping the fuel pump - use a piece of wire or a paper clip to connect FP to GND in the diagnostic box under hood. That'll make the pump run whenever the ignition is on. If the problem is in the AFM wiring, it'll keep running in this case. You didn't just do any work involving the AFM, did you?
That pressure is about right for idle. Spec is 31-38.
If you had a CAS problem, it likely wouldn't start. This sounds like the pump is running for cranking but shuts down afterwards - and not always running when cranking in your original post.
Hi Keith, if the pump had stopped running after cranking, I would have expected the rail pressure to drop very quickly, but that was not the case. I pulled the plugs and verified that they are sparking when grounded to the head. Given that I have spark and fuel pressure in the rail, I now suspect that maybe the injectors are clogged. The car was sitting out in the cold for a while, and for all I know, they might be the original injectors from 1990. The car has just over 300,000 kms on it.
Try jumping the pins in the diagnostic box first, it's a 30 second test. It certainly won't hurt to get the injectors cleaned, but that's not how I'd expect them to behave.
If you didn't have spark, it wouldn't run at all. This is either fuel or the ECU turning off the injectors. Any error codes?
Keith Tanner said:
Try jumping the pins in the diagnostic box first, it's a 30 second test. It certainly won't hurt to get the injectors cleaned, but that's not how I'd expect them to behave.
If you didn't have spark, it wouldn't run at all. This is either fuel or the ECU turning off the injectors. Any error codes?
Hi Keith, thanks for your continued support. I tried jumping the fuel pump terminals in the diagnostic port and confirmed that the pump was running when the ignition was on. I did a bit more searching online and found this response that you gave to someone with a Miata starting issue:
https://grassrootsmotorsports.com/forum/grm/i-compression-tested-my-miata-now-it-wont-start/170860/page1/
Perhaps my fuel injector relay is failing? I'll do some online searching to figure out how to read and interpret the OBD1 light flash pattern codes.
UPDATE: PROBLEM SOLVED!!! Turns out that it was water in the gas tank. After pumping the water out of the bottom of the tank, it fired right up!
