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Miata dies, does not start until like 20 minutes later, no fuel/spark
I've been having a weird issue where after driving for a while the car either dies, or when I stop it and start it up a few minutes later, it doesn't start. It's usually remedied by waiting like 10-30 minutes then it starts up like normal. During the times it doesn't start, I've done a few tests, keep in mind there is no spark or fuel when cranking. This is what I've found so far, the CAS (NA 94) connector reads 0-12-5-5 volts, I can fire both coil packs through Tunerstudio's test mode, the fuel pump primes when turning the key to run position, and any log taken during the time its down shows basically nothing (attached). Grounds are clean and read low resistance. I have had recently some sync loss codes relating to the CAS/4G63 where the tach would drop to zero for a split second then shoot back up to normal, car misfires during the tach drop too, feels like hitting a limiter for a sec. When it dies, it isn't subtle, one moment it's running then the next moment it's completely dead, no misfiring or stumbles as it dies. Is this a CAS issue? Coil packs?
I've already gotten ahead of myself and have torn into the CAS and will be replacing the hall sensors inside of it. Perhaps I should've been a little more patient...
Logs and tune posted, running on a diy MS3X using Brain's guide.
I have had similar issues with a Mazda 323 which is very closely related to Mazda Miata, and of a similar age.
There are a couple of relays that supply power to the ignition system and the injectors. The contacts burn, and after about twenty to thirty years and do not always make such good contact.
Sometimes the engine runs, sometimes a momentary stumble, sometimes it stops and will not start. But comes good by itself after a time.
I have had similar issues with a Mazda 323 which is very closely related to Mazda Miata, and of a similar age.
There are a couple of relays that supply power to the ignition system and the injectors. The contacts burn, and after about twenty to thirty years and do not always make such good contact.
Sometimes the engine runs, sometimes a momentary stumble, sometimes it stops and will not start. But comes good by itself after a time.
Perhaps I should've checked my fuses/relays and stuff before tearing into this CAS. I'll go check fuses and relays and whatnot though.
Its not likely to be a fuse.
Fuses do not come good again by themselves.
More likely to be either a relay or a suspect plug/socket somewhere if you have intermittent power to the ignition.
Also check the ignition switch itself, they do wear out.
Its not likely to be a fuse.
Fuses do not come good again by themselves.
More likely to be either a relay or a suspect plug/socket somewhere if you have intermittent power to the ignition.
Also check the ignition switch itself, they do wear out.
If the ignition switch is bad, would the car still crank? The engine cranks, it just spins and spins. Ill check out the switch anyway though. How would the lack of fueling be explained?
There are a couple of relays that supply power to the ignition system and the injectors. The contacts burn, and after about twenty to thirty years and do not always make such good contact.
Sometimes the engine runs, sometimes a momentary stumble, sometimes it stops and will not start. But comes good by itself after a time.
Came here to say exactly this when I saw the thread title. They don't last forever!
Originally Posted by Spei
How would the lack of fueling be explained?
Lack of fueling points strongly at under dash fuel pump relay, especially if there is an aftermarket fuel pump involved. The "Main" relay is a good suspect as well. Time to bust out the DMM and start doing some diagnostics
If the ignition switch is bad, would the car still crank? The engine cranks, it just spins and spins. Ill check out the switch anyway though. How would the lack of fueling be explained?
Yes.
There are three positions of the ignition switch (apart from off), accessory, ignition, and cranking.
You can have all your accessories work, and the engine will crank. But no ignition power means no fuel pump and no spark and nothing to the injectors.
I have had this problem myself, and when you pull the ignition switch apart, you will be appalled how crude it is, and shocked by the cost of a new one.
The copper tracks, burn, pit, and wear out. If the car is driven every day for twenty plus years, hardly surprising really.
Main relay and as @Warpspeed said, ign switch are where I'd look first
Bummer, I should've posted here before I started tinkering with things. The good news is, I put in those new hall sensors into the CAS and everything seems to be working normally so far, although a little different, have to retune. I really do hope I didn't ruin a perfectly good CAS by tearing into it like I did... I did recently put in a DW200 fuel pump which would make sense that the main relay is failing... But, if that relay fails, would the fuel pump still prime? I wouldn't be able to connect my laptop to the ECU while it was dead right? I feel like other things would be going awry if it was the relay. Or is it just electrical voodoo?
I'll be cleaning/checking out my ign switch tomorrow. I did clean it about a year ago though, maybe I messed it up or something.
Locate your fuel pump relay, can you reach it from the driver seat? When you go for a drive, reach under the dash and give it a pinch, see how hot it gets. I'm betting its going to be scorching. Mine gets uncomfortably hot with a DW200 in the tank. I carry a spare.
What I've done in the past with "thermal" troubleshooting is to take a can of computer duster (dust off, etc) and flip it upside down and then spray the suspect overheating component and see if that magically fixes it. The instructions specifically tell you not to do this, and for good reason. Some of that **** is flammable, and it leaves that concentrated "bitterant" on whatever surface you spray it on, and its sure to cause condensation as well. Get it anywhere near your mouth or eyes and you'll be sorry. BUT! Its a quick and dirty way to cool down a suspected overheating component for troubleshooting when you are in a pinch. I wouldn't make a habit of doing this.
Car dies, car won't start, find super hot electrical component, cool with duster stuff, see if car starts. If still doesn't start, move to next suspect component. Etc. I'm sure you get the idea.
Originally Posted by Spei
I did recently put in a DW200 fuel pump which would make sense that the main relay is failing... But, if that relay fails, would the fuel pump still prime?
If main relay fails I wouldn't expect the pump relay to trigger and prime the pump, but then failing fuel pump relay would cause the same symptom
Originally Posted by Spei
I wouldn't be able to connect my laptop to the ECU while it was dead right?
I believe the ECU power is fed off the main relay, so if main relay fails I wouldn't expect you to be able to connect to the ECU. I think. I'm sure someone else in here knows better than me.
Originally Posted by Spei
I feel like other things would be going awry if it was the relay.
All kinds of stuff run off that relay, but I'm not sure which specific things because I don't have a wiring diagram for your car I know my NA will crank with the ECU sitting in my garage, but it sure as heck won't start.
Originally Posted by Spei
Or is it just electrical voodoo?.
I find most electrical systems to be voodoo without a wiring diagram
Locate your fuel pump relay, can you reach it from the driver seat? When you go for a drive, reach under the dash and give it a pinch, see how hot it gets. I'm betting its going to be scorching. Mine gets uncomfortably hot with a DW200 in the tank. I carry a spare.
What I've done in the past with "thermal" troubleshooting is to take a can of computer duster (dust off, etc) and flip it upside down and then spray the suspect overheating component and see if that magically fixes it. The instructions specifically tell you not to do this, and for good reason. Some of that **** is flammable, and it leaves that concentrated "bitterant" on whatever surface you spray it on, and its sure to cause condensation as well. Get it anywhere near your mouth or eyes and you'll be sorry. BUT! Its a quick and dirty way to cool down a suspected overheating component for troubleshooting when you are in a pinch. I wouldn't make a habit of doing this.
Car dies, car won't start, find super hot electrical component, cool with duster stuff, see if car starts. If still doesn't start, move to next suspect component. Etc. I'm sure you get the idea.
For sure I'll see how hot it gets while I'm driving. Do people put like heatsinks on these things? Or get an upgraded one? And yeah, I've gotten that bitterant **** on my mouth before, not fun.
For sure I'll see how hot it gets while I'm driving. Do people put like heatsinks on these things? Or get an upgraded one? And yeah, I've gotten that bitterant **** on my mouth before, not fun.
Oh yeah, that stuff is gross AND it sticks around forever. I got some on my glass top desk and I was picking it up for weeks. Eventually had to clear everything off the desk and just "detail clean" it :P
You can buy new OE Denso relays for the main or fuel pump for $30-40, or harvest one from the junkyard and keep it as a spare. Another option would be to wire the fuel pump through a basic relay directly to the battery in the trunk. You are still using the OE relay to flip the second relay, but at least you can buy a basic, easily replaceable 40/60/80 amp relay (and a spare) upgrade the pump power wiring AND you take the load off the factory wiring. There are details here on the forum on how to wire it up safely
Good luck with the troubleshooting, let us know how it turns out!
Oh yeah, that stuff is gross AND it sticks around forever. I got some on my glass top desk and I was picking it up for weeks. Eventually had to clear everything off the desk and just "detail clean" it :P
You can buy new OE Denso relays for the main or fuel pump for $30-40, or harvest one from the junkyard and keep it as a spare. Another option would be to wire the fuel pump through a basic relay directly to the battery in the trunk. You are still using the OE relay to flip the second relay, but at least you can buy a basic, easily replaceable 40/60/80 amp relay (and a spare) upgrade the pump power wiring AND you take the load off the factory wiring. There are details here on the forum on how to wire it up safely
Good luck with the troubleshooting, let us know how it turns out!
For sure, I'll do some research on those relays. Thanks!
I will post an update if things seem fixed or break again. If all ends up well I'll probably post a write-up on rebuilding the CAS. I can hardly find any info out there on it. If the rebuild I did works and is safe to do, I'm glad I only had to spend like $5 on new sensors So far its got like 40 miles on it, all is well. We'll find out soon...
So far....... It seems to be fixed. I've done several hot starts, and tried to recreate the issue. So far so good. It's got only like 70ish miles on it since the incident, but it's looking like it's fixed... I hope..
Welp! Looks look I spoke too soon. Car cutout on the freeway for a second then caught back up. I then brought it back into my garage for diagnosing stuff and it just quit while idling. Same issue, no fuel (so it seems) or spark, fuel pump primes. I tested the main relay. Put it on a copper plate and sprayed brake clean on it to cool it off, no fix. I did touch the fuel pump relay under the car and man does that thing get hot. I couldn't figure out how to get the thing off in time before the car was able to start up again. I'll go figure out how to take that damn thing off... Also I did clean the ignition switch the other day, looked fine to me.
Logs are attached. They are shortened version of the full ones, but I think they convey the issue well enough. Sync loss.msl is a log that captured some sort of sync loss. No reason, the car also did not buck or do anything, just a CEL then it went away.
PO left a rats nest for the ignition switch wiring. It might be fine, but I'll be redoing the wiring. Coil pack is missing a screw and is jiggling around in the carrier. Not sure if it's ok, but I'll be fixing these two issues and seeing what happens next.
I'll start thinking about re wiring the fuel pump with a separate relay for the dw200 as well.
12-22-2020, 11:55 PM
Miata dies, does not start until like 20 minutes later, no fuel/spark
0
The good news is, I put in those new hall sensors into the CAS and everything seems to be working normally so far, although a little different, have to retune. I really do hope I didn't ruin a perfectly good CAS by tearing into it like I did... 
I did recently put in a DW200 fuel pump which would make sense that the main relay is failing... But, if that relay fails, would the fuel pump still prime? I wouldn't be able to connect my laptop to the ECU while it was dead right? I feel like other things would be going awry if it was the relay. Or is it just electrical voodoo?
I know my NA will crank with the ECU sitting in my garage, but it sure as heck won't start. 
