I've had issues with this relay too.

Same symptom, no ECU power (no CEL when keying on).

Replaced the relay with a new one, old one tested fine. Assumed the relay intermittently failed.

Had the same issue pop up with the new relay.

Ended up that the contacts for the relay in the box were a bit wonky. Move the relay around a bit, and it would work. Tightened them all up, all has been well since then (9ish months ago).

Would you ever have an issue with the car is driving? i.e. Cruising along and the tach dithering or the car just stalling out while sitting still?

If you were referencing me, yes, I did.

Sometimes just the right bump in the road would give a quick stumble and the tach dropping to (or attempting to drop to) 0 RPM. It would always just be a quick on/off, never stalling out fully (would restart by itself).

I have had that too. But I've also had it happen when stopped. That .25 seconds is enough to make you look a fool at a stop light :facepalm:

Here is the weird thing for me. When mine crapped out, I took one out of a friends MSM and my car fired right up. SO I left the house and not but 10 minutes later, it did a quick cut off/on while crusing. This relay never did it in the MSM, but did in my car. I wonder what is up with that. I wonder if I should look into the wiring/power supply on the signal side of the relay...maybe something in the ignition cylinder?

I've experienced the SAME exact symptoms as everyone else in this thread! I have a 2000 NB and I pulled the B5B4 relay today and took the top cover off to manully engage the relay and it shows continuity. I also plugged the relay back and watched/heard it click over. So everything points to a good relay. However upon closer inspection it looks like the plastic around "ON" pin has slightly melted.

[IMG]https://www.miataturbo.net/attachmen...ine=1403564080[/IMG]


I'm going to try another relay and see if my car starts up and double check to make sure that the terminals are clean and making good contact.

Has anyone found an upgraded relay?


-B

*knock on wood*

I have not had a problem with mine since I started this thread, nor I have not heard of any better quality relays though. That one in the pic is definitely bad.

UGH!!!! My car died on the freeway again even with the new relay! I wonder if it's possible to bypass/jump the main relay with a paper clip or to get me going?

-B

I played it safe and had the car towed home. When I yanked the mainly relay it was REALLY hot! I'm assuming it's handling too much current and something inside fried on the new relay.

The only thing that I can think of is the Toyota COPs and maybe the Deatsch Werks DW300 320lph fuel pump pulling too much power?

I also took apart the new relay and discovered that it's a solid state relay! So in theory it should be able to handle a higher load.

https://www.miataturbo.net/attachmen...ine=1404423360

-B

I know this thread is old, apologies for the massive thread revival.

I've been having this issue lately as well, stock ECU (car is a '95 1.8 Eunos). I've gone through probably 5 relays in around 8mths (both the black Denso and green Imasen kind). I have a temporary fix/bodge wired in from the fuel-loom to a permanent live in the fuse box so when the relay dies, I can just plug it in and get the car home again. Symptoms usually involve a sudden misfire, tacho needle dropping and usually the aftermarket temp gauge shooting up to 90deg (OEM gauge doesn't move though so assume the temp isn't actually changing) followed by a complete loss of power. When I pull the relay out it's hotter than the Sun (no scorching/melting marks though).

I'd like to get to the root of the issue instead of just buying new relays all the time. Any ideas? An auto-electrician at work guessed something is drawing more power than it should be but said it could be expensive/time-consuming trying to problem solve. Anyone have a good idea of where to start?

I had a similar problem a few years back. I don't have the diagnostic equipment to determine the loading but my empirical information was exactly that - that I was drawing too much load through the relay, causing it to overheat and not function correctly.

What seemed to be the problem was that the (mechanical) relays would get hot enough so that the support for the contacts would move far enough away (due to heat-loading?) to make intermittent, or no, contact. I only "know" that because when my relay "failed" I took it apart and used pieces of paper as shims to move the support arm enough to get the relay to work again.

Since then I created a heat-sink from an old computer CPU and cut an opening in the fuse box cover for the heat-sink to poke through. That made it better - as in fewer no-start conditions. As a fail safe, I ran some heavy-gauge wire from the fuse block to a heavy-duty switch in the car interior. When (if) the relay flakes out, I simply remove the relay, plug in the spade lugs on the wire ends into the appropriate places, flip the switch and away I go (I just have to remember to turn the switch off later).

Of course, since I've done all of that, the latest relay hasn't "failed" in over a year!

....and a month later, the relay shit out on me. Awesome.


blown33- where'd you get that replacement/ss relay?

Add me to the list. I just had my second failure in 4 months. Went to go start the car and nothing. Same as last time and same pin as others here.

Must be overloading with either:

- AEM 320lph fuel pump
- Zeitroinix ZT-2 with EGT, AFR, MAP, and Coolant temp

....and mine is dead again.


Curious to order a new one from Mazda to see if it's the solid-state like the one pictured above. Fucking thing is $83.

I'd just like to say: Whichever mod changed the thread title, I like it. That should be a thing.

DG - I hard-wired my AEM 320 pump with it's own 40a relay and I haven't had any issues since with main relays. I think the issue may be due to fuel pumps that draw more voltage that the system is designed for. Are you running an aftermarket fuel pump?

You can also try the 80a drop-in replacement I am currently running. Part number JE16.

I got fed up with this too.

Took a fried one, gutted it except for the diode, did a major clean up on the terminals. Soldered wires to the cleaned terminals, passed them through a hole in the case. On the other end of the wires I mounted a standard relay base with a $4 relay. The wires I made long enough to exit the fuse block and mount the base to a nearby 6mm bolt.

No relay failure since and I keep a couple of $4 spares in the glove box.

AFAIK- the pump was stock up until this past Sunday when I replaced the dead stock unit with a DW. I think this failure was just bad timing and not related. If I could up the amp rating on the relay, would it be safe to do so?
The one that died didn't look bad/melted...it was even clicking with the key on/off, likely the diode is dead.

Looking around on the web, it seems some people have the problem regularly and others never have it. Who knows what idiosyncrasies are involved here...

No problem upping the amp on the relay, that just refers to its ability to pass and switch current.

I had one that clicked just fine. When I pulled it out and disassembled it I found that the contacts were so badly burned that there was no connection. When I cleaned those contacts it worked fine for a few months.

Your observations around the web are astute. I've known guys with stock cars have repeated failures and guys with heavily modified cars have no problems (and of course, vice versa).

I like Barbycar's solution. Use a bad one as a plug, make good soldered or crimped connections to a base plug, and buy a bunch of cheap relays in case it burns out. Seems like the problem would be solved then, or at least the cost of the repair greatly reduced.

Well, the Mazda dealer by me wanted $73 for one, Arlington Mazda online wanted $19. So I ordered 2. I might temporarily wire in a generic 30A/12V relay in until they get here....or modify the 2(if they aren't SS) and see how the wired-solution works.