Help! Car died. Fuel pump not priming. SOLVED: Main Relay - Miata Turbo Forum - Boost cars, acquire cats.

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Old 03-24-2012, 12:14 AM   #1
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Default Help! Car died. Fuel pump not priming. SOLVED: Main Relay

Ok so I'm stuck in the city. I pulled into a gas station to get something and when I got back in the car it won't fire. I can hear that the fuel system is not priming when I turn the key. Turns over fine but will not start. I checked the fuse and it's fine. What else can I look into that signals the fuel system to turn on? I'm running hydra 2.17 FWIW. There have been a few time in the past where when I am driving the Ecu seems to lose power for moment and the car fires right back up. Jeremy at FM said that some of the older hydras have a twitchy 5v power supply that can go bad. Id rather it not be that so I'm looking for some other things to check before takin the down time to send the ecu back to hydra for diagnostics.
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Old 03-24-2012, 12:45 AM   #2
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Ok so I plugged the wirin harness back into the stock ecu and I'm still not getting fuel, don't know if that rules out the ecu or not :(
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Old 03-24-2012, 12:54 AM   #3
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I think it does
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Old 03-24-2012, 01:00 AM   #4
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Something is blocking power to the ecu, the CEL doesn't light up when turning the ignition on
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Old 03-24-2012, 01:10 AM   #5
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Bang on the top of the tank a few times. It's worth a shot.

eh...nevermind.
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Old 03-24-2012, 04:52 AM   #6
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Main relay is shot. Has happened to me 2 times so far. The CEL and battery light should light up when you switch the ignition on.
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Old 03-24-2012, 09:27 AM   #7
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Rev- if you're right, I'll PP you $20 lol (seriously). I'm up for just a moment and will go down to the car in a bit. I had a hell of a night and took 2 Tylenol pm at like 3am....I'm going to sleep the rest of this off.

Where is the main relay again? Oh ---- why am I asking, I have sprinted FSM in the garage.
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Old 03-24-2012, 10:13 AM   #8
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Big green relay in the engine fuse box.
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Old 03-24-2012, 03:08 PM   #9
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Car is alive. Thanks Rev. I honestly wouldn't expect that to shit the bed considering my luck with breaking things.
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Old 03-26-2012, 09:18 AM   #10
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I find it quite amusing that I went to my car today, only to have this problem...again. I'm going to swap that thing out for a solid state relay.
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Old 03-26-2012, 10:12 AM   #11
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What would cause this? Why are you blowing so many?
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Old 03-26-2012, 10:24 AM   #12
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I'm going to end up buying a spare one to keep in the car....Rev is going to make me paranoide with his third relay failure lol

The failure on mine was the pin that runs to the side that gets switched...it got so hot it turned the pin blue. Maybe the diode **** out? I understand how a relay works, but don't know how one side (don't know if it's main power coming in or going out) could get that hot without flipping a fuse.
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Old 03-26-2012, 10:29 AM   #13
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Apparently all NB2s do for some weird reason. Most likely the relay is underrated.
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Old 03-26-2012, 11:48 AM   #14
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The B6S8 relay from the NA is a interchangable part. I wonder if its construction is any better since it is a different mfg.
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Old 03-26-2012, 11:53 AM   #15
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I'm thinking more like that the NB2 has more current passing through the relay. Not that the relay itself is bad. Just not capable for the amps that flow through it on the NB2.

Or it could be the specific make/model of the relay as you've said.
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Old 03-26-2012, 04:00 PM   #16
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I'd be curious to hear other chime in of having relay issues as well...and if they are on the stock ecu or aftermarket.
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Old 03-26-2012, 04:02 PM   #17
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The first time around I was still on the stock ECU. I know at least 2-3 other cars that were on the stock ECU (but had band-AIDS on them, ie Powercards).
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Old 03-26-2012, 04:29 PM   #18
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Interesting. This is my first dealings with having a main relay having issues.
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Old 03-26-2012, 10:46 PM   #19
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Keith Tanner had the main relay fail on his V8 Targa car during the event last year. In this post he seems to suggest that it's a not-infrequent failure on Miatas of all vintages:

http://www.flyinmiata.com/projects/t...ld.php?UID=212

--Ian
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Old 03-26-2012, 11:34 PM   #20
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Quote:
Originally Posted by Doppelgänger View Post
I'd be curious to hear other chime in of having relay issues as well...and if they are on the stock ecu or aftermarket.
I'm going to look into solid state relays (noob w/ electronics). I've spares in the trunk now at all times though.

I actually haven't had one die on me (stock ECU everything), I thought it did though one time. Wasn't getting power to fuel pump, picked up a relay from Alex/2ndchanceroadster but while there, tested mine on his race car and it started up fine. Went back home and his relay worked on my car.

Days later, fuel pump dies, but wasn't the pump. The fuel pump assy wiring burnt a hole the ground wire to the FP, the plastic clip crumbled (literally) trying to pull it out. The positive wire was perfectly fine. As I said, I'm a noob w/ electronics but i'm guessing it has to do w/ the relay... maybe sennding too much power, overheating the ground wire? There's a burn mark on the plastic that the interior fuel tank wiring plugs into..
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