jrmotorsports55

Again, why I bypassed the Miata relay and am running off the Ford relay.

Lateralgeez

Apparently he drifts it! Can't imagine how awesome that must look.

But what yellow relay? The big one in the engine bay fuse box is black. Looks like I'll have to do some research on the matter because those things aren't cheap.

Oh ok thanks Jason now I get it. Just need to find it and... :/ I hate wiring.

charchri4

Yeah they are cheap you can buy them new on ebay for less than 15 bucks shipped but I usually get used OEM ones either on ebay or for a couple bucks at the you pull it lot. I never leave the you pull it lot with out a fist full of fuses, light bulbs and relays!

It's called the main relay and it's in the fuse box under the hood by the wiper motor. Some are yellow, some are black and some are green but they all do the same thing and there is tons of interchange across Mazda and other Asian cars.

It's fed with an 80 amp fuse which is an insane amount of current to run through that light of a relay. The fools that designed the car to need a relay closed to run (thus energized all the feeking time) deserve to be left on the side of the road for their own stupideness! I am not running my fuel system through it anymore either but it still runs a lot of stuff and will leave you on the side of the road WHEN it toasts.

The only up side is I break the clip off it so it's very handy to pull that relay when I park at a hotel over night and pretty much the only security measure on the car. That and when you turn the key and it doesn't start it's an easy first thing to check. In other words it has no redeeming value what so ever!

Lateralgeez

Ok I was on the side of the road and this guy in a first gen rx7 pulls up. He noticed another relay that was the same size and swapped them out. He saved me a tow.

The question is how to reroute it and what size wire to use. I'm way over my head already but it's high time I learned about wiring.

1. Is there more than one relay that size on the ford harness
2. after I do all that it can still blow?

Thanks for the pull a part tip

tbone heller

If you are having to keep replacing the same relay over & over again, you have a serious electrical issue. Relays don't just go bad.

Lateralgeez

Yeah it was new, lasted 10 miles and a burnout. I may have screwed something up during the NB dash swap.

Atlanta motorsports park is pretty awesome. Did a 1:11.2 on the cart track but it took 30 min lol. The elevation changes and blind hills make it more like a mountain road than a track. Late afternoon sun will blind you on two corners.

You Atlanta guys have it good there isn't a straight road anywhere that's including i-75! St route 53 to AMP is fun too.

Turns out I missed the Alpharetta meet and won't be here for the Gwinnett one.

Lateralgeez

Well I should be happy to find something but kinda want to soak the whole car with gas and torch it.

Behold the charred remains of the starter wire. Resting against the cylinder head was bad for its health.



So instead of a butt ton of butt connectors I could solder and heat shrink each one...

Sometimes I would try to start it but nothing would happen when I turned the key. It always cranked after a few tries.
Is it even possible that this short could blow the main relay? I don't know crap about engine wiring.

MX-Brad

That could 100% be the cause of the blown fuse. Glad you found the problem. I'd be going through all the wiring on this car to look for any other potential future problems.

Lateralgeez

I think this was my own ignorance, I had the starter out while fitting headers. Anyways, only one 18ga wire was melted through so it turned out ok. Tbone you're a life saver.

Lateralgeez

Now it cranks but won't start. The fuel pump makes a strange noise when it primes. Here is a video for sound but its really quiet so turn up volume.

tbone heller

Glad you found that before you went up in flames. I covered all of my battery cables in the engine compartment with some fireproof heat sleeve that I got at a racecar supply place.

Lateralgeez

Good suggestion! I hate how harnesses typically look so messy.

First I'll test voltage at the pump.

If it's too low...
I've got a terminal, relay, switch, 12ga wire for the pump & 18ga for the switch. This is to direct power from the battery to the pump.

tbone heller

I did away with all of the Mazda wiring & wired the fuel pump to match the Ford diagrams. Makes it much easier to diagnose a problem.

Lateralgeez

I may have screwed something up with the dash conversion.

https://www.v8miata.net/v8-miata-wir...uel-pump-1429/

Unfinished business:
I had to cut the power and ground to Autometer tach in order to remove it.
I had to cut a red wire somewhere else because it was looped around the dash support bar.
I can't find the other wire for the volt meter.
So ya I keep shooting myself in the foot.

Seems like all my problems are self induced. That said, do you have the ford pump wiring diagram tbone?

tbone heller

I do, but don't know how to post it. I can text you a picture of it if you p/m me your number.

Lateralgeez

So last night in an adderall induced hyper focus I poked through every wire in this scrap heap. Found at least 5 open ended wires not taped. Maybe they aren't part of a powered circuit and it's ok.

Lateralgeez

Got some used 12v 20amp relays from the yard. The pump seemed to work a bit harder but not enough to start. Nowhere near it's typical walbro noise, still pulsing.

I found an odd looking 5 pin relay on the Ford harness. Kinda sorched and very dirty. Not sure what it is.

Lateralgeez

Looks like it is the Ford fuel pump relay (bottom right corner). Because it only uses 4 pins of the 5 pin relay. If they wired the Miata pump through this relay, then it could be the problem.

However, this diagram is for 88-91 not 87.

Lateralgeez

Here's another diagram (thanks tbone!) The fuel pump relay is dead center. Again, mass air 5.0 but it shouldn't be too much different.

Lateralgeez

Found a speed density EEC diagram!

Lateralgeez

And some more gold. Should keep me busy for a bit.

Lateralgeez

And what I should have got before I even got the car... factory service manual.

http://www.mellens.net/mazda/index.html

jrmotorsports55

That looks like the EEC power relay.

tbone heller

I have a Ford 1988 Mustang wiring book (EVTM) if you need some info. In 1987 & 1988 the 5.0 Mustangs came with speed density (except for California models).

What is the issue that you are having?

Lateralgeez

It must be the eec relay going by wire colors. However, a parts store fuel pump relay fit... still won't start though.
Don't see the fuel pump relay anywhere

Engine turns over but won't start. Fuel pump is much quieter than normal and makes a low pulsing noise instead of loud whine.