DanBrown

iTrader: (1)

I'll try to make this short...

I recently had det occur on my 1.6. Before it finally lost compression in cylinder #2 it was running lean and asking for more fuel. (I had touched nothing, and it was asking for more fuel... I know... that should've been my sign.)
So I gave it more fuel by adding roughly 20% throughout the higher end of the table. (Was only making about 15psi, Duty cyle on the 640cc injectors peaked about 80%) But eventually they couldn't keep up.
Even after it let go it would run, but barely and I'd have to give it gas to keep it alive. I didn't run it long like this for obvious reasons.

So here's the info I've gotten through testing Coils and Injectors as well as my components/setup.
-MSPNP2 v1.3
-Walbro 255
-Flow Force 640cc Injectors
-2 large SPAL fans (wired in parallel)
-COP (toyota Denso)
-1990 chassis

First course of action was to test injectors and coils.

Injectors were sent off and flow tested.
#1, #2 , #3 tested normal, while #4 tested at about 70% of what the others did.
(I would have thought #2 would be dead, thus causing the det.)

Coil Testing Through Tunerstudio
Still on batch fire, hadn't made the switch to sequential.
Coil A - Fires Fine
Coil B - Fires Fine
Coil C - Will fire, but only with the connector from the Coil B or A plugged into it.
Coil D - Will fire normally but kicks the fans on. (Trips the Fan relay.)

Now I assume the Coil C not sparking is caused because of the batch fire style ignition set up, but I'll be clear, that's an assumption. (Hence why I'm here.)
Also this led me to chasing down why the fan relay is being triggered when ignition is firing.

I have tested the Main Relay (Fuel Inj), Cooling Fan Relay, Circuit Open Relay (under dash), the engine 15A, and all of the fuses in each fuse box. (engine bay pass side, and driver's floorboard)
All the relays click over when supplied with 12v, and all the fuses have cont.

I have read emilio's post about the main relays being mechanically moving but not connecting enough to supply current/signal correctly. While mine has clicked over, and shows no signs of melting from the outside, I can't help but think that's the issue.

So now I'm at this point.... I really just want to know if I'm barking up the right tree. Does this sound like a relay issue? Should I inspect the old ones/buy new ones? Buy new generic relays and wire the fuel pump and fans on their own circuits?
Or is it clearly something else and I'm just blind?

Any help is appreciated. Sorry if I missed any info, I'll try to fill you guys in if you need more.

--Dan.

Chiburbian

iTrader: (1)

If you are running a larger than stock fuel pump, you should do the trackspeed relay mod. The stock relay and wiring is not sufficient to power a bigger fuel pump such as you are running.

https://tarmac88.com/products/tracks...0-05-mx5-miata

DanBrown

iTrader: (1)

I have read about doing this in a DIY sense, but it's good to know there is a pay-to-play option.

I'd like to figure out the issue before blindly spending money... I know thats a pipe dream.

skylinecalvin

iTrader: (2)

Spal fans alone require way more amperage than the stock fans. I went through 2 main relays (2 spal fans + an AEM320 FP) before putting moving the AEM320 on its own relay. I've been fine for 6 months so far after separating. Main relay could show a partial failure where it's not supplying all the power it should be.

Regarding TSE's relay options, cheaper to do it yourself. Shop at BMotorsports for the connectors and relay.

DanBrown

iTrader: (1)

Plan as of now is to buy new OEM Main Relay (the better one that FM sells) and a new circuit open relay OEM.
Then build a circuit for Fuel Pump and Fans, respectively, with Relays and Fuses.


I know straight forward answers aren't assured, just wish someone could have said "Yes, that's a relay problem."

SpartanSV

Post your tune.

A relay issue is possible but it isn't something I'd be replacing without some troubleshooting.

Wingman703

If you are running batch, only A and B will fire coils. Normal MS wiring is to have Coil D running the fan relay(for ease of troubleshooting fan issues), and I can't remember what coil output C runs, but I think its something else fan related. If you plug in all 4 sparks and test, you will see two sparkplugs firing with coil A, and two firing with coil B. You shouldn't see any spark with C or D.

DanBrown

iTrader: (1)

Wingman, thank you for confirming that. When I was testing them it was just me and couldn't see, was just listening.

Icedawg

Not sure electrics are the way to go here, for the finger pointing. What about a failing pump, or very plugged fuel filter, or other fueling problem? It would read lean, and if detonation damages the engine then all following symptoms are mechanical. The final inability to run seems most closely related to your detonation damage. But may be a consequence of the main problem, not a symptom.
Obviously it is easy to check the filter.
Not sure how to test the pump without a working engine, because you need to know what happens to fuel pressure when under significant load, not at idle. I am not sure if a bench test of gph with no load will give you the info needed about the pump.

DanBrown

iTrader: (1)

The pump is relatively new, I'd say about 1k miles on it, but definitely an piece.
I'm going to a 1.8 NA for awhile and in the process doing new fuel filter and socks on the pump. Also got an aftermarket FPR to see how the pump holds up.
I've also heard that the walbro 255's like to eat stock FPR, which will then cause spikes/drops in pressure, so that could be another alley way.

Like I said, fuel monitoring on the new 1.8 will show whether pump is bust or not. And who knows maybe when I pull the sock from the tank it'll be clogged.

Chiburbian

iTrader: (1)

Dumb thought and also along the lines of what you posted above - my understanding is that the NA miatas have a fuel pressure regulator that is referenced to manifold pressure so that fuel pressure is always roughly 43psi above manifold pressure. That would make sense that your stock FPR might not be able to keep up.

Btw, I agree that throwing parts at it isn't the right way to go about it. The only reason I mentioned the relay above was because I have been stranded multiple times by my stock fuel relay going bad and if I were to do it again, I would install upgraded fuel pump wiring from the beginning. Every time my car took a flatbed home it reset the faith I had in my car to near zero.

SpartanSV

Buy and install one of these. https://www.harborfreight.com/Fuel-I...ter-62623.html

Run your fuel pump using test mode. See if it maintains proper pressure. I haven't read that pumps "eat" stock FPR. What I have read is that the stock regulator can't return enough fuel when used with large pumps which creates a very difficult to tune rich condition at idle. That isn't your problem.

More testing less guessing.

sixshooter

iTrader: (12)

This