"New" RB20 Won't Start (And Now Won't Stop!)

[Lethal240SX93]

I've finally got my swap all finished up. RB20 into 93 S13 auto. Went fairly well overall, but now it just won't start. Cranks, no attempt to fire. Checked for codes, only 55 (no problem). Fuel pump works. It has fuel at the rail. Pulled CAS and could hear injectors firing when turning it by hand. Unplugged MAF, no different. Sprayed carb cleaner into the intake and she ran just briefly till all the carb cleaner burned up. Ok so it must have spark. So no fuel? I put in an ISIS 255lph fuel pump and a used Nismo Type-A AFPR with the swap. I didn't have a gauge when I installed it, so I was hoping the previous owner had the regulator adjusted in a good spot. Maybe not. Got a hold of a gauge and put it in line before the regulator. Yikes, 85psi (pump on, engine off, vacuum line on). Tried turning it down but wouldn't go any lower than 80psi. For the heck of it, I tried putting the stock FRP back on. Now it's up to 90psi. Checked fuel flow to the rail. Fills up a bottle very quickly. I'm thinking the pressure is just too high for the injectors, either they physically can't open or the fuel blows right by them. But why? Why doesn't the AFPR limit the pressure?

I guess my next step will be to check fuel flow out of the rail to check for possible clog. I didn't have fuel problems with the KA so there shouldn't be a clog in the lines to the tank.

Also might put the stock fuel pump back in just to see what difference that makes.

Now that I've gotten to clear my head a little bit, I'm pondering something. Was I right by putting the fuel pressure gauge in the feed line before the regulator? Or should it be in the return line? I'm used to working on returnless systems, that's why I'm unsure now that I think about it.

Any other ideas/suggestions? This seems really strange, but maybe it's just me. It's been a long couple weeks lately, maybe I just need sleep

[ST240]

The feed line becomes pressured in front of the regulator, so yes thats the right spot for it.

[Lethal240SX93]

Alright that's what I figured made the most sense. I just didn't take a moment to think about it while I was actually doing it. Unfortunately that means the pressure readings are correct lol.

[Funktown240]

Take the gauge off and connect the feed line directly to the rail, your not getting any fuel to the engine. The stock regulator should be fine.

[Lethal240SX93]

That is exactly what it seems like. Do you mean hook the feed line to rail without the regulator somehow? The gauge I was using was strictly for diagnostic, not meant to be left on there all the time. I did just order a gauge to install into the line permanently. I had it in the feed line between the filter and the regulator. So before I hooked it up, the feed line went directly from the filter to the regulator. Are you implying the gauge itself was the blockage or cause of high pressure?

[Funktown240]

That's your problem, the feed line is supposed to go straight to the rail. The regulator is on the return side of the fuel. If you have the feed line connected to the regulator it WILL NOT let fuel enter. Switch your lines.

[Lethal240SX93]

Dammit you're right. I don't know how I did something that foolish, and then didn't even catch it when I was messing with it!

This car has seriously drained every last ounce of energy from me, not to mention I just had my second kid 2 weeks ago. I can't wait to get this thing done so I can sleep (sort of) lol.

I won't be able to touch the car until tomorrow evening. I'll let everyone know what happens.

[Lethal240SX93]

Sure enough that was the problem. Fired right up. Set fuel pressure properly. Runs like a champ!

Only problem now is, it doesn't stop running! I can turn the key off and take it out of the ignition and the motor doesn't shut off lol. Not sure what the problem is. I imagine it must be in the converted wiring. Would that be the black/red wire that's ignition control to the ECU?

[Funktown240]

Can't help you there. Lol, sounds like the wiring.

[Lethal240SX93]

Yeah it definitely seems like an electrical thing. I've gone back and rechecked my wiring. It matches the "Wiring Guide for Dummies" exactly. So I checked the black/red IGN wire to the ECU. There's no voltage with key off, battery voltage with key on. I've driven it a couple times now, and it is shutting off, but not properly. The fuel pump is the only thing that shuts off when the key is off. So have to wait for the engine to stall from lack of fuel. The two green relays near the ECU do not shut off until it stalls. That can't be right. I've found an image someone drew of the relay wiring.



The ECU controls the relays by grounding the orange wire, pin 16. But for some reason it keeps them grounded with key off until it stalls. Is the ECU supposed to open the ground when the key is turned off to shut the engine off? Otherwise, how does ECU actually shut down the motor? Surely it is not supposed to stall from lack of fuel.

Or, should the white/black power wires to the relay coils be ignition swithced like in the diagram? Because that's not the case. They have 12+V all the time like all the other white/black wires. They all have continuity to each other, starting at the white/black wire used in the conversion wiring at the fuse box.

[S13Gene]

Sounds like something is having power after ignition is turned off. how long does it take to completely shutoff? Sounds like a sticking relay, try swapping them and see what happens.

[Lethal240SX93]

Yeah exactly. I would think those relays are supposed to shut off immediately with key off. On average, it takes about 10 seconds to shut down after removing the key. And it's not an actual shut down, it's a lack of fuel stall. The white/black wires to the relays have battery voltage all the time. And I've monitored the orange ground wire after key off and it stays grounded by the ECU. So the question is, is the orange wire supposed to be ungrounded immediately, or should the white/black wires to the relay control coils be ignition switched?

[worx2323]

100 bucks says its the engine cont fuse under the hood. take that thing out and throw it far far away and never worry about it again.


well its not the fuse, its the circuit. Its for all the dumb KA s*** that 99% of people clip off the stock harness. Take the fuse out and everythings solved.