Special K Posted February 22 Report Share Posted February 22 With hat in hand, I swallow my pride and refer my troubles to the forum gods for help. Finally putting the 2000 miata back together. After reconnecting all the wires and crap to get the harness under the dash put back in, the fuel pump isn't switching on and priming. Everything under the hood was put back together after the engine was rebuilt and put back in its home. Plugged the old fuel pump in and it's not doing poop either. My question is this.... what in the fanciful hell did we miss?? After clambering all over the car, annihilating the tops of our heads on bars and sharp things, ruining my back and overstretching my groin, I can't figure out whats missing. Is there a commonly missed plug or ground somewhere? Or some ridiculous nonsense part that will cause the car to give me the finger until it's reinstalled? We never had this issue with the NA and its been apart a couple times. The relays were never removed and the car ran perfectly fine before its days of transporting two twin men around town in Marlboro Man level coolness came to an end. So the likelihood of something being broken or failed is next to none. Quote Link to comment Share on other sites More sharing options...
Team Infiniti Posted February 22 Report Share Posted February 22 (edited) Have you gone back to the basics yet?Verify power and ground present at fuel pump when it’s expected to run, see what leg is missing, follow diagrams to the problem. Edited February 22 by Team Infiniti 2 Quote Link to comment Share on other sites More sharing options...
mender Posted February 22 Report Share Posted February 22 Wire in a switch and turn it on manually. Get it running again then decide if you want the ECU to run it. Quote Link to comment Share on other sites More sharing options...
ben 594 Posted February 22 Report Share Posted February 22 @Special K, @Team Infiniti and @mender are both better mechanics than me. heck a monkey with a wrench is on par with me. What ECU do you have in the car? I have had problems on my NB running an aftermarket ECU. We've zapped an internal in the aftermarket ECU to where the generator wont charge, then a different time to where the injectors wont fire... headaches. If your running an aftermarket ECU, please try a factory one real quick to before you rewire the car. I am yet to have a problem with a factory ECU. Quote Link to comment Share on other sites More sharing options...
ETR Posted February 22 Report Share Posted February 22 I’m pretty sure the 99-00 ecu does not prime with key-on. Is it also dead while cranking? Quote Link to comment Share on other sites More sharing options...
MMiskoe Posted February 22 Report Share Posted February 22 Here's what I can tell you. Two fuses that could be the issue - one small one under the dash and one big-ass one under the hood. Did you try the data link connector? (the black thingy under the hood with a flip open cover and a bunch of places to plug crap into) There is a terminal on that block that if grounded, should run the fuel pump when the ignition is on. If this triggers the pump, then it is a connection between the relay and the ECU. Sorry you'll have to look up which terminal, I simply marked it in paint marker so I don't have to look anything up and I'm at work the car is at home. The signal to trigger the relay is on the ground side, the relay should have 12V in at two pins, 12v out (switched) to the pump and a signal wire to the ECU. The signal wire will complete the circuit when grounded. You should be able to hear the relay click. I am not sure where the FP relay is in that car, in my 2002 it is at the B-pillar on the passenger side. On the NA's it was under the dash, not sure about yours. I disagree that the pump won't prime when you turn on the key, I think it does, I can check. I have a 99/00 street car sitting in the yard. I don't think that car has an "immobilizer", the NB2's did, don't know about your NB1. If you have one and it isn't plugged in you'll be SOL. If the pin-out of the ECU I have is correct, it should be pin # 3N (biggest of the three plugs, 7 pins in from either end). "LG" wire which should be some variation of green. The plug is 2 rows, opposite your "LG" wire is one that is "O" In my experience, it is usually a wire problem, not an ECU problem. Unless you re-wired something backwards and powered parts of the ECU that shouldn't be powered, but that's still a wiring issue. No shame in asking. If you took that harness out then put it back in, you're a brave man. 1 Quote Link to comment Share on other sites More sharing options...
MMiskoe Posted February 22 Report Share Posted February 22 Found a different diagram. Fuel pump relay should be up under the dash, left side. Wire from the ECU to the relay is green. Did you check to see that you've got spark? If not you may not be getting power in/out of the ECU. Quote Link to comment Share on other sites More sharing options...
ETR Posted February 22 Report Share Posted February 22 33 minutes ago, MMiskoe said: I disagree that the pump won't prime when you turn on the key, I think it does, I can check. I have a 99/00 street car sitting in the yard. It does not in the oem ecu. I have a couple 99/00’s myself. I set my standalone ecu’s for 3-5 seconds of prime because I like it. Quote Link to comment Share on other sites More sharing options...
T-PAP Posted February 22 Report Share Posted February 22 (edited) I haven't read all the replies yet so bare with me. I swapped out the main relay under the hood just to check that off the list. No difference. Then I jumped the pump via the diagnostic box under the hood, turned the key to on, and the pump turned on. Still not cranking though. Also stock ecu is in. No aftermarket electrical stuff anywhere. Only aftermarket is the Deatschwerks fuel pump which I just got to power on. Edited February 22 by T-PAP Quote Link to comment Share on other sites More sharing options...
MMiskoe Posted February 22 Report Share Posted February 22 So if the pump triggers with the diagnostic port it is either a function of the ECU signal wire not making connection from FP relay to ECU or the ECU doesn't know the car is cranking. Check that you get spark when you're cranking. If not then sort out why the ECU doesn't know it is cranking. Not sure if it decides to go based on cam sensor or crank sensor, or both, but they're all it needs to know the thing is trying to start. 1 Quote Link to comment Share on other sites More sharing options...
Hugh Jass Posted February 22 Report Share Posted February 22 Make sure you did not wire the power and signal wires on the crank sensor backwards, that will make it not spark. Quote Link to comment Share on other sites More sharing options...
T-PAP Posted February 22 Report Share Posted February 22 Got it to finally turn over. Everything is pointing to the fuel pump relay. I have a few more things to button up before I actually start it but I think I've got it sorted out. Thank you guys for all the help! We would have been stuck on this for days on our own haha Quote Link to comment Share on other sites More sharing options...
MMiskoe Posted February 23 Report Share Posted February 23 If jumpering the diagnostic box runs the fuel pump, it isn't the relay. All that diagnostic port does is to ground the relay, which is the same as what the ECU does. 1 Quote Link to comment Share on other sites More sharing options...
T-PAP Posted February 23 Report Share Posted February 23 (edited) Ah....ok. Somewhere I read that it did, and somewhere else said it didn't. Sorry for my ignorance, wiring is the one thing I hate dealing with. I'm wondering now if I just have a grounding issue somewhere I can't find because I have no continuity on the fuel pump connector. Are the 2 grounds that are originally on the factory dash bar tied into this stuff or are they just for the radio and misc buttons on the dash? Edit : Those 2 grounds are on bare metal so regardless of what they're for, I don't see that being related. I can tell you though that I do not hear that relay click at all. I have no dash and no windshield so I can get my ear right next to it and the only thing that clicks in that group of 5 relays is the flasher relay. Edited February 24 by T-PAP Quote Link to comment Share on other sites More sharing options...
MMiskoe Posted February 24 Report Share Posted February 24 Is it a ground issue? Most likely. Most issues are. Are the two grounds under the dash part of it? Yes. My experience is that the car has grounds all over the place but also has ground wires tied together. I don't understand it. Sorry if I missed it, but do you have spark when you crank? If not then it seems that the ECU doesn't know the motor is spinning, thus not triggering the pump to run. If the pump runs with the diagnostic jumper, then the FP circuit is good, it just isn't getting signal to the relay (grounding the signal side of the relay). If you can, have someone jumper the diagnostic plug while you listen to the relay to confirm what you need to be hearing. If you want to take this offline, PM me and we can email diagrams. I feel your pain. 2021 season was fraught with wiring issues, in the end I rewired the whole car from the cab forward. I learned a lot, it would be cool to let someone benefit from that learning. 1 Quote Link to comment Share on other sites More sharing options...
Hugh Jass Posted February 24 Report Share Posted February 24 56 minutes ago, MMiskoe said: in the end I rewired the whole car from the cab forward. I learned a lot, it would be cool to let someone benefit from that learning. There is more than 28lbs of wire in a Miata, after years of issues, I cut it all out too and started over, best decision ever. Quote Link to comment Share on other sites More sharing options...
T-PAP Posted February 24 Report Share Posted February 24 @MMiskoe PM sent. Thank you! Quote Link to comment Share on other sites More sharing options...
tommytipover Posted February 24 Report Share Posted February 24 15 hours ago, MMiskoe said: Is it a ground issue? Most likely. Most issues are. HaHa, that should be the first sentence of any wiring/diagnostic book. Wonky ignition switches have also sent me on some wild goose chases as well. 1 Quote Link to comment Share on other sites More sharing options...
Special K Posted February 26 Author Report Share Posted February 26 (edited) Ok. After fiddling with it today for a couple hours, here's what happened. -New fuel pump relay -Found power going to the relay but the relay wasnt doing anything -Traced entire harness 3 times from mass air sensor, through the injectors and coils and to the relay -Checked all the grounds -Got pissed off -Offered to sell the car to future sister in law -She didn't want it -Stared at the car and contemplated the life choices that got me here while searching my dull life for meaning -Said screw it, let's see what happens when I put the Supermiata clutch interlock override in -Fuel pump came on when the engine turned -Final result.... one of two things. 1) Me and T-Pap are idiots and should enjoy racing from a distance 2) Clutch switch was bad. The pump never turned on the other day with the clutch in and no override installed. So who the hell knows. But it works now Edited February 26 by Special K 2 2 Quote Link to comment Share on other sites More sharing options...
MMiskoe Posted February 26 Report Share Posted February 26 Good. It Runs. So was it not cranking before or just not starting? My opinion is that over-riding the clutch switch comes right after removing the steering lock from a racecar. If I'm stalled on track, I'll gladly abuse the starter to hop the car out of harms way in 1st gear using the starter move it along. My guess there could be a very long thread about huge amounts of work done, races lost, money spent because of a mis-diagnosis or small detail overlooked. I know I did a complete motor build once when I thought I had a rod knock, turned out it was a bad input shaft in the transmission. 3 Quote Link to comment Share on other sites More sharing options...
Special K Posted February 27 Author Report Share Posted February 27 20 hours ago, MMiskoe said: Good. It Runs. So was it not cranking before or just not starting? My opinion is that over-riding the clutch switch comes right after removing the steering lock from a racecar. If I'm stalled on track, I'll gladly abuse the starter to hop the car out of harms way in 1st gear using the starter move it along. My guess there could be a very long thread about huge amounts of work done, races lost, money spent because of a mis-diagnosis or small detail overlooked. I know I did a complete motor build once when I thought I had a rod knock, turned out it was a bad input shaft in the transmission. It was cranking, but the fuel pump wasn't coming on. It's coming on now. Why? No idea. Maybe the new relay, maybe the override, maybe the universe got tired of watching two clowns fill the air with so much profanity that it hung over the house like a cloud and blocked out the sun. This is the first car we've torn apart with a clutch interlock. I'm a bit confused as to why the fuel pump did NOT turn on with clutch in, but DOES turn on with the override installed. I would think if the clutch switch was bad, it would never have cranked in the first place. Quote Link to comment Share on other sites More sharing options...
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