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trying to startup my rb25


bryan01

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so i bought a rb25det w/ tranny and full harness, all accessories and sensors, and computer. it's currently mounted in the car, but i cant get it to turn over. i've gone thru the wiring sticky above but most of that is how to hook up gauges and the like. all i want to do is get it to turn over once before i move (december 10th).

 

i called a shop to see if they could help out and they wouldnt touch it b/c i had removed the stock wiring from the z car. what does not having the dash wiring or the rear tail light wiring (even thou i think that's still in the car) have anything to do w/ starting the skyline motor? shouldnt the rb25 be able to turn over and run with only the rb25 wiring harness, sensors, and ecu? i found the main power, ign, and starter wires on the interior harness section via the wiring sticky. wiring them together how i thought it should go didnt work (i dont have the wiring coming off the ignition as of now so i couldnt wire it to the key like in the sticky) so i was just going to make it a switch and a button, but i cant even hot wire it ...? i've hardwired the pump to a switch but like i said the motor wont even turn over so it doesnt matter if it has fuel or not yet. i then tried jumping the starter directly and it sounded like it was spinning but not engauging the flywheel. just about everything on the harness is hooked up (except headlights etc and then the white dash plug on the interior).

 

any ideas?

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i like how i'm replying to my own questions.

 

anyways, i got it to crank/turn over, it's just not starting. one step away...more or less ... the first time it turned over i found an oil leak in the oil filter gasket, so i replaced that and it's ... cranking ... fine ...

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Wish I had some good info to give you, but I'm lost when it comes to the RB oem wiring....

 

Just keep pokin at it, you'll get it. Have you thought about trying RaceBread.com or Nico? There are quite a few guys on those boards that have the rb25 in their cars....

 

Anywayz... good luck to you.

 

 

j.

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would have offered you help sooner but rarely come to the Rb forum now..

 

anyway, Okay so you got it cranking. in order to start the engine, you need: Power. make sure the ECU, MAF, CAS, all six coilpacks, and the ignitor are getting power. If all of those check, then check if fuel is being passed through the fuel rail ( you can actually hear the fuel when the fuel pump turns on). Last, VISUALLY check to see if there is spark from the plugs by pulling the coil packs and putting a plug in it. Have a friend crank the engine when you check for spark. if they all check ok, then it should fire. let us know if it doesnt.

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thanks for the help, i just got it to fire. but it wont stay on. i realized i didnt have an eccs and ign relay plugged in, so i got some at the local parts stores and wired them up. when i hit ignition wire to power i heard both relays click on, but when i hit the starter to that, nothing happened. so i left the ign on power, and went under the car and jumped the starter. well it fired and scared me to death. all the dust that's collected under the car, and little bits of metal from welding etc etc all flew out of the garage and i thought my ear drumbs were goin to pop. it'll fire once or twice over every time i jump the starter but it wont keep going. any ideas? one of my friends helping on it says if i can figure out why i cant hot wire the car i will figure out how to start it. and keep it started.

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if you were to take a test light and hold it to the soldered back of the ignition switch or go even from the ignition switch's plug and go from wire to wire and turn the key to run position you'd see a couple of em get hot, but when you go past run into the start position you see it's no longer hot, that's not the ignition wire you want, that'd be something you'd want for like the radio, so it wouldn't pull any voltage when you're cranking the car but soon as you're done cranking and the car's running it comes on, what you want is a true ignition wire which will stay hot even in the start position. double check your ignition source.

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i checked the ignition and it's good. i actually ended up rewiring everything i had already done just to check my connections. one interesting fact though, i previously had my fuel pump wired independently from the computer, but decided that maybe the ecu wouldnt let the car run w/o knowing there was a fuel pump hooked up. when i jump the starter with the ignition on it sounds like it starts then something cuts it off. anyways, i hooked up the switched ground like in the wiring guide that goes from the ecu to the fuel pump (black/pink) which is supposed to turn the pump on when the ignition is on, but it wont turn on the pump. maybe i'm missing a ground on the other side of the ecu?

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i checked the ignition and it's good. i actually ended up rewiring everything i had already done just to check my connections. one interesting fact though, i previously had my fuel pump wired independently from the computer, but decided that maybe the ecu wouldnt let the car run w/o knowing there was a fuel pump hooked up. when i jump the starter with the ignition on it sounds like it starts then something cuts it off. anyways, i hooked up the switched ground like in the wiring guide that goes from the ecu to the fuel pump (black/pink) which is supposed to turn the pump on when the ignition is on, but it wont turn on the pump. maybe i'm missing a ground on the other side of the ecu?

 

 

somethings wrong with the fuel pump wiring. If you ground the wire thats going to the fuel pump does it come on? Im assuming that you hooked up the pump sp that the positive is continuous power and a ground switches it on.

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yes if i ground the fuel pump myself and wire it directly to the battery and turn the switch ON the pump will turn on. when i use the switched ground black/pink wire that is supposed to switch on the pump by grounding it when the ignition is on (instead of using a realy i just put a switch inline of the ground like i did when i wired it directly to the battery), however, it doens't work.

 

i'm going back over the alternator hook ups tonight. does the interior start wire (grey/red) go thru the ecu to the alternator and then to the starter or does it go directly to the starter from the ecu? i might have mixed up my alternator connections ... but that wouldnt exactly expain (i dont think) why the fuel pump wont turn on when i use the actual fuel pump switched ground wire to the ecu.

 

i'm sooooo close i can smell it. thanks again for everyone's help so far, this board is awesome

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i was finished with this guy's s14 sr20 and he was still waiting on the ecu, so he borrowed one of my friend's and i finished and everything worked, then my friend needed his back so he borrowed one of his friends...when i hooked up his friends ecu it wouldn't start, it wasn't getting any fuel, but i know everything was correct because with my friend's ecu it started right up, so i called the kids friend and inquired about the shop that did his swap, did they hard wire the fuel pump into ignition, and he said they did, anyways, the fuel pump circuit in the ecu may be fried, you can see if when you power up the ecu (turn the key on) the fuel pump wire get's a ground, or see if you can borrow a friend's ecu, if not try hardwiring your fuel pump

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That's what I would do, if the ecu is not working the pump, make one side of the relay to ground and use a "hot when on" to turn the pump on with the key. When using the ecu it will turn the pump on for 4 seconds to pressurise the fuel rail, then turn off until the motor rotates, then will turn back on. Wired directly it will run constantly with the key on.

Chris Rummel

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