250ZR Posted November 10, 2009 Share Posted November 10, 2009 Ok guys so its a bit of a copy and paste thread but i am just asking around and since i got pretty much this far with my RB25 Z31 200zr (250zr now) with the help of all your documentation on RB swaps. I'm hoping someone has come across this or has a some thoughts and theory on it. the problem i just can't rap my head around. I has just installed an RB25det out of an 95 r33 gtst into a Z31 and everythings completed bar the fuel pump. we've determined that the ecu and motor are actually series 2 items as the wiring has only 1 ign relay and 1 large white dash loom plug as apposed to the earlier models. when attempting to wire in the Z31 fuel pump to a relay controlled by pin 18 "fuel pump relay" (which is supposed to be a switched earth) on the r33 ecu nothing happens...we chucked the multimeter on it and got 4V for 5 seconds on accessories and then 0 untill the motor was cranked and get another 4V again. This seems the reverse of what i want??? as the ecu should earth ignition power through the relay into pin 18 not provide it... but we also realised that our relay needs 10v minimum to close so with a really expensive relay that trips on 4v and can hold the amps of the fuel pump we wired pin 18 in as the hot side of the relay switch and earthed the other side to the body. On first test The multi meter shows a 4V for 5 seconds on accessories as the fuel pump primes then off then 4v on again when cranking, from here the car fires up as normal and will continue to run and is quite drivable. However this is when the real problem starts. turn the car off. pin 18 provides a constant 4V's keeping the fuel pump running for well over 1min (didn't dare let it run any longer) to turn the pump off you have to turn the keys to accessories again and in 5 seconds the fuel pump shuts down as it would after priming the fuel rail and realizing the motor isn't turning. now there are probably a million simple ways to fix this however i want this to function as it should so that in the event of an accident my pump doesn't keep running after the engines stopped. i just need some help figuring out why my pin 18 puts out 4v's and does everyone else's r33 rb25 ecu do that? and is there pin 18 actually a switched earth? (noob question, what is the best way to tell a switched earth?) and what tells the ecu that the motors running and what tells it when its stopped? any help at all would be greatly appreciated. Thanks Steven. pic http://www.skylinesaustralia.com/forums/post-a255674- Quote Link to comment Share on other sites More sharing options...
RS Speed Posted November 10, 2009 Share Posted November 10, 2009 first off are you sure you have the right wire? Is it a black wire with a pink stripe? You need to hook up the test light to a power source like your battery terminal (alligator clip side) and put the tip of the test light on the black pink wire. If the light turns on and then off when the ignition is switched on(priming the pump) then you have the right wire (switched ground). Don't check for voltage (there will obviosly be voltage if you are connecting a positive wire and a switched ground) if you ground you alligator clip and put the tip of the test light on the black/pink wire and it lights up you are on your own.... lol You run the black pink wire to pin 2 along with a switched ignition to pin 1. Then you run a direct line from battery with 20 amp inline fuse to pin 3 on relay and run pin 5 on the relay to the pump positive. Ground the pump and you have succesfully hardwired your fuel pump... mine reads around 14.5v at the pump and runs of the factory ecu... 300zx ecu for what its worth but it should be the same. Here is a cute diagram I drew for some guy at one point or another lol if you are not using a standard nissan blue relay just follow the drawing on the relay, they are all very simliar. http://rspistons.com/images/fuelpump.jpg Quote Link to comment Share on other sites More sharing options...
250ZR Posted November 11, 2009 Author Share Posted November 11, 2009 Cheers for the response, I think i'm on my own lol I will however double and triple check the wire i have when i get home, i do know that the wire i am using at home doesn't draw enough power to light up the test lamp, (at least not during previous tests.) My wiring is quite similer except that my fuel pump is constantly hot and connected to pin 3 on your diagram and pin 4 grounds the pump to complete the circut. this is the way the origional RB20 red top was wired... (as my car is a Z31 200zr) flip side is it never used a relay... the ecu grounded all 12-13v and 11amps its self (no idea why they would do that but thats how it was from factory...) my current thought for a solution at the moment is to install a gas safety switch as its only on with a pulse signal generated from say the CAS or coil packs etc. however i am un-aware if i will still get the 5 second prime with this switch. (might just be dodgy and install a press button to manually prime my pump before start). if anyone has any other safe alternative ideas to make a fuel pump only run during engine operation I'm all ears thanks Quote Link to comment Share on other sites More sharing options...
RS Speed Posted November 11, 2009 Share Posted November 11, 2009 Sorry I couldn't have been more help, must be a weird 200zr thing or is it possible your ecu is a bit screwy. Most nissan's I have worked on in the states use a ground from the ecu to activate the fuel pump relay which in turn powers the pump... good luck man. On a side note, the priming really isnt all that important, if you can manage to wire it somehow that the pumps shuts off when the motor turns off you should be fine. This would save you incase of an accident which I would say is the most important part. Other than that I've seen lots of people run it direct off ignition which poses the danger of a fire in case of a fuel spill/accident but we all hope for the best and assume this situation will never happen lol. Quote Link to comment Share on other sites More sharing options...
yo880 Posted November 12, 2009 Share Posted November 12, 2009 doesn't the R33 GTST have some sort of fuel pump controller box in the rear somewhere? i was under the impression that it regulated the fuel pump speed too giving a high and low output (giving a boost of fuel when running hard).. i am sure there is something about it in the service manuals.. unfortunately i havn't reached this stage yet, but i had briefly looked at it in passing interest Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted November 15, 2009 Share Posted November 15, 2009 doesn't the R33 GTST have some sort of fuel pump controller box in the rear somewhere? i was under the impression that it regulated the fuel pump speed too giving a high and low output (giving a boost of fuel when running hard).. i am sure there is something about it in the service manuals.. unfortunately i havn't reached this stage yet, but i had briefly looked at it in passing interest Maybe so. The supras do that as well. To the OP, just try wiring it precisely as he listed it. That is the de facto aftermarket method of fuel pump control for imports. Quote Link to comment Share on other sites More sharing options...
gibbon Posted November 16, 2009 Share Posted November 16, 2009 are you using the tinduck racing wiring diagram? (its a pretty common one on the net). there is an error in it with regards to the ignition and ecu relays, i had 4 volts mysteriously running to my black faced gauges until i worked around it. if you are running your fuel pump relay associated in any way with the ignition/ecu relays then you might be having the same problem Quote Link to comment Share on other sites More sharing options...
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