Fuel Pump Wont Stop...

[z3dh3d]

First off,

I've been a member for a while but a relatively new poster on these forums and i've got a 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 not provide it... but we also realised that our relay needs 10v minimum to close so with a relay expensive relay that trips on 4v and can hols 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 y my pin 18 puts out 4v's and does everyone else's r33 do that? and is there pin 18 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.

[axe s]

It should go by oil pressure..

if ur motor is off you have no oil pressure, cuts pump..

when u start the car and the latching circuit times out after 5 sec, if u have oil pressure the pump will continue to run if not it cuts the pump..

i don't have a multimeter here to tell you what voltage i get through mine..

[z3dh3d]

that sounds about right but i can't for the life of me work out why mines wrong, you would almost assume that the oil pressure switch isn't connected therfor my pump isn't turning off... but because it turns on and continues to run it doesn't make sense.

and as far as i can tell i've got pin 18 on the wrong side of the relay according to the fsm... and every other faq i've read about putting an RB series engine in your Z,S13,240sx,R31 etc.

[blind_elk]

Pretty certain the ECU will know the engine is running because it is getting signals from the CAS.

The ECU has 2 processes for the fuel pump. At IGN ON, the ECU runs the pump for 5 seconds to prime the system with pressurised fuel. Then at IGN START, the ECU turns the pump on full time, and keeps it running as long as the engine is running.

You need to wire the relay so that the ECU pin 18 switches the relay switching circuit to earth. Then, as soon as the IGN is turned off, the pump should stop.

[axe s]

If it shuts off after 5 seconds when u put it on accessories it should be working, i would think there is something else wrong causing it to keep the oil pressure switch to stay closed and not give you enough voltage through your relay.

Try checking ur pressure sensor, and work back from there..

have you got a wiring diagram for the R33 to see how the safety circuit works?

Or what he said...

Edited November 10, 2009 by axe s

[MBS206]

If it shuts off after 5 seconds when u put it on accessories it should be working, i would think there is something else wrong causing it to keep the oil pressure switch to stay closed and not give you enough voltage through your relay.

Try checking ur pressure sensor, and work back from there..

have you got a wiring diagram for the R33 to see how the safety circuit works?

Or what he said...

The ECU doesn't look at oil pressure for the fuel pump, it monitors triggering from the CAS.

[axe s]

yeah i've never looked at that side of an r33 just going by the wiring i had to do to put an RB30ET into my stepfathers EH.. thought they would run along the same lines..

[z3dh3d]

I think my best solution is to wire the fuel pump independently of the ECU by using a gas fuel pressure switch. i know this only runs on a pulse signal generated from a coilpack or cas, i'm not too sure if it willl have a 5 second prime such as the ECU does.

as at the moment the only way it is running (and not switching off) is with pin18 from the ecu wired to the + side of the trigger in the relay and the - side wired to earth

the FSM shows IGN power wired to the + side of the trigger and the - side of the trigger wired to pin 18 (which also makes sense in my head) however if i do this i get absolutely nothing.

anyone know much about gas safety switches?

cheers for you help

Steven.

[blind_elk]

Using pin 18 to pull a relay switch to earth seems to work in just about every other EFI Nissan. You should have 12V at the power side of the switch.

Maybe the relay you are using is too "strong", in that it requires too much current to switch.

[z3dh3d]

The reason for this crazy solid state relay that i have installed now is because we could never get pin 18 to draw more than 4v's and a standard 4 pin relay requires at least 10V to close the switch.

we managed to find a relay that closes with a 4v signal wire and the switch side that could handle the amps and volts of the fuel pump.

but i can't figure wire i'm getting 4V between pin 18 and ground?

with pin 18 at the (-) side of the trigger in the relay and ignition power at the (+) side nothing happens

but pin 18 and the (+) side of the switch and body earth to the (-) side of the switch it primes, runs and then wont turn off as the 4V coming from pin 18 remains constant after the car has started and the motor stopped.

I'm thinking about manually re-wiring everything in the fuel pump circut manually to just simply test pin 18.

but that seems alot like a pain in the arse.

cheers for the input guys.

[axe s]

Have you checked what your getting out of your crank sensor?

[femno]

LOL fuel pump runs off oil pressure thats funny.

Anyways I think you may have the wrong wire as its not at 12V, it should be.

Try and source another pinout, theres plenty of incorrect pinouts floating around the web.

If not, just try and find the right wire by trial an error. And it should prime for a sec or 2 when the key is turned to IGNITION not accessories.

[JonnoHR31]

my pinout diagram shows it as pin 18 aswell. 3rd from the bolt in the bottom row on the left looking at it from the ecu side with the bit that sticks out round the bolt pointing up

[daisu]

If it's putting out 4V instead of sinking to ground then perhaps the ECU has issues?

[z3dh3d]

Yeah, i think the ECU may have issues, but i drove the R33 wreck (big rear end pole dent) to my place just fine, however i did wire the ECU based on all the info i could find from all the other RB conversions detailed in other sites.

but basically all you really needed to do to get it running was a couple of ign power wires, constant power here and there and a few earths, getting all the gauges going was the hardest part.

however i have solved my problem, the gas safety switch works perfectly and for about $70 you can pick on up from LPG gas ppl who do the car conversions, it even primes and then only runs off tach signal.

but cheers for all your help guys, maybe i might find a spare ECU sometime and test to find out if it wiring or my ecu.

regards

Steven.

[axe s]

LOL fuel pump runs off oil pressure thats funny.

Anyways I think you may have the wrong wire as its not at 12V, it should be.

Try and source another pinout, theres plenty of incorrect pinouts floating around the web.

If not, just try and find the right wire by trial an error. And it should prime for a sec or 2 when the key is turned to IGNITION not accessories.

obviously you don't work on a variety of cars... it was a pretty common way of controlling the fuel pump..

it is also good coz it you lose oil pressure your fuel pump cuts out... hopefully before it damages anything..