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Missing In Low Revs In 1St, 2Nd And 3Rd After Fuel Pump Install

rondofj

By rondofj,
in Engines & Forced Induction

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Thelen
Thelen

If the old pump had some issues keeping proper pressure for some reason then maybe it is the tune, but I'm fairly sure the old pump would have problems keeping pressure once you got on the gas even mo

KiwiRS4T
KiwiRS4T

The maximum draw I have seen on any chart is under 30 amps - maybe there is an error in the wiring?

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

Ill come for a drive down rewire the pumps then if u can organise a dyno and ill get em both done. Just do the power runs on the dyno do the rest on the road.

Then do some Tandem skids

rondofj Veteran

rondofj

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I'm goin to mount my relay in the bonnet beside the battery and ground it (pin 86) to the chasis or battery -ve. Battery +ve goes to relay pin 30. Relay Pin 87 goes to pump +ve. And the switch wire, relay pin 85 goes to ECU +ve. Finally the pump -ve and the ecu -ve are grounded to chasis - can they be grounded to the same point on the chasis?? There's 3 grounding points isn't there - pump -ve, ecu -ve, and relay pin 86.

Please tell me if I missed anything. I think I will get the relay from jaycar I posted above as it has a 30A fuse, but its got 15A contacts, if this is a problem? Supercheap dosent have any relays with fuse, and the guy at Jaycar told me I dont need a fuse as there shud be one from the battery.. All this conflicting info spinning in my brain lol..

rondofj Veteran

rondofj

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I read somewhere that I can just cut the wires going onto the top of the white fuel pump lid/cap and connect the battery and relay wires to these so I dont have to take out my pump and bracket.. Theres 2 plugs and 3 hoses on the lid so just gotta figure out if its the bigger plug or the smaller one.

rondofj Veteran

rondofj

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I dont see the point of getting him here from Newcastle to rewire 2 pumps - you and me - I will be doing a dyno tune only afterwards - and that depends if the wiring is sorted first. If Jez was Sydney based, then diff story of course, I would book him in..

This wiring thing is now finally making sense, one thing i dont understand is how to find out if my car is +ve or -ve trigger from the ecu - cut the wires and hold a test lamp to the terminals and ground? And from the 2 wires the one that lights up the lamp is the trigger?

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

Yeh cause jaycar will pay for ur car if it burns to the ground. The fuse in the bonnet is good for ur thick stereo wiring. If it shorts out and it gets hot enough to blow the 60amp fusr (or 100amp depending which u have).

But if ur fuel pump shorts out all the wiring except for the thick amp wiring will cause a fire.

Mount it where ever but its easiest in the boot. U only need to run 1 wire which in ur case is already there.

Ur way requires finding the correct ecu wiring then run it to ur fuse. Then run a power wire all the way to the fuel pump.

Both will work. 1 is easier.

Im on the central coast not newcastle. Took michael 1 hr from cronulla to get to my place.

rondofj Veteran

rondofj

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Ur right, I have the Kicker amp wiring already with a monster fuse just after the battery (its in a case, havent checked how many Amps). That wire goes to the boot so I can just connect it to pin 30 on my relay which I will mount in the boot. Plus the ground wire from my ex-amplifier is there in boot too - I can connect this to my pump ground.

Then I am left with the 3 wires from the relay - pins 85, 86 and 87 which needs to go to the pump +ve (pin 87) and the ecu wiring (85 & 86). But what do u mean by "Ur way requires finding the correct ecu wiring then run it to ur fuse' - do I need another fuse or what and to which wire?

The wires going into the pump lid from ecu are pretty skinny, in fact - theres 5 of them - I know 3 of them is for the fuel sender, and 2 supposedly slightly thicker ones are for the pump - these r the ones I need right? They are supposed to be blue and white (from an R33 wiring thread) - but I have yellow/black, black, green, white and another I cant remember.. So would be gud if someone knows the R34 color codes..

But still havent understood how to find out if my car is +ve or -ve trigger from the ecu..

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

Just connect the power wire going into the fuel pump now to pin 86 (test with a test light, or disconnect one plug at a time to see which powers the fuel pump. Car will stall) then test light on that plug to find positive when the pump primes(initial key on)

Connect the negative wire that is going to the fuel pump to pin 85 on relay. This should make the relay click(turns on) when u turn the key on. Leave key on and make sure the relay clicks again (turns off) if it doesnt let me know. Dont drive the car if this relay doesnt turn off or there a risks if u have a crash.

Then if the above is all good. Connect 87 to the fuel pump power in ( the old positive wire to the pump) and the kicker amp wire to pin30.

Then turn the key on. The pump should prime and then turn off.

Then go for a drive and see if the issue is fixed.

rondofj Veteran

rondofj

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Some posts have said that the -ve from ecu into pump needs to be grounded to chasis, pin 85 on relay needs to be grounded to chasis and of course the fuel pump -ve needs to be grounded as well - I wanna get all these 3 points to a common ground point on chasis? And then other posts say to connect the -ve from ecu to pin 85, is this the same thing, there are diagrams of these 2 connected together and then grounded to 1 point?? Man I sound dumb I know!

89CAL Grand Master

89CAL

Posted
Posted

Heres a wiring diagram that I found on google.

horn_relay_wiring_diagram.gif

If you get rid of the wire from ground to the air horn compressor to the earth at the bottom then it would be similar wiring to what is required with the pump (from what I can gather)

But There seems to be a debate about wether the fuel pump switches through ground or through the power wire to/from the ecu

If this is wrong someone correct me with the aid of the drawing...... I havent done the rewire so I'm only guessing how it is supposed to be but this seems the most logical

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

Thats because im unsure if ur car has a negative trigger.

If its negative trigger this uses the ecu trigger wire as an earth.

If its positive trigger than then relays earth wire needs to be grounded to the chassis. Understand?

Thats why i have posted different options.

But try my last post above 1st which uses the stock positive and negative into the relay. This should work fine. U have my number. Its in my sig. If ur unsure when u do it just call me.

rondofj Veteran

rondofj

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thanx guys will get the gear today and let u know how it goes - I get it that regardless whichever of the two ecu wires is the trigger (+ve or -ve) THAT wire is goin to pin 85, and the other wire along with pin 86 on the relay and the pump -ve will be commonly ground to the chasis through one point?

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

Yep. 85 and 86 have to complete a circuit from power to ground. So +ve can go to either. And the other one has to be earthed.

But this is where the trigger comes into it. Eg:

+ve trigger goes to 86 and 85 has to be grounded to the chassis.

Or

-ve trigger goes to 86 and 85 has to be from a 12 volt switched( meaning only when key is on)

When 85 and 86 have a completed circuit this energises the coil and pushes the circuit closed between 87 and 30 (the coil is like a reverse magnet, which pushes the bridge closed as per 89cal's diagram above)

boostn0199 Grand Master

boostn0199

Posted
Posted

While were on the issue Im about to wire up my external 044 for the surge tank in my r33 and I plan to splice into the standard fuel pump trigger and just in regards to the ground used on the relay should I just ground it separate to the chassis or splice into the standard ground used by the fuel pump wiring. R33s dont have the negative trigger do they? so I would be right in saying I can ground it direct to the chasis and just use the positive trigger to the relay?

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