Fuel Pump Rewire Acting Up.

[Daboss]

Hello forum seeking some sound thesis and advise from fellow skyliners. Okay here is the story wired my aftermarket fuel pump for the full voltage and after about six months of perfect working order now it doesn't. I wired it like this using the bosch style automotive relay: Fuel pump negative straight to battery negative, fuel pump positive spliced into the 86 for the signal to prime the fuel pump, 85 earthed, 30 directly to the battery with fuse and 87 directly to the fuel pump. Now this setup has been working for me for months and now it doesn't. When I cut the battery on instead of the fuel pump priming I get a clicking sound that seems to be coming from within the latch area for the trunk right behind the skyline sign is where it seems to b located. Funny thing is when I plug the stock plug back in it works excellently without fail. I didn't get rid of the stock plug if you are wondering how I was able to use it just spliced off the stock plug positive to get the pump to prime and stop as the stock setup had it. That is also how I know the relay is getting power cause the pump operates fine as soon as I plug in the stock wiring so i know that the signal is getting to the relay cause the pump wiring is spliced into tht. I tried replacing the relay that did nothing, so I am turning to you guys for more ideas. Maybe it was just my luck to have two bad relays I will try another tomorro but something tells me it won't work either!!! Any suggestions????????????

[tridentt150v]

Check your earth?

[Daboss]

Check your earth?

Did that and its fine. Checked it by holding the negative lead of a voltmeter onto ground and the positive to the battery positive and I got the battery voltage on the meter. So earth is fine.

[discopotato03]

Hi , I've not done this to my R33 because it doesn't have a fuel supply prob ATM .

In later cars I've read about silly things going on when std citcuitry is used to control relays instead of actually carrying the electrical load .

Does the std plug you mention also have earth wiring and if so what is it not connected likely to do ?

Is is possible to earth the relays switch or coil back through the std plug - assuming it also has earth wiring ?

You could check all the fuses to be sure I suppose .

Just my 2c , cheers A .

[Daboss]

Hi , I've not done this to my R33 because it doesn't have a fuel supply prob ATM .

In later cars I've read about silly things going on when std citcuitry is used to control relays instead of actually carrying the electrical load .

Does the std plug you mention also have earth wiring and if so what is it not connected likely to do ?

Is is possible to earth the relays switch or coil back through the std plug - assuming it also has earth wiring ?

You could check all the fuses to be sure I suppose .

Just my 2c , cheers A .

Yea the standard r33 plug has two wires earth and power. I didnt use the standard wiring ground just left it alone. Yea I guess I could earth it back through the standard wiring and try it like that. Just that I had the earth str8 to the battery and was using thicker wire so I didnt want to bother with the stock wiring at all.

[discopotato03]

Yeah sometimes these earth circuits need to be complete , it never ceases to amase me if I pull looms apart how many earth wires are linked to so many different things rather than having a local body earth .

I tend to think that if the original pump power and earth wiring did a half ok job with the pump it would be more than enough to just trigger your new relay .

Cheers A .

[Daboss]

Yeah sometimes these earth circuits need to be complete , it never ceases to amase me if I pull looms apart how many earth wires are linked to so many different things rather than having a local body earth .

I tend to think that if the original pump power and earth wiring did a half ok job with the pump it would be more than enough to just trigger your new relay .

Cheers A .

Yea exactly. I just came from trying all types of scenarios with my ride and none worked so I just gave up and left it with the stock. I proved that the relay is ok by testing across the ground and power wire with stock wiring priming the pump and sure enough got 13.5 volts across my wiring. With car on got a steady 13.5 volts across my wiring, switched it around to have my wiring powering the pump and got nothing. The pump would not even prime, switched it right back to stock and it ran with no problem. I even used the stock wiring ground as suggested and still nothing, I have given up for the life of me I can't find this problem out.

[tridentt150v]

Has your mod hot wire/s got circuit? it could be an internal break?

[Daboss]

Has your mod hot wire/s got circuit? it could be an internal break?

Hmmm don't really understand your question!! I can say that when testing voltages at priming the voltage gets to the pump through my wiring, meaning right at the point were the stock plug would go I am getting voltage with car on I am getting voltage out of my wires at the at that same point also, just that it does not activate the pump for some reason . If it were an internal break wouldn't that mean that I wouldn't be getting any voltage from the wires going to the pump? Its like my car does not want any other wiring there except stock.

Edited November 29, 2008 by Daboss

[NZM.031]

could it be that your pump has shit itself??

[tridentt150v]

I've had this before. What you have is an airgap somewhere in your wiring. When you test for circuit the airgap is small enough or just touching so that voltage will show as being normal 12-14v. But when you have it under load, it will fail, amps don't like airgaps. Remember you need certain thicknesses of wire for working loads, with the airgap the 'thickness' is missing. It could be in your connectors/spade terminals. There could alternatively be a break internally in a wire, you can't see it for the plastic insulation. Make up a wire say half a metre long and use different connectors etc and substitute it for each wire in turn. BTW the clicking sound is probably the power trying to get across the airgap.

[Daboss]

could it be that your pump has shit itself??

No it works fine and its basically new. Just doesn't work with the rewire, stock wirirng it primes and runs great.

I've had this before. What you have is an airgap somewhere in your wiring. When you test for circuit the airgap is small enough or just touching so that voltage will show as being normal 12-14v. But when you have it under load, it will fail, amps don't like airgaps. Remember you need certain thicknesses of wire for working loads, with the airgap the 'thickness' is missing. It could be in your connectors/spade terminals. There could alternatively be a break internally in a wire, you can't see it for the plastic insulation. Make up a wire say half a metre long and use different connectors etc and substitute it for each wire in turn. BTW the clicking sound is probably the power trying to get across the airgap.

Tried your method and everything works fine until I splice the stock power wiring. I connect the spade connector I get no voltage goin through it to prime at ignition on but if I take it off and test the spade connector at ignition it get full voltage for the ignition prime. With car running, obviously with the stock wiring, and testing the wiring I put in i get the full voltage of the battery. As soon as i disconnect the stock setup and use my own, pump doesn't even prime. I also tried just hooking directly to battery with the same wiring I am using and the pump came on so it isn't the spade connectors or the wiring , I splice my wiring into the stock power wiring and hooked my wiring to the pump, it comes on and operates fine, but as soon as I separate the pump power wire to use one side as a signal for my relay the pump doesn't work. It isn't the relay cause it gets signal at prime without being connected to the pump and also with car running voltage across its circuit is same as at battery. The problem is when I separate the stock power wiring to use as a signal to activate my relay, when that wire is separated and used as signal to trigger my relay it sends the signal, but not when connect to the pump. When I connect the spade connector to power the pump and test at ignition on no voltage, but if I disconnect and test I get voltage at ignition through the spade connector, put it back on and test no voltage. My next option is to find another ignition source and try to use that.

[lolar33]

i believe fuel pump relay is negatively switched (activated). (i would make sure before reading the rest of this lol). find the negative switched wire (i think its black with pink stripe from memory, (it was on my car anyhow)) splice into it run it out the the 85 on your relay 30 to battery (with fuse) loop 86 back to 30(so that 86 has bat + on it) and 87 out to the fuel pump.

[Daboss]

i believe fuel pump relay is negatively switched (activated). (i would make sure before reading the rest of this lol). find the negative switched wire (i think its black with pink stripe from memory, (it was on my car anyhow)) splice into it run it out the the 85 on your relay 30 to battery (with fuse) loop 86 back to 30(so that 86 has bat + on it) and 87 out to the fuel pump.

I don't have a problem with the fuel pump relay. That works fine I think I can even hear it click when ignition is on the problem I see is when I connect MY wiring to the pump, more particularly the wire out the 87, no voltage goes to signal it to prime now with it disconnected their is voltage but when connect no voltage for some reason. Also if that was the case, wouldn't that mean that I would have never got my wiring to work? I was driving around with the rewire for sometime now it just started acting up like maybe a week ago. Got no priming thought fuse was blown looked at it changed it got it to work, stopped at a friends went to start back up no priming fooled with the fuse again took many tries but it finally worked decided to go back to stock plug and wiring that gets it to start and prime everytime. Just wanted to rewire to ensure full voltage at pump and cant figure why it would just stop working all of a sudden and why the rewire doesn't work. It should, Hell it was working fine for months before.

[lolar33]

Hmm, you may have tested it wrong imo (not to be an ass or anything) my suggestion would be to grab yourself a test light/lamp much easier then multimeters, make sure your bat+ to 30 on the relay is all good not loose dodgy connections, broken wiring etc., do the same for the 87 side. if you still cant get it working grab your test light out (with ign on) and probe the wire from the battery terminal to the fuel pump you should get a light all the way through if it doesn't light up then there is a problem between the place you probed last and where you just probed... the other thing i can think off is it is probably just a faulty relay. the other thing i would check is make sure where you have put your earths that you have scrapped/sanded the paint off

[Daboss]

Hmm, you may have tested it wrong imo (not to be an ass or anything) my suggestion would be to grab yourself a test light/lamp much easier then multimeters, make sure your bat+ to 30 on the relay is all good not loose dodgy connections, broken wiring etc., do the same for the 87 side. if you still cant get it working grab your test light out (with ign on) and probe the wire from the battery terminal to the fuel pump you should get a light all the way through if it doesn't light up then there is a problem between the place you probed last and where you just probed... the other thing i can think off is it is probably just a faulty relay. the other thing i would check is make sure where you have put your earths that you have scrapped/sanded the paint off

No all help is welcome, thats why I do things in pairs because something small I may have missed you could spot. I will get a test light and go through the process again. Thanks for your input.

[Daboss]

Happy to report I have found the problem. Thanks to everyone for there time and suggestions helped a great deal. You wouldn't believe what it was. The dang fuse wasn't big enough had a 30 amp fuse in there needed a 40. What gave it away for me was when I was checking it with my wiring I could hear the pump start to prime struggle and then die off. Indicating voltage going there was not enough, only other thing besides wiring that would cause that is fuse size and thats what it was. So once again thank you all. Excellent job.

[lolar33]

hahah good to see you found the problem. If its drawing more than 30a i would suggest to make sure your wiring is capable of more than 30a, otherwise stuff starts to get hot hah.