Fuel Pump Problem --- HELP

[bustiegtr]

I recently did the swap of the s13 motor in a 91 nissan hardbody and the wiring is all similar to the 240. The fuel pump wiring is simple but now that I did the swap the pump has no power. The relay has power to 3 of the 4 wires the only wire that doesnt have juice is the wire that trails back to the fuel pump. I have no clue why? The fuse is fine and the other wires have power. The fuel pump is upgraded to a walbro 255 any help would be appreciated.

Also if anybody would like like any info on this swap, wiring schematics of the truck and 1990 240, modification tips, anything let me know email me with questions.

[180fan]

when you put your key in the "on" position, do you hear the pump whirr?

[mygodrulz]

All electronic fuel pumps will cycle for about two seconds at the initial turn on. As soon as you start the vehicle, the MAF sensor will send a signal to the ECM telling it that the vehicle is running and the fuel pump is kept running. The two second rule is common across the board.

[bustiegtr]

no sound at all when the key is in the on position. what else could it be??

[s13sr20chris]

3 wires have power at the relay? thats no good. should be two power, one ground, and one to the pump. if no ground(i believe its the ecm) you have a problem causing the relay not to energize.

[bustiegtr]

So would my ecm be causing the problem of the pump not kicking on? Is there a way to test? The fuel pump relay has the four wires 1 which runs to the fuel pump (no power), 2 that run to the fuse panel (power), and the other wire that runs to ecm that has power.

[180fan]

No sound from a walbro in the "on" position is probably either 1. like the man Chris said, your relay, or 2. your pump's bad.

[bustiegtr]

The relay is fine I switched it with one of my friends relay to see if that was the porblem and nothing it still has no juice. I will try and jump the fuel pump and see if the pump works. If the pump is good could the wire be bad?

[benemorius]

Chris isn't saying the relay is bad. What he's saying is that only two of those four wires at the relay should have power. As in - wiring problem perhaps.

One wire should read 12v (for the relay coil)

One wire should read 0v for a couple of seconds after you turn the key to on (this is the signal from the ecm, if Chris is correct about that)

One wire should read 12v (for the power to the fuel pump)

One wire should go back to the fuel pump, and I couldn't say what random readings it may give...

These readings should be taken with the relay disconnected.

Report back your findings and we'll go from there.

Oh, and does the relay click when you first turn the key on by chance? That would have been the first and easiest test.
Modified by benemorius at 12:03 PM 2/20/2005

[bustiegtr]

benemorius I will try what you said and see what readings I get. The relay I cant tell if it clicks I will try and listen. Also is there a way I could email you or fax you the wiring schematics. Let me know thanks for the help.

[s13sr20chris]

i know on the 240 the ecm grounds the fuel pump relay. i think the hardbody would be the same. some older nissans use the ecm for a power source instead(like the s12).

[bustiegtr]

if the ecm grounds the pump relay could the ecm be bad?

[benemorius]

I guess so, but....

I think you're getting too far ahead here. The very first thing I'd do is see if the relay clicks, then pull it out and short the wire that goes to the pump with the wire that supplies 12v. (look at the diagram on the top of the relay - you should be shorting the two wires that don't have a coil between them) This should cause the fuel pump to run. (you may need the key on - not sure)

From that, you can get a pretty good idea of what's going on. That is where I would start though.

[bustiegtr]

OK tonight I checked to see if the relay was clicking I couldnt tell because i was doing it by myself. Anyways I jumped the wire with power from the battery leading to the fuel pump and nothing it didnt turn on. I then disconnected that wire from the battery left it connected to the wire that leads to the fuel pump and tried using the power from the ecu/relay splicing and the fuel pump relay clicks. So could it be that my pump is bad and why would i have no power at all through the wire leading to the pump?

[navysnail]

http://nissaninfiniticlub.net/...age=2

thats a flow chart on were to start and how to check everything down the line to test the fuel pump.