NAS D90 fuel pump issues. Help!
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4th Gear
Joined: Nov 2017
Posts: 4
Likes: 0
From: Atlanta
NAS D90 fuel pump issues. Help!
Hi lads,
my my defender has been reluctant to start lately, until it just won't. I noticed the fuel pump wasn't kicking on when I turned the key, so I replaced the fuel pump relay. Still won't start. Tested the relay which works fine. Looked at the fuse, not blown. Tested fuse, it's fine. I checked the fuse panel under the hood, all of those fuses were fine, too. It must be the fuel pump, so I did the nasty, dropped the tank and soaked myself in gas. I hope I never have to do that again. Anyway, no joy. Fuel pump won't kick on. Tested old pump, much to my dismay, it's fine.
Replaced the coil and amplifier, in case the spark was weak. Tested it with a plug against the block. Sparks great.
If if the relay is getting power, and it clicks... And the fuel pump is brand new, why won't it start?? I'm starting to think the ol girl is jealous of the muscle cars.
Any thoughts of of what I might check?
my my defender has been reluctant to start lately, until it just won't. I noticed the fuel pump wasn't kicking on when I turned the key, so I replaced the fuel pump relay. Still won't start. Tested the relay which works fine. Looked at the fuse, not blown. Tested fuse, it's fine. I checked the fuse panel under the hood, all of those fuses were fine, too. It must be the fuel pump, so I did the nasty, dropped the tank and soaked myself in gas. I hope I never have to do that again. Anyway, no joy. Fuel pump won't kick on. Tested old pump, much to my dismay, it's fine.
Replaced the coil and amplifier, in case the spark was weak. Tested it with a plug against the block. Sparks great.
If if the relay is getting power, and it clicks... And the fuel pump is brand new, why won't it start?? I'm starting to think the ol girl is jealous of the muscle cars.
Any thoughts of of what I might check?
TReK
Joined: Mar 2010
Posts: 2,778
Likes: 626
From: NYC
what year? what engine? (best to put this info in your signature so you don't need to repeat it continually)
Here is the text from the ETM for a 1997MY.
Possibly the inertia switch.
FYI, most of the workshop manuals and electrical manuals can be found in the link in my signature. Help yourself to whatever you need.
Here is the text from the ETM for a 1997MY.
STARTING - OPERATION
When the ignition switch is in position 'II', power flows across the switch to fuse 20 of the
passenger compartment fuse box (C581-13) on the white wire. Fuse 20 (C581-20) is
connected to the fuel pump relay winding in the ECM relay module (C154-2) by the
white/green wire. The fuel pump relay winding (C154-1) is grounded through the ECM
(C634-24) on the blue/purple wire. The ECM grounds the fuel pump relay winding for a
short time when the ignition is switched to position 'II', and continuously during cranking
and while the engine in running. With the fuel pump relay winding energized, the fuel
pump relay closes and power from fuse 6 (C575-2) of the engine compartment fuse box
flows through the fuel pump relay (C157-7) on the purple/white wire. The fuel pump relay
(C157-4) is connected to the inertia switch (C123-3) by the white/purple wire. Assuming
the inertia switch is closed, power flows across the switch (C123-1) to the fuel pump
(C113-4) on the white/purple wire. The fuel pump is grounded on a black wire.
Turning the ignition switch to the crank position 'III', allows power to flow across the
switch (C90-1) to the starter relay winding (C151-85) on the white/red wire. The starter
relay winding is grounded on the black/yellow wire to the starter inhibitor/reverse switch
(C69-5). With the gear selector lever in park or neutral, the route to ground is from the
inhibitor switch (C69-4) to the immobilization unit (C57-10) on the black/orange wire.
Assuming the engine has been mobilized, the immobilization unit is grounded on a black
wire. With the starter relay energized, power from fusible link 5 of the engine
compartment fuse box (C570-2) flows across the relay (C151-87) on the brown wire.
The starter relay is connected to the starter motor solenoid (C179-1) by the brown/red
wire. The starter motor solenoid is grounded through the starter motor fixing. With the
starter motor solenoid energized, feed from the battery is connected to the starter motor
(C178-1) through the starter solenoid on a red wire.
When the ignition switch is in position 'II', power flows across the switch to fuse 20 of the
passenger compartment fuse box (C581-13) on the white wire. Fuse 20 (C581-20) is
connected to the fuel pump relay winding in the ECM relay module (C154-2) by the
white/green wire. The fuel pump relay winding (C154-1) is grounded through the ECM
(C634-24) on the blue/purple wire. The ECM grounds the fuel pump relay winding for a
short time when the ignition is switched to position 'II', and continuously during cranking
and while the engine in running. With the fuel pump relay winding energized, the fuel
pump relay closes and power from fuse 6 (C575-2) of the engine compartment fuse box
flows through the fuel pump relay (C157-7) on the purple/white wire. The fuel pump relay
(C157-4) is connected to the inertia switch (C123-3) by the white/purple wire. Assuming
the inertia switch is closed, power flows across the switch (C123-1) to the fuel pump
(C113-4) on the white/purple wire. The fuel pump is grounded on a black wire.
Turning the ignition switch to the crank position 'III', allows power to flow across the
switch (C90-1) to the starter relay winding (C151-85) on the white/red wire. The starter
relay winding is grounded on the black/yellow wire to the starter inhibitor/reverse switch
(C69-5). With the gear selector lever in park or neutral, the route to ground is from the
inhibitor switch (C69-4) to the immobilization unit (C57-10) on the black/orange wire.
Assuming the engine has been mobilized, the immobilization unit is grounded on a black
wire. With the starter relay energized, power from fusible link 5 of the engine
compartment fuse box (C570-2) flows across the relay (C151-87) on the brown wire.
The starter relay is connected to the starter motor solenoid (C179-1) by the brown/red
wire. The starter motor solenoid is grounded through the starter motor fixing. With the
starter motor solenoid energized, feed from the battery is connected to the starter motor
(C178-1) through the starter solenoid on a red wire.
FYI, most of the workshop manuals and electrical manuals can be found in the link in my signature. Help yourself to whatever you need.
Thread Starter
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4th Gear
Joined: Nov 2017
Posts: 4
Likes: 0
From: Atlanta
Point taken, sorry! I thought NAS 90 was enough. It's a 1995 Defender 90SW with a 3.9 petrol engine and a 5 speed. I'll look into the inertia switch next. Eventually I'll replace the part that's boogered up! 
Thanks for the link to the tech docs, too I'll dig into those more tonight.
Thanks for the link to the tech docs, too I'll dig into those more tonight.
Thread Starter
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4th Gear
Joined: Nov 2017
Posts: 4
Likes: 0
From: Atlanta
OK. Frustration time. Here's where I am with the fuel pump issue...
Basically, I've checked every single component between the battery and the fuel pump and they all check out. Is there anything I'm missing? I really don't want to have to go through the tank thing again (though I'm sure I can do it in half the time now). The only think I haven't checked is the current to the relay on the pump side. If that checks out, then it has to be a broken wire, I guess?
Thanks in advance!
- I've replaced the original fuel pump with a new one (then bench tested the original, only to find it works). Taking that tank out is something I hope I never have to do again!
- I've removed all the fuses from the fuse box under the dash and bench tested them, they're fine.
- I've removed all the fuses from the panel behind the engine compartment and bench tested them, they're fine
- I've removed the inertia switch and bench tested it, it's fine. I even bypassed itt o make sure, still no fuel pump.
- I replaced the fuel pump relay, and bench tested the original... it's fine as well.
Basically, I've checked every single component between the battery and the fuel pump and they all check out. Is there anything I'm missing? I really don't want to have to go through the tank thing again (though I'm sure I can do it in half the time now). The only think I haven't checked is the current to the relay on the pump side. If that checks out, then it has to be a broken wire, I guess?
Thanks in advance!
1st Gear
Joined: Jan 2018
Posts: 1
Likes: 0
fuel issues
OK. Frustration time. Here's where I am with the fuel pump issue...
Basically, I've checked every single component between the battery and the fuel pump and they all check out. Is there anything I'm missing? I really don't want to have to go through the tank thing again (though I'm sure I can do it in half the time now). The only think I haven't checked is the current to the relay on the pump side. If that checks out, then it has to be a broken wire, I guess?
Thanks in advance!
- I've replaced the original fuel pump with a new one (then bench tested the original, only to find it works). Taking that tank out is something I hope I never have to do again!
- I've removed all the fuses from the fuse box under the dash and bench tested them, they're fine.
- I've removed all the fuses from the panel behind the engine compartment and bench tested them, they're fine
- I've removed the inertia switch and bench tested it, it's fine. I even bypassed itt o make sure, still no fuel pump.
- I replaced the fuel pump relay, and bench tested the original... it's fine as well.
Basically, I've checked every single component between the battery and the fuel pump and they all check out. Is there anything I'm missing? I really don't want to have to go through the tank thing again (though I'm sure I can do it in half the time now). The only think I haven't checked is the current to the relay on the pump side. If that checks out, then it has to be a broken wire, I guess?
Thanks in advance!
Hey man,i'm having the exact same issues as you... did you ever find out what the problem was, and if so, what was it... Thanks,DB
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