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Fuel Pump Relay

1340 Views 13 Replies 5 Participants Last post by  GAD90
Hey everyone. Trying to troubleshoot some suspected fuel pump problems on my NAS 97 D90. I have a new “Fuel Pump Relay” part no. YWB100820L that I am going to try to replace.

Now my google-fu is usually pretty good, but I’m just not having any luck finding where this relay is located! Anyone know where to find this thing on the truck??

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Old post but I hope you guys are still at it!
So been having some weird misfire codes,and just running poorly last fall. Seemed to have corrected after a battery swap. This winter pulled and rehabbed the heater (a project). Got everything back together, start ran fine, for a bit , stalled, barely got it home. Throwing codes, misfire, cats…
Checked and replaced wires. Though I was all good… nope , no start! Cranks fine, I just noticed no hum of the fuel pump. So, I guess my question(s) , does it make sense the pump just crapped out, does the pump relay make a click sound, is there a method to check wiring w/o dropping the tank??
Any ideas you have are welcome! Oh, 97 NAS 90 GEMS
Where should I check continuity, and what should it be if it’s good? I’ll check the fuel rail, but no sound coming from the pump.
Thanks for the reply! That link to LR Workshop may be the single best piece of info ever! I don’t know how I never heard of it, for the 26 years I’ve owned this thing!
Really good points, I am a little concerned I may have broken a wire in one of those connectors while I was “working “ the heater in and out. Electrics isn’t my strong suit. The electrics manual I’ve downloaded isn’t much help (even if I knew how to read it). The one I’ve found says it’s for NAS 97 , but it doesn’t reference the GEMS at all. I’ll get some help and listen for the relay. How can I test it to see if it’s getting power? How would I go about isolating the pump as the issue, if I don’t find a physical problem (broken wire) ?
Thanks for the help. I LOVE THIS FORUM !

Do a fuel pressure test, and to check wiring use a Vohm Meyer. Set it for continuity and then to resistance.
Probably the fuel pump has seen its day. When you first turn the ignition key on you should hear the pump cycle on for about 7 Seconds then shut off.

If it doesnt sound, you shld still hear the relay click off under the hood just after. When testing at various points (like the inertia switch or the relay) be aware you only have 7ish seconds of power to test until the relay clicks circuit off.

Check your ground on the passenger side at frame under door. There's also a harness connection bundle passenger side under hood at bulkhead tucked in farthest corner, you can barely reach your hand in there to find 3 various connectors 1 of which is in the circuit and believe another connector at rear of engine that may lead to the inertia switch. Reference wire diagram and cross with lrworkshop link for location to test. Most likely the pump.

gems discovery 1 is the same as defender including 10as alarm, when reading codes on 96 to 98 defender you use discovery model as defender does not exist on diagnosis equipment.
Oh, good to know, thanks!
I wanted to follow up. It was the pump, guess I got my money’s worth 26 years is a good run.
Tested the fuses and relay best I could, all good. Last thing was the connector at the tank, power and ground to it were good. New pump went in well, the stub fuel lines were pretty rough, but got them connected.
Thanks for pointing me in the right direction!
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