In-tank Fuel Pump Relay Issue

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EatLiftWeld

Greenie N00B Member
I just replaced the in-tank full pump assembly with an OEM Mazda assembly. Everything is wired right, torqued to spec, etc. The problem is that the pump is only pushing 4.5-5.5 PSI with the key on/engine off. Which is the reason I replaced the pump in the first place, same issue. Tested the old pump, it was going out, so went ahead and got the new one. If I jump the circuit relay at terminals C & D as per the FSM (not F/Pump 2), the pump kicks on and runs perfect. KOEO/KOEF. Car runs perfect, fuel pressure is good, everything. Drove it 5 miles with the jumper in just to make sure. I replaced the relay with a brand new one, still having the same issue.

I checked the fuel pump resistor, it IS showing 0.8-0.9ohms versus the 0.32ohms it “should” be showing. But, I also jumped the resistor terminals at the harness just to check, and nothing different happened. I haven’t cut and spliced the resistor wires yet, as someone recommended in another forum/discussion.

Why won't the fuel pump kick on, or push 50+ PSI, without the jumper in??

Help. I need my car fixed asap.


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Do you have FP prime power at the in tank fuel pump? Test light should kick on, then turn off

Also, check the ENG fuse in the interior fuse block. That fuse controls both fuel pump relays aswell.

Year of car also please.
 
Last edited:
ALPINEST4RS said:
Do you have FP prime power at the in tank fuel pump? Test light should kick on, then turn off

Also, check the ENG fuse in the interior fuse block. That fuse controls both fuel pump relays aswell.

Year of car also please.
Click to expand...

I have power at the pump harness, yeah. But it won’t prime without being jumpered. It’s an 07 MS3. Where is the interior fuse box?


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EatLiftWeld said:
I have power at the pump harness, yeah. But it won’t prime without being jumpered. It’s an 07 MS3. Where is the interior fuse box?


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Click to expand...

Interior fuse panel is behind the glove box. Gotta pull the glove box out which basically you pull that passenger side trim piece, take the two screws out, then pop the bottom clips out. Fuse panel is right behind.
 
EatLiftWeld said:
I have power at the pump harness, yeah. But it won’t prime without being jumpered. It’s an 07 MS3. Where is the interior fuse box?


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Click to expand...
Was wondering if you ever figured out what the problem was. I'm have the exact same issue. 07 cosmic blue. thank you
 
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