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Fuel Pump current supply issue

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Dear All,

This post may not be related to tuning but more towards wiring problem but I am hoping that I could get some basic guidelines as I consider myself still new in the arena and still got a lot to learn

I am currently using Link G4+ Monsoon on a 3SGTE ST246 engine on my Toyota MR2. Car was running great for the past few months until recently I could not get my car to start. After I did the basic check-up I found that the fuel pressure is '0'. Therefore my focus would definitely be the fuel pump. For your information, the wiring was not done by me but I am now learning to do such wiring myself.

My fuel pump uses AUX 6 of the Link G4+ Monsoon via a relay. I try to run the test using PC Link and can hear the sound of the relay clicking but I don't hear the priming sound from the fuel pump. Then I try to directly run the fuel pump from the battery (12v current) to its connector and I can hear the fuel pump priming. For that, I concur that my fuel pump is working and is not the fuel pump issue itself.

Next from the connector that I have disconnected from the fuel pump, I tested it with a multimeter. What I found that there is a current supply of 8v-9v to the fuel pump when the key is ON (after finish the 2-second priming that I have set at Link G4+). When I set at PC Link Software 'test ON' for AUX 6 which is the pump, the current supply becomes 2.8v-3v along with the clicking sound. Picture attached is as per my explanation.

Picture #1 8v-9v before TEST ON fuel pump at PC Link

Picture #2 2.8v-3v during TEST ON fuel pump at PC Link

Next, I try to test all the fuses that I can have my hands on but all the fuse seem okay. As my logic and understanding of wiring, I don't feel its the fuse as there are still current flows to the pump but it just seems that the current is low for the pump to operate. As I mentioned above, the wiring was not done by me, therefore, I try my best to detect the wiring with the limited knowledge that I have.

I seek the advice here to guide me on how could i further diagnose and solve this issue myself. Your advice and guidance is very much appreciated.

Attached Files

Did you try replacing the relay? Perhaps it's not rated for the current the pump draws at initial startup, or it may have just failed.

Problem solved..yes David, you are correct, it is the relay. That also explains why when the test 'ON' at PC Link the voltage drop.

That makes me think, what could cause a relay to fail? what is the lifespan of a relay?

Every relay I've seen fail that wasn't exposed to extreme heat was due to improper manufacturing/was a brand I wasn't familiar with.

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