No power at fuel pump

iLLogicaL · Post by **iLLogicaL** » 31 Oct 2023, 18:36

Hello,
I encountered a small issue with my Volvo 850 T5, and I can't seem to find the source of the problem.

I went shopping, and when I tried to leave, the car started and then stalled.

I brought the car back home and began to look for the problem.

I couldn't hear the fuel pump, so I checked the voltage on the fuel pump connector. With the key in position 0, I had 0 volts, and in position 2, I had 50mV.

So, I checked the relays, starting with relay 103. I can hear it click. Then, I checked the gray relay next to the fan, and I couldn't hear it click, nor could I feel it when placing my hand on it.

So, I tested fuse #2 (Fuel pump fuse), and I had 12V at the fuse.

Is it possible to have 12V at the fuse if the gray relay isn't working (I suspect the connection underneath the relay because the relay itself is relatively new)?

Can I bypass the gray relay? If so, how?

I connected the fuel pump directly, and the car runs fine, but I had the impression that my pump was stuck.

My diagnosis before knowing that the gray relay wasn't clicking was that the cable from fuse #2 to the pump's connector might be damaged in that area.

I noticed that the fuel pump connector is a bit burnt (not melted but brownish in color).
I tested the continuity between the positive and negative terminals of the fuel pump connector and got a resistance of about 50 ohms, if I remember correctly. Is that a sign of a short circuit between 12V and ground, isn't it?
My battery was disconnected. No key in the key switch.

I'm turning to you before removing the seats, dashboard, and fuse box to follow the cable and check its condition.

I hope I've managed to make myself understood well enough as English is not my primary language.

Thank you for reading, Florian.

Post by **Chuck W** » 31 Oct 2023, 18:47

Did you check the connector at the main FI relay near the fan?

iLLogicaL · Post by **iLLogicaL** » 01 Nov 2023, 04:00

Yes, wires are ugly.

Could it be my problem if I have 12v on fuse #2?

Thanks for your answer.

Edit: The grey relay isn't the reason why i have no power.

I bypassed the relay, and there is still no power to the fuel pump. (I know the bypass is working because after doing so, I can hear the idle motor running. The same thing happens with the relay plugged in, so I assume it's in good condition.)

What path does the power cable for the fuel pump follow? Fuse #2 -> Red Relay -> Gray Relay -> Fuel Pump?