https://www.r3vlimited.com/board/ en Wed, 02 Sep 2026 13:44:14 GMT vBulletin 60 https://www.r3vlimited.com/board/images/misc/R3V.jpg https://www.r3vlimited.com/board/ https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/10165392-no-power-to-fuel-pump-after-removing-the-pump Wed, 12 Aug 2026 02:36:51 GMT
I have been chasing a slow start issue for a bit. My car is a 91 318is with an M50NV swap. It's pretty basic, essentially didn't change anything from the original car except the motor and have been using a PNP harness adapter the whole time. It's been in there for 12 years and has barely given me an issue in the 45K miles I've put on since the swap.

The car would usually take 2-3 decent cranks to start and would then sputter to life and then run perfectly fine. Behaved like it lost fuel pressure every time I turned it off. It's been doing this for a bit and I recently got tired of dealing with it and wanted to find the issue. I replaced a few things like fuel filter, CPS, tried different relay's etc. Whenever I would completely fill the tank the symptoms would usually disappear at first and then reappear once I ran about an 1/8 of tank out of it. I started to wonder if I had a loose line that was letting the fuel pressure bleed once it was turned off so I decided to pull the pump over the weekend.

I pulled the fuel pump fuse to bleed the system before disconnecting the battery and pulling the pump out. I replaced the odd connector from the pump to the metal line with some solid fuel hose and reinstalled. Once I got everything button back up I went to turn it over. The car cranks just fine but the pump wouldn't prime. I rechecked everything, tried again and still nothing. I started digging around with my multi meter and quickly found I had no 12v power at the fuse box for the pump, all other accessories work fine. I tried a different relay, no change. I checked for power at the relay and have 12v at terminal 30 and when I jumped to terminal 87 I have 12v there but still nothing at the fuse. I then pulled the engine/body harness apart and checked pin 13 that should be the wire for the fuel pump and got like 1.2v so something in between the relay and there.

I'm asking because I'm quite stumped as to why this worked perfectly fine before a simple battery disconnect and now is an issue.

Pics for clicks.

My mess tonight
Untitled by Nick Smith, on Flickr

Untitled by Nick Smith, on Flickr

]]> General Technical Nick_S https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/10165392-no-power-to-fuel-pump-after-removing-the-pump https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/10165058-which-line-is-the-return-and-which-is-the-output-on-my-early-model-in-tank-pump Thu, 06 Aug 2026 05:37:57 GMT


I figured the larger hose was the output, but I saw a video that said that was the return. Which is it?]]> General Technical rogerscgreg https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/10165058-which-line-is-the-return-and-which-is-the-output-on-my-early-model-in-tank-pump