Early 350i fuel pump relay position

Early 350i fuel pump relay position

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Discussion

Markymark21

Original Poster:

52 posts

47 months

Friday 18th November 2022
quotequote all
Hi All,
My early 350i (1984) doesn’t start. It’s not getting fuel to the rail. Putting a voltmeter on the fuel pump shows 0.3v once ignition is on. When cranking it stays at 0.3v. I understand I should see 8v.
A quick check shows that I have a good earth at the pump. The wiring looks good otherwise. I’ve pushed the flap on the airflow meter too and no change.
So, I think it’s probably the relay. Now I need to identify which relay it is.
Searching this forum tells me that the layouts changed. I have found a diagram with same layout as mine but it has two fuel pump control relays shown. Why two relays? Is that correct?

Here is a blurry pic of my car:-


Which relay should I investigate? I want to bridge the terminals first to see if that powers up the pump…..

Thanks,
Mark

Adrian@

4,390 posts

291 months

Friday 18th November 2022
quotequote all
Q. have you checked the inertia switch? A@

Markymark21

Original Poster:

52 posts

47 months

Friday 18th November 2022
quotequote all
Hi - no I haven’t. Where would I locate it?

Adrian@

4,390 posts

291 months

Friday 18th November 2022
quotequote all
IF it has one directly behind the glove box fixed to the shell...otherwise presume the relays are as the pictorial (but as they all the same mark and swap them around). A@

Markymark21

Original Poster:

52 posts

47 months

Friday 18th November 2022
quotequote all
Good idea. Will try that…

KKson

3,443 posts

134 months

Friday 18th November 2022
quotequote all
On to my third V8 Wedge and none have had inertia switches. Issue is every one has a random relay location that does not follow the diagrams. Best look at wire colour and trace it back, or run a direct feed to test the pump.

Markymark21

Original Poster:

52 posts

47 months

Saturday 19th November 2022
quotequote all
Thanks. I’ve bench tested the pump and it works fine. I’m going to look for the yellow feed wire at the relay box and see if that has continuity next.

Markymark21

Original Poster:

52 posts

47 months

Sunday 20th November 2022
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Fixed. Turned out to be a loose earth on near side cylinder head. Running well now.

KKson

3,443 posts

134 months

Sunday 20th November 2022
quotequote all
Brilliant. Glad you got it fixed. Cheers