I have, what I belive to be, a loud intank fuel pump - there is a loud buzzing coming from the back, and when I pull fuse #4; it stops.

Thoughts?

How do I shut off the main fuel pump? I want to figure out if that's working. Can I assume that if both pumps are shut off the car will shutoff due to lack of fuel? WHich is the right fuse?

couple of ideas -

- the intank pump is overworking (and therefore buzzing) because the main pump is dead...


- The main pump is fine, and the intank pump is just dying (and buzzing)

Are they difficult to replace?

What's my best plan of attack?

When I turn the key to "on" without turning the engine over, I don't hear any of the pumps running... Shouldn't I?

When I turn the key to "on" without turning the engine over, I don't hear any of the pumps running... Shouldn't I?

No—not with LH2.2. That Key On buzz came with LH2.4 on the '89 240.

There is no fuse you can pull to test/kill the Main pump. (Ignore the fuse label for Fuse 6, it's just a dummy/spare on U.S. cars.)

But you can test either pump individually by removing fuse 4 and applying a +12V jumper wire to either fuse 4 contact...

• Right side contact will power the Tank pump
• Left side contact goes to the Main pump

You can get +12v for the jumper wire from the Left side contact of any fuse 6 thru 10, even with the Key Off.
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

The car seems to be running fine. I did pull both 4 & 6 but I did notice #6 had no effect... Just wondering about the in-tank pump buzzing...

The Tank pump's short feed-out hose may be rotted, possibly affecting the sound.
--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

I replaced my in tank pump a few months ago. I have had a buzzing noise ever since. I figure the pump was sub par or something. The hose sounds like what it would be for me since I just replaced the pump. Might be for you.

The buzzing sounds distinctly electrical in nature - seems odd it would be a hose, doesn't it... or maybe I am missing something

Heres a link to a page on the matter. I remember something being said about getting rid of the buzz.

"I discovered that the 5th fuse (in-tank fuel pump) got busted, replaced it and the buzzing dissappeared."

http://www.swedishbricks.net/faq/fuelpumps.html

I believe it refers to the sound that the main pump makes when working harder when the pre-pump in the tank is bad. I believe you can drive for a while with the pre-pump not working? OR maybe when not working very well? Anyways.

I've replaced all my fuses recently and I still have a constant little buzz sound from the in tank pump.