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Old 04-03-2021, 10:08 PM   #1
dandeluca
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Default 91 240 fuel pump behavior

So I’m just trying to find a clear answer for this, sorry for the basic question. When I turn my key to the “on” position I hear my fuel pumps turn on. It seems like they would just stay on forever if I left the key like that. (Though I never left it on for more then 30 seconds or so.) The car starts and runs fine. Should the pumps stay on or should they cycle off after a second or two?

If it’s supposed to turn off could it be fuel relay or did someone modify it to run this way?

Thanks!
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Old 04-03-2021, 11:03 PM   #2
dandeluca
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Okay, so after some research it seams that the pumps should only really run when the car is running. I went to look at my fuel pump relay someone cut the green wire and spliced in a new wire. For the sake of safety I will try to revert it to original.
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Old 04-04-2021, 01:23 AM   #3
Mr. V
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Hold on: before you tinker check a wiring diagram: there's gotta be a reason they did that.
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Old 04-04-2021, 04:32 AM   #4
Otto Mattik
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Quote:
Originally Posted by Mr. V View Post
Hold on: before you tinker check a wiring diagram: there's gotta be a reason they did that.
That's what I was wondering, maybe the wire was just replaced ?
Any chance you can post a photo or a link to a photo ?

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Old 04-04-2021, 05:56 AM   #5
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The ECU could have failed so some smart person ran a power feed directly from the ignition to the fuel pump wiring or relay
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Old 04-04-2021, 09:50 AM   #6
dandeluca
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There have been a few head scratchers with the car when I think the PO was just throwing stuff at the wall. He hardwired 12V to the alternator exciter even though the normal wire works perfectly. My in-tank pump was just missing.

Here is what the fuel pump relay looks like.



I believe that the green and blue wire is the signal wire. It will take a little contortion but will cut the wires so I can swap it back and forth and see what happens.
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Old 04-04-2021, 02:20 PM   #7
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I always reference 240turbo.com relay info pages when I deal with fuel relay crap
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Old 04-04-2021, 02:21 PM   #8
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check out realy info and diagrams on 240turbo.com
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Old 04-04-2021, 03:00 PM   #9
RickATL
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Default Fuel pump relay

You will hear the one pump prime when you turn the ignition to where it all lights up. That is normal.



Also, don't assume the relay is good if its new. I had a Uro one that was dead on arrival. Mechanic pulled them both apart to show me the difference and it was crazy how cheap the new one was made.



I recently replaced both pumps and now I can always hear the tank pre-pump running, even though I didn't before. Mechanic who double checked it for me said the tank pump will always run. I couldn't confirm that.
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Old 04-04-2021, 03:11 PM   #10
2manyturbos
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The ECU kicked the bucket so they grounded the relay in order to keep the car running. The ECU grounds the relay through that blue-green wire. You need a replacement ECU.
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Old 04-04-2021, 03:13 PM   #11
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Quote:
Originally Posted by RickATL View Post
You will hear the one pump prime when you turn the ignition to where it all lights up. That is normal.



Also, don't assume the relay is good if its new. I had a Uro one that was dead on arrival. Mechanic pulled them both apart to show me the difference and it was crazy how cheap the new one was made.



I recently replaced both pumps and now I can always hear the tank pre-pump running, even though I didn't before. Mechanic who double checked it for me said the tank pump will always run. I couldn't confirm that.
Your mechanic has no clue what he is talking about. Both pumps are turned on/off through the ECU via the fuel pump relay.
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Old 04-04-2021, 05:55 PM   #12
dandeluca
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Volvo 240 now with customizable fuel pump control!



In all seriousness the pumps work correctly now that it is wired correctly. I don't know if ECUs can have intermittent failures, but this wouldn't be the first time I found something "fixed" that should not have been on this car.
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Old 04-04-2021, 06:27 PM   #13
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I doubt it. The "fix" was probably temporary until the PO could get a replacement ECU, then forgotten about.
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Old 04-05-2021, 02:42 PM   #14
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Quote:
Originally Posted by 2manyturbos View Post
I doubt it. The "fix" was probably temporary until the PO could get a replacement ECU, then forgotten about.
Or until he could unload the car.

If you want it corrected "for safety" without spending money on another ECU, I have cures here:
https://www.240turbo.com/fuelpumprel...rsalcontroller
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