Not getting 12 volts to fuel pump.

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douglas vincent
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Not getting 12 volts to fuel pump.

Post by douglas vincent »

So when you turn key on, you should get 12 colts for a second to prime fuel system. Then the voltage drops to 3.5ish and sits there till car is started and the voltage is turned back on to 12.

Mine has decided to not do the 12 part and just sits at 3.5. The relay is clicking when key is turned off and on.

What am i missing?

Currently just hotwired the pump.
Reddevil, Awaiting new heart, will it ever happen?
1990 wagon, EJ25 12.3 @ 116.5 FAST Family wagon getting new motor soon
1992 wagon, wifes daily, high compression
1992 Touring wagon, should I keep it?
Legacy777
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Re: Not getting 12 volts to fuel pump.

Post by Legacy777 »

Hi Doug,

Long time no talk. Hope you are good!

If you connect the green diagnostic connectors do you get 12v on and off when the relays engage or still the 3.5v?

If you're still only get the 3.5v then it could be the fuel pump relay or something in the wiring from the relay to the pump. Have you tried checking things with a multimeter and tracing down the wiring diagrams?

https://surrealmirage.com/subaru/files/ ... rical1.jpg
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
douglas vincent
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Re: Not getting 12 volts to fuel pump.

Post by douglas vincent »

Relay is clicking.

Do you know what causes the 3.5 to 12 volt action?

Hot wire is working fine.
Reddevil, Awaiting new heart, will it ever happen?
1990 wagon, EJ25 12.3 @ 116.5 FAST Family wagon getting new motor soon
1992 wagon, wifes daily, high compression
1992 Touring wagon, should I keep it?
Legacy777
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Posts: 27884
Joined: Tue Oct 15, 2002 11:37 am
Location: Houston, Tx
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Re: Not getting 12 volts to fuel pump.

Post by Legacy777 »

Sorry Doug....just seeing this post.

If with the green diagnostic connectors connected you're seeing voltage go from 12 to 3.5v then that would tell me that the relay is working and the ECU is working because it's telling the fuel pump relay to cycle. Check the voltage on the ECU's F47 connector, pin 23. With the ignition switch on (engine off) you should have 0.7V. With ignition switch off you should have 10-13V. With the engine running you should have 0.7V.

It appears that something is not allowing the ECU to turn on the fuel pump. I do know that the ECU will prime the pump on key on and then will only apply voltage to the fuel pump when it detects cranking. Are you getting any other codes? Does the engine run if you "hot wire" the fuel pump?

I checked "notify me when a reply is posted" so should be a little quicker with the reply :)
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
arse_sidewards
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Re: Not getting 12 volts to fuel pump.

Post by arse_sidewards »

Does the engine run if you give it a good bunch of starting fluid down the intake?
'93, '93 and '94 Legacy L, wagons, FWD and AWD, all are NA 2.2 w/ 4EAT.
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