No power to fuel pump

VRBROOKS

MEMBER
2004 HYUNDAI SANTA FE
70,000 MILES

On 2004 santa fe, 4yl, auto, I am not getting power to fuel pump. Checked all fuses, relays, I think the computer is not grounding fuel pump relay based on a similar problem answered by razmataz

" Replied on April 27, 2009
Could be the computer not grounding the fuel pump relay
Do a continiuty test on the orange and gray wire at the fuel pump relay connector to pin 20 at the computer
Answered by rasmataz"
Continuity good, if the computer is not grounding the relay, does that mean the computer is bad? The fuel pump relay is good, it does not close when key is turned on, if I run a jumper from orange and gray wire to ground, turn key on relay closes pump turns on, still wont start.
Also am not getting spark at plugs, could that be caused by the fuel pump problem? Another response to that was-
"Replied on April 28, 2009
Check and test the engine control relay and ignition failure sensor-
Answered by rasmataz"
How do I test those?

8 Replies

KHLOW2008

MECHANIC
41,814 POSTS

Start by checking for battery voltage to the relays and testing the relays for input and output voltages.

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Saturday, May 8th, 2021 AT 10:13 AM

VRBROOKS

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Yes there is battery voltage at relays on the power circuit side, When I turn on the key I get voltage to the control circuit side of the relay, however the relay does not close to complete the power circuit, if I ground the other side of the control circuit ( did this by accident trying to check with test light) the relay closes the circuit and the fuel pump comes on.
I know the relay is good I tested it and have swapped it out with other relays to be 110% sure.
I put a jumper wire across the power circuit of the fuel pump relay and pump does come on. Also when key is turned on all ECU fuses get power to them.

P.S.
I have been looking for the wiring diagram you put in your reply for days.

Thank you your reply, any assistance I can get is greatly appreciated.

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Saturday, May 8th, 2021 AT 10:13 AM

KHLOW2008

MECHANIC
41,814 POSTS

The diagram don't seem to work when I click to enlarge. Are you getting the same problem?

The fuel pump relay is grounded by the ECU, terminal #20, Grey/Orange wire. If you ground this terminal with a test light and fuel pump works, the problem is most likely a bad ECU.

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Saturday, May 8th, 2021 AT 10:13 AM

VRBROOKS

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Yea that's kinda what I thought, I did not ground it at the ECU it was at the fuel pump relay but that should be the same thing, it was just on the other end of the orange gray wire. Did continuity test to be sure I was in the right place.
Now can a used computer be out in or do I have to go to Hyundai ($1500) to get to get a new one, can I put it in myself?

Thank you again for your help
and yes the image does enlarge when clicked.

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Saturday, May 8th, 2021 AT 10:13 AM

KHLOW2008

MECHANIC
41,814 POSTS

If grounding by the ECU does not produce the same result, that would mean a break in wiring circuit between the ECU and relay

Presently I am away from my main computer and database and is using a lap top that does not allow me to access the required information so I am not sure if you can just plug in the computer. I am not sure how soon I would be back home so no promises yet.

Most likely you would need to have it programmed whether new or used.