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No power to fuel pump

Tiny
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?
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Sunday, August 11th, 2013 AT 11:02 AM

8 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,815 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
Tiny
VRBROOKS
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  • 5 POSTS
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
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 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
Tiny
VRBROOKS
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  • 5 POSTS
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
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 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.
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Saturday, May 8th, 2021 AT 10:13 AM
Tiny
VRBROOKS
  • MEMBER
  • 5 POSTS
Thank you for your help,
Believe it or not I actually talked to a Hyundai dealer service on the phone and he said a bad crankshaft Pos. Sensor could cause problem, bought code reader and crank sensor came up, so I am going to replace it and cross fingers. $87 is alot better than $1500,
let you know how it goes

thanks again for you help
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Saturday, May 8th, 2021 AT 10:13 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
It is possible the CKP can cause non starting but at initial key on, it should not affect the priming. Anyway good luck.
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Saturday, May 8th, 2021 AT 10:13 AM
Tiny
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Yea Crank sensor fixed it thank you.
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Saturday, May 8th, 2021 AT 10:13 AM

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