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FC S5 T2 fuel pump relay

Old 10-19-18, 09:33 AM
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FC S5 T2 fuel pump relay

Hi,

This morning i've had a strange issue.

Basically I went to work and on my way i refilled the tank.
I parked at work and one hour later when i had to leave to another place, the car wont start.

After checking during my lunch break, the issue was that the fuel pump was not receiving the +12V.
So it's look like it's either the plug of the harness, the harness itself or i suppose the relay.

I finally have it working again with no real explanation. What i notice was that while it couldn't start, i couldn't hear the relay switching and once the car managed to start, it was ticking.
I wonder where this relay is, and how could I test it. is it one the 4 install on the front crossbeam, in front of the radiator ?
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Old 10-19-18, 10:13 AM
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Hope this helps: Google results for FC pump relay

You can also download a copy of the FSM here: Foxed.ca
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Old 10-19-18, 10:36 AM
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The fuel pump circuit opening relay, which cuts the fuel if the engine stalls, is located under the dash next to the steering column. The circuit opening relay has a yellow connector.

The fuel pump also has resistor/relay located in front of the air filter box. Here is a photo: https://www.google.com/search?q=rx7+...BNIAl5sNahK1M: The fuel pump receives full voltage at start-up and then drops to low voltage shortly thereafter. If the resistor had failed, than when the relay opens to drop the voltage the fuel pump will lose power and the engine will die. Check the relay and resistor as per the FSM.
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Old 10-19-18, 10:47 AM
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i was posting will you replied.

Thanks that helps.

Basically what i've done was measuring voltage at fuel pump connector on the black/white wire.
there was nothing and by tinkering next to the connector, at some point it got a solid 11V that allowed to start the engine afterward.

I would have said the harness is at fault, but even when moving the harness it doesnt cut now.

So i've seen the method to test the resistor and it seems feasible.

Last edited by Grunswald; 10-19-18 at 10:53 AM. Reason: d
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Old 10-19-18, 11:27 AM
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Quick update, just drove back from work, the car ride smooth as usual...

I remembered one thing, while I drove back from the petrol station to my job (5min drive) two times i've had the warning buzzer going for maybe half a second.
So i suppose it's because the fuel pump got "offline" for a second.

If one of the two relays discussed above would fail, would it turn on the buzzer alarm ? would either of them turn it on?
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Old 10-19-18, 02:08 PM
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Originally Posted by Grunswald View Post
Quick update, just drove back from work, the car ride smooth as usual...

I remembered one thing, while I drove back from the petrol station to my job (5min drive) two times i've had the warning buzzer going for maybe half a second.
So i suppose it's because the fuel pump got "offline" for a second.

If one of the two relays discussed above would fail, would it turn on the buzzer alarm ? would either of them turn it on?
No. Check your coolant and oil levels.
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Old 10-20-18, 04:10 AM
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i'll check but for the oil, i have a baffled oil pan so i dont really have issues with oil ( but i agree that if there aint enough oil anyway i'll have an alarm).

For the coolant it's even weirder... recently i've changed the radiator and the piping. I had previously an aftermarket radiator from another car cutted and welded by a shop to fit on my car... more or less a piece of ****...
On this one, they had removed the coolant level sensor because there was no place to install it (and also the original radiator brackets...). I suppose they put a jumper in the harness plug and hided it cause i can't find where it is.
Basically i've now a proper koyo radiator where the new coolant sensor that i bought additionily is only used to cap the top passenger side hole be cause i don't know where is the harness plug
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Old 10-30-18, 03:45 AM
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The wire for the coolant sensor should be right by that hole where you put your new sensor.
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Old 10-30-18, 03:50 AM
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Look under your air box /air filter for that wire , maybe they just wrapped it and put it under there somewhere.
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Old 11-25-18, 11:03 AM
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ok...

i've had lot of work and the rx7 was driving correctly, so i didn't really took care of it.
But now, she doesn't drive anymore so i've checked it.

First thanks for the picture of the coolant probe harness, i looked and it seems to have been completely removed...

I removed the fuel pump resistor and measured the resistance. here is what i have :
A-B : 0.04ohm
C-D 79.5ohm
E-F 1.2ohm

so i believe that i'm good for A-B and C-D but E-F seems toasted (should be between 0.70 and 0.94).
Am I correct ?

If I am, that means that only the resistor with the fins has to be replaced, the relay seems ok.
Is that possible (and cheaper) is it factory sealed to the little bit of harness ?
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Old 11-26-18, 02:04 PM
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Now for the fuel pump circuit opening relay:
it behaves as described in the FSM except that it seems to deliver only 10.9V

i've checked the resistance :
STA-E1 gives 26 ohms
B-FC gives 140 ohms
B-FP gives infiny

so this is perfectly in bound.

I've checked my battery and it says 11.3V... I hadn't expected that, moreover than when it first broke it was after a 30-45 min drive where it started perfectly before.
I'm charging the starter booster to see if it helps but it's weird... or my multimeter is shot...
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Old 12-21-18, 02:59 AM
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so since my last post the car was in running order (don't really know why) so i didn't really cared...

This morning i went to start the car and it was not starting again...

i will order the a new fuel pump resistor and hope it fixes it.

additional question : while it was running this month, my idling speed was at 2000rpm when cold and it lasted until the oil reach 90C.
Can it be linked to the resistor somehow ?
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Old 01-12-19, 04:18 AM
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Ok, so i received the resistor and changed it but the problem is still there.

Yesterday when leaving work the car wouldn't start. I tried several time with no chance.
I went in the boot and moved the fuel pump harness in hope that if it's a short cut, i'll have contact at some point.
didn't work.
I have a battery booster in the car so I thought i would try using it.
So I pop the hood And then (before installing the booster) i hear this sort of ticking noise. I know it's the sound of something fuel related (the pump priming ?) so i try to start the engine and it works.

this ticking noise comes from what ?
a mechanic friend of mine told me to inspect the neyman contactor before going further. I believe it's a good idea but i don't know how to do it. Do you have a procedure ?
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Old 01-17-19, 03:24 AM
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any idea on what should be the way forward ?
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