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220
Joined: 15 Jan 2011
Posts: 28
Location: Southern NSW Aus
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 Posted: Wed Nov 19, 2014 11:32 am Post subject: Fuel pump running continually |
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Fuel pump on the 77 we are doing up is running continuously and Im having trouble chasing the fault.
Relay is a 6pin 477906059 with the fuse on top and pins numbered 15, 30, 31, 31b, 50 & 87
30 to battery (constant power)
15 to ignition (power with ignition on)
87 to pump (powered constantly with ignition on and relay installed)
31 & 50 to earth
31b???? coil? when should I have power at this pin. |
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emoore924
Joined: 13 Apr 2004
Posts: 2822
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| Posted: Wed Nov 19, 2014 12:04 pm Post subject: |
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| Pull the fuel pump relay and see if it stops. |
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220
Joined: 15 Jan 2011
Posts: 28
Location: Southern NSW Aus
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| Posted: Wed Nov 19, 2014 12:15 pm Post subject: |
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| emoore924 wrote: | | Pull the fuel pump relay and see if it stops. |
No power at the pump with relay removed and ignition on so it hasn't been bypassed to run directly off ignition. It is being powered through the relay but like I said has constant power with the ignition on.
Trying to work out if I have a relay that is faulty or if someone has played with the wiring feeding it which is highly possible. |
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Fasteddie313
Joined: 29 Sep 2013
Posts: 2595
Location: MI
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| Posted: Wed Nov 19, 2014 12:16 pm Post subject: |
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running continuously while engine running?
while engine off key on?
while engine off key off?
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80 Turbo - Slightly Modified |
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220
Joined: 15 Jan 2011
Posts: 28
Location: Southern NSW Aus
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| Posted: Wed Nov 19, 2014 12:20 pm Post subject: |
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| Engine off key on, if I turn the key off fuel pump stops |
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Fasteddie313
Joined: 29 Sep 2013
Posts: 2595
Location: MI
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| Posted: Wed Nov 19, 2014 12:28 pm Post subject: |
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ok..
sounds like the safety feature in the relay, tack signal input to 31b, has failed..
it makes the fuel pump only run while it gets a tack signal from the coil in case of an accident the fuel pump shuts off if the engine stops running..
also something about some of those relays having a rev limiter that can cut fuel in the event of an over rev..
be careful your injectors arent spraying while the engine isnt running because of this, it can flood your engine and ruin your oil..
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80 Turbo - Slightly Modified |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Wed Nov 19, 2014 1:01 pm Post subject: |
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| emoore924 wrote: | | Pull the fuel pump relay and see if it stops. |
It will. Power passes through the relay to get to the pump. It will stop if the relay is good or bad. The relay would need to be unplugged & tested for continuity if you think the relay is stuck. The pins should be tested for power with the relay pulled.
31b goes to the AFM. Should have power when the sensor plate is depressed. |
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!tom
Joined: 28 Aug 2006
Posts: 1941
Location: Victoria, BC Canada
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| Posted: Wed Nov 19, 2014 1:16 pm Post subject: |
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| Fasteddie313 wrote: | sounds like the safety feature in the relay, tack signal input to 31b, has failed..
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The tac signal is on late model cars. Early models used a different mechanism.
See some details of how a '78 relay works here (same as '77.5; I'm not sure if the '77 is the same or not).
Your problem could be as simple as the connector to the AFM has come undone, as seen from the details in the above post.
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78 924 NA
5-lug |
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220
Joined: 15 Jan 2011
Posts: 28
Location: Southern NSW Aus
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| Posted: Wed Nov 19, 2014 1:27 pm Post subject: |
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With the relay pulled and key off I have power from the battery only (30)
With the relay pulled and key on I have power from the battery (30) and ignition (15)
Same result when the car is cranking over
With the relay fitted and key on I have power at (30) (15) and (87) about 12.5v
31b is showing 8.5v
The relay must be feeding power back out 31b as there is no power at 31b with the relay removed |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Wed Nov 19, 2014 1:55 pm Post subject: |
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31b is actually a switched ground hooked to a solid state circuit in the relay.
Check the switch on the AFM for continuity to ground with & without the sensor plate depressed (relay pulled). |
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220
Joined: 15 Jan 2011
Posts: 28
Location: Southern NSW Aus
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| Posted: Wed Nov 19, 2014 4:00 pm Post subject: |
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| jason c wrote: | 31b is actually a switched ground hooked to a solid state circuit in the relay.
Check the switch on the AFM for continuity to ground with & without the sensor plate depressed (relay pulled). |
Chasing wiring I found the wiring cut to the AFM.
Reconnected and with the plate down I have no power at the pump, with it raised I have 12V at the pump. Looks like Ive solved the problem.
Thanks for the help. |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Wed Nov 19, 2014 4:10 pm Post subject: |
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