Full Version: Dual relay bad?
My buddy's car just quit running. It's a 1974 1.8L. He said he only has 1 volt coming from the coil. When he disconnected the yellow wire going from the dual relay to the negative side of the coil the voltage is 12.7. Is this a bad dual relay?
Why would there be a wire from a relay to the - side of the coil? I don't know L jet but that doesn't sound right to me. Should only be points to -side, and tach wire to - side.
L-Jet uses the neg side of the coil for triggering the fuel injectors. There are some good write-ups on testing the double relay, search for them. 
QUOTE(Root_Werks @ Jan 10 2011, 10:50 AM) 
L-Jet uses the neg side of the coil for triggering the fuel injectors. There are some good write-ups on testing the double relay, search for them.
Ah, that makes sense then.
Hopefully it was a white/beige wire.
L-Jet uses the neg side of the coil for triggering the fuel injectors. There are some good write-ups on testing the double relay, search for them.
Ah, that makes sense then.
QUOTE(underthetire @ Jan 10 2011, 11:56 AM)
QUOTE(Root_Werks @ Jan 10 2011, 10:50 AM)
L-Jet uses the neg side of the coil for triggering the fuel injectors. There are some good write-ups on testing the double relay, search for them.
Ah, that makes sense then.
The dual relay gets power from the coil when the key in on or in the start position. This in turns trips one side of the relay and powers the ECU, the resistors, and the AFM.
When the key is in the starting position, the other half of the relay gets power through the terminal at the starter. This trips the second relay and power goes to the AAR and the fuel pump.
Once the engine is running, the AFM flaps stays open, letting power go to the second half of the relay and powering the AAR and fuel pump.
When the key is in the starting position, the other half of the relay gets power through the terminal at the starter. This trips the second relay and power goes to the AAR and the fuel pump.
Once the engine is running, the AFM flaps stays open, letting power go to the second half of the relay and powering the AAR and fuel pump.
The yellow wire from the dual relay should not be going to the coil if it has the original wiring.... There is a series (3) tests you can do to verify a dual relay works properly. It only requires a 9 volt battery and two leads. Shoot me an email with your email address and I can send you a copy--it's in excel.
See pic:
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