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Testing Combi-relay Outputs
Any of you guys have experience with '74 1.8 F.I. system dual relay? I'm having a tough time trying to test the little black box that sends voltage to the following components:
Air flow meter terminals 86b and88a F.I. resistors terminal 88b Aux. air valve terminal 88c Cold start valve terminal 86 Coil terminal 86c Fuel pump terminal 88d Sure would like to know the voltages at these terminals with the ignition on. Thanks in advance for your help. Al |
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03-21-2003, 04:41 PM
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Join Date: Jan 2001
Posts: 400
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the voltages are all 12 volt or ground,
the power comes from the coil to turn on the relay which sends power to the fi brain it also send power to the fuel pump switch in the air flow meter the big red wires are the power to the fuel pump ignore the white wires they go to the fuel injectors and the brain the coil gets it power from the reg board if you need mor einfo email me and we can talk i have just about rebuilt mine
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scott thacher 75 914 with 2.5 l 98 suby engine on the road |
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03-21-2003, 06:10 PM
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Join Date: Apr 2001
Location: Massachusetts
Posts: 190
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First check for battery voltage (12V+) at 88z (power from battery) then voltage at 86c (power from coil terminal 15) with the key on and make sure that terminal 85 goes to a good ground.
88a - power out to air flow meter contact - 12V with the key on 86b - power in from air flow meter contact - 12V when cranking (with no big vacuum leaks) or moving the airflow flap by hand 88d - power out to the fuel pump - 12V when cranking or moving the airflow flap by hand 88c - power out to the aux air regulator - 12V when cranking or moving the airflow flap by hand 88b - power out to ECU and resistor pack - 12V with key on 86a - power in from starter terminal 50 - 12V when cranking 86 - power out from 86a to cold start valve and ECU - 12V when cranking |
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03-21-2003, 06:11 PM
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Scott & EJ: Thanks for the quick response, your information is just what I need. I was getting 12v. on 88a & 88z but 0v. on 88c, duh, need to crank! O.K. Tomorrow I'll check all the other terminals per your instructions. I have been having unexplained shutdowns with a usually good running engine, thought it may be a broken wire or bad terminal so as I moved the plugs on the relay I noticed it was real hot 140 degrees, that led to checking it out. Maybe tomorrow will tell. Thanks again, Al
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03-21-2003, 09:16 PM
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