MG Car Repair: Starter Relay, starter relay, ohm meter

Question
QUESTION: Can you translate the numbers : 85 86 87 30/51 on the starter relay to the wiring codes from the diagram? The car is a 1977 MGB.
         Thanks, Jeff

ANSWER: Hi Jeff,
Those numbers are universal on most relays today. 85 & 86 are the electromagnet wires in a relay. 87 is output to whatever is being operated. 30/51 is a power supply.
The original Lucas relay was labeled C-1, C-2, W-1 & W-2 .
On your diagram, C-1 (30/51)was the power supply (Brown wire). Output to the solenoid C-2 (87) is (white W/brown tracer) and W-1 (85 or 86) is the trigger wire (white w/red tracer) from the starter switch. And 86 or 85 is the other end of the electromagnet and must be grounded (black wire)
I say "85 or 86" because I don't remember which is which. On most relays it does not matter except when the relay manufacture adds in a diode to the electromagnet. This is easily tested off of the car with the use an ohm meter to test between 85 and 86 in each direction. If the ohm meter test is ok in either direction then it does not matter which way you connect the two. A test light and battery can also be used to test for a diode.
Howard


---------- FOLLOW-UP ----------

QUESTION: Hi Howard,

Thanks for your fast response. I received my new starter relay today and I am still not able to getting the B to run. I have 5 wires that need to go to the four terminals. The wiring diagram I got from Autowire list the following:

W/1: is the dual connection with one (white/red) going to the hand brake switch and the other(white/red) also going to the ignition switch

W/2: is Ground which I am assuming is the black wire.

C/1: Is brown and runs to the solenoid

c/2: Is white/brown and also runs to the solenoid

Now for my dilemma, the wires are old and the stripes on the 3 white wires are faded.
1 is all white and the other 2 are white/brown. One of the white/brown's is the same gauge as the brown wire, maybe 10 gauge. The other is the same as the all white, 14 to 16 gauge.

I tried the following and got it to turn over, but would stall as soon as I moved the key from start to run.

W/1: the 2 white 16 gauge wires (86)
W/2: the black ground wire (85)
C/1: the 10 gauge white/brown wire (87)
C/2: The 10 gauge brown (30/51)

Also, In this configuration,the brake light does not light while the key is in the on position but does while the key is in the start position, leading me to think at least one of the wires is wrong.

HELP!!!
         Thanks again, Jeff

Answer
Jeff, if the car starts and runs as long as you have the key in the start position, the starter relay has done everything it should. Running after the key is released to run position has nothing to do with the relay any more.
Power to the coil comes direct (12v) from the small spade connector on the solenoid when the key is in the start position. When the key is released to run position, the power to the coil comes from the ignition switch to a resistor wire and on to the coil at a reduced voltage. So just turn on the ignition (not start)and check for power on the coil to see if the run system is connected correctly.
Howard