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Old 08-04-2005, 08:26 AM
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Relay issue? Starting problems

The '74 Jaguar that I am working on won't start. It has a relay on the firewall that powers the starter solenoid (GM starter, Chevy engine) when the key is turned on.

The original relay appeared to be dead...the wire powering the starter solenoid never showed any power going to it when the key was switched on. Jumpering the power wire on the relay to the starter energizer wire next to it resulted in the engine turning over normally without even turning the key. I replaced it with a unit from NAPA that some people on a Jag board told me was a better choice. It is wired correctly. The power wire feeding it shows a constant 12+ volts, and the battery shows 12.3 volts at rest. However, the wire feeding the starter shows only 10.6 volts at the relay when the key is switched on. Furthermore, using a jumper wire on the stud on the solenoid that holds the power wire, it shows that I have only 2.7 volts when the key is turned on. The result of all this is that trying to start the car yields only a clicking noise. Resistance from the starter's power wire at the realy to its connection at the starter itself is about 1.3 Ohms.

Oh, and the people at NAPA load tested my battery and said that while a little low, it was good, and a trickle charge should be all it needs.

Any ideas?

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Old 08-04-2005, 09:59 AM
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"the wire feeding the starter shows only 10.6 volts"

What wire are you talking about? The big hi current battery cable or the small wire that energizes the coil?


Rich
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Old 08-04-2005, 10:16 AM
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The small wire feeding the starter solenoid. The terminal to which it is plugged, on the relay on the firewall of the car, shows 10.6 volts with key on. The other end of that same wire, at the solenoid of the starter, shows only 2.7 volts with the key on.
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Old 08-04-2005, 10:39 AM
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OK not sure what style of starter you have. If its the old style with the starter solenoid built on the top with the battery cable attached and then a small wire???

BUT, all that a side. If you have a wire and one end shows one voltage and the other end shows considerably less in a low current situation like this the wire/connectors are bad or there is something in between that you dont know about.

The old style traditional starter with the solenoid on top do not need an external relay. Might be something to do with the conversion. As a Jaguar owner you will get pretty good at solving electrical problems

Rich
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Old 08-06-2005, 04:13 PM
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Starter

Doc here,

To Clarify...

You have a Starter, mounted on the Block, with also a GM solenoid mounted atop it, and a "Ford Type" Solenoid mounted on the firewall?? Yes or no?

If that's the case, I would say the layout will be as follows for each) From the battery to the solenoid, constant 12 volts, The big terminal (opposite side)going into starter, 0 volts (until energized)

The "S" terminal (18 gauge) 12 volts ONLY when the key is in "Start" ..

The "I" terminal (18 gauge) 12 volts (if ignition resistor not used, 6 to 9 volts if one is used) ONLY in "Start" position.

If you are getting 12 volts in (on the big cable) and 2 volts out (on the other side to the starter) you have a loose connection, bad starter winding, or a bad ground at the starter motor. Check that. A Burned Starter solenoid contact (at either solenoid) will also cause the same problem.

If you are just using a relay to control the "Start" Function, and you get 12 volts in and 2 out, it's a burned contact on that relay.replace Or bypass it.

Doc
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