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MG MGB Technical - Starter Solenoid

I have had a few problems getting the MG starter to turn over this spring. I have a new battery and terminals installed in Feb. What is happening, I turn the key, hear the fuel pump, but the starter doesn't turn. If I try it 2 or 3 times, it usually catches, turns over and starts easily. Will I need to remove the starter to replace the solenoid, could it be the key switch? I plan to clean all connections tomorrow, the starter area looks oily, probably from spilling oil at filer changes.
Joe

I had the same problem and asked the same question 27.11.08 and got a lot of help from the forum. It could be the connections on the starter, especially if the cover is missing. But mine was the solenoid.
c cummins

I cleaned the inspected the terminals on the starter and solenoid, and the it starts on the majority of attempts. I am beginning to suspect the ignition switch, last winter, having problems with the key sticking when turning it over, I squirted a bit of graphite to lubricate the mechanism, which helped. Today I blew out the excessive graphite with compressed air. The only thing that leads me to believe this is the problem is that while turning over the key, it feels different than in years past. I also checked the battery charge while running, a little over 14 volts @ 1000 rpm, so I guess it is charging. The ignition switch is around $70, I believe I will try this if the problem persists, or gets worse. When the starter doesn't turn over, I don't hear any sound except the fuel pump ticking, the red ignition light does not dim. If I try the key 2-3 times, it catches. But the key mechanism feels different than it used to, 37 years of wear might do that. Anyone else ever encounter this?
E. Dufresne

Have you tried testing the starter using a "bump" starter switch?

If the starter engages and spins smartly using it - then I would suspect either the starter relay (it's next to the fuse box) or the
ignition switch.
Daniel Wong

What year? From 69 on there should be a starter relay. You should be able to hear this click if the ignition switch is operating the relay. If the relay is operating the solenoid the clonk from that will drown out the relay, and if it cranks then the grinding of the motor drowns out the clonk of course. So it depends on your year and what you can hear.
Paul Hunt

Keep a 3 foot stick in the car. If it won't turn over just open the hood and tap the starter a bit with it. Works for me! Bob
Bob Ekstrand

If you suspect the switch I would do what Daniel suggests. Hook in a temporary starter button across the start terminals on the back of the switch and use that to start the car. If it starts every time then you know the switch is bad. This is much easier in an early car with the switch in the dash rather than the later steering column ones.

The starter solenoid will wear out over time. There are copper contacts in there that arc and eventually erode away. There are also little springs in there that can break eventually. I put some pictures of mine here http://asciimation.co.nz/pics/page12.html.

When the contacts errode like that you get intermittent contact. I got exactly the symptoms you describe.

A new solenoid was surprisingly cheap (and made in Japan!) and was easy to fit and that cured my problems.

Simon




Simon Jansen

The only sound I hear is the fuel pump. I retry the key, and it starts the 2nd or 3rd try. Sometimes the car starts on the first try, which makes all of this harder to diagnose. With the binding problems I have had with the ignition key in the past year, could this lead to a failure of the switch?
Joe

Like so many things on our old cars, there are so many connections that can wear or corrode.

You've been given a great deal of good advice already, but in my experience, when I run into this condition it clears up when I clean the connections at the starter solenoid that are prone to corrosion and fouling.

Also, other than what's been mentioned already, there are the pin connections in the white (ignition) circuit, too.

Good luck, and please report back.
John Z

"tap the starter a bit with it. Works for me"

Oh dear, that's what makes a DPO!

Joe - you still don't tell us the year of the car. Without that or otherwise knowing whether it has a starter relay or not (beside the fusebox) it is difficult to diagnose or give other than general hints.
Paul Hunt

It is a 1972 MGB, I believe the relay is next to the fuse box and is a Lucas 6RA. Other than cleaning the 4 external connections, is there anything I can do to test it with a simple multimeter and an even simpler person operating it?
Joe

If you can't hear the relay click when you turn the key to start then test for 12v on the white/red on the relay when you turn the key to start, the connector on the wire as well as the spade on the relay.

12v on the wire connector but not the relay spade means that connection is bad.

No 12v on the white/red means the fault is back towards the ignition switch. Test again both sides of the multi-plug where the ignition switch harness joins the main harness, and again on the ignition switch itself. That should tell you whether the connector is at fault (12v one side but not the other) or the switch itself (no 12v from that), or possibly is a broken wire between the multi-plug and the relay (12v both sides of the connector, unlikely).

If you have 12v on the white/red at the relay test again on the relay spade that feeds the black wire and the connector on the black wire itself.

12v on the relay spade but not the wire connector means that connection is bad. 12v on both means the ground connection to the body is bad, it is a bolt-through terminal where the harness is clipped to the body by the fusebox.

If you have 12v on the relay spade for the white/red, and no 12v on the relay spade for the black, then either the relay is faulty or the wires are on the wrong spades. White/red and black should be on W1 and W2 in either order, brown and brown/white should be on C1 and C2 in any order.

Paul Hunt

This thread was discussed between 28/03/2009 and 04/04/2009

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