Starter won't engage when key is turned.

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mattmatthew

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When key is turned in the ignition, starter won't engage. However, when the key is merely in the ignition, and I manually bypass the relay by connecting the constant 12v line in to the solenoid out, it starts right up.

I replaced the starter relay pretty recently (about a year ago). And I also fully charged the battery a few days ago. I haven't yet eliminated the relay as the problem, as I realize that the stuff being made in China these days is absolute garbage.

But at the same time, I don't want to just start randomly replacing parts. Ideally I'd like to trace the problem back to the source, and fix just the thing that's causing the problem.

(BTW, this is for a slant 6 225 motor, A904 trans.)

Anyway, I'm trying to wrap my head around how all this stuff works. I read some stuff on how relays work. And I'm not the greatest at reading or comprehending lengthy explanations especially when I don't understand the fundamental principles at work (I've already read over a dozen past forum posts on similar subjects).

I drew this diagram based on what I saw under the hood and what the wiring diagrams in the service manual show.

I'd like to know if I got this right.

starterrelayA_zps88b2dc73.jpg


And if this is right, if I apply battery voltage to the ignition "in", if the relay is working properly it should trigger the relay to allow voltage to the solenoid? And if it's not the relay then it must be the ignition switch?
 
is the wire to the neutral safety switch on the transmission hooked up?
that would be the G terminal on the starter relay switch...

make sure the plug is on the neutral safety switch on the trans...

and to do quick check...just ground the G terminal to the car...see if starter spins with key...that will tell you if the NSSW is hooked up or not.
 
AS above, here's how these work.

The coil of the relay is hooked to the two "push on" terminals, which are interchangeable. One is hot "in start" coming directly from the IGN switch, and in order for the relay to pull in, the remaining "push on" terminal must see a ground from the neutral safety switch.

Yes, the "s" wire (traditionally yellow) should be "hot" in "start."

I would first hold the key to start, then wiggle the shifter in/ out of park and neutral. If you get a start, or kick out of the starter, you've found the area of the problem. NSS could be bad, or linkage out of adjustment.

A further check would be to use a clip lead, and ground the relay terminal running down to the neutral safety switch. This should result in the engine cranking in "start" CAREFUL it will now crank "in any gear."

If you don't get a crank or relay "click" with the NSS terminal grounded, now try pulling the yellow "start wire" and jumpering from that exposed "push on" relay terminal over to the big battery stud terminal. If this final act results in no crank, replace the relay.

Also, if you can hear the relay click but the starter won't, jumper from the big battery stud to the "square" solenoid terminal. If the starter operates, and you can hear the relay click "with the key," you also have a bad relay.
 
Great explanations above. I'll add:

The starter relay rarely fails.

The problem is usually the NSS. Not the part itself, but the transmission is not exactly in P or N due to a mis-adjusted linkage.

If you are sure the transmission is in P, connect a jumper wire from the NSS terminal to ground. Before you try starting, block the wheels and stand to the side in case you aren't really in P.

If the key still doesn't work, try by jumpering 12 V from the big stud to the "Start" terminal (yell wire).
 
Jacked the car up today and put her on jackstands.

I forgot to mention this earlier - I have an early 63-66 A-body with a 71 slant and a later model A904. Based on my web research the later model has the 3 prong male. When we did the motor/trans swap a few years back (a friend helped me), I didn't recall hooking up the NSS, and since I was (and still kinda am) a noob at all of this, I think to just get the motor to crank, my friend grounded the prong on the relay to the motor, bypassing the NSS. He warned me that I wouldn't have backup lights but not super sure he knew to ground it via the NSS.

So anyway, after I jacked it up today, I poked my head under and confirmed that it's a 3 prong male switch. And I also confirmed I don't have anything hooked up to it. So that's something I plan to remedy, as well as the backup light switch for my aftermarket B&M Starshifter.

But I wonder: is this the problem? If my NSS prong on the relay is already grounded to the motor, shouldn't it start up?

The relay as mentioned before, is still fairly new. Could the problem be with the ignition switch at the key? How would I go about testing this?



[To complicate matters, I swapped out the old positive terminal cable for a new one. The insulation was cracking on the thick wire that goes to the starter so I figured as long as I put everything back the way the old one was (large wire to the starter, smaller wire to the relay), it should at least crank if I bypass the relay. Instead I got a click on the starter. I tested the voltage at 3 spots: 12.25v at the positive terminal on the batt, 12.25v @ the positive IN on the relay, and 12.25v at the starter solenoid. I know, I know, I should learn to fix a problem before I create a new one. Any thoughts?]
 
Is this by chance a 1974 model car ? If it is a seatbelt interlock relay could be the problem
 
mattmatthew said:
But I wonder: is this the problem? If my NSS prong on the relay is already grounded to the motor, shouldn't it start up?

The relay ...... is still fairly new. Could the problem be with the ignition switch at the key? How would I go about testing this?



I swapped out the old positive terminal cable for a new one. ............ it should at least crank if I bypass the relay. Instead I got a click on the starter. I tested the voltage at 3 spots: 12.25v at the positive terminal on the batt, 12.25v @ the positive IN on the relay, and 12.25v at the starter solenoid. I know, I know, I should learn to fix a problem before I create a new one. Any thoughts?]
Click to expand...


I tried to explain this earlier so once again

You have TWO "push on terminals on the starter relay which are the coil. You can switch the wires to them, they simply go to the magnetic coil in the relay.

1---One push on comes from the IGN switch, through the bulkhead and to that terminal. It should be HOT when key is held to start

2--Remaining "push on" goes to NSS or in your case ground to the block.

So with the key in "start" the relay should pull in.

3--The BIG STUD is one side of the relay contacts as well as a battery junction point. This is the large wire coming from the battery, and going TO the large starter MOTOR terminal.

4--The "square" screw terminal is the "switched" side fo the relay contacts and feeds power to the starter solenoid This is the no10/12 wire going to the starter SOLENOID

A--Start by jumpering across the two starter terminals with a screwdriver. The engine should crank.

If not, battery cable or dirty terminals, hooked up incorrectly, or bad starter Clip your meter directly onto the large starter stud, and the other to the engine block. Jumper across and read the meter. It should read more than 10.5v, the more the better. If you get more than 10V and the starter won't crank, bad starter.

B--IF the starter works, in test "A" above, move up to the relay.

Jumper across the battery stud and the "square" screw terminal. Starter should again crank. If not poor connection/ bad wire from the relay to the starter solenoid, that is the smaller no 12/ 10 wire. IT IS COMMON for this wire to break inside the ring terminal at the starter because of engine vibration

If starter operates in "B" above:

C--Clip your meter to the engine block, and back probe the "start" wire on one of the "push on" terminals Prop up the meter or use an assistant, and twist the key to "start" You should get "same as" battery voltage

If not----Check at the ignition switch, and if you get voltage there "in start" then the switch or the connector is bad or you are not getting power TO the switch

Check the bulkhead connector -- you may have a bad connection there

IF the above checks OK, that is you DO get battery voltage in "start" but the relay will not operate, you only have two options left----

either your "fake" NSS ground wire is not actually grounded, or the relay is bad.

SO leaving everything hooked up as before, back probe the terminal which is grounded to the engine, other probe on the engine block. Twist the key to "start" and if you read voltage, the ground wire "is not really grounded."

If you get NO voltage reading, REPLACE the relay.
 
67dart,

Thanks! Using your advice and the help of a friend we traced the problem to both the starter and the relay.

We opened up the relay, and found a small piece of manufacturing debris between the coil and the contact plate, which was preventing the circuit from being consistently completed.

(Opening up the relay also showed me how the relay works, wow, really simple!)

And there was no voltage on the starter stud when the two were connected. Opened the starter up just for fun, and brushes on the inside looked hammered and a few key wires were cracked. Turned the starter in as a core last night and bought a warrantied remanufactured starter.

Put it all back together this morning, and it fired right up. To be honest, I don't ever recall EVER hearing the starter sound that strong. (And I've been with this car since 1992.)

Thank you everyone for all your advice and patience! I feel like I'm beginning to understand how the electrical stuff works just a little bit more. And I need to pick up a testing light, that thing is awesome.
 
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