Starter Solenoid Bypass

[Kittrell]

My buddy's '90 XJ wasn't starting, so I took a trip down to his place. When you would turn the key, it'd just click. He thought it was the starter, so he replaced it with a reman. from checker. When I got there, it was doing the same thing. So I jumped the starter, and she fired right up. Jumped the starter relay and got the same click. So I am assuming the solenoid on the new starter is bad. Sound about right?

 

[8Mud]

It sounds like the wire from the stock starter relay and the solenoid may be bad or the connectors. Or possibly the starter relay is corroded inside. It's possible the solenoid isn't getting enough juice to seat the contacts completely. The spring inside of the solenoid is pretty stiff.
Try jumping the solenoid wire from the relay directly to the battery and see what happens. I think it's the green wire that goes to the "S" connector on the starter relay.
Solenoids rarley go bad. Brushes inside the starter do, the wire from the starter relay to the solenoid kind of flops around fatigues and frays (sometimes under the insulation) and the starter relay gets full of water and rusts inside. Batteries get weak and/or the connections are faulty.

 

[5-90]

The start solenoid does two things -
1) Engages the start motor drive pinion (the "solenoid" part) by extending it.
2) Closes the circuit to allow current to flow through the main start motor windings (the last part of the solenoid's travel, usually actuated by the plunger used to pull the pinion gear forward.)

If the start motor worked properly once the solenoid was fed directly, and worked again neatly when the relay was "jumped," you've probably blown a start relay instead. Later models (1991-up) seem to use the standard Bosch/Hella relay, and earlier models (1984-1990) used an OEM contraption, which may be replaced with a standard Bosch relay (I've really got to remember how I did that...)

The starter solenoid usually draws something like 15A or so (with a current spike as well!) so the start relay is used to take that load and strain off of the ignition switch on the bottom of the steering column. The start motor relay is usually FAR easier to replace...

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[Kittrell]

Try jumping the solenoid wire from the relay directly to the battery and see what happens. I think it's the green wire that goes to the "S" connector on the starter relay

I did jump the relay, hence "Jumped the starter relay and got the same click."


Jon, the only time we got it to start was when I jumped the starter directly, via a hammer head connecting the posts, bypassing the solenoid. Any other time, I just get a click.

 

[5-90]

Did the starter actually crank the engine, or did it just "whir?"

A valid question - if the starter just "whirred," the solenoid is shot and not drawing out the pinion gear (which means it won't energise the motor windings, either.) If the starter worked normally, the problem is elsewhere - and the starter is fine.

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[Kittrell]

Did the starter actually crank the engine, or did it just "whir?"

A valid question - if the starter just "whirred," the solenoid is shot and not drawing out the pinion gear (which means it won't energise the motor windings, either.) If the starter worked normally, the problem is elsewhere - and the starter is fine.

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It just threw sparks until he turned the key over, so I believe it just "whired"

 

[5-90]

Since I wasn't there, this may be losing something in the translation. What, exactly, did you do, and in what order - and what happened and when? In detail, please - if I don't need to know something, I'll just ignore it. Leave out something important, and I'll be wrong (and that won't be much help, will it?)

Help me help you - I'm still thinking "start relay," but I'm not so sure...

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[Kittrell]

Alright, when I got there, he had already put in the new starter. At that point, when you turned the key over, all you got was a single click. So I crawled under the Jeep, stuck a hammer on the starter to bypass the solenoid (connected the posts), and it fired right up when he turned the key. After that I took the lower green wire from the relay, and jumped it to the battery. All it did was click, basically the same result as turning the key.

 

[5-90]

Alright, when I got there, he had already put in the new starter. At that point, when you turned the key over, all you got was a single click. So I crawled under the Jeep, stuck a hammer on the starter to bypass the solenoid (connected the posts), and it fired right up when he turned the key. After that I took the lower green wire from the relay, and jumped it to the battery. All it did was click, basically the same result as turning the key.

Wiring fault, then. If the key was on and bridging the two terminals with something metal (hammer head?) cranked the engine and it started otherwise, then there's nothing wrong with the starter.

I'll be busy to-morrow, but later I can pore over my 1990FSM wiring diagrams and see what I can offer. I've also got 1989FSM wiring diagrams posted in my XJOG (I think - may be RENIXPower) group - groups.yahoo.com/group/XJOG or groups.yahoo.com/group/RENIXPower ("Files" section.) From there, you can see what's causing the trouble, but it's probably the wiring (if you can hear the relay click. Take a DVM and trace backwards from the start solenoid until you find +12VDC...)

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[Kittrell]

Wiring fault, then. If the key was on and bridging the two terminals with something metal (hammer head?) cranked the engine and it started otherwise, then there's nothing wrong with the starter.

I'll be busy to-morrow, but later I can pore over my 1990FSM wiring diagrams and see what I can offer. I've also got 1989FSM wiring diagrams posted in my XJOG (I think - may be RENIXPower) group - groups.yahoo.com/group/XJOG or groups.yahoo.com/group/RENIXPower ("Files" section.) From there, you can see what's causing the trouble, but it's probably the wiring (if you can hear the relay click. Take a DVM and trace backwards from the start solenoid until you find +12VDC...)

5-90

As far as I am aware, it's a single wire from the relay to the solenoid, correct? Help me out here, but I'm not sure how simply bridging the posts on the starter would correct that.............:dunno:

 

[5-90]

Because when you bridge the posts on the starter, you take power from the mains connection (the large one) and apply it to the solenoid. The solenoid then draws the plunger (extending the pinion) and makes contact with the mains feet to the motor windings. This is also how a "bump switch" works - you clip one lead to the solenoid lead, and the other to a convenient mains lead, and everytime you press the button, you "bump" the engine around a bit with the start motor. If you have the key in and turned ON and hit the "bump" button long enough, you'll start the engine (if you haven't already disabled the ignition.) Likewise, you can turn the engine with the keys in your pocket, using the bump switch.

There may be a "single wire" from the relay to the solenoid, but I don't recall how many connections it may have, nor do I recall what mechanical hazzards may be involved. Also, any time you have wiring "bridging the gap" between the frame/chassis (point of reference) to the engine (relative motion,) you will eventually fatigue the conductors from vibration - I've seen it happen before.

If the starter is tested "on the bench," you have a high-current earth lead, a high-current mains lead, and a low-current solenoid actuation lead. Neither of the leads is HOT until the switch is thrown (typically,) and you can actually do the test with just the high-current mains lead, if you can touch it to both terminals at the same time. Ditto testing a start motor with a set of jumper leads - just clamp the earth lead to the start motor body (usually a mounting ear serves,) and then open the jaws on the HOT mains lead, and touch it to both the starter mains terminal and the small solenoid terminal.

If you remove the solenoid from the starter, you'll see the plunger it uses to draw the pinion gear out, and if you look down the solenoid barrel, you might see the springloaded actuator or actual contacts that close to provide power to the start motor windings.

Make sense now? You'll want to start by backtracing that green wire to the start solenoid, until you find voltage with the key turned to START.

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[Kittrell]

You think that maybe the wire has been damaged, and cannot activate the solenoid. But direct contact to the starter will get it going? I'll have to get after it with a meter.

 

[5-90]

Yep - stripped of all the explanations, that's what I'm thinking. I just wanted to explain what I was thinking, to help you understand what I was thinking and why.

I've seen this a couple times before, on different cars. Typically, the wire breaks internally (according to experience and what I've heard) either near the starter or the chassis.

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[langer1]

If seen this also and it was the battery cables.
Try and start it with the light on, and see if they stay on or go out.

 

[90xj06]

in the relay box wiggle the i think green cable. what it sounds like is the solenoid is engaging but not kicking the starter motor. so have some one turn the key to start while you jump the starter and see if it starts. but be careful.

 

[Kittrell]

in the relay box wiggle the i think green cable. what it sounds like is the solenoid is engaging but not kicking the starter motor. so have some one turn the key to start while you jump the starter and see if it starts. but be careful.

Did you read anything in this thread?

 

[90xj06]

it sounds like the same problem i have so i keep a shovel in the back seat and while im smacking the starter solenoid im hotwireing it . usually it will start up. and then work for about a week. but them again i do have 220,197 miles on it. so things need to be replaced

 

[5-90]

Click the link in my sig, and go to "San Jose Generator." I'm trying to get business for a buddy who:

A) Does damn good work (I've found his parts to be nearly bombproof...)
B) Is willing to do mail-order for rather less than most other guys...
C) I'm trying to talk into doing some "specialty" stuff to be made available for us, or at least give Mean Green a run for their money!

You'll be dealing with Rod directly, if you decide to go that way.

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