doghead starter relay mod rebuilt gear reduction starter run away

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a68cudas

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Have couple questions. I done the doghead starter relay mod about 3 weeks ago and at that time i had my old direct drive starter in it. The relay would start the old starter fine but the old starter needed replaced as it was never shimmed and was sticking every now and then. I got a rebuilt 24v gear reduction starter and hooked it up with the coorect support bracket, turned the key and it turned engine over but when i shut key off the starter stayed engaged. What will make this do this ? I did the doghead starter relay mod so that my stater doesnt run away. Does the gear reduction starter get wired the same as the direct drive starter? The gear reduction starter has only one post on solinoid for the lil wire and the direct drive has 2 post on solonoid is there a special way the gear reduction starter is wired compared to the direct drive? Could my starter relay have gone bad in such a short time? The doghead relay ran flawlessly while old direct drive starter still worked? Any help suggestions on trouble shooting my dilemma will be greatly appreciated . Thanks
 

Warthog

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When you say the starter stayed engaged, are you saying that it continued cranking?

The starters hookup the same way. On the direct drive starter there are two small terminals. One marked S and one marked I. The "S" terminal is for the start circuit. The reason for the "I" terminal is for a gasser ingine with a distributor. When the starter is engaged the "I" terminal will send current to the distibutor so the plugs will fire. Not needed on a diesel engine.

The relay used for the DH conversion is just like any other mechanical device. It can fail at some point. The manufacturing standards these days are not what they used to be.
 

a68cudas

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When you say the starter stayed engaged, are you saying that it continued cranking?

The starters hookup the same way. On the direct drive starter there are two small terminals. One marked S and one marked I. The "S" terminal is for the start circuit. The reason for the "I" terminal is for a gasser ingine with a distributor. When the starter is engaged the "I" terminal will send current to the distibutor so the plugs will fire. Not needed on a diesel engine.

The relay used for the DH conversion is just like any other mechanical device. It can fail at some point. The manufacturing standards these days are not what they used to be.
Yes the starter stayed engaged and continued cranking engine over when key was shut off!!!
 

a68cudas

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Is this starter shimmed properly? A tight starter can run on. Just hang it with a ground jumper for a test.
I read posts where some say to shim and others say that the 28mt gear reduction drive starter does not need shimmed? I even started a thread asking if it would or wouldnt need shimmed and also got mixed opinions So We decided to try the new gear reduction starter without a shim first and when we had the starter bolted up and got the support bracket for it bolted up and cycled glow plugs once and turned engine over. The engine cranked and when i went to shut key off the starter kept cranking engine. Luckily my friend was in front of blazer and hood was up and he had the battery wrench and he took terminals off as fast as he could. All the wires look good for batteries etc. The starter got extremely hot and i suspect what ever was inside melted as we seen smoke and it smelled of burning plastic/wire. We let the starter cool and took off and its junk now it got cooked and the outer casing where one of the long bolts holds the motor part of starter cracked up by where bolt head is.
 

doghead

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Some members that have had this happen, found they had the wires touching(each other) at the starter.

Are you sure your new starter is 24V and the solenoid?

If the gear stays engaged(because it is binding) the solenoid cannot disengage(causing starter run-on).

Did you check for gear engagement clearance when you installed the new starter?
 

doghead

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The only way to know for sure if you need shims, is to check(measure) gear engagement clearance.

This is covered in the -20TM.
 

a68cudas

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Could the solinoid on the starter itself malfunctioned and hung open? Is there any way to check to find out if the starter solinoid is working properly? I thought the doghead relay mod was suppose to remedy this problem? If it is the starter relay that went bad is there anyway to check and see if it is working properly? The doghead relay mod i just did about 3 weeks ago and i had the old direct drive starter in when i did the mod. I drove the blazer up untill the starter was getting worse and was starting to stick and that is when the blazer sat untill i got the rebuilt 28mt 24v starter. Has anyone else had this same problem after doing the doghead relay mod? Id like to trouble shoot the problem so i know exactly what went wrong or bad and replace or fix before purchasing another rebuilt 28mt 24v starter. Could there be a problem anywhere else causing the starter to runaway besides a bad starter or bad relay? Any suggestions or guidance greatly appreciated. Thanks
 

doghead

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You can test your under dash relay by simply doing a voltage test at the starter wire(small one).

What your missing is, the under dash relay supplies power to the solenoid. The solenoid moves(engages) the bendix drive AND pulls a large contact in the end of the solenoid together that then energizes the starter motor.

At the other end, if your bendix drive gear is jambed into the starter ring gear, the solenoid shaft cannot freely move back into the non energized position(where the starter motor contact opens).

You must have a properly clearanced gear engagement or what happened to you can happen. It has nothing to do with the under dash relay.

Did you realize, when you turn the key into the start position, 3(three) "switches" are used to make the starter function?

One last(slightly possible) issue could be, your starter switch in the steering column could have stuck.

But, since you previously never had a problem with the steering column switch or your under-dash(DH) relay, and you just changed your starter and did not check/shim it, logic says there is your problem.
 

doghead

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Could the solinoid on the starter itself malfunctioned and hung open?​
It would "hang" closed, to cause the starter to stay engaged.

Improper gear mesh could/would cause this.
 

doghead

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I drove the blazer up until the starter was getting worse and was starting to stick and that is when the blazer sat
I would throughly inspect your starter ring gear for damage, since your saying that you has continued and worsening starter sticking prior.(again, most likely due to lack of proper shimming)
 

a68cudas

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How come the starter stays engaged or stays cranking even when the key is turned off? "If the gear stays engaged(because it is binding) the solenoid cannot disengage(causing starter run-on)." why doesnt the key in off position kill the juice going to the under dash relay and also the starter solenoid? Thanks
 

eagle4g63

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Doghead will keep you in the right path, but a quick answer to your "why" question......think of it like this....the large wire is a direct connection to your battery, the amount of current that is needed to turn the starter would fry a switch, so they use a relay, and solenoid to activate the contact between the large wire and the starter......after the large wire makes contact it no longer "needs" the power from the switch(technically). so if the solenoid is "stuck" in the on position the large wire to the battery is still active on the starter.

The solenoid is a mechanical switch that makes the contact between the battery and starter, so if it doesn't let go(like doghead said by the gear clearance holding it in that position) then battery will keep turning the starter until something gives.....battery dies or starter burns up.
 

doghead

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This should help. Notice that the motor contactor is closed/directly connected to the main battery cable, when the gear is "out" or engaged with the ring gear. So, when the gear is jambed into the ring gear, the contactor can't open, the motor keeps running.
I said all this in the post above.

http://www.youtube.com/watch?v=_f6kM1e1fBA
 
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doghead

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Persistence!

I try real hard to help, I really do.

I get great satisfaction from helping others.

Oh yeah, and with some luck too...
 

a68cudas

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The only way to know for sure if you need shims, is to check(measure) gear engagement clearance.

This is covered in the -20TM.
I read the -20 TM about checking clearance and i have been looking for a wire guage so i can check and install the new starter properly. I am having one **** of a time locating a wire guage to check the clearance, every time i search all i come up with are wire guages for measureing the diameter of wires? I even called a cpl auto stores and the people whom i spoke with their were clueless. Can anyone steer me in the right direction as to where i can purchase a wire guage and a link would be great? Anyone know of any stores that carry them and are they specifically called a wire guage or something else? Thanks
 

doghead

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In the old days, we would just straiten out a small paper clip and use that.

Or, just visually check that there was clearance.
 
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