No-Start Sce­nario

How to di­ag­nose and fix a starter

Jp Magazine - - Ta­ble Of Con­tents -

You turn the key on your Jeep and are greeted with a click­ing sound, or maybe only si­lence.

Whether you’re run­ning late for work or headed out for week­end wheel­ing, that’s a sit­u­a­tion that can ruin your day. It could be a bad bat­tery, fail­ing starter, or some other com­po­nent in the elec­tri­cal chain that com­prises the start­ing sys­tem.

The starter typ­i­cally con­sists of two main com­po­nents: the mo­tor it­self and a so­le­noid used to switch pos­i­tive bat­tery volt­age to a mo­tor ter­mi­nal. The mo­tor has a small, toothed gear that meshes with a large ring gear on the out­side di­am­e­ter of the en­gine fly­wheel (man­ual trans­mis­sion) or flex­plate (au­to­matic trans­mis­sion). The large dif­fer­ence in the two gear sizes al­lows the elec­tric mo­tor to fully turn the en­gine enough to start it once ini­tial com­bus­tion com­mences. The starter mo­tor can draw sev­eral hun­dred amps of elec­tri­cal cur­rent dur­ing this op­er­a­tion, and it re­lies on the in­tegrity of the so­le­noid con­tacts to de­liver that heavy cur­rent flow. If this flow is di­min­ished any­where along the path, in­suf­fi­cient cur­rent will make it to the starter mo­tor.

When turn­ing the ig­ni­tion key re­sults in the starter mo­tor not turn­ing, this is re­ferred to as a “no-crank” is­sue. A “no-start” is­sue oc­curs when the starter spins the en­gine at nor­mal speed, but the en­gine does not be­gin run­ning. When faced with a no-crank is­sue, it’s wise not to im­me­di­ately as­sume the starter is the cause of the prob­lem.

First, con­sider the con­di­tion of your bat­tery. Has the starter been crank­ing a bit slower than nor­mal the last few times you started it? If so, that could be a clue that the bat­tery is grow­ing weak. A quick check of head­light bright­ness can give a rough idea of bat­tery con­di­tion. If the bat­tery seems to be ok and you get no solid click­ing sound from the so­le­noid, then you may have a bad so­le­noid or the ig­ni­tion feed to the so­le­noid is faulty. This could be due to power not get­ting to the ig­ni­tion switch, a blown fuse some­where, bad ig­ni­tion switch, faulty un­der­hood starter re­lay, faulty trans­mis­sion neu­tral safety switch, or a prob­lem with the wiring or con­nec­tors that make up this ig­ni­tion cir­cuit.

You can check to see if you’re get­ting a solid 12 volts at the “S” (so­le­noid) ter­mi­nal when the ig­ni­tion switch is ap­plied. Or, you can sim­ply use a length of wire to di­rectly jump 12 volts to the ter­mi­nal from the pos­i­tive bat­tery post. Be­cause you are in fact by­pass­ing all safety switches, please be ab­so­lutely pos­i­tive the trans­mis­sion is in Neu­tral or Park.

When the so­le­noid is click­ing but the mo­tor does not spin, the prob­lem could be fail­ing so­le­noid con­tacts, a faulty starter mo­tor, or a faulty pos­i­tive bat­tery ca­ble run­ning from the bat­tery to the so­le­noid. Cor­roded or dam­aged bat­tery con­nec­tors can cause is­sues, and they should be easy to di­ag­nose. Some­times it’s pos­si­ble to run a jumper ca­ble from the bat­tery to the large so­le­noid ter­mi­nal to de­ter­mine whether or not the bat­tery ca­ble is fine. Also, en­sure your bat­tery ground ca­ble is in­tact and in good con­di­tion.

Once you’ve worked through some of these trou­bleshoot­ing tech­niques and bet­ter iso­lated the starter as the sus­pect com­po­nent, then it prob­a­bly makes sense to re­move it and check it fully out­side the Jeep. Just make note upon re­moval of any­thing prob­lem­atic with the con­nec­tions that may be the true fail­ure. Non-crank trou­bleshoot­ing is gen­er­ally not that dif­fi­cult. You just need to de­ter­mine if the prob­lem is in the ig­ni­tion cir­cuit or the high-cur­rent cir­cuit, then find the fail­ing piece of the elec­tri­cal path.

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