Replaced Starter now there is no spark (1 Viewer)

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Hi there new to the forum here did a bunch of searching but i did not find any info regarding the instant loss of spark when replacing starter. I got the truck to start and it ran fine, the starter solenoid was failing so i swapped out the starter with a rebuilt non oem model (maybe i should have picked up a gr unit) and a new battery. Installed the starter and battery expecting instant success and the starter works but i get no spark now. I cleaned all the grounds and the battery voltage is 12.6. Any insight would be great. I have a 2/78 fj40 with trollhole distributor. Thanks
 

78fj40mg

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It sounds like there's an open connection, on my '78 there are several connections, and one that goes directly to the ignition coil. Check all your electrical connections. Did you snap a pic of the old starter with all connections intact so you can compare?
 
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Here's an ignitor wiring diag for the 78. make sure the connections are tight. hope this helps--

Igniitor wiring-1978.jpg
 
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Thanks for the quick replies. All the connections on the starter are wired up except the resister bypass wire, I figure it isn't required for this setup and the gr starters don't use them so is this the right way of thinking? i am using just the coil with 12 volts because of trollholes dizzy. I can wire up a ballast resister but for testing purposes it should not matter. all wires are clean and tight. I did take a peak at the ignition switch last night and it is filled with copper dust and extremely warn down. could this cause issue? The vehicle has only been started once since i have owned it.
 

78fj40mg

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I suspect the rebuilt starter has an electrical issue, how about transferring the good solenoid to the old oem starter.
 
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I get full battery voltage at the coil + on its way to the dizzy. I should have kept the old starter but i gave it back as a core but it wasn't to expensive could always get another one maybe a GR would be a good upgrade, rather not buy another if i don't need to. Is there a bench test i can do on the starter to make sure it functions properly?
 
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?! I thought you said that the starter works. The starter won't keep you from getting a spark if it turns the engine.
I would triple check the wiring. If the ignitor in the distributor is wired up properly and is getting power, it may be bad.
 
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Having battery voltage at the + side of the coil is not a reliable indicator that the circuit connections are OK because you may be reading a voltage on an open circuit. If you ground the - side of the coil to complete the circuit and you still have battery voltage on the + side, then the connections are OK.

Since this just happened when you swapped out the battery and the starter, check all ignition related connections near where you were working.
 

78fj40mg

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The other solution would be to return the current starter and get another one and see if it makes a difference. I still believe there's an open circuit, use a VOM and check the continuity of each wire running from the starter to the igniter/coil, disconnected on both ends. Visually the wires may look good but it could be a broken wire even though the wire insulation looks intact.
 
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The bypass wire is not necessary.
The fact that you have 12V at the coil with the key on proves that the ignition circuit is not "open" up to that point.
It does not prove that the circuit has low enough impedance to provide enough power to run. Run a temporary hot wire from the battery + to the coil+ to see if it runs. If so the ignition circuit has a high resistance dirty/corroded/loose connection.
 
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Thanks for the quick replies. All the connections on the starter are wired up except the resister bypass wire, I figure it isn't required for this setup and the gr starters don't use them so is this the right way of thinking? i am using just the coil with 12 volts because of trollholes dizzy. I can wire up a ballast resister but for testing purposes it should not matter. all wires are clean and tight. I did take a peak at the ignition switch last night and it is filled with copper dust and extremely warn down. could this cause issue? The vehicle has only been started once since i have owned it.
The GR starters do not use this wire, but the OEM does. It helps with getting a full 12 volts
 
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To be clear, the oem starter has a connector where you MAY connect the wire, but it is not required or necessary.
Your vehicle will start just fine without it. Almost everyone who has put in a GR starter runs without it.
If you are not getting a spark, this is not your problem.
 
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edw is correct--the wire "steals" 12 v off the oem starter connection to supplement the nominal 7.5-8v normally present. assuming all other connections and ignition system components are ok, you don't need it.
 
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Update. Thanks to all the replies. Had a few buddies come around and there is a good spark going into the distributor but a weak spark from plug leads. It is recommended to replace the rotor and cap, this is a fairly new trollhole unit.
 

Coolerman

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I'm a bit curious about something: If this is a 78 won't it have the built in resistor wire? How are you getting +12Volts to the coil if this wire is in place? If the wire were in place, it should be reading 7-9 volts. Are you powering the distributor from the Large BY wire? Just wondering...
 
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The resistor only drops voltage when there's current running through it.
In a points system, if the points are closed you will see 7-9v but if the points are open you will see 12v because the circuit is open.
Similarly for an electronic system, if the igniter is drawing current then the resistor will drop voltage (IR) and you'll see lower voltage at the coil.
If the igniter is not drawing, you'll see 12v.
 

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