PanDulce037 Posted January 3 Report Share Posted January 3 I have a 1982 Datsun 720 with the SD22 and a couple nights ago I had changed out the ignition lock with a 1980 Datsun 720 I have for parts I made sure it worked that night and it did crank over just fine after switching it over, the day after I tired to get it started and all I hear is a thunk from the starter pushing out to engage but doesn’t spin, I checked to make sure the motor didn’t seize somehow and that’s not the issue either I even put the old ignition lock back in and had the same issue, i then just bought a hitachi starter motor off of rock auto to see if that fixed the issue which it didn’t it did the same thing, i even tired pulling the starter out and had it all hooked up and it would kick out but not turn over but did work at an oreillys when hooked up with their machine, has anyone ran into an issue like this? Or is their some sort of reprogram I don’t know about with these old trucks you need to do for new ignition locks or got an idea of what to test wiring wise and see what my issue is? Quote Link to comment
datzenmike Posted January 3 Report Share Posted January 3 Your battery is almost dead or the battery posts/cables need cleaning. Quote Link to comment
PanDulce037 Posted January 3 Author Report Share Posted January 3 I have battery that’s at about 600 CCA and I tried a jump pack as well and as far as my connections for the positive and negative theirs no corrosion on the battery side or leading to the starter Quote Link to comment
datzenmike Posted January 3 Report Share Posted January 3 Connect the jumpers: ground to transmission case and positive to the starter lug. Corrosion can't be ruled out till the cables are removed from the battery posts. The stock ground on the PS mount may be loose. Quote Link to comment
PanDulce037 Posted January 3 Author Report Share Posted January 3 I’ll have to try that tomorrow then thanks for letting me know so positive to the starter positive stud and ground to bell housing should bypass the ground and positive wiring yeah? Quote Link to comment
datzenmike Posted January 3 Report Share Posted January 3 If it worked at oreillys the should work at home. One other thing.... If it still does not work try applying 12v directly to the solenoid. The small terminal. If that fixes the problem you have a weak start signal from the ignition switch. That's fixable. Quote Link to comment
PanDulce037 Posted January 3 Author Report Share Posted January 3 Got it alright and how can I test for a weak signal from the ignition switch or fix it? Quote Link to comment
datzenmike Posted January 3 Report Share Posted January 3 If it works with a 12v jumper but not with the ignition key that's a good sign the signal is weak. If you have a meter pull the wire off the solenoid and have someone turn ignition to start and read the voltage. Both my 620 and my 710 were below 8v. Old small gauge wires and long runs. Battery to ignition switch and back out to the starter is got to be over 15'. Then there are the harness connections. Quote Link to comment
PanDulce037 Posted January 3 Author Report Share Posted January 3 Alright sounds good do you know of any manuals that give wiring diagrams for 720s also? Quote Link to comment
datzenmike Posted January 3 Report Share Posted January 3 If the start signal is weak the easy fix is a "Hot Start Relay". More on this if this is the problem an not just a bad battery cable connection. Quote Link to comment
PanDulce037 Posted January 3 Author Report Share Posted January 3 Got it ok well thank you again I’ll look more into it tomorrow Quote Link to comment
wayno Posted January 4 Report Share Posted January 4 I myself have had this issue, my fix was to add another relay connected to the positive battery post with a 30amp fuse at the battery post, then the other side of the relay a cable to the motor side of the starter bypassing the solenoid, then I put a button in the dash to the relay exciter post, when I hit the key if it does not start turning over I hit the button to get it turning and let off the button and it has kept turning until the engine starts ever since, the reason mine does not work is because of the China made solenoid they used on my rebuilt starter. I had an issue when I used a 40 amp fuse and the fuse holder got so hot it melted and started a small fire, I believe the hot wire going into the fuse holder rested on metal and melted thru till it hit wire and started the fire which I seen, lifted the hood and put the small fire out, now that wire is insulated and held away from anything that could rub threw the wire insulation which may have been the cause of the fire and not a hot wire from too heavy of a load, it took years for this fire too happen, this is why I believe the wire insolation was worn threw before the fuse, as the fuse never blew. I did this because it takes me all day to change a starter in my 1969 Datsun 521 kingcab SD25 turbodiesel truck with power steering and power front disc brakes, I cannot even see the starter anymore with all the turbo related stuff in the way, there is no room left in my engine compartment. Quote Link to comment
PanDulce037 Posted January 4 Author Report Share Posted January 4 That build is insane and I love it and thanks for letting me know I’ll have to try that if I can’t get it to work I got home late and with cold weather all I could figure was that my battery is good as I tested it with a battery tester and had 545 CCA and my power wire to the starter doesn’t have an open or high resistance, I’m still gonna check for when I crank it how much voltage is it drawing and go from their but definitely a option I will do if I can’t figure it out and how often do you normally gotta use it? Quote Link to comment
wayno Posted January 4 Report Share Posted January 4 (edited) 32 minutes ago, PanDulce037 said: That build is insane and I love it and thanks for letting me know I’ll have to try that if I can’t get it to work I got home late and with cold weather all I could figure was that my battery is good as I tested it with a battery tester and had 545 CCA and my power wire to the starter doesn’t have an open or high resistance, I’m still gonna check for when I crank it how much voltage is it drawing and go from their but definitely a option I will do if I can’t figure it out and how often do you normally gotta use it? Until recently I had to use it(the relay) 50 percent of the time, a week or so ago the starter started acting up, it would not engage the flywheel, but given enough tries I could get it started, I checked everything as I thought the starter was loose(top bolt loose), but it was tight, so I checked the relay cable at the starter motor and it had tilted some towards the drivers side, I tilted it away towards the engine and it has worked great since, I have not used the button since, it just got a lot better by itself, maybe the solenoid arm got sticky and freed itself from all my trying to get it to turn over, or maybe the solenoid cap got loose and me moving the starter motor side cable fixed something, I cannot see this area, and everything being black does not help either. This clicking thing is not new to me, it did it on my 1982 Datsun 720 KC diesel also, a few times I had to push start it to get it started, but I sold it after getting the 521 kingcab SD25 running. Edited January 4 by wayno Quote Link to comment
PanDulce037 Posted January 4 Author Report Share Posted January 4 Got it ok well mine wouldn’t have the best luck starting up rn with a push sadly as it’s like 20 degrees where I’m at currently but after I see if my power wire to the starter is getting its correct amount of voltage I may just do that suggestion you had and see if that can fix my issue Quote Link to comment
datzenmike Posted January 4 Report Share Posted January 4 2 hours ago, PanDulce037 said: That build is insane and I love it and thanks for letting me know I’ll have to try that if I can’t get it to work I got home late and with cold weather all I could figure was that my battery is good as I tested it with a battery tester and had 545 CCA and my power wire to the starter doesn’t have an open or high resistance, I’m still gonna check for when I crank it how much voltage is it drawing and go from their but definitely a option I will do if I can’t figure it out and how often do you normally gotta use it? Current flow is the same in all parts of an electric circuit generally from negative to positive direction. This means that 545 CCA has to flow through both cables so check the ground cable connection too. Quote Link to comment
PanDulce037 Posted January 5 Author Report Share Posted January 5 On 1/2/2025 at 8:06 PM, datzenmike said: If it works with a 12v jumper but not with the ignition key that's a good sign the signal is weak. If you have a meter pull the wire off the solenoid and have someone turn ignition to start and read the voltage. Both my 620 and my 710 were below 8v. Old small gauge wires and long runs. Battery to ignition switch and back out to the starter is got to be over 15'. Then there are the harness connections. Got some more testing done today and I found that to my starter I do have 12 volts going to it and at my red/black wiring from the key ignition I have 9 volts when trying to turn over is that a sign of bad signal wire connection should it be 12v? Quote Link to comment
ElliotV Posted January 5 Report Share Posted January 5 the signal wire should be 12v. I would try jumping the signal wire straight from the battery. you can just use a piece of wire coming off the battery positive or you can use a bypass switch or just some test leads. Personally my favorite is the bypass switch which can be had at advanced auto. I have used mine a few times diagnosing stuff or just so I can look at a engine while its cranking when working on my own and have more control. Quote Link to comment
datzenmike Posted January 5 Report Share Posted January 5 4 hours ago, PanDulce037 said: Got some more testing done today and I found that to my starter I do have 12 volts going to it and at my red/black wiring from the key ignition I have 9 volts when trying to turn over is that a sign of bad signal wire connection should it be 12v? Unplug the Red/Black start signal wire and see what you get. Quote Link to comment
NC85ST Posted January 5 Report Share Posted January 5 You can always check it the old fashioned way. Take a screwdriver and touch the terminal where the positive battery cable attaches to the starter and where the small wire attaches to the solenoid. Make sure it’s out of gear of course. Easy way to check the starter. Quote Link to comment
PanDulce037 Posted January 5 Author Report Share Posted January 5 2 hours ago, datzenmike said: Unplug the Red/Black start signal wire and see what you get. I used a back probe/t pin to get my 9v reading that should be the same if not better reading no? Quote Link to comment
ElliotV Posted January 5 Report Share Posted January 5 16 minutes ago, NC85ST said: You can always check it the old fashioned way. Take a screwdriver and touch the terminal where the positive battery cable attaches to the starter and where the small wire attaches to the solenoid. Make sure it’s out of gear of course. Easy way to check the starter. For some reason at least on my z24 starters I cannot get the positive to touch the signal contact so I have always used a jumper wire or button Quote Link to comment
datzenmike Posted January 6 Report Share Posted January 6 18 minutes ago, PanDulce037 said: I used a back probe/t pin to get my 9v reading that should be the same if not better reading no? If connected, the starter may be pulling the reading down. Pull the Red/Black wire off the starter and check. Should be battery or 12v. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.