# No spark - how to test power transistor?



## mattlok (Apr 21, 2005)

87 sentra with 2bbl. I have no spark at the coil. I have signal coming from the distrbutor wires (crank angle sensor) to the cpu. I have constant power on 2 of the 4 terminals on the power transistor(one is supposed to, the other is the lead going to the tack which doesn't seem right.), There is signal coming from the cpu to the power transistor when turning the motor over. I have a constant 12v to the coil and i have a signal wire putting voltage to the coil when turning the motor over. I have the service manual on how to test the power transistor and its not testing correctly according to the book. I have went to the salvage yard and tested 5 more transistors and they all tested exactlly the same?? (are they all bad or is the book wrong?) Oh yes all of the fuses tested good. Any ideas? Please help!


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## rimawc (Apr 24, 2005)

*Bad Coil??*

I read somewhere that ingition ignitors(power transistor) rarely go bad. Instead, purchase a replacement coil. Connect everything up without mounting it to the firewall, and see if your car will start. If it does, finish installing the coil. If is doesn't, you know that your coil is good, and you can return the replacement coil to the parts store for a refund. It might be helpful if you read my posts. I had a similar problem, and Twiz helped me out.

I wish the best of luck to you,


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## mattlok (Apr 21, 2005)

rimawc said:


> I read somewhere that ingition ignitors(power transistor) rarely go bad. Instead, purchase a replacement coil. Connect everything up without mounting it to the firewall, and see if your car will start. If it does, finish installing the coil. If is doesn't, you know that your coil is good, and you can return the replacement coil to the parts store for a refund. It might be helpful if you read my posts. I had a similar problem, and Twiz helped me out.
> 
> I have tried that already. With no change. It will start for about 10 seconds every now and then, but that is it. The haynes book has a test for it (power transistor) and it test's bad, but i went to a junk yard and test 5 of them and they all tested the exact same. So i don't know if i should believe the book or not.


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## blownb310 (Jun 10, 2002)

I have had a couple power transistors fail over the years on customer cars. I always have an extra one around to plug in and test with. However, it sounds like in your case the crank angle sensor is most likey the culprit. Try changing the distributor. I have those around to test with too. They are quite a common failure. They should be easy to find at the boneyard. I can send you one for $25 if you need one. I've moved on to B13's now so I'd be happy to part with all of my B11 ans B12 stuff. Even my last remaining B12 car has a B13 engine in it.


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## mille-16i (Jun 16, 2004)

I would agree with blown swap out a distributor and see what happens. I got one for 25 but didn't need it and gave it to my dad for his shop.


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## mattlok (Apr 21, 2005)

Do you have a good used power transistor that you would get rid of also? Just in case?


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## blownb310 (Jun 10, 2002)

mattlok said:


> Do you have a good used power transistor that you would get rid of also? Just in case?


 I sure do. I can ship you one for $15. PM me if you need it.


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## mattlok (Apr 21, 2005)

Is there anyway the ignition condensor could be causing my problems?


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## blownb310 (Jun 10, 2002)

mattlok said:


> Is there anyway the ignition condensor could be causing my problems?


 No, that's not the problem. My money's on the crank angle sensor.


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## rimawc (Apr 24, 2005)

*Crank Angle Sensro*

Just to let you know, and it's in my posts, you don't have to replace the whole distributor. Kragen Auto Parts, and other parts stores, sell the sensor seprately.

I wish the best of luck to you,


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## recycled_toddler (Feb 4, 2004)

rimawc said:


> ...you don't have to replace the whole distributor. Kragen Auto Parts sells the sensor seprately.


Hold the phone...Kragen (aka Schuck's here) sells the guts for the non-vacuum-advance Sentra/Pulsar distributor? Seriously??? How much? I didn't know that was all possible, the books all say that the whole distributor has to be replaced as a unit. If you're right, I'm getting the guts!


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## blownb310 (Jun 10, 2002)

Yes thanks rimawc,

I am aware that you can replace the internals, but I'd rather get a used distributor for $25 because it's quicker, easier, and cheaper. Either way, it's nice to know we have options.


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## mattlok (Apr 21, 2005)

Is it cheaper than $ 25 ???


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## rimawc (Apr 24, 2005)

The replacement sensor is priced at around $225.


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## Nats (5 mo ago)

I have 89 nissan senta no spark.replaced coil and ignition module still nothing


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