engine spark troubles

[herculesinwyoming]

im still pretty new to the datsun world.

 

i tried to start my 76, 620 truck for the second time since i got it in april.

its not getting spark, the resistor by the coil gets really hot, too hot to touch. i tested the coil as described in the chilton manual.

 

any ideas or advice on this, im figureing since the resistor is getting real hot that maybe it isnt letting any voltage pass.

 

what specs should the resistor test at?

 

thanks for any help.

[banzai510(hainz)]

76 is this a point distributor?

 

Current is passing alot as that why the resisitor is getting hot. Too much current. a 1 ohm difference can be almost a 50% increase on current on the POINTS IGNITION system.

Example a 510 has 3.2 ohm total resisitance.

12volts divide by 3.2 ohms = 3.75 amps

Now if the coil shorted out, the battery will only see the ballast resisitor of 1.6 ohms. 12volt divide by 1.6 ohms = 9.2 amps. Now the ballasts has to handle 9amps and will get HOT untill that frys the points fry and or the fuse pops in the fuse box. or worse melts wires . Im using this as a example as I never seen a ballast short out or a coil short out myself. I have seen wrong match coil balsst installed from other vehicles and not matched up correctly.

 

Datsuns are pretty much wired the same as this 510 drawing Im going to post.

is the resisitor the stock one ?

 

a point coil should be in the range of about 1.2 , 1.4 ,1.6 ohms I would say is good. and the ballast would be close to 1.6 ohms. Like I said above if the ballast is 1.2 -1.8 I would not worry about it.

 

was the coil changed?????? maybe a low ohm coil was installed also and the ballast has to drop the extra current or cant handle it.

 

does coil feel HOT also?

 

 

look on "Rockauto" for your model and see if they have some specs on Ohm values.

Even "partsamerica" has some good photos of stuff.

importedcarparts.com

Edited June 23, 2009 by banzai510(hainz)

[herculesinwyoming]

thanks for the reply,

its a points dizzy, and all the parts look stock, the resistor got hot, and the coil stayed cool,.

 

i was able to get the truck started the one time, i havnt changed any parts or even touched the distributor or electical parts at all.

 

im going out to clean the grounds, and test the coil again,

it really seems that the coil must be bad so i will check and recheck it.

 

its gotta be a simple issue that i just need to find.

[herculesinwyoming]

i went out and really cleaned the coil posts and tested it again.

i tested it with the wires removed

this time it showed 0 ohms of resistance, so the coil must be junk.

 

the resistor tested at zero ohms too,

the secondary on the coil was around 11,000

Edited June 23, 2009 by herculesinwyoming

[banzai510(hainz)]

be honest i think most made in china analog meters will read Zero.

Is this a digital meter.??????If so set to lowest setting possible.

remember 1 .6 ohms to a very inaccurrate meter will look like short or Zero.

 

 

I dont know if somebody can test that out for you with a better meter but I highly dought the ballast went bad as most break in half behind the ceramic.

 

but I have a few extra coils and I swap it out and test that way. I dont know if another truck is around to test with but besides from buying another coil I dont what more to tell you.

Edited June 23, 2009 by banzai510(hainz)

[herculesinwyoming]

im doubting the accuracy of my meter too,

i can get my hands on a high quality one and see how it does.

since the resistor got hot, i still suspect the coil.

i will let you know when i get it figured out.

[MikeRL411]

Look to see if your points are pitted. If so, open capacitor, the points may be bridges with fine "hairs" of alloy. If not, outside chance that you have a shorted capacitor given the troubles you are having. Swap in a new capacitor before splurging for a new coil and see what happens.

[herculesinwyoming]

thanks for the idea, the points looked pretty good, they had a tiny burn spot, maybe i will just change them too.

[datzenmike]

Be sure the points are opening and closing. Pull them open by hand and the coil should spark.

[herculesinwyoming]

solved!

 

i did some testing with a test light, and then used a jumper wire across the resistor, and tryed it, it started instantly. i shut it righ back off to avoid burning stuff up.

 

 

i will order a new resistor soon.

 

thanks for the input guys

[banzai510(hainz)]

Well the truck should START cause there is a HOT start wire that bypasses the resisitor(notice in the diagram) the blk/blu wire . which does the same as what you did jumpering over the ballast

.just when you go back to ON on the key switch it goes thru the ballast then to the coil.

 

o wit will be hard to start if somebody took out the HOT start wire but I dont know why the ballast got hot. I can only assume the coil is bad. or maybe the ballst went bad somehow. was cracking or something.

[herculesinwyoming]

i bypassed the resistor and it fired up and ran great, i ran it a good 15 minutes yesterday,

still i plan on replaceing the coil and resistor, just for future peace of mind.