Checking coil for 74 fj40 (1 Viewer)

[H2o]

I broke down the other day. 40 was driving fine and it suddenly died. Could not get it started. After I got back home, removed distributor cover. There was spark at points. I could not get spark at spark plug. I am suspecting coil. Coil is a toyota coil that has little miles on it but is about 10-15 years old.

The F engine manual says that the primary coil should be 3-4 ohms. Secondary 6.750-8.250 ohms (I assume they mean 6,750-8,250 ohms).

My coil primary was reading 1.4 ohms. Secondary 11.86 Kohms.

A spare coil I have was reading 1.2 ohms. Secondary 9.39 kohms.

Are both my coils bad?

 

[pedwards]

Is your spare know to be good? New in box?
If so then your coils are probably ok.

 

[H2o]

Both are used...

 

[John Smith]

You haven't told us if your coil has a resistor or not. If it has a resistor, your readings are in spec. My money is on your points being bad or your primary wire.

 

[76technician]

When I killed a Toyota coil (somehow by wiring it incorrectly after years disconnected) I had 0 ohms on the primary and less than 2 ohms on the secondary. It was pretty obvious it was dead.

 

[H2o]

Are you supposed to measure the coil through the resistor? There is a resistor on top of the coil. I think I checked the resistor by itself and I was within spec? I will have to check again.

 

[Pin_Head]

The values are fine for a coil that uses a ballast resistor. I have never seen a stock coil fail ever. They are extremely reliable.

 

[H2o]

I am confused, how are they fine if they seem to fall outside of the Toyota spec?

 

[GA Architect]

I am confused, how are they fine if they seem to fall outside of the Toyota spec?

See if this helps:

 

[shelfboy1]

dont forget the condensor after 40 + years of driving fj40s i have never had a coil fail ,usually the points or something you dont suspect .

 

[H2o]

@ GA Architect, Thanks. What manual is that from (much more detailed than the F manual i have) and does it still apply to F engine?

@ Shelfboy1- I tested condensor and it is within spec.

Points were dirty, but generally in good shape.

I am going to put it all back together and see. I will check fuses too since I did not think of testing/checking those.

BTW, Distributor, coil, carb are all new, purchased about 15 years ago, and have little miles. They are 1974 non USA.

 

[H2o]

Also, it seems like my spare coil is just outside of spec. Would it still work?

 

[GA Architect]

@ GA Architect, Thanks. What manual is that from (much more detailed than the F manual i have) and does it still apply to F engine?

@ Shelfboy1- I tested condensor and it is within spec.

Points were dirty, but generally in good shape.

I am going to put it all back together and see. I will check fuses too since I did not think of testing/checking those.

BTW, Distributor, coil, carb are all new, purchased about 15 years ago, and have little miles. They are 1974 non USA.

Water - Post a photo of your coil in your rig. As Pin_Head mentioned, your readings are fine for a coil using a ballast resistor.

If you have a Toyota coil, I believe it should have the part number, 90919-02025 on it.

 

[H2o]

My coil is a Toy 90919-02102. It could have been a non-usa since i remember the distributor being non-usa.

The spare must be after market. it says CIT-61 12v Full TR with 9L9 009 at bottom.

 

[H2o]

Toyota coil installed.

This is after market coil.

I tried to rotate images but could not figure out, sorry.

 

[GA Architect]

View attachment 965058

Toyota coil installed.

View attachment 965059

This is after market coil.

I tried to rotate images but could not figure out, sorry.

I'm no expert, but I believe you have the ballast resistor type coil. Thus, per your readings, the Toyota coil is well within the specs.

FWIW: Your coil number 90919-02102, it replaced the old part number 90919-02025.

 

[H2o]

Ok. Thanks all. Very helpful. I will proceed with re-installation and see if i can find another cause of trouble. I may order new coil, points, and condensor as spares anyway.

 

[John Smith]

Have you checked your primary wire resistance along with your other plug wires? I still think your points are the issue.

 

[H2o]

No, did not check. What should wire resitance be?

 

[FJ40Jim]

The values are fine for a coil that uses a ballast resistor. I have never seen a stock coil fail ever. They are extremely reliable.

Unless the vehicle is driven in mud or snow. In which case the crimp will get corrodey and allow the oil to leak out of the can. A coil without oil will overheat & short out. That is the only way I've seen Denso coils fail. And the rusty leak is always visually obvious.

I am confused, how are they fine if they seem to fall outside of the Toyota spec?

The specs are a guide. If the spec is 6-8K ohms and the part is reading 9K or 5K, the part is good. If it is reading infinite (burned out open circuit) or it is reading 5.2 ohms instead of 6K (internally shorted), then it is bad.