[rdmgwinn]

Do you still have glass fuses?

Yes. They have been changed twice and checked with multi meter along with all the wiring. THINK I did all the applicable checks per the John Deere manual. A little bit weird on some things being a repower. Still has B43G starter etc. PTO switch changed also. checked good but was irratic on omhs. Thank you for the response.

 

[rdmgwinn]

Robert,

Regarding the replacement of the electronic module you stated you did -- you mentioned you used a new insulator and a new ring as recommended. Did you use a new condenser as well??

View attachment 302040


Chuck

Have a new condenser but was questioning if it was correct just as my replacement coil. Thank you.

 

[rdmgwinn]

Robert,

Regarding the replacement of the electronic module you stated you did -- you mentioned you used a new insulator and a new ring as recommended. Did you use a new condenser as well??

View attachment 302040


Chuck
[/QUOT

Robert,

Regarding the replacement of the electronic module you stated you did -- you mentioned you used a new insulator and a new ring as recommended. Did you use a new condenser as well??

View attachment 302040


Chuck

Robert,

Note that the secondary coil resistance value is in thousands of ohms (K-ohms...) but I suspect your meter is auto-ranging so the numeric value is what we can take as being the right scale. The question about the fuses is more than just if the glass cartridge fuse is good -- since it also has been quite common that the CONNECTION integrity of the plastic holders is very unreliable, and changing those glass fuses out completely with the later automotive blade/tab style as used in later tractors is always a good idea.

Thanks for your confidence Bo -- here is some useful information about the coils. Note particularly the difference in secondary resistance value from Onan manual versus the one published in the TM1950 for the later coil... Since these manuals were written during a time when resistance measurements were made with analog meters, it is likely that any value for the secondary between about 15 K-ohms and 40 K-ohms would indicate a good coil. If you want to be a stickler for Onan recommendations, then use the 15K to 20K range...
View attachment 302035

The values given by Robert for the 'aftermarket' coil would be the right version for the P218 engine. As mentioned in some posts, the condenser is the same part but connects to a different terminal for the electronic ignition compared to the points style version. See the diagram below:
View attachment 302039

Note that for the electronic ignition, the condenser must connect to the + terminal of the coil, whereas with the points style ignition the condenser must connect to the negative (-) side of the coil.

Finally, it should be mentioned that intermittent ignition issues can often be caused by poor ground connections so check those as well...

Good luck, and let us know what you find.

Chuck

Thank you for the reply. Yes understand the coil resistance is in K-ohms. BAD habit that I shouldn't do while asking questions. Actually checked with both a newer auto ranging meter and an old school Snap-on digital. Verified the same value on both meters. Now you bring up a Simpson 260. Now that will be a challenge. Haven't seen that thing in years. Hope I took the batteries out when it was retired?? Finding it could be an issue.

Condenser was connected to the + hadn't installed new one yet as I was questioning the coil / condenser. I'm a retired A&P so yes I could tell you a few stories of odd problems caused by grounds. Have gone through cleaned and verified all grounds.

With trouble shooting have had consistant 12v to the white wire from three pin connector. with white wire connected got 1.4 at + on coil. When checking the module got only 1.4 never got the alternating 1.4v / 12v. I had gone through pretty much every wire and switch by the John Deere manual to avoid pulling the engine. Really, really hoping the module solves the problem. Was concerned with the coil due to the significant difference between what I have vs what the manual says for 42000- engines (34-41.6 k-ohms) require. Really didn't want to fry the new stuff I installed because I had the wrong coil.

From what you are saying either coil the original onan coil with primary windings 3.5 ohms, secondary 17.0 k-ohms and the new aftermarket coil with primary windings 3.6 ohms, secondary 21.0 k-ohms should be fine?

Will get back with you but will be a few days as there are quite a few things I need to do while the engine is out. Starting with the foam insulation on the firewall.

 

[rdmgwinn]

Bo,

The two condensers are electrically the same, but have slightly different mounting methods and wire lengths.

Here is the 312-0256: View attachment 302043



And the 312-0246: View attachment 302044

The longer lead on the later version allows it to mount a bit further 'out of the heat' than the location of the points style one, and yields a bit longer component life...

Chuck

Thank you, Have the upper one on hand. Actually also have the lower one as my 1983 is a B43G, still has it's old school points in use.

 

[rdmgwinn]

Robert,

Regarding the replacement of the electronic module you stated you did -- you mentioned you used a new insulator and a new ring as recommended. Did you use a new condenser as well??

View attachment 302040


Chuck

Hope I'm not doing a double response. Didn't see my answers?? Likely didn't hit the post???

Anyway, Thank You for your reply. Yes I know Coil windings are k- ohms. Sorry bad habit that I should know better when asking for information. Actually checked with both an auto ranging Fluke meter and an old school Snap-on digital meter. Verified repeatable readings on both. Now you want me to break out my OLD Simpson 260. Hope I took the batteries out of it when it was retired? Finding it, now that could be an issue.

Yes condenser was connected to the + on the coil. Have a new condenser was just questioning it and the coil. Have pretty much gone through the tractor end to end, wire by wire using the John Deere Tech manual. Hope I didn't mis anything. As things progress I had found anytime it quit it had 12v at the three pin connector and 1.3- 1.4v at the coil. When doing the modual test per the John Deere tech manual I got the 1.4 v but never got a 12v reading while rotating the engine by hand. Had tried just about anything to avoid pulling the engine.

As a retired A&P mechanic I can tell you some crazy stories about chasing problems that are JUST a bad ground. Aircraft are terrible for ground related problems. One of the first things I decided to keep this tractor instead of parting it out. Got the tractor + for a very reasonable price and had intended to part it out. When I decided to keep it first thing it got was a major pressure washing. Second I went through every ground I could find on the wire diagrams, plus made up a few.

Sooo Does all that mean my original onan coil, 3.5 ohms primary 17.0 k-ohms secondary. And my aftermarket coil 3.6 ohms primary and 21.0 k-ohms secondary are both ok to use with the electronic ignition.

Was just concerned that after changing the module etc that I might fry something with the wrong coil or maybe just reduce something in the systems reliability.

Will get back with you with results. Will be a few days as there are a few things I need to do while the engine is out. Again Thank you for the help.

 

[rdmgwinn]

Robert,

Either coil should work, but the later one is the better choice perhaps. I may be a bit confused, have you run the engine since you replaced the ignition module? Does it now pass the test when turning flywheel by hand?

Chuck

No it hasn't been run yet, was concerned about what coil I needed. Plus a number of things to do on the tractor while the engine out. Have to modify the sheet metal a bit for the aftermarket coil. Then I can wire the engine up and redo the test. I'm crossing my fingers. It is an interesting critter half B43G (starter, oil pan etc.) anything for engine ignition is electronic. IF this doesn't work will be back to page 1 of the trouble shooting guide. Wish me luck. Thanks again!

 

[rdmgwinn]

The 0246 is a pita to mount, the 0256 is much easier. More room. Less strain on wire coming out of it. Change to blade style fuses, it will change you intermittent life, I promise.

Good Idea think I will. Pretty sure a have a few left over from an RV project. Thank You.

 

[rdmgwinn]

Robert,

Note that the secondary coil resistance value is in thousands of ohms (K-ohms...) but I suspect your meter is auto-ranging so the numeric value is what we can take as being the right scale. The question about the fuses is more than just if the glass cartridge fuse is good -- since it also has been quite common that the CONNECTION integrity of the plastic holders is very unreliable, and changing those glass fuses out completely with the later automotive blade/tab style as used in later tractors is always a good idea.

Thanks for your confidence Bo -- here is some useful information about the coils. Note particularly the difference in secondary resistance value from Onan manual versus the one published in the TM1950 for the later coil... Since these manuals were written during a time when resistance measurements were made with analog meters, it is likely that any value for the secondary between about 15 K-ohms and 40 K-ohms would indicate a good coil. If you want to be a stickler for Onan recommendations, then use the 15K to 20K range...
View attachment 302035

The values given by Robert for the 'aftermarket' coil would be the right version for the P218 engine. As mentioned in some posts, the condenser is the same part but connects to a different terminal for the electronic ignition compared to the points style version. See the diagram below:
View attachment 302039

Note that for the electronic ignition, the condenser must connect to the + terminal of the coil, whereas with the points style ignition the condenser must connect to the negative (-) side of the coil.

Finally, it should be mentioned that intermittent ignition issues can often be caused by poor ground connections so check those as well...

Good luck, and let us know what you find.

Chuck

Advise please. Should I need to start a new thread???

Finally got projects done with engine out and got it back in. Problem solved / NOT. Initially engine still had no spark to plugs. Backed through the trouble shooting guide. Module checks good now, 12 volts to 3 spade connector plug on engine (Pink wire). Connector to engine 12V at white wire (wire removed from coil). Jumped 12V power direct from the battery to coil. Sparks like crazy. With wire connected directly from battery to the coil starts and runs charges great until i remove the jumper wire. Dies instantly when jumper wire is removed.

Thinking I have the volts to the coil through the ignition but not the amperage?? Did I say I re rechecked grounds, right? Also coil, condenser, ignition switch (Checked good but was quite corroded) and inline fuses changed to spade type.

This is a B43G tractor (s/n 362785) repowered to P218 electronic ignition (mid 90s engine ???). Does the B43G tractor have a resistor wire somewhere (like the old Fords) to slow points errosion??? Does the TDCM unit have any internally serviceable parts??? Seems to check out externally. By the schematic don't see anything that could cause my problem in the TDCM??? Only ground for the TDCM is the black wire??

This was a used and quite abused / neglected tractor. Got it cheap and planned to part it out. It was caked with "stuff" end to end, I don't believe the ignition module was really bad, think it was just caked with c--p. There was no gap it was completely filled with crude. After looking it over saw that overall it looked to be in really good shape. Decided to make it our summer tractor and leave the 47 blower and weights on our 1983 318. That old style 47 blower moves snow beautifully here in the UP of Michigan BUT it and the maxed out weights gets harder and harder to swap out every year.

 

[rdmgwinn]

The 318 tractor has only 12 volt coils for every version without any resistor. The only differences in the ignition area between the B43 and the P218 are shown in the simple wiring diagram excerpt below:

View attachment 302928

For the p218, the condenser is connected to the positive terminal of the coil. As you can see in the green box alternative wiring for the B43 engine, the capacitor is connected to the negative side of the coil where non-ground side of the points connect. Other than those differences the circuit is basically the same -- no resistors are used with these coils.

From OHMS Law, since the primary side of these coils is about 3 ohms or a bit more, they will draw around 4 amps. Yes you might see a visible spark when initially connecting. Sparks "like crazy" may be a simple sensitivity from your lack of familiarity with these components...

The 12 volts that SHOULD be on the + terminal of your coil when the key is in the ON position should come from the TDCM. If it is not there, then check for the safety conditions being met at the inputs of the TDCM (either voltage at the seat switch sensing terminal X22 pin 9, OR at the cranking bypass terminal X23 pin 7) You do not need voltage at both places constantly, but at least one of these must have it all the time to sustain spark.

If you have such voltages, but still do not get power out of the TDCM X23 pin 2, then there may be something amiss internal to this module. Usually it is a simple diode failure, so let's discuss it thoroughly before you spend the $300+ for a replacement module...

Chuck

Some how my last message didn't show up. Anyway thanks for the reply. Appreciate your suggestions. I did finally break into the TDCM. John Deere "says" replace when it checks bad. Every thing excluding the board look to be off the shelf parts. Found 2 dry solders and a dry / loose solder on a resistor. Coil and both point sets where covered with crude can't see how the points worked at all. Guessing this may of plagued this tractor since new. Now have a good solid 12.8 v (= Bat V) at the coil. OPT checked good. Tractor going back together. Time will tell if long term reliability is fixed. Thanks much for all the insight / help.