[volvo4fun]

Last Friday, I removed a loaner engine from my 318, in preparation for the install of a rebuild engine.
Every worked, no problems at all.

Today, I was done putting the new engine in and it was time to see if it would crank. Turn ignition on and no lights, no crank either.

Turns out the 20A fuse was blown. Put a new one in and again it blows just by turning the ignition on.

Now I have disconnected all wires (coil, starter, rectifier, 3 connector terminal block etc. Jumped the battery cable to the other red wire that would normally be joined at the starter.

Fuse stays intact. However when I turn on the ignition, the battery light comes on, I hear a relay click inside the TDC and the battery light goes out.

Any suggestions?

 

[chuckv]

Robert,

You have a short somewhere that you will have to find and clear... Do this before you jumper around any more wires and run the risk of damaging your wiring harness further.

Do you have the TM1590 which includes the wiring diagrams for your tractor? The 20 amp fuse goes to the X23 pin 3 of the TDCM and also to the PTO switch, the headlight switch, and one side of the oil pressure and charging indicator lamps on the dash. The power supplied by the 20 amp fuse at X23 pin 3 of the TDCM is also switched by an internal relay to the ignition system of the engine and comes out of the TDCM at pin 2 (the #830 pink wire) and should go to the plus side of the ignition coil. Verify that it was not placed on the minus side of the coil, as this would blow the 20 amp fuse each time the key is turned on. Is your 318 a points version (B-series engine) or a solid state ignition (P-series) Onan? Below are a few partial wiring diagrams, but should get you started...

Chuck

 

[volvo4fun]

Found it (and found a new problem)!

Points connected to the wrong side of the coil! Once that was straightened out the engine started fine.

Started it at least 10 times, while adjusting points gap and idle speed.

Put the air filter back in place, cleaned up some things here and there and got ready to go on my first test drive with the new engine.

No start! Checked - no spark!

Fuses OK, 12V on plus side of coil, points still working correctly. Changed out condensor, checked with other spark plug, still no spark.

Changed the coil, still no spark.

Primary side of coil 4.4 Ohm
Between spark plug outlet and primary side I get infinite.
Same readings for the first coil that worked earlier in the day.

Any further suggestions?

 

[chuckv]

Robert,

There is no connection on an Onan coil from the primary side to the secondary side like many single cylinder engines. The secondary (high tension) side is completely isolated from ground, in fact the two spark plugs are in a series circuit from one high tension terminal to the other with the series connection being completed by the two threaded parts of each plug being in the metallic block of the engine. If either plug is not connected, the other will show no spark.

Since you changed the condenser, check carefully that there is no grounding of the points terminal where the wore of the condenser attaches.

What exactly did you change/clean up prior to the no starting symptom showing up? I take it that the engine still cranks over with the starter but does not fire...

Chuck

 

[volvo4fun]

Wire from points to coil was replaced by previous owner with one that was too big around. Ignition cover pinched cable and caused a ground fault.