HAVE YOU EVER...electrical delemma

[docrocky]

I would like to share with the forum a very unusual occurrence. I have just completed replacing a cracked head on my MF 205 diesel (Toyosha 2 cylinder) engine. Did all the necessary tasks such as reseat the valves, new gaskets, checked out cylinders and bearings etc. My engine re builder and I hooked up every thing back as needed and used our digital photos as check list. The engine turned nicely manually. We then hooked up a brand new battery and gave the tractor a try. Turning on the key, the engine oil light flickered on but when the key turned to the start position, nothing. Checking all the fuses and making sure the clutch safety was properly depressed, nothing. Battery checked out but to insure even used the battery charger to supplement the starting power, but again nothing. Tried jumping the starter at its terminals, but again nothing. I then checked the + battery cable to the solenoid with a test lite grounded to the engine and there was current to the solenoid. I then went to the instrument panel to see if I could check out the ignition switch but this was very difficult to evaluate since I did not have a wiring diagram. I then removed the starter and bypassed the solenoid and it would engage with power. I took the starter to a friend's electrical shop (starters, generators, alt repairs) and replaced the solenoid, the brushes etc. Worked beautifully on the bench. I returned it to the tractor and after recharging the battery gave it a test, again nothing. I then repeated jumping it at the posts and again nothing. After repeated testing as many switches as I could with a continuity test light still could find no fault. I then started checking grounds especially at the battery terminal to the frame. I cleaned and removed all potential corrosion but still no response.

Now to shorten this narrative, I used the test light touching the negative battery terminal to the frame and had strong current. I then connected the test light to the frame connection of the negative battery cable, and no current. The cable was totally intact with good post and frame contacts. I then substituted a different negative cable and lo the current passed. I then turned on the key, lights were bright on the dash and the started engaged. Problem solved. It was a faulty battery cable whose external appearance revealed no faults. I then opened the insulating cover and still found no break in the continuity of the copper fibers. I tested the cable with the continuity test light and the current would not pass within a fraction of the cable attachment to the post.

I'll try to attach some photos of what I encountered. I am sure some of you may have encountered this problem but for an ametur like me and a few others we haven't. If there is a lesson to learn from this it is to carefully check your grounds.

 

[banjodunn]

G'day good to see you found your elec gremlin they can be a real PITA at times. Some years ago over here mitsubishi bought out a range of cars that had those moulded terminals and after about 5 years they started to give us all sort of dramas. Just need to go through these things with a fine tooth comb and you will eventually find it


Jon

 

[Redneck in training]

Bad connection to copper wires are common issues at plants such as steel mils, power stations, refineries etc. When wires are exposed to various combustion gasses in humid environment copper gets coated with black non-conductive layer. To provide good reliable connection the contact has to be air tight. Either soldered or clamped with reasonable large force. Crimped contacts, unless done with proper tools and proper way, are the least reliable.

 

[kebo]

You should measure the dc resistance of the cable from end to end with an ohmeter to see what it measures. That will really tell you something. Although, it might not be easy to get a good connection on the ends of the cable with the test probes so you can measure it but, that cable should measure near 0 ohms from end to end.

 

[Gordon Gould]

Good meassage here. I have gone thru similar tribulations. It is not easy when the last thing you suspect is a big rugged looking fully intact cable.
On the bright side you have a nice rebuilt starter to go with your rebuilt motor.

 

[Ed of all trades]

Ben there done that. Have the bald spot where I pulled my hair out to prove it. Not after a rebuild but just happened. Glad you found it, how is your bald spot??

 

[stevem5215]

I've had the same thing happen on a L Gravely with the electric start. It started out as a intermittent and got worse till it quit. I checked the same as you and found that when i replaced the battery connector all was good again. Just corrosion with dissimilar metals building up a resistance and when the corrosion got the better end of it finally that was the end.

Steve

 

[Agent Blue]

Just finished two vehicles with ground problems. Talk about a pain to determine the cause. One would run for ten minutes and quit. Wait five minutes and repeat the process. By the way I have a new in tank fuel pump as the mechanic told me this was the problem ...... NOT ! A corroded ground was the culpret in the middle of the wiring harness nicely hidden under the carpet.
At $90.00 an hour this solution can find its way to the thousand dollar repair bill quite quickly. Unfortunately most don't have this to experiment with and sell the older vehicle cheaply.