The Art of Troubleshooting

by Nick Haycocks

My experience with this goes back more years ago than I care to calculate. I was training maintenance staff in a UK snack manufacturing company on the first industrial bagmakers that were Programmable Logic Controlled (PLC).

My role was to provide general instruction to staff with different engineering backgrounds to help “multiskill” them. I was working with the head of the service department, and we had the idea of breaking the training down into sections—the average span of concentration according to research at the time was about 20 minutes.

The first section was an overview of how the machine worked, followed by a shop floor visit to show and demonstrate the unit.

We then put a fault onto the machine, and let the engineers try to sort it out in 20 minutes. One of the teams had half the machine pulled apart in bits! It took the entire lunchbreak for the Service Manager and me to get it back together and ready for the next part of the training.

The lesson is: it pays to define the fault and do some analysis of possible causes before picking up a screwdriver, spanner or hammer.

I can use the entertaining article from Ned Serleth from the previous issue of Moss Motoring as an example (Sorry, Ned).

First, define the problem:

When Ned operated the starter, excess current was being drawn, as evidenced by melting wire!

Next, identify the potential causes:
1. There is a short in the wiring to the starter.
2. There is a short in the starter motor.
3. There is a short in the starter switch.

Now determine how each of these conditions can be tested, for example:
1. Disconnect the wire from the starter and try the switch.
2. Try a separate wire to the Starter motor with an alternative switch.
3. Disconnect the wire from the switch to the starter motor and try the switch.

Considering these options, there is a logical sequence to testing each of the possible scenarios, in this case:

If test 3 works normally, go to test 1. Now, if you were lucky, you would have noticed the actual cause of the problem when removing the wire from the starter motor. And that’s when Ned saw that the cable was shorting out on the starter switch case and solved the problem. And if we tried test 2, we would have seen that the starter was okay, so the location of the problem would have been further highlighted.

Of course, it’s not always easy to find causes of problems…

I had a 1967 Mini Cooper S when I lived in the UK. The engine was fitted with 1 1/2″ SU carburetors. As a consequence, the engine had been over-revved by the previous owner and the land between the piston rings broke up. It still drove very well; the only issue was if you took your foot off the accelerator it became a remarkably effective smoke screen generator. Consumption of oil was not that far away from that of petrol!

The engine was rebuilt, and I went to start it. No luck. I checked everything—fuel, spark, timing—all looked good. My Father offered to help. He was an “old school” engineer. He was also a chauffeur at one time and was tasked with picking up an Isotta Fraschini chassis and driving it to the coachbuilder to get its body. He claimed to have had the chassis over 100 MPH en route! In those days you had to make a lot of the spare parts you needed. I very much prefer the convenience of having Moss Motors to rely on.

My father rechecked everything. I began to wonder; did I get the cam timing wrong? Would I have to take it all apart again? Then he suggested trying to start the car by towing it. He thought there might be too much oil from the rebuild preventing a good seal on the valve seats. The theory being a bit more gas movement by spinning the engine for longer would blow the seats clean. I can’t say for certain if that was the problem, but sure enough, it started.

Many times, when working on cars, logic is your most trusted tool. And then there are other times when luck and fatherly advice are exactly what’s needed to save the day.