No Spark

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Derek Clarke
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No Spark

Post by Derek Clarke »

My old traveller has been hickuping for several weeks and I'd booked her into a garage this week for a check up. Today she just wouldn't start. Took the dizzi cap off and looked for a spark on the contact breaker when turning the engine over- nothing at all. Any suggestions? I'm sure its something simple.
les
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Re: No Spark

Post by les »

Start by cleaning and resetting the contact points or even replace them.

simmitc
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Re: No Spark

Post by simmitc »

Given the previous hickuping, I suspect that yo might need a new condenser, but let's be logical...
Check that no wires have fallen off the coil or the side of the distributor.
Do you have a multimeter available? If yes, check that 12 volts is present on the white wire to the coil (ignition on).
If all in place, then remove the king lead from the centre of the dizzy cap, fix it about 1/4 inch from the cylinder block and turn the engine over. Do you see a good healthy spark?

Report back and we can go from there.
myoldjalopy
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Re: No Spark

Post by myoldjalopy »

A car which has been "hiccoughing for a while" may simply be in need of a good service so, as Les suggested, a closer look at the points may reveal they need cleaning /re-setting/replacing. Do the plugs at the same time. However, a better first test in diagnosing ignition troubles is to check for a good, blue spark at the king lead rather than at the points. Whether there is one, a weak, yellow one, or none at all, is the first step in identifying the problem. As simmitc suggests, firstly make sure all connections are good. At this point, I am assuming that there are no issues on the fuel side......which could also cause 'hiccoughing'.
oliver90owner
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Re: No Spark

Post by oliver90owner »

MOJ is spot on. Remove the distributor cap and king lead and turn the engine untill the points are closed. Turn on the ignition and open the points with an insulated screwdriver, or similar, while holding the king lead about 6mm from any earth surface.

A strong blue spark indicates that the spark is there at the distributor.

A weak, yellow spark could mean the condenser needs checking. Only change it if necessary.

A weak, or no spark, could mean the points are burned/dirty and there is little or no current through the coil. That may indicate a poor supply connection to the distributor so check the coil current if you have the facility - should be about 4A. Loose connections, or the pigtail lead going open circuit, are often the causes.

If there is a strong blue spark, your problem is between the coil and the plugs. It could be the rotor arm shorting, the distributor cap tracking (wet or cracked). Even the plug leads leaking too much HT.

The coil primary resistance should be about 3 Ohms. A wide variation from that figure (or too much/too little current at 12V) may mean the coil is faulty.

The condenser is easily checked once out of circuit - the resistance, when tested with a multimeter should initially be close to zero, rising to several mega Ohms over a few seconds (depending on the meter).

Most faults can be traced to the faulty part in just a few minutes of testing.

Other simple faults to look for could be the wrong points gap or a worn cam on the distributor, or even a worn out distibutor bearing.

It is often a good ploy to check under the bonnet in the dark (safety!) with the engine running to see if there are stray sparks visible. Clearly, if there are they should be eliminated.

Hopevthat helps. Let us know what you find.

Contrary to what some people think, the simple diagnosis route is the easiest and most reliable way to sort the fault. Lowest cost and you know what the actual fault was, how to fix it and perhaps recognise it if it re-occurs.

RAB

Edited to add that a simple check at a plug lead, for a spark while cranking, should be used to determine if the problem is with the ignition circuit - although tracking across terminals in the cap might mean it was only firing on the one checked plug!
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