Ever since 2002 when my engine was refitted my stag has been sometimes hard to start from cold. Not impossible but just a bit difficult. As some of you may remember its been pretty much laid up since then. I need the engine running despite all the welding I need to do as my garage is very narrow and its impossible to push the car in and out to do the work.
Lately it been really hard to start, easy start being the only way. First I traced a leaky needle valve causing flooding. Replaced both and set the float heights and it was a bit easier to start. Spark seemed weak so I replaced the coil. Things improved a bit but not much. The spark from the king lead would jump a good half inch but was reddish. I replaced the dizzy cap and rotor arm. seemed a it better but not much. I replaced the ignition leads with some silicon would ones and things improved further. I thought maybe a carb rebuild was needed and I started to doubt the spark was as weak as it appeared. Then last weekend it flatly refused to start. Easy start didn't help.
I took the carbs off and there were too small lakes in the manifold. I thought it must be flooding again. Replaced the fuel filter and blew out the needle valves. Put the carbs back on and still it wouldn't start. I thought it must still be flooding so I took the dashpots off and put the ignition on to run the fuel pump. I expected to see a small fountain in one of the carbs but no the carbs aren't flooding.
I went back to the weak spark theory. I measured the coil voltage with the points closed (i had removed the electronic ignition in case that was at fault). It was 6v. I measured the voltage cranking as I had theorised that maybe I wasn't getting full ballast bypass but it was 10v.
Today I had the front jacked up looking to see what else might need welding when I noticed there was a red and white lead to the starter motor, the main starter cable and er..... that was it. I poked around underneath and found a wire taped up and shoved out of the way. the wire was white with a yellow stripe and the haynes manual confimed my suspicion. The ballast bypass was never replaced when the garage refitted the engine in 2002!!!!!
I put the wire back on and low and behold it fired first time and started.
So it seems that you can't easily check for correct functioning of the ballast bypss using a voltmeter. Logically it makes sense. You only measure 6v when the coil is being fed by the ballast *if the points are closed* . Therefore as its 12v when they are open, when cranking it will be some sort of average between the two i.e 10v!!!!
I think the only way is to seperate the the wires that go to the +ve on the coil and check that the ballast bypass is getting a full 12V or damn near it when the engine is cranking. If you don't seperate them you simply cannot tell that the bypass is working as you can't measure the ballast bypass as the ballast itself is supplying the full voltage, a resistor (as was correctly it seems previously argued on this forum) is *not* a voltage control device.
Anyway I thought i'd put this on the forum in case any other poor soul spends the hours I have trying to find this fault!!!!
Lately it been really hard to start, easy start being the only way. First I traced a leaky needle valve causing flooding. Replaced both and set the float heights and it was a bit easier to start. Spark seemed weak so I replaced the coil. Things improved a bit but not much. The spark from the king lead would jump a good half inch but was reddish. I replaced the dizzy cap and rotor arm. seemed a it better but not much. I replaced the ignition leads with some silicon would ones and things improved further. I thought maybe a carb rebuild was needed and I started to doubt the spark was as weak as it appeared. Then last weekend it flatly refused to start. Easy start didn't help.
I took the carbs off and there were too small lakes in the manifold. I thought it must be flooding again. Replaced the fuel filter and blew out the needle valves. Put the carbs back on and still it wouldn't start. I thought it must still be flooding so I took the dashpots off and put the ignition on to run the fuel pump. I expected to see a small fountain in one of the carbs but no the carbs aren't flooding.
I went back to the weak spark theory. I measured the coil voltage with the points closed (i had removed the electronic ignition in case that was at fault). It was 6v. I measured the voltage cranking as I had theorised that maybe I wasn't getting full ballast bypass but it was 10v.
Today I had the front jacked up looking to see what else might need welding when I noticed there was a red and white lead to the starter motor, the main starter cable and er..... that was it. I poked around underneath and found a wire taped up and shoved out of the way. the wire was white with a yellow stripe and the haynes manual confimed my suspicion. The ballast bypass was never replaced when the garage refitted the engine in 2002!!!!!
I put the wire back on and low and behold it fired first time and started.
So it seems that you can't easily check for correct functioning of the ballast bypss using a voltmeter. Logically it makes sense. You only measure 6v when the coil is being fed by the ballast *if the points are closed* . Therefore as its 12v when they are open, when cranking it will be some sort of average between the two i.e 10v!!!!
I think the only way is to seperate the the wires that go to the +ve on the coil and check that the ballast bypass is getting a full 12V or damn near it when the engine is cranking. If you don't seperate them you simply cannot tell that the bypass is working as you can't measure the ballast bypass as the ballast itself is supplying the full voltage, a resistor (as was correctly it seems previously argued on this forum) is *not* a voltage control device.
Anyway I thought i'd put this on the forum in case any other poor soul spends the hours I have trying to find this fault!!!!
It reinforces the simple rule that you should not assume anything when it comes to fault finding.
Comment