MG Car Repair: mg 1973 midget, mg midgets, compression gauge


Question
QUESTION: I did all that you mentioned.
It almost fires up.
When you start it it kicks 2 times then goes out.
I gapped it at .015.
There are a couple of black and yellow wires hanging out that do not go to anything.....could that be something?
We are really close to having it start .... I can feel it.
I have a picture of the black and yellow wires...where do I send it...cannot attach to this email???
thanks!!
david




ANSWER: Hi David,
It will do me no good to look at a picture of a black and yellow wire. There are black wires used by MG Midgets but there are no yellow wires used. Yellow was only used as a strip on other colors. But all of that does not matter. It takes three items to make any engine start. Compression, fire and fuel with conditions on each.

Compression test must be 125 to 180 PSI on a compression test. (Throttle open and at least 4 or 5 revolutions)

Fire (spark) must be about the correct time and at the plug be a thick blue spark. (a thin orange or yellow spark is no good)(not done in sun light)

Fuel must be roughly the correct mixture of air and fuel and the fuel must be a combustible fuel and available to the combustion chamber.

All three are easy to test and take very few tools. Pull all of the plugs and place the spark plugs on the wires. Spin the engine over with the plugs laying on any metal part of the engine and with your thumb in the #1 plug hole watch the #1 plug. As the engine spins your thumb will make a "Pop" sound as that cylinder comes up on compression. If you are watching #1 plug it will seem that the "Pop" is causing the spark. If the spark is before or after the "Pop" you will see and hear "Pop"-- "click" or "Click"--"Pop" which indicates that the timing is off so far as to prevent starting. This is a mechanics quick check to see why and engine will not start.
If you have a compression gauge go ahead and do a compression test while the plugs are out. Reinstall the plugs and have some one try to start the car and spray something like WD-40 into the intake. If that makes it run for a second or two you have a fuel problem and then you must check fuel pressure first.
Let me know the results and we will go to the next tests.
Howard

---------- FOLLOW-UP ----------

QUESTION: yes the wires are black with a yellow strip....2 of them just hanging there.

how do I know what spark plug wires go where?
I tried matching up left to right.
there is a left rear and left front location on the distributor for the spark plug wires (if you are standing in front of the distributor looking at the engine from the side)
thanks


ANSWER: Do the set up as I listed in the previous question but this time when you roll the car forward in gear with your thumb in # 1 plug hole and feel the pressure on your thumb. look inside the dist. cap and note where the rotor is pointing. This is #1 plug wire. Label it with a piece of tape or what ever. Looking at the top of the dist. cap the firing order is 1,3,4,2 in a counter clockwise rotation. Which is the firing order on almost all inline 4 cylinder engines.
Don't try to orient the wires as for their location because that depended on, if who ever was inside the engine last set it up correctly. The set up as I listed above will work on any engine anywhere.
Let me know if you have a problem,
Howard

---------- FOLLOW-UP ----------

QUESTION: no pressure on my thumb ....when I roll car forward...push in clutch or NOT...
I had the clutch pushed in.
#1 plug hole is located....where?
thanks

Answer
#1 is the front spark plug hole and yes you have to have the clutch out and in 4th gear and brake off or you will not be able to move the car to rotate the engine. (do this on level ground or you might find your car at the bottom of a hill) with the plugs out it rolls very easily. Roll the car forward to get the pressure on your thumb. As soon as you feel pressure on your thumb STOP. Then with a light look under the front of the car at the bottom of the front pulley where you will see the pointers on the timing cover pointed straight down. Put the notch in the pulley in line between the first and second SHORT pointers. The long pointer is TDC and each short pointer is 5 deg. so 7 deg is in between the first and second short pointer. Once you have the crank pulley in that position DON'T move the pulley (take the shift lever out of 4th into neutral) Now loosen the pinch bolt on the distributor and turn the dist so the points are on the high point of the cam and set the point gap to .015 in on a high point of the cam. Turn the distributor so the rotor is pointing to # 1 plug wire, then turn the dist. slowly counter clockwise until the points close. Now connect your test light to the small post on the coil that has the white wire with a black stripe on it (dist. wire) and turn the key to ONLY ign. Your test light would be OUT. slowly rotate the dist. clockwise until the test light just turns on. Lock the dist pinch bolt. Now, Put the gear lever back into 4th gear and back the car up just a little until the test light goes out and very slowly bump the car forward until the light just does come on and look under the front again and if the notch in the pulley is lined up between the first and second small pointer, You are done. If it is not, you were not careful enough and you must do it all over until it is correct. Timing is very important so you must be very accurate with this.
Let me know,
Howard