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MG MGB Technical - persistent non-starter
|I have a 1966 MGB that is entering its 3rd month as a persistent non-starter. Iíve had this car for 25 years, and Iíve never failed to get it to start before. It is all stock except for a Weber 32/36 carb., and it was starting and running fine before I decided to improve it. Hereís what Iíve done:|
1. Converted the car from positive to negative ground, following the usual instructions. I reversed the wires on the tachometer loop and made the necessary changes inside the tach. A continuity check shows that I donít have broken wires anywhere in the ignition circuit.
2. Replaced the 3-synchro transmission with a 4-sunchro overdrive. This includes changing the engine back plate and flywheel and adding a pre-engaged starter, plus a starter relay.
3. Reassembled everything, using the Weber 32/36 carb, all set up as before. I added a fuel pressure regulator, set to 3 pounds. The fuel pump is sending a steady stream of gas to the carb.
4. Cleaned the carb. To be sure that there is no dirt in the jets or passageways. I also replaced the gasket in the middle of the carb . The float level is unchanged from the way it was running before, and the floats are in good condition.
5. Checked that the firing order of the plugs is 1-3-4-2. The rotor points to the #1 lead on the distrib. cap as the piston comes up on its compression stroke.
6. Set the static timing to 12 degrees BTDC.
7. Determined that all 4 plugs are sparking by connecting an inductive timing light to each lead. A voltmeter shows 12 V at the new coil.
The starter turns the engine over rapidly and smoothly, but it will not fire. In fact, it has never so much as coughed in all the time Iíve been working on it. Iíve cranked it for about a minute at a time, using full choke. Iíve tried all the combinations of choke and accelerator that used to start it right up before.
The engine clearly is flooding, since the plugs are wet, but it is flooding because it wonít fire, or the reverse?
I also have a new Weber 32/36 DGV carb, which I put on in place of the old one. The engine still remains dead, and the flooding continues.
I have disassembled, checked, and reassembled several times, all with no result. What am I missing??
|The only thing I can come up with is asking you if you are using fresh fuel, it helped with me sometimes when starting up laid up vehicles. Modern fuel evaporate the lighter particles quite quickly, thus loosing a lot of the cold starting ability.|
|Willem vd Veer|
When you set the fireing order, did you get the rotation correct? I think the rotor turns counter clockwise.
Though not likely, it is possible to foul spark plugs with an excess of gas, and they will never fire again no matter how you clean them.
|C R Huff|
You added a pre-engaged starter and relay. Assume you are talking about later model starter with solenoid attached. Wanted to clarify. Also, w/regard to start and proper relay, what did you do about wires going to previous solenoid on inner fender?
More importantly, have you checked to see if you have 12 volt (approximately) or any voltage going to the points? Test light or otherwise with key in the on position. May need to disconnect lead in wire or take cap off and make sure points are open when checking. If you have voltage to points when key is, need to also make sure that you still have voltage to points when key is in start position.
|Willem and Charley: |
Thanks for the comments. I've put fresh fuel in the car. I have the firing order correct for the counter-clockwise rotation. I've sandblasted the plugs clean several times, and I even put in a new set, but still no joy.
Are you certain you have sparks at plugs? Have you reverse polarity on coil?
Have you follow that procedure?
Cheers Jean G.
|Jean Guy Catford|
|Does the tach needle quiver while spinning the engine?|
Also, try swapping in a new distributor rotor. Some rotors are
notorious for shorting out (invisibly) through the insulator onto
to top of the distributor spindle, to ground.
|I've done just about the same thing to my '67. I installed a '72 4 synchro/od trans using the later backplate and pre-engaged starter. I kept the original solenoid mounted on the fender as the starter relay and connected both wires on the starter motor solenoid together so that they are both energized st the same time. The only difference between our cars is that I'm running a Moss supercharger system. I would try hot wiring the positive side of the coil and then turning the engine over with the starter motor to eliminate any problems introduced by the ignition switch and its wiring. RAY|
|Thanks to everybody for your comments. Unfortunately, the car still remains dead. Here is what I've done most recently:|
1. Hot wired the + side of the coil to a brown fuse wire to by-pass the ignition switch/tachometer. Car still won't start.
2. Used a jumper wire to by-pass the new starter relay, just in case it isn't set up right. Car still won't start.
3. Drained the gas tank and put in fresh fuel. No joy.
4. Checked with a volt meter to see that I have 12 volts all through the system, including to the points. This is all ok.
5. Checked with a clip-on timing light to see that cueernt is getting to each spark plug. All have spark.
6. Made quadruple sure that the firing order is correct (1342)and that the #1 plug is firing on the compression stroke, when both #1 valves are closed.
7. Made sure that fuel is getting to the 32/36 Weber DGV carb at about 3 psi.
8. Sprayed Quick-start into the carb, without result.
9. Determined that the starter is turning the engine over at about 120 rpm, which should be fast enough to start.
Through all of this, the car remains completely dead. It has never so much as sputtered. I am rapidly approaching both autocide and suicide! Can anyone help with this?
Thanks in advance for your comments, Mike
I think most of us have had the starting problem after servicing or tinkering, I forgot to put the rotor arm in once. also connected the fed to my Luminition on the 4th fuse instead of the 3rd, follow everything through with a volt meter it's proberly something simple. Bill
|Putting an inductive timing light...........don't know what voltage they require to trigger. Take a plug lead off and connect to a spare plug..earth it then crank. Healthy spark?? If not do the same with the centre lead. If still no spark on the test plug suspect the coli, points and condensor; if there is then change the rotor arm then the cap. Speaking of which is the carbon contact in good nick, moving freely............is it even there??|
|When you checked to see that the #1 plug wire was pointing to TDC on the compression stroke, did you have the valve cover off to confirm this? If not, you may simply have the ignition wires set up 180 degrees out. A small thing to overlook, but a very common one. Plus it's easy and cheap to rectify. RAY|
|When my '70 has set for some time, and the battery has started to go low, I find that connecting the charger gives an easy start (even when not in the "start" position). It clearly turns the engine faster --- and it starts on the first click.|
|Mike, as you know, getting the correct amount of fuel, compressing it and then delivering a spark at the correct time should make the thing run (easy for me to say all the way over here!). The fact that the quick start makes no difference suggests this is a spark timing issue.|
However, have you checked for full and correct compressions? Also, try moving the static timing in a little to say 8 or 9 degrees.
Do you have any vent pipes in the intake which could cause a weak mixture? If so, block them all off and try the carb straight in.
This thread was discussed between 14/04/2011 and 27/04/2011
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