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MG MGB Technical - Engine Rebuild Complete: Startup Help Needed

Well I took Friday off and made it a 4 day Memorial Day weekend. I worked some long hours each day and night (until 2 am Thurs, Fri, & Sat night), and have my engine back together and painted. I'll post some pics later (it's really pretty now).

Here's the problem I'm having though... When I crank the engine, the starter turns but the engine doesn't try to fire. I've gone through the wiring and everything is connected properly (at least I think it is). I put a test lamp to the positive side of the coil with the ignition switch on and it lights up (though not too brightly). The last time the engine ran was in February. I had the battery disconnected during the rebuild. Is it possible the battery is drained enough to turn the start but not be able to fire the engine? What other problems can I look to?

FYI - I did not remove the distributor or any of the timing components - so that shouldn't be a problem. The car ran well before I started the rebuild (due to a crack between #2 and #3 cylinder).

Jack Caulder

Have you connected a timing light to verify that everything is still set properly? Was this a rebuild or just a cylinder head repair? You definately need to put your battery on a charger if it has sat that long.

Try putting the test light on the negative side of the coil while cranking and verify "pulses" of light. If that's ok, check for spark at the plugs. Is the engine getting fuel? If so, put a timing light on the engine to verify nothing has changed.

Are the carb and intake gaskets well sealed? Is the vac hose hooked up to the intake/distributor? Is all your emissions stuff properly tied in or removed? Is the fuel pump ticking properly? Are the carbs clean, or could the floats be sticking shut? Is there oil in the dashpots? There are SO many things to check. Give us more info and we'll try to help.

Jeff Schlemmer

Thanks for replying and giving me some ideas.

I did a little more than a head repair, but not a full blown rebuild. I replaced the oil pump and con rod bearings in addition to the head repair and radiator replacement. I cleaned the carbs - so they shouldn't be sticking. I replaced all the gaskets on the intake/exhaust manifolds and torqued them to the specified values. I did put oil in the dashpots. I have a pertronix ignitor instead of points.

I charged the battery yesterday to remove that from the equation. I put a test lamp on the positive side of the coil with the ignition on and have light. I also get light when I put the test lamp on the negative side of the coil - with either the ignition on or when cranking (it does not flash on and off when cranking). I get no spark at the plugs. My guess is the distributor plate is not properly grounded. Does this sound correct?

Thanks for the help.

Jack Caulder

Without the points, I'm not sure if the distributor plate needs to be grounded. If the Pertronix is a 1-wire system, then yes that could be it. Check the trigger in the distributor and make certain that it is functioning properly. Sometimes a wire can get out of position and get cut by the trigger wheel, or the wheel can rub on the sensor and damage it. Make sure your plug wires are correctly routed too.

You can make a new ground wire for the distributor with a short piece of fine braided wire and a couple solderless connectors. That's what Moss is selling now for a replacement.
Jeff Schlemmer

I had a similar experience when I rebuilt my engine at age 19. Double check that the ground strap from the engine to the frame is making good contact. (May need to clean away some of the new paint.) No ground, no spark.

(I learned this the hard way, paid to have the car towed to a professional shop. Fixed in twenty minutes, felt like a fool.)

Well the ground wire that runs from the distributor base plate to the body was frayed and connected by two strands of copper. I replaced it, and then found out the hard way you have to tie down the wires for the Pertronix inside the distributor cap. I tore that up. I then put the points back on, and the test lamp was "blinking" when I cranked it, so it looks like the points were opening and closing. The car still won't start. I adjusted the points again to make sure they were right, and started the car again. Then the distributor itself starting rotating in relation to the engine. I did not mess with the clamp, so not sure why this started happening. I guess she's rebelling against me since it took so long to get her put back together...
Jack Caulder

Sure that clamp is tight and properly gripping the flange on the distributor? If so I'd pull the distributor and strip it pdq as I would guess something (bob weights?) has jammed. If not tighten it and reset the timing statically.
Steve Postins

If the distributor clamp seems tight, there is a possibility that it cracked. The point of the distributor body where the clamp mounts it relatively thin and can break if overtightened or handled/removed roughly. Make certain your timing is set properly, and if everything was done correctly on the rebuild, it should run.

If you still have problems, double check the valve lash. Make certain that all the settings are as close to perfect as you can get!

Jeff Schlemmer

Jack. There is a tech article on my website, which discusses ignition timing and another on ignition system troubleshooting. They may be of use to you.

I would agree that you need to remove and inspect the distributor to see what the problem is, then, install and time it.

There are two ground straps of concern. The one inside the distributor, grounding the base plate to the distributor body. (Also make sure you have the points connected properly. The top insulator goes in into the holes on the wire from the coil and the condensor wire and allows the wires to make contact with the spring arm. If you do, as is common with American points, simply connect the wires under the nut, the system shorts out.)

The second ground strap is the engine/transmission ground. On early cars, this was on one of the motor mounts in front. With the RB cars, it is from the transmission mounts to the tranny cross member. If this is not in good contact, you will not have the system working properly.

After that, it is a case of getting the ignition timed, making sure you have good compression and that fuel is going to the cylinder head. Also make sure the connections at the starter are tight.

If you can perform these checks, and the car will still not start, we can focus more on what the problem might be. Les
Les Bengtson

I have a rebuilt distributor from O'Reilly Auto Parts on order. It should be here tomorrow. I had good luck with a rebuilt starter from them, and for $60 and a lifetime warranty how can you go wrong? I'm considering replacing the weights and springs in the rebuilt unit with those out of mine...heard they weights and springs aren't always correct on the rebuilt units.

Thanks for the website referral - very helpful!
Jack Caulder

Jack, you also want to use the piece that the weights slip onto. It determines the amount of total advance your distributor allows. Double the number stamped into the plate for crankshaft degrees. anything stamped 10-13 will give good power on a desmogged engine. You may want a higher number if you are all stock.
Jeff Schlemmer

I picked up the distributor from O'Reilly the other day - it looked real nice. I then proceeded to tear it apart. Jeff was correct to replace the piece the weights slip onto. I have a 10 degree part, and the part in the rebuilt distributor was 9 degree. I replaced rebuilt distributors part the weights slip onto, the weights, and springs from my original distributor. I then installed the distributor, set the timing, adjusted the valves, and.....she fired right up!

I didn't see any oil or coolant leaks. It smelled pretty bad as the install lube burned off.

I can't wait to drive her again. Thanks for the advice and suggestions!
Jack Caulder

Unfortunately by taking the base cam, weights and springs from your old distribotor and fitting in to the new you are re introducing some of the worn parts from the old and so the curve will still be incorrect. The other thing is the vacuum capsule, does it have the same numbers on it as on the original...if not then the vac curve is also incorrect and you will also have to take this from the original if it is still intact.

All in all I think you would have better to have imported an Aldon which would have been bench tested to an exact profile.
Iain MacKintosh

Jack, If the holes in the weights were not "sloppy" when you reinstalled them, you should be fine. You could always peen them with a hammer to get a proper fit. The springs may or may not be correct for your application, and the old springs may be loose. If you would like your old distributor gone through and the timing curve corrected and mapped, give me an Email. I've got all the parts and equipment. I can also do a custom curve for a little more power.
Jeff Schlemmer

This thread was discussed between 31/05/2005 and 10/06/2005

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