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MG MGB Technical - Difficult Starting First Thing In The Morning

I have the darnest time starting my 70B every morning. The car sets out of the garage every night. (The TD and wife's car take priority). I hit the starter switch for 10 minutes sometimes before the engine kicks over. Then it runs great like nothing is wrong. On several cold mornings (particularly after a rain the night before) the engine will not start at all until later in the day when the temperture increases.

So far, I have changed the fuel filter, installed a new coil, checked and adjusted the points and tuned the SU carbs.

This problem is not new -- it has existed since I bought the car about 10 years ago. But it seems to be getting worse.

I also own a 52TD which I did a frame off full restoration. It always starts on the first rev of the engine. I can sure use some suggestions at this point so my nerves will not be on edge every morning! My thanks in advance.

Hal K.
Hal Kramer

Have you checked for condensation in the distributer cap?

Yes, I did check for condensation in the distributer but I'll try installing a new dry one in the morning before trying to start the car.

Hal K.
Hal Kramer

Hal - Is the choke actually setting whe you pull the choke cable out? Without the choke, it is almost imposible to start the car first thing in the morning (sort of like that first cup of coffee in the morning)
David DuBois

What David says would be my first guess, but it should also cause very poor running as well until it has warmed up. When it *is* running, pulling the choke 1/4" should cause the idle to speed up, and pulling it any more should make it obviously rich running.

First thing with any non-starter (that is cranking with the key) is to clip a timing light onto the coil lead and each plug lead and watch for the flashes as you crank. They should be regular and consistent, with the coil lead four times as often as any plug lead. While on 1 and 4 check the timing is approximately right i.e. about 8 to 10 degrees BTDC (manifold vacuum distributors should have the vacuum disconnected for this test).

No flashing is ignition LT. Good flashing on the coil lead but erratic or not at all on one or more plug leads is the cap, rotor or leads breaking down. Erratic flashing on the coil lead could be iffy points adjustment. A had a similar problem on my V8 where every now and again it would not start, until I put new plugs in, even though the plugs had on done a few k miles. Every time this happened I had to be somewhere so only had time to fit a new set (kept ready gapped in the car), until one time when I *did* have time to do this test, and found some plug leads not flashing. A new cap (rotor was already nearly new) and it's been fine ever since.

A bad condenser could cause weak sparking, with the coil lead eased out of the coil the spark should jump at least 1/4" and quite possibly 1/2". If it barely jumps a plug gap the condenser has probably failed.

If all that's OK after cranking a bit remove plugs 1 and 4 at least. If they are wet it is flooded, but then you should be able to smell that anyway. In which case crank it with the throttle fully open and the choke closed, and get ready to release the throttle and half-pull the choke when it catches. If there is no fuel smell on the plugs there is none getting through. Does the fuel pump chatter momentarily when first switching on the ignition in the morning?
Paul Hunt 2

Paul -- Thanks for the abundance of good info you had provided. I'll go through the items and see what works and what does not work to isolate the problem. The last two days have been dry so the car started with very little cranking (about a minute) but I feel that is still too much since during the day (after it had been started earlier) it starts within 1 or 2 revs of the cold engine.
You seemed to focus on the ignition system. Anything in the fuel or pollution systems that might be considered? Of course the few components for the pollution system have been removed before I acquired the car but there are still a few small hoses running around the carbs. And I checked the choke cable operation and it checks out fine.

Hal K.
Hal Kramer

Hal - If you suspect the fuel delivery, see my article, Fuel Delivery Troubleshooting Guide at:
The other thing to check for is vacuum leaks. Although a vacuum leak would also affect normal running, it is possible to have a leak that loses up as the engine bay warms up. Cheers - Dave
David DuBois

1 minute is still way too long, even for stone cold in the middle of winter.

A problem in the pollution system is a possibility, particularly on cars with the anti-runon valve fitted but that wasn't until 73. But if the large air inlet pipe on the bottom of the canister is blocked, or canister itself is choked, then its possible that the puging system is actually sucking the fuel out of the carb jets. The easy way to eliminate/confirm that is to remove the hoses from the float chamber overflow/vent pipes (that go to the canister) and then try starting.

You say "The last two days have been dry so the car started with very little cranking (about a minute)". Is this a regular thing? That it starts better when dry than wet? If so I'd suspect dampness in the HT system, or coil, cap, rotor, plugs or leads breaking down. However the timing light test would reveal any of those with the expection of the plugs, but new plugs would soon cure it, and I'm sure you done that in the past 10 years.

Otherwise, we won't really know any more until you confirm the ignition is good (looking at the flashes and checking the timing while cranking), and the fuel is good by removing the plugs after cranking for a while with no start and checking them for fuel smell/wetness.

I'd also like to know what happens when you pull the choke right out when the engine *is* running. Does it speed up? Does it obviously start running rich? It should do both. A 1970 should have HS carbs on which the choke (or more correctly enrichment) system is all external and can be confirmed visually. But if your car has HIFs for any reason (these started to be used in 1971) other than the cam operated by the cable the enrichment system is a separate jet inside the carb body and so cannot be verified visually, only by pulling the choke when the engine is running.
Paul Hunt 2

This thread was discussed between 13/06/2007 and 16/06/2007

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