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MG MGB Technical - Ran great, now won't start..again...

Happy Holidays. I thought I had my problem (alternator or not) fixed. The battery is holding a charge, etc. Still had problem starting but after I cleaned all contacts on the fuse box (coolant sprayed from overflow tank) car started right up and ran like a top (as usual) Went and got gas Thursday and drove a bit and it ran great. Went out to start it today and it fired but stalled soon after and would not start. In fact it would not hold an idle and kept dropping below 500 rpms without me giving it gas. What gives? Ran ok the other day and I did not touch any thing, etc. I did find a gas leak near charcoal canister. Lower hose to it was cracked. I replaced the hose, no more gas leak from what I can see. Don’t know if the two were related or not.
What do I check next? I put my voltmeter on the coil and it read 1.6 ohms. I see it needs between 1.5 and 3 to be ok according to book. Voltage seemed low. I read 11.1 (KVol?)on one scale of voltmeter and zero on other scale (reg. Volts?). Is the coil bad?
The 1977 MGB cranks fine but just wont kick in. I do smell gas like he engine is flooding.
Another note, found oil on all 4 spark plugs when I removed them to check them. Could this be the problem or another problem?
A lot I know but this is the best place to get expert advice.
Thanks,
Joe
joe fabian

Did you get gas from your usual dealer -- or do you skip around when getting gasoline.

If that was the only change from running good to running bad was a fuel stop, it's the first thing to consider.
glg

Was it oil, or gas and carbon on the plugs? I'd start checking the fuel system. Work backwards from the carbs. Could the choke be stuck? How about a carb piston?
Fred H

Joe - You mentioned coolant spraying ont he fuse block, could some of it have gotten as far as the distributor? A little bit of coolant inside the distributor would stop everything cold. Good luck - Dave
David DuBois

I got gas from the place I get it for my Jeep (first time for the B). As for the plugs, it sure looked and smelled like oil. After I cleaned them off I could see they were burning correctly (light tan color, etc).

You know come to think of it, the manual choke has not acted correctly since I let the car sit for over a month while I was moving. I will check it out. Maybe it is stuck open.

I did remove the distributor cap and wiped up the little moisture that had gotten into it.

One last question, could some "gunk" got stuck in the fuel filter and stopped gas flow for a bit and after a tie the "gunk" settles back into the tank and the fuel flows ok till the "gunk" gets picked up again and blocks the filter? Just a shot in the dark.

I'll check things out after work and let you all know what happens.
Thanks,
Joe
joe fabian

Joe, Check for spark at the points and at the plugs.
Sound like you're getting gas.
Dan H.
Dan Hanson

Joe. This needs to be examined in a logical manner. First the ignition, then the fuel supply.

With the ignition, your coil should read about 1.6 ohms resistance. You have a "6 volt" coil and it should have two wires going to the positive side of the coil. One coming off the starter and providing full 12V input and the second coming off the white wire circuit (when the key is in the run position) which provides the reduced voltage input. So, I think your coil is good, but we will check it out in the next step.

To test the ignition system, have someone crank over the engine while you hold the coil wire close to the block. Insulated pliers are good for this, especially if there is a leak somewhere in the high tension circuit. You should see a good, blue spark of 3/8" or more in length. If so, check out each of the spark plug wires in similar fashion. To do this, you have to insert a bolt or a screwdriver into the boot and hold it near the engine block. You should have a good, strong spark from each of the plug wires. If so, replace your spark plugs with a new set of properly gapped plugs (I like NGK BP6ES gapped to .035"-.040"). This will guarantee that the ignition circuit is working correctly.

If you do not get a good spark at the coil lead, it is a bad low tension circuit problem--wires going to the coil, coil, distributor. Good time to note what dizzy you have and how it is set up. That will be important in troubleshooting. If you have a good spark at the coil wire, but bad spark at the plug leads, it is an HT circuit problem--coil, leads, rotor and distributor cap. Be aware that a bad coil lead can indicate either an LT circuit problem or a bad coil lead. Check by hooking up your ohm meter to the lead and reading its resistance. Normally about 700 ohms as I remember it. If you find a problem, fix it and go on.

You mention a problem with a manual choke. What carb(s) are you running? The standard was the Z-S with water choke. Are you still running a Z-S or are you running a Weber or SUs? This will make a big difference in what needs to be done to troubleshoot the problem. Cannot say a great deal more until we know what carb you are running.

As to picking up gunk in the pick up tube--not very likely on a 77. It has the one piece pick up tube with sending unit and the pick up tube has a large, plastic strainer on the end. I have never seen one which was completely clogged, even with rusty fuel tanks. One of the clear fuel filters, in line directly before the carb, will show if there is fuel present.

Let us know what you find and we can come back with a more focused dianosis program. Les
Les Bengtson

Dan. The 77 came with the Lucas 45DE4 distributor, which is a known problem. That is why I mentioned knowing what dizzy he was running and how it was set up was important. We, however, were cross posting. Les
Les Bengtson

If you had gas coming out of a hose by the charcoal canister you have a float valve stuck and it is overflowing. This will cause all manner of running problems.

Paul Hunt

Thanks for the info. I started it up today with no problems however it would not idle and stalled when I stopped giving it gas and would not start up again. Smelled like it was flooding. I am thinking, since all else is ok, that the manual choke ( I installed over 2 years ago) is sticking in the open position. Thus the starting ok after sitting for a while, stalling when not on the gas pedal, the gas/flooding smell. I have noticed the choke is not working like it did a month ago.
What do you think? Choke stuck? (Oh, its a Zenith carb).I am going to remove the choke and take a look at it after work tomorrow.

Joe
joe fabian

Joe: take the top off the Zenith and check the rubber diaphragm for splits or holes.
Terry

Joe,
I would advise opening the charcoal canister(s). Renew the charcoal and the filters. They could have gotten drenched with the fuel that backed up to them. I had the same problem a while back with my '79. Idle would not hold above 500 rpms unless giving it throtle. It has worked fine since renewing the canisters. Also I had to disconnect the large hose that runs from the canister to the front of the engine bay and blow it out with compressed air. It too had fuel(and sludge) in it. Because of the way it is routed this fuel gets trapped at the low point in the run of the hose.
Hope this helps.
John
John F

John,
My canister is less than a year old and I just have 1 question. How do you open it? I don't want to pry in the wrong place and break it(the other one broke when I was taking off the top hose-original canister, so I had to replace it and these baby's are expensive if you can find them).
Thanks,
Joe
joe fabian

The bottom of the cannister unscrews.
Check out Gerry Masterman's great description of
the cannister rebuild

http://www.shadetreemg.com/cannister.htm

You should be able to check if the manual
choke is working by the position of the
throttle lever against the slow idle adjust
screw. With the choke knob pulled out, there
should be a gap between the lever and screw,
and with the knob pushed in, the lever should be
flush against the screw. (This is the small
idle adjust screw, not the spring loaded one.)

The o-ring inside the choke body can also
leak, causing a too rich mixture and flooding.
Ronald

Ronald,
I can not unscrew the bottom of the canister. Any hints? It is on there solidly. I don't want to use anything that may break it.

Joe
joe fabian

This thread was discussed between 01/12/2003 and 06/12/2003

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