More electrical problems

First time posting, but have enjoyed all of the helpful advice through this forum. I have a 75 MGB, which usually runs well. Starts up with no complaints, all electrics work (Hallelujah!!) except...the engine will just die. All lights work, horn, etc. With 10 seconds to a couple of minutes, she'll start back up and run for 2 to 15 minutes and cut out again. Shel'll do this 2 or 5 more times, and then for an hour or more. Happens cold or hot. No sputtering, as if a total loss of power to the engine. I'm not strong with electrics although I should be...this is my third MGB. Appreciate a logical troubleshooting senario. BTW, replaced plugs, coil, condensor, points, checked ground, ignition, replaced fuel pump,(was split and shooting fuel towards the exhaust...not good). already did a complete brake overhaul from master cylinder, lines, hoses, shoes, pads and wheel cylinders. Thanks again for all of the sage advise. jim

Have you checked your fuel filter?

New fuel pump and filter, plus new tank. i'll pull the filter and check the flow rate again. I guess it could be that simple...these little cars keep me scratching my head.

I would revisit the distributor too. A bad condensor can cause the symptoms you are describing.
Even though it is new.

Jim: Lights and horn are on different circuits - when you say "etc", does this include the tach, wipers, and fuel / temp gauges? The ignition relay powers all of these (with the ignition turned on).

When it won't start do you have spark at the plugs?

May not be electrical???

Everything electric works, wipers, all lights, heater fan, etc. At times I wonder about the fuel pump, it is one of those square boxes that run all of the time, noisy. But it is as if a switch turned off, only to the motor. It restarts within a minuter or two. Get her home and she'll sit and idle quite happily for an hour, with no duplication of the problem. Can't get the problem to happen when I'm home, with all my tools, in a nice warm garage....

My next available play date is thursday, so I'll replace the fuel filter(s), I have a spare condenser, so that'll be changed,and just continue to keep at it. thanks for the help.

These "intermittent" problems are the worst - since you can only check for the cause when the problem exists. At all other times "everything works".

Let us know what you come up with the next time it happens.

So I have a possible crazy solution for you to check. I also have a 1979 and a 1975. On the 1979 the fuel pump was replaced with a Facet unit (the small cube style fuel pumps that run all of the time)like yours. The car would run fine for five minutes and then stop. It would idle forever with no problem.

I tried everything but every time I was "out on the track" it would stop. If I waited 5 minutes it would be fine. Turns out that it was the fuel line! They had a nice loop in the line going to the new fuel pump and it was soft enough that it had a slight kink. Enough fuel for slow speed and idle but "on the track" it was not providing enough fuel! Rerouted the line and it has been great ever since.

I thought for sure that it was electrical, distributor, fuel pump, filter and everything else but it was a simple kink in the fuel line.

Scot

Thanks Scott. My pump is also a Fascet. I'll check for fuel line kinks and also replace filter. Sometimes the craziest things are the cause of these intermittent problems.

Intermittent Spark issues? I would R&R the coil.. or go electronic..

Check the gas tank vent as well. If no air is able to get the tank, it will starve for fuel. If you replace the fuel filter, get a clear one so that you can see if it's empty or not the next time it happens.

I'm no expert, but the fact that it "just dies" as opposed to "sputter to a stop" would seem to be electrical though....

Removed previous fuel filter and installed clear one up in the engine bay...very very poor flow. Now, is it the pump or blocked lines??? Removed gas cap to eliminate venting potential problem and still poor flow to filter. Replaced all soft lines and still... My son has semi=permanently borrowed my compressor so,until it returns, my question is, how much pressure does my fuel pump need to pump?? It is a Facet style, only 6 months old. Tomorrow I slide back under the little thing for more "fun".

The SU's output is roughly a qt/minute.

I like Scotts idea of where to look and .. Coil ? Sounds like a coil to me..

Regarding the fuel pump, my BL shop manual says that the MG pump delivers about 1 pt/minute flow rate at a 4 foot head pressure. Assuming 32 feet of head = 1 atmosphere = 14.7 psi, that gives a pressure of about 1.8 psi You may want to use these values as a starting point to see if your pump is up to snuff.

If it were something in the fuel system the car would not suddenly cut/die, it would sputter first. It sounds electrical to me and is probably in the ignition circuit. Check the ignition switch and it's connector under the dash. You will need a multimeter for this.