QuestionQUESTION: Howard - 1977 MGB w/electronic ignition: I changed the oil/filter and now the oil pressure seems to be a little higher than it was before the change. Also, changed plugs & wires and adjusted the timing. Had to advance the timing from where it was to get it to 10 BTC. Took the car for a test run and 1/4 mile from the house it just dies, like it was out of gas. After about 5 minutes it started back up and I drove it home. Coincidence, or might I have done something wrong? Thanks. Hugh
ANSWER: Hi Hugh,
It is normal for the oil pressure to be higher with fresh oil because oil can't ware out, It just gets contaminated and thus thinned out with gasoline so it is good to see the oil pressure rise after an oil change. However, it is also an indication you don't change your oil often enough. Should be changed every 2000 miles or close to it.
If your sticker on the hood says 10 degrees BTDC then that is what you should use. The sticker always overrides what is in the books. (It just so happens I use 10 degrees too as long as you use high test gas)
Howard
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QUESTION: Thanks Howard. Could the engine dying be vapor lock? The engine was hot today and it was hot out. Would an electric fuel pump alleviate that?
Hugh
ANSWER: Yes, it could be vapor lock but that is just one of a hundred things that can shut it off.
If this happens often you need to see what is cutting off, fuel or fire. Connect a timing light to the coil wire not a spark plug wire, and run the wires out from under the hood and place the timing light under a wiper arm so you can see the flash of the light and tape the trigger down so it flashes all the time. (If you run the test in the bright sun light tape a piece of cardboard on the windshield so you can see the flash.)
Then drive the car until it dies and quickly look at the light to see if it continues to flash all the way to a stop or if it stops flashing while the car is still moving. This tells you if it is fire or fuel. Then at least you know which to go after. If it looses spark you need to first feel the coil to see if it is overheating as a coil that overheats can cause it to die and after cooling off can come back. If you have the original ignition system with the box mounted on the side of the distributor that is highly suspect as they had a high failure rate.
If it was not ignition then you need to put a fuel pressure gauge on the fuel line close to the carburetor in a "T" fitting and run the gauge out from under the hood and tape the gauge upright so you can see it or with a long piece of hose you can also put the gauge under a wiper arm so you can see fuel pressure at the time of failure. (1.5 to 3 PSI) (be sure to put hose clamps at each joint in the hose)
A timing light and a fuel pressure gauge are not expensive compared to buying a lot of parts trying to find a bad part that fails at times.
Howard
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QUESTION: This morning I attempted to take it out for a morning ride and it will not start. I should have left well enough alone and just changed the oil, but I thought I would do the right thing and since I just bought it establish a base line with a fresh tune-up, plugs, etc. I know, I know, I should have bought a Miata lol! YUK!
AnswerIf you think a Miata is always going to run you have a sad newscast coming to you sooner or later.
Any mechanic will tell you that the easiest car in the world to fix is one that don't start. The hardest car on earth to fix is one that don't start on occasions. So it don't start now? Good! now you can fix it.
All gasoline engines only require 3 things to run, Compression, fire and fuel. It it don't start one or more of the 3 is missing. You need a few simple non expensive tools to do the testing. Since it had a history of cutting off and then starting up later you can put aside the compression test as compression can go away for many reasons but it never comes back by itself.
So all you need to test is fire and fuel. A few simple preliminary test will get you to where you will know in what section the trouble is. You need a can of spray starting fluid (available at any auto parts store) and a spark plug wrench (or just an extra spark plug)
Spin the starter to confirm a "No Start" condition and spray a little starting fluid into the intake. If it fires off for a second or two then you have a fuel problem. If it don't you have an ignition problem. If you see that you have an ignition problem pull a plug wire off of a spark plug and put it on any good loose spark plug (if you don't have an extra plug remove one from the engine and put it on the plug wire and lay the plug on any metal part of the engine so you can see the gap. then spin the engine and watch for a spark.
If you have no spark let me know and I will go over the next set of tests.
Howard
