I have a 1971 MG Midget which is mostly true to it’s year. The engine is a 1275cc with a 25D4 distributor and twin SU carbs.
I use it as a daily driver and have had no significant issue (at least one I couldn’t fix) yet - until now. I was driving on the highway last week when the engine turned off. I pulled to the side and triewd starting it/ No luck. I waited a few minutes and tried again; I checked the wiring in the ignition as best I could on the highway while waiting for AAA.
Once I got home I spent the next week replacing the coil, condensor, re-gapping the points, going over it with a voltmeter and reseistance meter, replcing the fuel filter (all items replaced were original or close to it) and finally rewiring the two wires in the distributor. No go. The engine turns with the starter but does not fire. I get power to all the right places (as far as the Haynes manual is concerned). I’ve cleaned checked the gap on the spark-plugs after multiple tries of starting to make sure they are dry.
The last thing I can equate this to is the fuel itself or the timing chain slipped; the latter I doubt. I suspect the fuel because early in the day I had the car refueled with “premium,” this is the only change I had made to the vehicles “go” system prior to the stop issue.q
Same thing happened to my '78 MGB. Once I got it home and fiddled around for a while, I realized the distributor had popped out of the engine block. It wasn’t enough to notice anything was wrong by looking at it, but it was enough so that the gears didn’t mesh and the dizzy wouldn’t spin. Very frustrating!
A friend of mine who also has an MGB was driving down the road one day. Hit a big bump and the engine died. It wouldn’t restart. Turn out the bump in the road tripped the inertia switch and cut out the fuel pump.
Start with the basics. Is there fuel getting to the bowls? Is there spark at the plugs? Is there compression? Don’t throw parts at the car! Good Luck.
Try shooting starting fluid down the carb. If it fires up and then stalls it’s a fuel issue. If it doesn’t fire up, it’s an ignition issue.
Tester
If there is no spark, and the points were changed recently, file the points one stroke or two; especially if there has been rain lately. Replace all condensers, especially an external one if there is one. You could disconnect that one and see if it helps. Usually an engine will start cold and quit when hot if there is a condenser problem. If the plugs were dry when checked, you might not be getting fuel.
The last thing I can equate this to is the fuel itself or the timing chain slipped;
Check the timing just for kicks. It is spark or fuel, can you eliminate one or the other?
I’ve made a remote starter and have discovered no-spark to the spark plugs. I am beginning to suspect the distributor cap. I noticed earlier today the the spring-backed center poll had carbon build up (which I removed) and the spring appeard the have sprung.
I replaced the condenser and coil - I’ll remove the condenser from the equation in the morning. My volt meter is telling me that when the contacts are open there is no voltage from the spring side to ground - which I thought was good; there is no continuity either.
I am intrigued by the jumping distributor mentioned before. The only reason I’ve rulled this out so far is the the rotor arm is in a different place after I try to start the car. Now that I have a remote starter I can actually watch this take place - unfortuantly that too will have to take place in the morning.
The spark plugs are damp when I pull them, then quickly dry off.
Thank you thus far.
Is there a ballast wire/resistor in the ignition system?
Tester
Not according to the wiring diagram. My understanding of the coil is it has one built-in. I also replaced all the spark plug wires 2 years ago with Duralast wires and noticed a huge difference at that time.
I tested the spark buy taking one of the spark-plugs out and holding it firmly against the engines ground cable.
I sounds like you are not getting voltage to the points. When the points are open you should have voltage, on the open side tied to the minus side of the coil, close to the battery voltage. Without that connection the field of the coil cannot charge up and colapse when the points close and open up. Check the wire to the disty from the coil.
Give the fuel pump a whack with a soft mallet. The fuel pump is an electric unit located either in the trunk or under the trunk floor. This is an SU unit and has points - they start to stick after a while.
Since the car failed in motion, check if you have a ground line running to the number plate mounting screws and verify that it is sound and not corroded. If you jiggle this wire and the fuel pump starts clicking - you know where the problem is.
If you need to, you can pull the top off the SU fuel pump and cycle the points by hand to get them started again. Joe Curto in NYC can rebuild the pump or supply you with new points if you need them.
Update:
This morning I scoped out the points. I have about 12v across them when they are open and a few millivolts across when they are closed. I took the condenser off to verify the readings are clean.
I thought about the fuel pump. I actually disconnected it this morning so that I could have the engine on “run” without fuel. I rulled it out because it has a very loud ticker and because when I changed the fuel filter post-incident (it was dirty after all) I had fuel shooting out of the hoses; I had not tightened them properly post-installation. I can also smell gas after unsuccesful starts. I didn’t know that SU fuel pumps had points. I have a generic aftermarket fuel pump and not an SU - for better or worse.
The biggest news is I disconnected the HT lead from the coil to the dist. and held it 1/4 inch from the engine block while cranking the engine. Spark! Yellow, but spark none the less.
In my haste to replacing the aged coil I discovered today it is perfectly good. I ran a resitance test on it and get nearly 4 ohms.
I also did spray starter fluid into the carbs yesterday with no-luck.
Thank you.
IT RUNS!
I managed to get my hands on a new distributor cap and rotor arm from Adanced Auto Parts. I have read when you replace one you should replace both - I suppose it is like replacing a chain and cog-set on a bicycle. I wired it up, turned the key and without hesitation the engine started.
I was thanked by a tenant in my building whose window I have been doing these repairs out side of - these have been street side. She sadi the engine was making a terrible sound.
THe engine runs without a feel of power at the moment. I attribute this to the spark plugs being slightly fouled, the battery being a touch low, and the points possibly being a bit off. Run the car, charge the battery, find my dwell meter.
I have attached a few images. One is of the two rotor caps, the old on of the left and the new one on the right. The other photos are of the homemade remote starter.
Thank you all. Hopefully I will be able to post something usefull here sometime.
Running is a good start, I can’t help but wonder if the lady was complaining about sounds from the engine or sounds from the mechanic. Glad you have a dwell meter, but as stated previously don’t forget the timing check, Your remote starter reminds me of a friend that made a rotor out of a cork and a paper clip! Stuff that works. You would be able to contribute alot to people who post here, as you probably have more knowledge than the average I have a problem poster. Good luck.
Did you ever actually check to see if there was spark??? Does it use a Lucas electric fuel pump?? It’s one or the other, no spark or no fuel…
I did - I did two tests. One was to unplug a cyclinder and look for a spark while holding the lead close to the engine block. The other test I did was to inscrew a plug, make sure it was clean nd in order, then olding the thread as tight as possible against the engine block crank the engine. These tests demonstrated no spark at the spark-plug ends of the HT leads.
The positive spark test I had was when I removed the HT coil-to-dist. lead and cranked the engine with it about 1/4 inch from the engine block. Since this produced a spark, and I should have probably done this higher in the order of tests - I was left with changing the rotor and dist. cap with “known good units.”
I will note since changing the condenser I do not have static on my radio anymore - should have done this a long time ago.
I was hung up on the LT side because I wasn’t aware that the dist. cap and rotor arm could “go bad.” Lesson learned.
Dwell meter time.