Mechanics

SPUTTERING ENGINE WHEN WARM

1975 MG Midget

Engine Performance problem
1975 MG Midget 4 cyl Two Wheel Drive Manual 68,000 miles

I'm the 3rd owner of a 1975 MG Midget. She starts great and runs fine until the engine get's real warm. The problem starts (i.E. The engine sputters like it's not getting enough gas or has the improper mixture) after an hours driving (at 55 MPH). This problem also happens if I fill tank up with the engine warm.
I can usually drive through the problem but she almost conks out.
I have tried the following fixes to no avail. I live way out in the bonnies of the N.E Georgia Mountains. No British car mechanics within 90 miles.
1) Checked fuel pump pressure. It was strong.
2) Checked fuel lines (there was no dirt/debris in line).
3) Carburetor was rebuilt one year ago. (I didn't drive much last year. The problem only started recently).
4) I was advised by a MG friend it could be a possible fuel boil issue. It was recommended I put 3 or 4 wooden clothes pins on fuel line to disperse heat. No luck.
5) I replaced fuel filter. No change.
6) I was told there a pressure choke in the Stomberg carburetor that be malfunctioning. The local shade tree mechanic says it is working fine.
7) I use only the highest octane gas.
8) Plugs were recently replaced.
9) A for a fee on-line mechanic says because the emission control system was disconnected by a prior owner that the disconnection was the problem.
The local mechanic sees no issues with the disconnect.
**
Please do you have any ideas/suggestions?
Avatar
Agtriebel
April 12, 2010.



This sounds like a vacuum leak. The best thing to do is get some choke cleaner and spray around the carb and inlet and see if the idle changes. It may be the throttle shaft on your carb or around the choke as I think that's vacuum as well. If this is a stromberg carb check to see if the diaphragm is ok and there is oil in the top of the carb.

Hmac300
May 8, 2010.
I check the Stromberg carb oil level once a week (that is not the issue). I also tried choke cleaner around the carb and inlet (no change). The carb had a factory rebuild a year ago.
A couple of days ago the engine just quit while it was running and I was unable to get it restarted. It felt like the engine was not getting any gas. I had the car towed to a shop. After it sat for a day it start immediately.
The fuel pump pressure was measured at 6 lbs. The fuel line was checked for dirt (was found clear). The fuel tank is clean.
Any other suggestions? I can't drive the vehicle now for more than 15 minutes and the problem starts all over. Suttering, stalling and then inability to restart.

Tiny
Agtriebel
May 11, 2010.
This sounds like a electrical issue if you have good fuel pressure/volume. Ground problems are a serious issue on MG/brit cars. Also you haven't mentioned what ignition system you have. If you have the ignition that has the electronic amplifieir on the outside of the distributor, they are J-U-N-K. This is a common problem with MG's as well as Midgets if they have this system on it. If you have ever driven your car and noticed that your tach and engine quit then got going again that is more than likely your problem. If this has points and condensor i'd try changing those and checking your coil for ohms to see if it's any good. Also another thing to check is see if there is any play in the distributor shaft, sideways. It may be getting more play after heating up and causing the problem. If this doesn't work what i've given you contact University Motors Ltd. Com. John Twist is an absolute expert in brit cars and he has a call in hour if you choose to do it. But do the other stuff i've suggested as it I think it may solve your problem. The only other thing that I can think of if its' a fuel problem is vapor lock and the carbs may be heating up if there is no shield between teh exaust manifold/carbs. A piece of aluminum foil along with some insulation would be a quick way to test.

Hmac300
May 11, 2010.
One thing I forgot in the last post was that pertronix and crane both make different versions of electronic conversions. Both are better and are different from each other. Pertronix and Crane( the cam company) are both on the web. Pertroinix is cheaper and they both are very easy to install.

Hmac300
May 11, 2010.