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MG MGA - Starting Problems
| Since fitting new carburettor spacers with vacuum off-takes about 6 weeks ago I have been plagued with poor / non existent starting when warm/hot. There are no air leaks in the intake system as a result of my disturbance to the manifold as the vacuum idles steadily at 18psi. This also shows that the ignition is set right. The symptoms have been excellent starts from cold. Choke can then be immediately put all the way in. Car then runs fine. Went for drives varying from a few miles to 75 miles without a hiccup. Switched off. Tried restarts without luck. Sometimes had to wait half an hour on a barely warm engine. Today I investigated. I decided to remove the carbs, but I did not get that far when I spotted the problem. See attached photo. That was how I found the gasket stuck firmly to the canister. I have given myself a bollocking for shoddy assembly work. Steve  |
| Steve Gyles |
| Steve, At least an easy fix for you. Why do you think it only caused a problem when starting from hot? Graham |
| Graham M V |
| Graham I am hoping that one of the airflow experts can explain it to me. The occasions I have managed a restart have involved pulling the choke out. That suggests running weak, but I admit to being confused. Those gaskets can be quite fiddlesome to hold in place while the bolt is located through the flange to the filter case. Steve |
| Steve Gyles |
| Steve, I "glue" mine to the filter casing with a little jointing compound, leaving the surface that contacts the carburettor flange dry for easy removal. Not a critical seal, so the gasket can stay there for years without replacement. Makes refitting the filters a doddle! |
| Lindsay Sampford |
| Yes it seems odd that the car drove ok and hot starting was the only symptom. I hope someone can explain to us simple folk... |
| N McGurk |
| Lindsay. Exactly what I have now done! Neil. I do not understand it either. I have been thinking about it and the hesitation I suffered once whilst playing around with the bilge fan deflector would have been in this canister gasket configuration. But other than that the car has been running fine. If it has been down on performance it has not been that marked that I have noticed. I am guessing that the MPG is down a bit. Steve |
| Steve Gyles |
| Hi Steve, Have you taken it for another 75 mile run and tested ease of starting to prove you have solved the problem? Mike |
| Mike Ellsmore |
| A thought bubble...and the only one I can blow ...... When cold there is enough cool air and fuel getting through on start-crank past the obstruction into the cold engine. When warmed the air mols are reduced and ....... just does not quite get sufficient fuel/air into two of the cylinders... |
| Neil Ferguson |
| Mike, I only discovered the problem mid afternoon. I have only done short runs so far, but restarts over these were no problem compared to the previous days. Neil, it must be something like that. I was definitely not flooding the plugs on the prolonged restart attempts as I inspected the plugs to rule that one out. Fuel starvation was more likely. Steve |
| Steve Gyles |
| Steve, If I forget to push the choke in (its my age) my car will run fine but with a hot engine it doesn't start well unless the choke is completely home. Having a choke part out is going to be very like the results from your misplaced gasket. Malcolm |
| Malcolm Asquith |
| Weird. Starting problem from hot has not gone away. I did two 170 mile non-stop trips over the weekend. The car went like a dream on both runs - probably never run smoother and overall performance better than I have ever previously experienced. But at the end of each run I shut down and then could not restart. Outside temp was about 28 in the shade, so quite hot for the UK this time of the year. Engine ran at 175 to 178 except on prolonged inclines when it rose to 188. The temperature was still under 200 when I tried the restarts. When I did eventually get restarts the engine immediately ran totally normal - no vapour lock type symptoms. The only odd symptom was just as I was turning left into my road at the end of the second run, slight incline, 2nd gear, power coming on and a couple of hesitations from the engine, then pick-up and all fine. Other info: electronic ignition; sports coil (3.9 ohm resistance checked). Not sure where to start looking. I just restarted again on the mildly warm engine with first spin of the starter. Could this be an oddball side effect of my stub stacks? Steve |
| Steve Gyles |
| Steve, If you refit the original stacks it might be informative. Might it have something to do with the vacuum take off altering the timing advance curve? Richard |
| Richard Atkinson |
| I am an advocate of these problems usually being electrical. I have just had a look at my distributor rotor arm and it has black carbon staining emanating from the leading edge of the rotor and a very small bright 'arc' point on the top of the leading edge. Could this be the source of my problem? Steve  |
| Steve Gyles |
| Steve, The end of the rotor arm looks normal to me, but i dont trust the black versions especially with a rivet (very thin distance to top of distributor shaft and shorting out with poor material quality). When you spin the engine, does it pop, fire at all or just spin as if there is no ignition? The (black) rotors can short out when hot. What about the wire inside the distributor (chaffed etc). regards Colin |
| C Manley |
| Colin Electronic ignition inside. When hot it just spins. No popping or banging. When it fires (eventually) it is immediately fine. Distributor is a Chinese repro (aren't they all nowadays). This one (45D) stood out from the rest in that its advance profile is spot on for the MGA - recommended to me by Bob West. It's performance over the last 3 years has been excellent. I just wonder about that rotor. Time for a new one? Steve |
| Steve Gyles |
| Hi Steve, My stub stacks have been great since I fitted them - so I doubt if they are responsible. Definitely replace the rotor arm - good luck in your trouble-shooting - cheers Cam |
| Cam Cunningham |
| Steve, I'm with Colin on the rotor arm being the culprit. Fix yourself up with a red one before you go chasing anything else. |
| Lindsay Sampford |
| Lindsay Who supplies them? Steve |
| Steve Gyles |
| I have just taken the metal spring plate out of the rotor inside. The plastic behind it was soft and burnt. Looks like it has been shorting through the rivet as per the information on Barney's site. Steve |
| Steve Gyles |
| Steve, they are now readily available over here (I had to get mine from the states a few years back). Just Google "red rotor arms" and the suppliers come up. Distributor Doctor has them and so does Moss UK. |
| Lindsay Sampford |
| The out of position gasket represents the other side of the same nickle as the improved response from the stub stacks; it is a matter of flow disturbances or not at the jet mouth. Quite possible that moving the gasket one way or the other would alter the effects. If you can immediately push the choke in on starting, then the idle mixture is too rich, no discussion. There are a dozen reasons this may be so. Weak spark will show up whenever the mixture is harder than usual to light. That could be either weak or rich. FRM |
| FR Millmore |
| Sta-bil fuel additive salespersons are spruiking that modern fuel starts to go off between 21 and 60 days depending on octane rating and ethanol content - not sure how much of a real problem this is but is the fuel in you car fresh? http://www.goldeagle.com.au/fuel_stabiliser.html Mike |
| Mike Ellsmore |
| Plan of action is to replace the rotor. Test the motor. Then adjust the mixture. I want to identify this problem. One action at a time. I have identified a rivetless red rotor supplier. Will order today. Steve |
| Steve Gyles |
| Thought you might like to see the evidence of arcing I found inside the rotor. Steve  |
| Steve Gyles |
| Steve, That's definitely the problem. The materials insulation properties are poor and given heat as well it just breaks down over time. regards Colin |
| C Manley |
| Finally, and just to confirm, I extracted the arm and rivet and found firm evidence of arcing on the rivet (ignore the bright silver marks on the arm. That is where I levered it out). Steve  |
| Steve Gyles |
| Finally, finally. I cut the rotor in half. The distance from the rivet to the spring retaining plate is 4mm. So, the electricity penetrated this distance of plastic. Seems a lot. Must be good conductive compounds in that plastic. Steve  |
| Steve Gyles |
This thread was discussed between 01/09/2012 and 13/09/2012
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