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MG MGA - Engine problem - help with diagnosis please
|I took the MGA (1600 Coupe 1961) out this morning and only got about 1/2 mile from the house before the engine died on me. The engine would struggle to fire up again but kept dying. A recovery vehicle had to tow me home. The newish spark plugs were pretty black and there was some wispy white smoke emitting from the crankcase breather pipe and when opened, from the oil filler. My concern is that it is an engine issue. It certainly isn't driveable at present. I'd welcome help please on working out the issue with the car. Thanks in anticipation. Tim|
|How was it driving just before it failed?|
Okay. I will offer a starter for 10 as it happened before anything got properly warmed up.
I wonder if the float in the front carb is sinking. Any sign of fuel pumping out of the overflow when you switch on the ignition? Easy to remove the top off the chamber and check the float. Remove it and give it a shake. You will feel/hear any fluid slopping about.
|If what Steve said doesn't work. Check out your electrics, especially wires associated with the distributor (not the spark plug leads). I had a wire that was almost severed and it caused intermittent cutting out. Another time, I had a coil with a hole in it from a loose mount and the oil had leaked out. The coil was good for a few miles and then it would overheat and the electrics would fail. In ten minutes or so it would cool down and you get a few more miles in. I went thru the entire fuel system before I finally figured it out.|
|Thanks for the kind responses. The car was driving okay prior to "dying" although it was still warming up and the choke was still out. There was no sign of fuel coming out of an overflow but I'll check out the front carb float as you suggest. I did check out the wires to the electronic ignition in the distributor and all seemed okay. I do have a spare new coil so might change that in case it is contributing the problem. My fear is that it might be a cracked cylinder head which I believe is a not uncommon issue for these engines. My hope clearly is that it isn't!|
|If it was driving fine and stated misbehaving without accompanying "noises off" I would strongly suspect an electrical issue. I would start with checking all HT connections, rotor arm, dizzy cap, and the LT connections at the coil. Also check that the ignition switch is making a good and steady connection.|
If the car isn't firing correctly, the plugs are going to look terrible whatever the cause.
|My guess is the black plugs are a false lead since it wasn't warm and the choke was still out. I would start by making sure the fuel pump is working, then proceed on to checking for spark. Need to narrow things down a bit first.|
|Electrics are the most likely culpret but carbs can be tiresome too - Did the engine die when (because) you pushed in the choke ?|
|Thanks all. I don't think it will be the fuel pump as I replaced this only around 6 months ago. I also replaced at the same time all the HT leads and replaced the points with electronic ignition. What I haven't replaced yet is the ignition coil but I'll do this first as it seems from comments and research that stalling & lack of power are symptoms of failing coil. Unfortunately (in some respects) I am on holiday from tomorrow for 2 weeks and I'll have to sort things out as soon as I'm back as the car is due an MOT at end June. I'm pleased no-one seems to think at this stage that it might be a cracked head! Thanks again. Tim|
|Having replaced a component at some point in the past doesn't necessarily mean you can eliminate that component as a suspect. It's easy enough to check that the pump is supplying fuel to the carbs, and since it doesn't sound like a carb problem, then you can concentrate on the ignition side of things. Also verifying that the pump works should also eliminate the ignition switch as a suspect at the same time.|
Be aware that the electronic ignition modules have been known to die without much warning.
Fuel starvation could certainly cause this problem. As Del says the fact parts are new doesn't mean they haven't failed, in fact it is quite common. I would check fuel flow arriving at carb as recently outlined by Colyn in a recent thread.
One possibility I suffered for a while was a blockage in a fuel pipe. In my case it was caused excess sealant used fitting a petrol gauge sensor. I have also suffered a small leak in pipe to pump which let air in.
One point that you were concerned about is the white smoke which would indicates some moisture in oil/crankcase but it could be irrelevant, and not likely to cause these symptoms.
I recently had issues with new Moss coils so yes change it as first easy step. I don't know about electronic disi issues as I only converted last year and so far so good.
I am not sure where exactly you are in the Lotians but I do have spare distributor and cols, and I am only just over the bridge in N. Queensferry if I can help.
Have a good holiday.
|Thanks folks. Paul - I'm in Edinburgh and we did attempt to meet up last year shortly after I bought the car but if I recall you were going on holiday yourself. Once I get the car going again and MOT'd I must pop over the bridge as it would be good to meet a long term owner of the marque. If I'm really struggling I may take up your kind offer and invite you across to Edinburgh (just off Colinton Road). Thanks. Tim|
|I had trouble with mine a year or so ago and it turned out to be the rotor arm - after having changed everything else as well. I continued to have poor running and eventually put the original Lucas dizzy cap back and all was well again - the replacement cap was an unbranded one that must have been arcing inside (probably made in the far east) . So yes - check all parts even if thy are new. Have you done a compression test yet to check for blown head gasket.|
|I had a fuel delivery problem on one carb a while back. Barney stopped in and we found that at idle both worked fine. At upper speeds, one failed to deliver. It was a bit of debris in the bowl channel to the body - it let just enough gas through to idle, but no more.|
|T.J, lots of favourite tips here, but we are all waiting for the true diagnosis!|
|Art. I'm back from holiday on the 17th and I'll provide an update ASAP ! Cheers. Tim|
|Back from holiday and I have now eliminated the coil as the culprit. Checked the fuel flow and it was pathetic. Weird as I only replaced the fuel pump last November. I guess it must be defective in some way. I'll contact Brown & Gammon tomorrow as it will be under guarantee. It was an SU AZX 1331. Car was due to be MOT'd on Wednesday which is not going to happen now. Will keep the BBS updated. Thanks all.|
|Replacement SU fuel pump from Brown & Gammon arrived today. Replaced it this afternoon and car now working as it should. B&G were very surprised at the failure of the pump after just a few months (and less than 200 miles) as they say they are generally very reliable. They recommended putting a fuel filter between the tank and the pump as they think there may be contamination coming through from the tank but there is no evidence of this and I note from Barney's site that it is not recommended for SU pumps. Thanks for all your advice. Hopefully better success with this SU pump. I have to say that B&G have provided excellent service and I'd not hesitate to use them again.|
This thread was discussed between 31/05/2017 and 21/06/2017
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