Tyrone Posted April 16, 2007 Share Posted April 16, 2007 A friend has an original 948cc A series engined ‘Frogeye’ which is misbehaving. On cold days it seems to run fine. On warm days it runs fine for a little while but when it’s up to normal working temperature it begins to stutter and cut out. He suspected fuel starvation but the bowls on the twin SU’s are full of fuel and there is apparently fuel on the plugs as well. Last year he suffered the same problems and suspected the coil (which got very hot), this and the wiring loom was replaced and initially seemed successful but then the problems returned. He has chased round several possible causes, such as a split fuel line and heat shielding the exhaust manifold and repaired them, but the problem persists. He has done a compression test and 1 of the cylinders is a little down on the others but still within 10% apparently. He carried out a bare metal restoration of the car some years ago and has done all work (with the exception of the electrickery) himself and is loathe to simply give it to a garage to speculate on possible causes and run up a significant bill. I suggested the power of Blatchat might help, so any thoughts would be gratefully received. Link to comment Share on other sites More sharing options...
mikevernontalktalk.net Posted April 16, 2007 Share Posted April 16, 2007 If the plugs are wet it sounds like it's running very rich, which explains why it is ok when cold but not when hot. The probable cause is that the choke levers are not returning the jets to the normal position. The 1 and 1/8th inch SU carbs on the frogeye were particularly prone to this problem. To check it just press upwards on the bottom of the jet assemblies. If either or both of them move by even 2 or 3mm that is the cause of the problem. It may need the cork seal replacing or simple adjustment of the lever mechanism. Link to comment Share on other sites More sharing options...
h_____ Posted April 16, 2007 Share Posted April 16, 2007 I had exactly these symptons on my 948cc Morris (same engine, single carb). When hot it would miss badly and cut out. And the coil was very hot. We got through a couple of coils in a short period of time (car was used daily). Turned out, our coil supplier was giving us non-ballasted coils which require a resistor to bring the voltage down. Not saying your friends problem is exactly the same, but may be worth checking the coil is the right type in terms of voltage and resistance. Link to comment Share on other sites More sharing options...
Sheds Moderator Posted April 16, 2007 Share Posted April 16, 2007 Get it Kryptonned by someone who knows how to use the old gear. Cost £30-40 and job done. Link to comment Share on other sites More sharing options...
Manxseven Posted April 16, 2007 Share Posted April 16, 2007 If it is still running points and a condenser, try a new set of both. Caterham Fireblade here Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted April 16, 2007 Share Posted April 16, 2007 ... and distributor cap too ? I recall having problems with an SU carb in the 1970s - eventually worked out there was a pinhole in the float in carb, which would fill up with fuel, and therefore no longer float. Supplied too much fuel. Easily remedied. ****************** And you run and you run to catch up with the sun, but it's sinking... And racing around to come up behind you again. photos Link to comment Share on other sites More sharing options...
Sheds Moderator Posted April 16, 2007 Share Posted April 16, 2007 Gents, this is why I have resorted to Krypton in the past if it isn't obvious what is going wrong. You replce this, that and the other item and before long you have spent the price of a tune and still not found the fault. Link to comment Share on other sites More sharing options...
Tyrone Posted April 16, 2007 Author Share Posted April 16, 2007 Thanks Guys for all your responses. I have forwarded them to my friend, I'll keep you posted on how he gets on. One of his other mates suggested he gets it converted to a K series, etc. by that company that was featured in C&SC a couple of years ago. The look on his face was priceless. 😬 Link to comment Share on other sites More sharing options...
oilyhands Posted April 16, 2007 Share Posted April 16, 2007 As suggested, try the condenser and points... Oily Link to comment Share on other sites More sharing options...
MADMALC Posted April 16, 2007 Share Posted April 16, 2007 Also make sure the dash pots on the carbs are topped up with oil, they do not like it when there is no damping on the needle. S7MAD Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted April 16, 2007 Share Posted April 16, 2007 ... and the right grade of oil. Hours of endless fun in my Mini (sorry - Austin Seven Countryman) with SU carb and oil. One time, the cap (and piston) came unscrewed - that caused some consternation at the time ! ****************** And you run and you run to catch up with the sun, but it's sinking... And racing around to come up behind you again. photos Link to comment Share on other sites More sharing options...
Trevor Gilby Posted April 17, 2007 Share Posted April 17, 2007 Another for the condensor. I recall a few decades ago my series 4 Sunbeam Alpine had just that same trait, and I limped home through London with it spluttering to get beyond 30mph, and an inability to rev freely, expecting a big problem. Someone then suggested a new condensor, cost absolute peanuts then, and it fixed it in 5 minutes flat. Still able to go out on a hot date that night 😬 Link to comment Share on other sites More sharing options...
h_____ Posted April 17, 2007 Share Posted April 17, 2007 to be fair to swap points, plugs, condensor, dist cap, rotor arm will cost you about £15 max. Even HT leads and a coil isnt going to hurt that much. I tend to do that as standard to eliminate them as sources of trouble. Link to comment Share on other sites More sharing options...
Tyrone Posted April 17, 2007 Author Share Posted April 17, 2007 Condenser and points changed these evening and a fuel filter installed so he could see if fuel was getting through to the carbs. Got a call from my mate saying he had got about 5 miles before the problems resurfaced. Now, when he fitted the fuel filter it was filling up to quarter full when cold, after it started misbehaving there was only a small amount of fuel in the filter and when he blipped the throttle only very small amount of fuel entered the chamber and there were air bubbles. When he got back home, his Haynes manual suggested taking the fuel line of the carbs to determine healthy supply, he did this and a healthy pulse of fuel came out. Anymore ideas? Could the carbs create a back pressure which doesn't allow the fuel to flow properly which isn't manifest when the fuel supply is disconnected from the carbs? Link to comment Share on other sites More sharing options...
JampJ Posted April 18, 2007 Share Posted April 18, 2007 Has the fuel tank got a vent pipe? Sounds like it may have a vacuum. Try running with the fuel cap off. Cheers J&J JFDI (Just F*****g Do It) Link to comment Share on other sites More sharing options...
mikes Posted April 26, 2007 Share Posted April 26, 2007 Do you have any further updates on this problem? A friend has got similar problems with his Sprite and so is very interested to know if it has been resolved. He also changed the electrics side of things to no avail, but I suggested that it may be worth changing things like the condenser again - it is not unknown for such 'new' components to be faulty. Mike Edited by - mikes on 26 Apr 2007 13:02:05 Link to comment Share on other sites More sharing options...
Sheds Moderator Posted April 26, 2007 Share Posted April 26, 2007 Try the fuel tank vent as stated. You may end up drilling a small hole, Link to comment Share on other sites More sharing options...
Tyrone Posted April 27, 2007 Author Share Posted April 27, 2007 I'll hopefully be able to give you a successful update after tomorrow afternoon. Link to comment Share on other sites More sharing options...
Unclefester Posted April 27, 2007 Share Posted April 27, 2007 Sounds like my Yam after I fitted a one way valve in the fuel tank breather pipe. It was sticking, and did allow a vacuum to build up quite quickly in the (small) fual tank....mind you, this has only gravity supply. Lucy in the Sky with Diamonds..ooooh hooo hooo!!... 😬 😬Abbey Road Time-Machine *eek* Link to comment Share on other sites More sharing options...
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