Broken down again, Miss fire when hot

Hi guys just got her back on the road after converting to petrol 2.25 from diesel. She starts and runs really well from cold. So i go for a drive get it hot and would be difficult to restart, when i do get her running she miss fires and dies if you dont rev the nuts off it. Broke down at some traffic lights yesterday, after 10 mins sat there she started but still miss fired, managed to drive home so parked up for contemplation. Whilst waiting it restart i noticed the coil body was very hot, is this normal? When i got home there apeared to be plenty of fuel in the hose from pump to carb.

Any thoughts? I'm wondering it its a crap coil that's got an internal fault as it was one i got in a box of spares. Also carb is of unknown origin.

Anyone had this issue before?

Got a great comment for a lady as i stood behind LR directing traffic round me. She said put your hazard lights on! Brilliant. its 50 years old i said. May be 50 years ago someone would have asked if they could help rather than look at me like i've just ruined their day.

Thanks

I wouldn't expect the coil to get that hot.

The one on my V8 never did.

I used to have a bike that did that when hot coil was braking down check points distributor cap and arm too

Replace the condenser - might be going short when hot which would cause misfire and overheating coil. If that doesn't fix it a new coil probably will. You might be using a 9 volt coil designed for use with a ballast resistor.

Thanks guys. Not used to petrols as always had diesel before so wasn't sure if hot coil was normal. Its got a new dizzy so hopefully not condenser, possibly coil then. Will get a new one as never hurts to have a spare.

Will let you know how i get on.

Cheers

Make sure it's a 12v coil too. They can get fairly hot. Are you sure it's ignition related?

Just checked it is a 12v coil.

Can't say for sure it is ignition related as had a few issues with carb float sticking if not used for many weeks. I know I am getting fuel to carb and can't see how it might be susceptible to heat other than float sticking again. Coil was too hot to hold on to.

Also coil is the cheaper of the two to replace.

How quickly does it recover (or not)? Could be like the fuel / heat problems I was getting? (Search "vapour lock")

I got it starting again after about 10 mins but still miss fired. Nto sure how long after it would run completely normally though. I have read dominicbeesley's vapour lock reply's, dont think i have an air leek as this would surly be consistent and happen even from cold. Fuel line from pump to carb is routed as per a few other LR's i've seen, from pump under oil filler bracket around front of cam cover to carb. When it gets hot and starts miss firing it does it across the rev range.

Gonna try a coil and leads. The Britpart leads i got are complete rubbish only been on 2 months and rubber boots are splitting.

Thanks

I'd try coil, points, leads and condenser first. Try and get electronic points or at least old genuine landy ones (not ****ty new ones!). I got some really crappy HT leads from a back-street taxi driver motor shop in Halifax. Dead cheap no two the same but work really well all the other ones have, like yours, ended up cracking...

Just ordersd coil and leads by snail mail so will let you all know how I get on some time this century. Fitted completely new dizzy assembly not long ago so hoping that OK

Ah, I have to say in that case I'd suspect the dissy at the top of the list. New replacement dissys can be very poorly made with the wrong weights, cheap points and crappy condensors. Have you checked the points gap and tried a new condenser. You need feeler gauge and about 3 quid for a condenser. Not sure if Halfords still sell condensers though.

So far replaced coil, HT leads, and condenser. Reset points gap and valve clearances. Cant tell you if hot running issue is sorted as it now wont run without choke.

What happens now is it starts and runs fine when on choke. Slowly put choke in and engine dies. Have tried increasing idle speed and screwing mixture screw in/out but makes no difference. It needs some choke to run.

Not sure of the carb origin as got in a whole job lot of land rover bits i got. Guess there must be something up with it. Assumed the fuel pump is ok as runs ok on choke meaning it is getting plenty of fuel. Have taken air cleaner ff and no change.

Any ideas?

Float chamber Height setting jet size you need all these details/ data before you start to tinker with the carb I presume you used a strobe light setting up the dizzy .

It shouldn't run without choke until the engine is properly warmed up. However, if I were you I'd get a carb rebuild kit and a set of manifold gaskets and strip it all down and rebuild it. Gaskets are cheap from Crad/Paddocks carb rebuild kit will depend on the model of Carb you have.

Before you do that I'd check for other obvious leaks:
- try blocking the servo pipe and make sure its nipped up to the manifold
- check the vacuum advance pipe is fitted properly and not holed
- check the breather pipe is fitted or the take off port is blocked.
- look for other leaks, spray brake cleaner around the carb / manifold (watch out for fires) if engine revs increase there's a leak

D

Take a load of pictures around the carb someone may spot something amiss.

Thanks for the advice guys. Will get the brake cleaner out and try hunting for leaks first. Not got breather system fitted as an early 2a.

Don't have pulley timing point so set dizzy via multi meter.

Won't get chance to fiddle till next weekend but will keep u posted.

I recently had a back firing problem with my Series 3 2.5 petrol. Turned out to be a crack in the exhaust near the manifold. Replaced it and cured it completely. I do however have a similar problem to yours, when it has warmed up only over a couple of miles it cut's out and will not start until it cools down. Will put a post on hear to ask if anyone has had a similar problem. (at least the back firing has gone!!)