Dr Commer to the Garage please

BigMonkeyMan

BigMonkeyMan

0
.. we need a diagnosis.

Jessica has developed a bit of a misfire when she's hot and the engine is under strain. It seems quite consistent (it hasn't got any worse so far) and it doesn't seem to be on a single cylinder.

I stopped to have a look in the engine bay on the way home today and the fuel filter was looking pretty empty - no snakeskin as far as I can see.

I'm thinking the fuel pump is on its way out. Do they go gradually like this? I checked for overheating the carb and the float chamber was pretty cool (with the tin/plumbers mat combo)

the points are ok (as they are currently in the toolbox and were replaced with electronic ones ;) )

any ideas?

thanks

Rupert

"With great cars comes great responsibility"

www.littleyellowcar.co.uk
 
Could be a bit of a blockage in the carb. Take the filter off and rev the engine then put the palm of your hand over the intake, the suction is something to behold and any minor blockage (with any luck) will be sucked through :)

Harvey the RV
 
could be a plug, try inspecting them and then run her up and disconnect the HT leads one at a time (with some insulated pliers)to pinpoint which cylinder it is.
also worth checking the tappets (hot)
fuel pumps have a rubber diaphram which perishes with age :)

"you were only supposed to blow the bloody SLIDING doors off"
 
Run the starter with the fuel lead off the carb (into a milk bottle) and see if the fuel pulses out regular & strong. If it does its not the pump.

Cheers
Jules

RatSport www.ratsport.co.uk
 
try the coil,they breakdown when hot and give a intermittent spark which could be why it seems cylinder to cylinder,take it on a run till it starts misfiring then put another coil on,problem would dissapear
also run it at night with the lid up to look for any blue sparks arcing about
 
thanks for the help so far. I had a go at your suggestion Panky - no joy unfortunatly.

I'll hopefully get to have a go at the other stuff later in the week

cheers

Rupert


"With great cars comes great responsibility"

www.littleyellowcar.co.uk
 
another small one that i have had on mine is the exaust and inlet gasket blow between each other but that normally causes a popping on over run just a thought,not as easy as the others but it happened to me
 
Hi Jato,
I have just replaced the manifold gasked so I hope its not that again (I don't think it is) the misfire was there before I changed it anyway - I had just forgotten about it.

Hopefully I'll get a chance to have a proper look tomorrow

cheers

Rupert



"With great cars comes great responsibility"

www.littleyellowcar.co.uk
 
well I've changed the plugs and oil/filter/cleaned the sump and went for a big run up the motorway tonight. Everthing seems a lot better (no backfires this time!) Still got a misfire, though at around 65 on the flat and 50 ish on a hill - may be pinging too?.

the coil is an aldon flamethrower and around 1 year old so I hope its not duff. I'll try swapping it out though. I had another look at the fuel filter and it was empty again when running fast.

I tried the trick with the bottle and the fuel line off (turning hte engine over) and the jet is quite er.. squirty... I don't have much to compare it against!

I think I might try the coil swap at the weekend and maybe the fuel pump too if I get time.

cheers

Rupert

"With great cars comes great responsibility"

www.littleyellowcar.co.uk
 
I think if the fuel filter is empty when its running fast then thats your problem. Fuel starvation under load. Although the pump is pumping (as you have tried it) the cam on it does wear so it may not be operating at full through and therefore not pumping enough. If you have an original glass bowl Delco one try cleaning the internal gauze filter, that may help. If you have a repro one then they are "sealed for life" as it says on the box. Sealed for death I call it.[:(!]

Cheers
Jules

RatSport www.ratsport.co.uk
 
thanks for that Jules, I take it I should be expecting the pump to be full all the time? I changed the pump tonight and fitted larger bore pipe. I moved the filter so its hoizontal (above the rocker cover - therefore not pulling fuel back out of the carb!) not done a test drive yet but I'll let you know how I get on.

I also have a cupboard full of spare coils now ;)

Rupert

"With great cars comes great responsibility"

www.littleyellowcar.co.uk
 
test drive today and she was tip top (still not perfect though) the filter was full of fuel every time I checked -yay!

still a little flutter at hight speed/up hills so the timing could need a tweak.


cheers

Rupert

"With great cars comes great responsibility"

www.littleyellowcar.co.uk
 
I don't think I have an ashtray... should I get Tim to skim port and polish it for me when I find it?

"With great cars comes great responsibility"

www.littleyellowcar.co.uk
 
its essential Rupert, and i can even fill it up for you for free ;)

"you were only supposed to blow the bloody SLIDING doors off"
 
You'll find the new rota arm you bought in there - you know the one you lost, you got it cos the old one's knackered;)
That the stuff that happens to me all the time:I

Harvey the RV
 
hello
we got back from Inverness on Sunday after a re-developing the nasty misfire (not enough to stop the engine though) it seems to happen when we have been going for a few hours (4 in this case!)

I changed the coil - no change (thanks for the tip steve!) I'm now thinking either:

ignition leads
aldon ignition module [:0]
carb dirty (but would misfire when cold too wouldn't it?)
or cracked head (again would happen when cold too?)

[V]

"With great cars comes great responsibility"

www.littleyellowcar.co.uk
 
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