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Dunc
03-01-11, 07:14 PM
Took my Sumo for what was supposed to be a 20 minute blast yesterday and ended up with a problem! She started fine and I then took it easy for 5 minutes to let her warm up. Pulled into a drive to turn around and reversed out on full left hand down lock and heard a small clunk. From then the car backfired and ran rough until I got to a junction where I noticed the idle speed was down at 500rpm, normally it's 800. Then she stopped. And wouldn't start. Luckily it was outside a pub and the landlord was very accommodating! Eventually got her to start on jumps and she spluttered her way home, not happy. Today I popped her up on jacks and looked at whether going full lock LHD snagged anything. I checked all the leads onto the plugs and then fired her up and she started fine. She then idled fine for 10 minutes and so I stopped her, got her off the jacks and started her again. This time she started rough and had the same idle problem as yesterday with backfiring when I increased the revs. So I put her back in the garage.

Any ideas?8)

Sidecarbod
03-01-11, 07:42 PM
More info required!

What fuel system are you running? EFI, carbs? (what carb/s)
What ignition system has it got fitted?

Dunc
03-01-11, 08:18 PM
Sorry! Its an Offenhauser manifold with a 4 barrel holly carb. That, I'm afraid, is as much as I know at the moment.;) It's got optronic electronic ignition from S & S preparations I think.

Sidecarbod
03-01-11, 08:31 PM
Sorry! Its an Offenhauser manifold with a 4 barrel holly carb. That, I'm afraid, is as much as I know at the moment.;) It's got optronic electronic ignition from S & S preparations I think.

I'm afraid that I know nowt about Holley carbs! The problem could be due to carb icing. Do you have an insulator between the carb and the manifold?

Your ignition could be at fault but since it is not an Opus jobbie I doubt it.

robcob
03-01-11, 08:40 PM
Took my Sumo for what was supposed to be a 20 minute blast yesterday and ended up with a problem! She started fine and I then took it easy for 5 minutes to let her warm up. Pulled into a drive to turn around and reversed out on full left hand down lock and heard a small clunk. From then the car backfired and ran rough until I got to a junction where I noticed the idle speed was down at 500rpm, normally it's 800. Then she stopped. And wouldn't start. Luckily it was outside a pub and the landlord was very accommodating! Eventually got her to start on jumps and she spluttered her way home, not happy. Today I popped her up on jacks and looked at whether going full lock LHD snagged anything. I checked all the leads onto the plugs and then fired her up and she started fine. She then idled fine for 10 minutes and so I stopped her, got her off the jacks and started her again. This time she started rough and had the same idle problem as yesterday with backfiring when I increased the revs. So I put her back in the garage.

Any ideas?8)

Start with the basic checks,
is it getting fuel and is the pump working ok
are the plugs all sparking
plug leads all working
check timing
could be the power valve in the carb

rob

slogger
03-01-11, 08:47 PM
Just a thought for what it's worth:
If it appears to start and idle ok jacked up but shows this fault when on the ground, could the float level be suspect? Does the thing smell of fuel when it is running rough/black or grey smoke from the exhausts?

Don't know what the connection to the clonk could be unless something mechanical is to blame.

Just a thought as I said. Crystal ball fault diagnosis is always a bit suspect.:D

Dunc
04-01-11, 08:30 PM
Thanks for the advice fellas. I re checked the carb on and its a webber 500 not a holly:confused:.... Getting to know the car slowly but surely. Anyone think this makes any difference?

Dunc
04-01-11, 08:34 PM
It does smell strongly of fuel, so I'll look at the carb. Could be carb icing too. Thanks again for the thoughts.

Sidecarbod
04-01-11, 09:13 PM
Thanks for the advice fellas. I re checked the carb on and its a webber 500 not a holly:confused:.... Getting to know the car slowly but surely. Anyone think this makes any difference?

I know a bit about the Webber 500.

If you are sure that its going rich when the idle goes rough then its very likely just crap in the float valves. The weber is easy to work on, you can remove the top of the carb in about 5 minutes, the floats will come off with it.

It would be worth posting up what fuel pump you have and whether you are running a fuel regulator. The Webber will not tolerate more than 6.5 - 7 PSI pressure. (Mind you if the pump pressure was too high it would flood all of the time)

When you remove the top of the carb make a note of the hole that the accelerator link was in and remove the air filter stud to prevent ripping of the gasket. If you are careful you can re-use the gasket many times.

Sidecarbod
04-01-11, 09:14 PM
It does smell strongly of fuel, so I'll look at the carb. Could be carb icing too. Thanks again for the thoughts.

Carb icing will make it run rough but not rich, just rough! I bet its just crap in the carb!

Dunc
04-01-11, 09:19 PM
Cool! I will make that my first port of call. What I find odd is that it seemed to happen after 5 minutes of normal running. Last time I took her out was 6 weeks previous with all the inclement weather and she went like a dream. Plenty of time to get her fixed before the spring though!:) Thanks again for the advice.

Sidecarbod
04-01-11, 09:26 PM
Cool! I will make that my first port of call. What I find odd is that it seemed to happen after 5 minutes of normal running. Last time I took her out was 6 weeks previous with all the inclement weather and she went like a dream. Plenty of time to get her fixed before the spring though!:) Thanks again for the advice.


What can happen is that the crap moves away from the float valve seat so the flooding stops, it ends up in the float bowl. Then another lump of crap travels down the fuel pipes and it all starts again. You really must use a good fuel filter in the system somewhere. If its in the engine bay then it has to be REALLY good, not glass or plastic. (Unless you like bonfires!).

It does not take much for the carb to flood, a spec of rust is enough.

If you are bored have a read of this, it might be of some help...

Fueling System - How To Build a Pilgrim Sumo (http://how-to-build-a-pilgrim-sumo.wikidot.com/fueling-system)

I wrote the bit underneath the fuel pump gumph!

tonym
04-01-11, 09:37 PM
just crap in the float valves.

How often do you have to do that then :confused::confused::confused:

You carb people have some strange ways about you, us EFI gods don't have to defecate into our engines to make them work :roll: :p:p

Purple AK
04-01-11, 09:40 PM
Just a thought. But has the carb got an electric choke? IF the wire has come off it it will be running on full choke all the time! Could explain why it goes rough after 5 mins warm up time.

Sidecarbod
04-01-11, 09:44 PM
Just a thought. But has the carb got an electric choke? IF the wire has come off it it will be running on full choke all the time! Could explain why it goes rough after 5 mins warm up time.



Good thinking Purple man!


I remember one chap that I helped who's manual choke was not locked up or connected to a cable, it would just come on and go off depending on how the engine vibrated the components! :D

Purple AK
04-01-11, 09:50 PM
How often do you have to do that then :confused::confused::confused:

You carb people have some strange ways about you, us EFI gods don't have to defecate into our engines to make them work cos they're crap anyway :roll: :p:p
You been watching Jim Davidson again :rolleyes:

Purple AK
04-01-11, 09:57 PM
Good thinking Purple man!


I remember one chap that I helped who's manual choke was not locked up or connected to a cable, it would just come on and go off depending on how the engine vibrated the components! :D
I do have the occasional thought between bouts of dementure :mrgreen:

karl_tanner
04-01-11, 10:14 PM
See, now you wouldn't get any of this with Efi... :p

Sidecarbod
04-01-11, 10:20 PM
See, now you wouldn't get any of this with Efi... :p

No, coz the f...er wouldn't even start! :p:p:p

karl_tanner
04-01-11, 10:25 PM
Ha-Ha!! Knowing my luck NO!!! :mrgreen:

Was the route cause the manual choke? Be interesting to know....

steve.hills
27-01-11, 10:28 PM
If you are running a distributor I would replace the condensor first as when the engine warms up, and the distributer the condensors are known to fail, mine would go very lump and then cut out, leave it for a few minutes and it would limp another few miles before cutting out again.
If left over night it would run perfectly until warm and then it all happemns again.

I now carry two or three spares in case

Nobby
28-01-11, 12:12 PM
No, coz the f...er wouldn't even start! :p:p:p

Ooh you little liar, remember when you were messing with that carb on that MDS model engine at my gaff last week?

I turned the ignition key in my Cob and it sprang into life without any choke, pressing of accelerator pedal, praying to the Gods of carburation or swearing? Despite not being started for 6 weeks previously?

Try that with your non EFI system. Hah so there :rolleyes:

Sidecarbod
28-01-11, 01:42 PM
Ooh you little liar, remember when you were messing with that carb on that MDS model engine at my gaff last week?

I turned the ignition key in my Cob and it sprang into life without any choke, pressing of accelerator pedal, praying to the Gods of carburation or swearing? Despite not being started for 6 weeks previously?

Try that with your non EFI system. Hah so there :rolleyes:


Coaxing an engine into life is all part of the fun, it sounds to me like your EFI system has turned your car into something similar to my VW Bora TDI

Hah!! :p


















(Yer git!)

Nobby
28-01-11, 02:38 PM
It sounds to me like your EFI system has turned your car into something similar to my VW Bora TDI



Correct, but not as fast :)

tonym
29-01-11, 10:10 AM
Coaxing an engine into life then trailing behind an EFI powered car is all part of the fun, :p

Fixed it for you Pete, no need to thank me (not that you could catch me :p)

rob marshall
02-02-11, 08:53 PM
Hi Dunc
I know its a stupid question and will probably get me shot down but how old is the petrol in the car and who long has the car stood recently as if the fuel evaporates ond carbs dry out it will leave a residue inside and could cause all sorts of problems.Get some fresh petrol or carb cleaner and fill the carbs &leave to stand for a cuple of hours then start and see repeat as necassary
Regards Rob Marshall