Fuel Mixture

Engine Oily Bits, Ignition, Fuelling, Cooling, Exhaust, etc.
Post Reply
Message
Author
johnfrancis898
Groupie
Groupie
Posts:47
Joined:Sun May 16, 2021 6:44 pm
Location:Berkshire
Fuel Mixture

#1 Post by johnfrancis898 » Sat Nov 11, 2023 6:53 pm

I’m having trouble tuning up the carbs. Tick over has always been a bit erratic and the old girl has always smelt a bit rich, however acceleration and power has been good but I have recently noticed fuel consumption has got worse. So today I decided to fit a set of new needles and clean up the dash pots. I then balanced the air intake with my carb balancer and established a good tick over. After reassembly she started fine but on a test run a misfire was evident on acceleration and also loss of power. Further adjustment to the jets has cleared the misfire. I have them set exactly 2 turns down from when they are flush at the bridge. Power and acceleration is now good as before but on tick over it’s still smelling rich and I can’t establish a good tick over. Any pointers or tips welcome!
Member no. 7941.

2500TC Mk 2 saloon 1976 od/PAS BRG

User avatar
Alec
Senior Member
Senior Member
Posts:2512
Joined:Sat Feb 07, 2004 7:23 pm
Location:Oswestry, Shropshire

Re: Fuel Mixture

#2 Post by Alec » Sun Nov 12, 2023 8:27 am

Hello John,

the two turns is an arbitary setting, i.e. a starting point, and should be adjusted to get the right setting. That said it shouldn't be far away from ideal. Presumably your air cleaner element is clean also as this affects the mixture.
When you have got the mixture where you want it, try small adjustments to the timing as mixture affects what timeing works best.

Alec
0465

MK1.5 2.5 P.I.
Jaguar MK 2 (Long term restoration.)
Hymer 564 Motorhome.

johnfrancis898
Groupie
Groupie
Posts:47
Joined:Sun May 16, 2021 6:44 pm
Location:Berkshire

Re: Fuel Mixture

#3 Post by johnfrancis898 » Thu Nov 16, 2023 10:52 pm

Many thanks for your reply Alec. I have done some further investigating and found the problem is when I use the choke. When the choke is pulled it pulls back the jet to richen the mixture for cold starting. I found that on the front carb the jet was not returning fully. The misfire then disappeared after ensuring the jets were in their correct position. I’ve now ordered a full refurb kit from Burlens.
Thanks again. John.
Member no. 7941.

2500TC Mk 2 saloon 1976 od/PAS BRG

Post Reply

Who is online

Users browsing this forum: No registered users and 15 guests