Jump to content

Running Rich


Recommended Posts

Morning all,

 

Just been out for a blast in the PI, running really well, pulls like a train with no smoke on overrun but a bugger to start. Ticks over well when hot and restarts fine, however, the problem is the mixture is very rich. The plugs are sooted up, but dry, and you can smell the petrol in the fumes. Its had a new pump and PRV plus rebuilt metering unit (from Prestige), lines and injectors plus rebuilt distributor (Distributor Doctor) and uprated coil and leads. Compression on all cylinders is about 180 and vacuum is about 8 although the needle seems to swing quickly between 7 and 9. I also checked the cold start lever and that always returns to home position. Also checked the MU diaphragm with the tongue test and that's all good as well.

 

So looking through previous posts, I'm a little confused (easy for me i'm afraid). Does the vacuum control the mixture? Could a low or fluctuating vacuum result in the MU allowing more fuel to the engine? When I disconnected the brake servo vacuum pipe, the revs rise so I'm guessing the vacuum is not too bad. Is there any thing else that controls the mixture that I'm missing?

 

Other than that, the car running really well.....

 

Cheers

 

Mal

Link to post
Share on other sites

Fuel pressure & vacuum control the fueling ( fluctuating vac. reading normal), if possible check fuel pressure first, if o.k. A2 adjuster on vac unit can be adjusted ( the central one) ,turn anticlockwise in 90" increments

( keep note of all adjustments ) to lean off mixture. Gas analyser ideal but colour tune a good substitute.

If neither available road test between adjustments to check plugs.

 

 

 

Harvey S. Maitland

Link to post
Share on other sites

Morning all,

 

Just been out for a blast in the PI, running really well, pulls like a train with no smoke on overrun but a bugger to start. Ticks over well when hot and restarts fine, however, the problem is the mixture is very rich. The plugs are sooted up, but dry, and you can smell the petrol in the fumes. Its had a new pump and PRV plus rebuilt metering unit (from Prestige), lines and injectors plus rebuilt distributor (Distributor Doctor) and uprated coil and leads. Compression on all cylinders is about 180 and vacuum is about 8 although the needle seems to swing quickly between 7 and 9. I also checked the cold start lever and that always returns to home position. Also checked the MU diaphragm with the tongue test and that's all good as well.

 

So looking through previous posts, I'm a little confused (easy for me i'm afraid). Does the vacuum control the mixture? Could a low or fluctuating vacuum result in the MU allowing more fuel to the engine? When I disconnected the brake servo vacuum pipe, the revs rise so I'm guessing the vacuum is not too bad. Is there any thing else that controls the mixture that I'm missing?

 

Other than that, the car running really well.....

 

Cheers

 

Mal

What series TR 6 have you got CP or CR? Vacuum S/B 10 Hg for CP & 14 for CR. Subject to this, look for air leaks from anywhere on manifold to M/U, leaking servo unit, worn valve guides and butterfly spindles etc. Do the tongue test on the vacuum pipe to M/U Do not go adjusting M/U as it has been re-conned.

 

Bruce.

Link to post
Share on other sites

It's a CP so maybe vacuum is not to bad?? If I blank off the outlet to the mu and cover the tick over valve the engine stalls but when connected the engine continues to run. Does that point to leaking mu?

Cheers

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.