Jump to content

Black Soot and Back Fires


Highland gow

Recommended Posts

Hi I have a problem with my series.

Landy starts pretty easily and when warmed up idles very nicely. It can drive downhill ok and can accelerate a little. Going up any kind of a slight incline there is no power whatsoever, and if I keep trying to go uphill it just dies. Sometimes it also backfires. When I check the spark plugs they are black with soot.

I have tried the following:

Compression test – all 125-140 psi, a little higher when oil is added

Adjusted tappets

Entirely new ignition system.

New genuine Lucas 45D distributor to replace the old 25D

Replaced condenser in this new distributor 3 times

Thoroughly filed, cleaned and gapped points

New plugs (2 sets), new wires

New coil, and then replaced that one with a known good coil from my Jaguar

Replaced old wiring from fuse box to coil and from coil to distributor

Adjusted ignition timing

Right on 6 deg BTDC at idle, advances (mark moves counter clockwise) when idle speed is increased

New vacuum line from carb to distributor

Entirely new fuel system

I rebuilt the Zenith 36IV with a genuine rebuild kit. Flattened all of the housings.

Replaced Zenith with brand new Weber

New fuel line from pump to carb and new filter (the filter does not fill up all the way, only a little less than half)

New fuel pump, inspected the old one which looked fine.

Removed fuel pickup line to check for clogs, all clear

Added 5 gallons of gas to tank to make sure I was not low

Fuel in glass sediment bowl is full and clean

New exhaust manifold (the old one was cracked by the down-pipe attachment)

New intake manifold gaskets and all new attachment hardware

Engine runs 50 psi oil pressure

Dynamo output seems fine, lights are bright and the battery does not run down.

Tightened fan belt.

Please can any one help?

Ali
Link to comment
Share on other sites

Did the problem occur after you changed the carb. has it ever flooded and hen wont re-start?

Mine behaved liek this and it turned out the "new weber carb" had the vacum advance takeoff on the wrong side of the throttle butterfly. ( it should be before)

Link to comment
Share on other sites

I know it is new, but don't discount having a tiny bit of dirt stopping the float coming up properly and closing the inlet. Do you run an inline filter? If not, you need to with a weber.

I don't know if the weber has a float chamber overflow, but if it does, make sure you have not connected the 'petrol-in' pipe to the overflow -ask me how I know.... it was a long time since I had an SU, honest... ;)

Link to comment
Share on other sites

Clogged air filter? Try running it with the air-filter pipe disconnected entirely from the carb.

(I have memories of a large agricultural engine that had serious smoking/gutlessness issues: after the owner spent lots of money on new fuel-system parts we found that it ran a lot better when I removed the mouse-nest and half-a-bucketful of chewed nut-shells from the air filter casing)

--Tanuki.

Link to comment
Share on other sites

I had similar problems on my Lightweight and replaced just about everything like you did, rectifying many faults which may have been contributory, but to no avail. In the end, it was setting the ignition timing by ear, not by static marks, which cured it. The static marks are for 2* and 4* leaded fuels, not modern unleaded, and so the timing marks don't always give good guidance.

Loosen the distributor clamp and idle the engine. Adjust the distributor position until maximum rpm is found and tighten the clamp in that position. You may need to adjust the carb settings after this.

Link to comment
Share on other sites

Air cleaner hose collapsed internally - take it off the carb and see if its any better.

Firing order correct ? - check leads on distributor cap and direction. - Go back to basics take no 1 plug out and find compression stroke - it will be the 'missing' one when you crank the engine over - and stop at what would be the maximum compression. Now check rotor arm really is pointing to no 1 lead - then check the other ones are in the right place (sorry think it goes anti-clockwise but would have to check)

Incorrect rotor arm - probably not as came with distributor.

Sure you're not using a ballasted coil? What age of Jaguar - All XJ6 and onwards may have ballasted - I don't think my 1969 Daimler V8 did. My 1971 Stag did.

Link to comment
Share on other sites

you have set the points by gap only. I have found setting by gap puts you in the right postcode but very rarely gets you to the correct house, You can get an automotive multimeter that you can use as a dwell meter for less than £30 very useful tool asides but you can use it to check & set the dwell angle properly.

Link to comment
Share on other sites

  • 9 years later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  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.

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy