Jump to content

Rattling when shutting the engin off - also hard to start when cold


Recommended Posts

Having had my SU carbs professionally repaired, I have been struggling to get my timing and SU carb set properly. Finally, I bought a set of colourtune, and set the carbs. I also set the timing to exactly 4 deg BTDC. However, although the car runs very well (when it is being ridden), when I want to shut it off, it rattles and huffs and puffs for a few seconds, and then dies! Of course, the reason I touched the timing was because since I installed the repaired CARBS, it takes several (TEN TO TWELVE) cranks to start the car when it is cold; once it starts, however, it runs perfectly, with lots of power.

 

I was wondering if you could tell me what causes the rattling when I try to shut of the engine. I alo had this issue last year, but then, the car was not set at 4 deg BTDC.

BTW, I am running Petronix electronic ignition.

 

Your help is appreciated in advance.

 

Regards,

Farid

Link to post
Share on other sites

Farid,

 

There is no longer a standard advance setting !

 

You probably need more then 4 degrees static advance due to modern petrols etc, up to 8 degrees static advance (or sometimes even more) are no longer any exeptions nowadays!

 

The best thing you can do is run the engine at aprox. 1700/1800 revs, and the turn by hand the distributor until the engine reaches it highest rpm, then turn it back with aprox. 100 revs.

I know it's a rough setting, but it is a good starting point what so ever.

 

Good luck - Raymond

Link to post
Share on other sites

The rattling is the engine running-on because, within each combustion chamber, there's something (could be metal or carbon deposit) which is so hot that it acts like a spark plug and ignites the mixture. It doesn't do the engine any favours to permit this running-on, so, when about to turn off, let the engine tick over, select first gear, bring your left foot up gently until the clutch is just beginning to slow the engine and then turn off the ignition.

Of course, if the timing is adjusted correctly (see advice from Raymond), then running-on may not occur.

Ian Cornish

Link to post
Share on other sites

I'm not sure Raymond is correct. It may be true that modern fuels need more static advance, but and this is more important, they need typically 4 degrees less at full advance. My understanding is that various manufacturers of electronic ignition that includes advance characteristics have been advised of this by fuel manufacturers after engine troubles with older cars and bikes in competition.

 

TR Ignition timing probably isn't as critical because we don't often run them at full throttle, but it may cause problems at motorway speeds. The suggestion is to restrict max advance so more static can be used.

 

 

Link to post
Share on other sites

Check that the distributor bob weights are free and the springs are connected, refit the old points and then set dizzy at 4 degrees btc static and then try the car, advancing the ignition until it will only just pink pulling hard uphill in a high gear. Every engine is different and must be tuned as such. As to running at full throttle its a sports car not a boulevard cruiser that's what you've got it for so use it!

Stuart.

Link to post
Share on other sites

I agree with all of the above re. advancing the ignition. There's one point worth mentioning: I had the same running on characteristics (not the starting problems) with my car after filling the tank with 95RON octane fuel. I carefully drove about 400 kms and refilled the tank with 98RON fuel. The running on problem is gone.

 

Menno

Link to post
Share on other sites

Stuart's advice is (as always) spot on. That's how we always did it in the days before we could all buy sophisticated tuning gear in Halfords, Machine Mart, etc. Problem is, most of us never really learn to use it and even if we do, then we will have forgotten the next time we need it. I was somewhat taken aback when I had my car set up on a rolling road this year and the guy effectively did what Stuart suggests and said that's how he has always done it. All the expensive equipment just confirms when he's got it right. Seems to work, judging by the trophies he has and the competition cars he tunes. Scariest part was when he first told me to floor the throttle - never done that before because I thought something would break. A couple of hours later, it had become second-nature!

Link to post
Share on other sites

Sorry

But I disagree any rolling road man worth his salt will check and know the advance curve on the runs, a 4 pot can strobe at 10 and run fine a 6 pot will take 16 at 800 rpm both in good order,You can retard to save stress but to go to the point of pinking is not a good idea bye bye pistons in the long term,or in the 4 pot case bye bye crankshaft

Link to post
Share on other sites

Folks:

Thanks very much for all your advices.

I have tried Richard's suggested tuning; I will give it a shot soon!

Wouldn’t advancing, however, make the initial starting a bit more challenging? What is the cause of hard start when cold then?

 

Many thanks again!

Farid

Link to post
Share on other sites

Sorry

But I disagree any rolling road man worth his salt will check and know the advance curve on the runs, a 4 pot can strobe at 10 and run fine a 6 pot will take 16 at 800 rpm both in good order,You can retard to save stress but to go to the point of pinking is not a good idea bye bye pistons in the long term,or in the 4 pot case bye bye crankshaft

 

 

I agree with this because ignition timing doesn't make that much difference to power at the top end, but it can cause extra vibration and it may do damage. With my limited experience of the 4 cylinder engine I'd say 4 degrees static gives the best compromise of power and smoothness.

Link to post
Share on other sites

Do you have a petrol pump with a manual lever, did you prime it before startup. I did have the problem of fuel running back to the tank earlier, but fitted a small inline valve just before the pump stopping the fuel running back to the tank.....like this one...

 

http://www.amazon.co.uk/10mm-Return-Valve-Petrol-Diesel/dp/B002WNYRWA

 

Cheers,

Esben

Link to post
Share on other sites

Farid, for the hard starting problem, have you checked that the choke is working properly ?. If you remove the aircleaners you should be able to see the jet lowering mechanism operate when you pull the choke cable out.

 

Is the choke cable locking on when you give it a twist ?. Sometimes the cable sneaks back in without being noticed. A clothes peg on the exposed cable or a small coin laid on its side are ways of keeping the choke cable out.

 

There's a TR Register Australia tour of Canada on at the moment and they are probably somewhere near Halifax about now, Shame they can't get in touch as there would be a couple of our members who could sort it out for you on the spot.

 

Viv.

Link to post
Share on other sites

I used to have both these problems with my TR3. I discovered that the poor cold stating was caused by the jets not moving when I pulled out the choke. I doubt that is the problem with yours if the carbs have just been rebuilt, but I solved it by taking the carbs off and greasing the cork glands.

It also used to run on until I rebuilt the distributor and then re-timed the engine. I am ashamed to say that I don't know what it is timed at. I set it up as per the book but it pinked dreadfully, so I turned the little knurled screw until it stopped pinking on acceleration. The engine doesn't run on any longer. The strange thing was that when it was "running on" it was actually running backwards!

Link to post
Share on other sites

I used to have both these problems with my TR3. I discovered that the poor cold stating was caused by the jets not moving when I pulled out the choke. I doubt that is the problem with yours if the carbs have just been rebuilt, but I solved it by taking the carbs off and greasing the cork glands.

It also used to run on until I rebuilt the distributor and then re-timed the engine. I am ashamed to say that I don't know what it is timed at. I set it up as per the book but it pinked dreadfully, so I turned the little knurled screw until it stopped pinking on acceleration. The engine doesn't run on any longer. The strange thing was that when it was "running on" it was actually running backwards!

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.