Diagnose My Problem

[trogboy 17]

I have a few odd symptoms with my car that I'd like your thoughts on but all are related to the engine setup I am running at the moment.

 

For those that don't know I have a TU3/TU24 hybrid which is making use of a standard but new alloy TU3 block and the head, cam, dizzy, inlet manifold and DCOM carbs from the TU24. I have been running this set up since november last year and have covered about 7000 miles and I can't tell whether the problems are getting worse in reality or just in my head so I figured i had just better sort them out.

 

The sysmptoms of concern are:

 

When it has has been sat for more than say 12 hours she always starts on 3 cylinders. Well that is what it sound like - kind of rough and uneven like a sick tractor or a harley davidson starting up. Once I have revved a few times she pick up on all four and sounds much smoother.

 

When running there is a hell of a ticking noise coming from somewhere - I have spent probably a couple an hour in total listening all over the engine with screw drivers and a mechanics stethascope but it's all a bit inconclusive. The tick is defintely worse in no.2 trumpet BUT the valve clearances are all spot on (checked, rechecked and bloody checked again).

 

Using my synchrometer I can see that No.2 choke is flowing considerably more air at idle than the other 3 . I don't know what the units are on the synchrometer but it is an SKF one and the others are 2 to 2.5ish whilst No. 2 is ~6. It this a sign of a bent spindle in the carb or could it be related to something in the head?

 

I have done a compression test and none of the readings are significantly different. When I get some spare time I'm going to dig out the bits I need for a leak down test which might give some more information.

 

So what do you think? Could all of these problems be related?

[Sandy 189]

That balancing is must be the cause, whip that carb off and have a good look at it, especially the throttle plate location.

[trogboy 17]

Cheers Sandy,

 

I had considered that but would have thought that the place that set up my carbs would have noticed it.

 

Here is a vid to make the symptoms a little clearer. Not as bad as it can be though as I only left her for about 6 hours.

 

Has anyone seen a tractor?

 

Cheers,

 

Ad

[christopher 5 1 Cars]

Ad...... the link to teh videp doesn't seem to work

[trogboy 17]

Ad...... the link to teh videp doesn't seem to work

 

Feck it! I hate being a techno flid.

 

The address is http://s182.photobucket.com/albums/x261/tr...¤t=31b638d8.flv

 

Does it work if you copy and paste that into a browser or do you need to be logged in as me?

 

Edit: that doesn't work either!

Edited July 18, 2007 by trogboy

[Jrod 7]

[Sandy 189]

I wouldn't assume a specialist would necessarily find the fault, I've got a 205 in at the moment that had a crushed fuel pipe and the customer previously had a £370 bill for attempting to set it up (and handing it back not running). It's usually something "obvious".

[trogboy 17]

http://s182.photobucket.com/albums/x261/tr...nt=31b638d8.flv

 

This seems to work

Edited July 18, 2007 by trogboy

[Jrod 7]

Carbs getting hot and evaporating the fuel?

 

 

Good to see you've fixed the bonnet stay.

[trogboy 17]

Carbs getting hot and evaporating the fuel?

 

That's from cold unfortunately and I'll have you know that that is a custom bonnet stay! It never gets in the way as I can swap sides at the click of the fingers.

[Jrod 7]

 

But is it from when the engine is switched off and the fuel evaporates, then when you come to start it it takes a minute for fuel to get flowing?

[trogboy 17]

hmmm - I'll go and measure the fuel levels in the bowls before I start her up and then once I've got to work. I'd be suprised if that was the problem though as if the fuel levels in one bowl were low due to evaproation it would take a bit longer to re-prime and it usually starts on 3 within a second or so

[christopher 5 1 Cars]

The TU24 has a fuel return which should dispell all problems with vapour lock. Do you used a fuel return Ad?

 

Incidently I have been negeleting mine for over a year now and she is in desperate need of a good seeing to. However recently I have had similar problems to you. She starts up a bit rough sometimes..but it may just need new ignition leads.

 

I always start using the choke let it rev to 4000 then blip the throttle 4 or 5 times and then put the choke in. She normally then runs fairly smooth then after the first km. But she will always pick up very hard with a more then feather touch to the throttle even when ice cold. I have my fuel return blocked off because the pressure of the fuel was not what it should have been. On VERY hot days I have had extreme tractor issues. But this is quite rare.

 

As sandy said I reckon most running issues originate from the balancing of the carbs. If this is not spot on you will find it difficult to get a good low idle and be rough running at partial pickup from low rpm's. Especially if you have a cam with a large overlap. The two barrels of each carb should be balanced with each other already but this also can be adjusted. If you have a balancing issue on one carb itself you either have a problem with the carb, it is not balanced or perhaps have an air leak in the mounting gaskets. The last is the most likely.

 

How are your spark plugs looking?

Do you use the three pinned TU24 ones?

How old are your ignition leads, dizzy rotor?

Edited July 19, 2007 by christopher

[Guest Parkesie]

ive had problems with the runing on 3 till it had warmed up. Cause was 1 duff spark plug nevery know you could be lucky try some new plugs

[trogboy 17]

Dizzy cap, rotor arm and leads are ~ 6 months old with the plugs being about 3 months old (changed when first set up and when given an additional tune up after I had changed the valve stem oil seals.)

 

I use the standard bosch plugs for the TU3S - can you recommend me anything more suitable?

 

Apart from the ticking she only runs rough when very cold and after I have blipped the throttle a couple/sometimes several times she settles down.

 

When loadings are very light such as when coasting down hill and lightly engine braking she pops quite a bit but doesn't seem to be running either lean or rich at those points. Is that normal? I certainly never got it on the old engine setups. I have an old Hawk exhaust gas analyser which I have been using on the move to keep a rough track mixture whilst driving to work and back and if anything the bias is well towards the rich end of the spectrum (or could that be over zealous use of the loud peddle?)

 

When I got to work today I had ~4mm more petrol in each of the carbs then when it had been cold this morning. As Jordan says this is probably due to evaporation of fuel from the hot carbs once I've switched off. I have got the fuel return hooked up but my reducers are a bit heath robinson to get the fuel pipe down to the size of the fuel return pipe! There is always some excess fuel heading back down the return pipe at all engine speeds so I think the my pump is fit and healthy.

 

The imbalance is within one of the carbs and not between carbs, just one choke taking more air than the others. If I get a chance over the weekend I'll take the carb off and look at the throttle plates. I'll also check out the idle bypass screws as I know one is a replacement that I had machined up when I broke one of the originals and couldn't lay my hands on another.

 

Could the ticking be related to the imbalance of the carbs?

[pugrallye 0]

your saying you have a misfire when first starting from cold on a cold day?

That normally indicates an igintion problem, used to be typical to find condensation in dizzy cap with this scenario