Engine (Ignition?) issues

[BobsYourUncle]

I've bought a colourtune with the intention of tuning with my SUs and (eventually) dellortos. I just tried it out, and noticed that there's often no colour (I can see the spark, but there's no colour to indicate ignition). It happens quite often at low engine speeds, and less often (at least that's my perception) at higher speeds. At idle, when there is colour, it's blueish white, indicating a lean mixture.

 

I figure there's always a spark, so it shouldn't be an electrical problem. When I rev the engine, the colour goes yellow briefly then back to blue, so shouldn't be fuel? Unless the carbies aren't working properly at idle speeds... The engine does appear to rev quite freely, but it's idling rough.

 

I think it's timing. If i loosen the bolt that holds the distributor in place and rotate clockwise, it gets better, but only just. Rotating the other way makes it worse.

 

Am I on the right track? Should I just read up on setting ignition timing?

 

I considered getting a new distributor cap and leads, as the ones I have are a bit old and loose, but there always seems to be a spark...

 

Oh, and the engine was warm. I'm such a newbie...

[ozconnection]

Do you have an electronic ignition or is it just a standard points type?

 

A poory adjusted points can cause your car to run rough....your colourtune proves what's happening in your chambers...intermittant non combustion of the air/fuel mix.

 

Now that you have a 'tool' that can help you with the mixtures, turn your attention to getting the spark spot on. Start with new points and rotor and cap. You said they were a little 'average' Sort it. Process of elimination applies here.

 

Optomise what you have. That doesn't cost too much if you don't have wads of cash ATM. I enjoy doing this. Consider it a challenge. 

 

Good luck...tell us how you get on.

[BobsYourUncle]

I've got electronic ignition (and I've tried two distributors). You think it's a weak spark? I'll have to measure the resistance of my leads...

 

edit: picked two leads at random, resistance was ~150 Ohms. At first I though that was large, but I googled and some places say 10-50kOhm is ok. What should they be?

[Scoota G]

I think the carbies are not syncronised accuratley. Do you have a way to test them?

[BobsYourUncle]

I don't, no. IF the carbs were out of sync, would that cause intermittent ignition?

 

As understand it (might be wrong), the front carb supplies cylinders 1-3, the rear 4-6. Doesn't synchronising them just makes the front act the same as the rear? I checked cylinders 1 and 5 with the colourtune, both had the problem.

[Scoota G]

This could end up a really long process. Do you know how many Klms the engine has done? Is it the original engine? Is it upgraded to an L28?

Have you set the valve gap?

 

I just need some more info buddy!

[BobsYourUncle]

Ok, here's what I know:

 

It's not the original L26, it's an N42/N42 L28. I don't know how many kms it's done. I've done a compression test - 165-170psi for all cylinders. I set the valve clearances a couple of days ago, 0.008" intake, 0.010" exhaust (cold engine).

 

Thanks for your help. Sorry if I didn't come off as appreciative, I'm just asking questions to learn

[WA240Z]

Hi,

 

If your leads are looking a bit worse for wear, I would start there. At least make sure the connections at the cap, coil, and plugs are nice and firm and the leads are very clean. Poor leads can really play havoc under engine load.

 

Also be careful not to advance your ignition timing too far by adjusting your distributor without using a timing light. You can easily start causing extra problems for yourself with knocking.

 

If your new to tuning, only adjust one thing at a time, and, always start with good or new parts, such as cap, coil, leads, plugs, fuel filter, air filter, and good fuel. Nothing worse than chasing your tail making a dozen tweaks and changes upsetting the tune of the engine only to find in the end the problem was an easy replaced consumable component.

 

Hope all goes well.

[Zedman240®]

Have you checked the timing with a stroboscopic timing light? Do you know exactly how many degrees it's running at? Have all the tools handy that you need when doing this sort of thing..

[BobsYourUncle]

Have you checked the timing with a stroboscopic timing light? Do you know exactly how many degrees it's running at? Have all the tools handy that you need when doing this sort of thing..

 

No, I haven't. I might have to buy one. Where can I get one? Supercheap?

[Wayne G]

please excuse my ignorance, what is colourtune? What does it measure? How does it connect to the engine?

[maddos]

http://www.autoexpertproducts.com/colortune-14mm.htm

 

google is your friend

[Zedman240®]

No, I haven't. I might have to buy one. Where can I get one? Supercheap?

 

Any good auto place should have them. Get a pretty good quality one; accuracy and reliability is pretty important..

[BobsYourUncle]

I looked at the two distributor caps I have, the one currently not on the car looks to be in good condition, so I'll put it back on. I'm going to get a new coil and new leads this weekend, and have a look for a timing light. I'll keep updating this thread...

[mick74]

Stupid question did you check if you have oil in your SU's, if not add. This can give a weaker mixture at idle and weaker mixture on acceleration. I would try to richen the fuel mixture at idle with colourtune in place and see what if any difference you get with the colour. This should eliminate fuel. Unfortunately the colourtune won't help in syncing the carbs. Then you can chase ignition ie timing etc.

You can do a static timing adjustment ie turn crank by hand until you are at the desired timing point ( ignition off) for #1 cylinder (ie 10 deg) then loosen distributor and turn back until points are closed or for me sensor in dizzy is covered by shutter wheel then turn on ignition and turn dizzy forward until you see/hear spark for points or me electronic module led lights up then tighten dizzy. This should get you close enough to the mark without having a timing light.

 

I hope this helps.

[ozconnection]

I'm a little 'confused'. You said you were able to adjust the valve clearances to proper specs but weren't sure where to buy a timing light?

 

I would think that removing the valve cover and 'knowing' how to properly set the valve clearances was a lot more technically difficult than setting ignition timing or where to buy a timing light....... :-\

 

Personally, I hate cheap timing lights. Do yourself a favour and spend some money on something decent. Snap on make a lovely professional grade timing light but they're way overpriced. Buying locally is expensive and with the strength of the Oz dollar, you should be looking at buying from O/S. Look on ebay. Even with the cost of postage, buying this way is cheaper. People may not like this, but I work hard for my cash and if I buy something that's the  same and leaves a few bucks in my pocket what the hell....

 

Try looking for timing lights by Innova on ebay. I bought model 5568.......awesome.

 

 

[BobsYourUncle]

I'm a little 'confused'. You said you were able to adjust the valve clearances to proper specs but weren't sure where to buy a timing light?

 

I would think that removing the valve cover and 'knowing' how to properly set the valve clearances was a lot more technically difficult than setting ignition timing or where to buy a timing light....... :-\

 

Personally, I hate cheap timing lights. Do yourself a favour and spend some money on something decent. Snap on make a lovely professional grade timing light but they're way overpriced. Buying locally is expensive and with the strength of the Oz dollar, you should be looking at buying from O/S. Look on ebay. Even with the cost of postage, buying this way is cheaper. People may not like this, but I work hard for my cash and if I buy something that's the  same and leaves a few bucks in my pocket what the hell....

 

Try looking for timing lights by Innova on ebay. I bought model 5568.......awesome.

 

Sorry, I knew I could get a timing light from supercheap, but was more looking for suggestions of good brands, and what a good one is. I could've been clearer. Thanks for the suggestion, I'll look them up.

 

Valve adjustment was done after studying the various books I've got and some stuff I found online. I'm pretty confident I did it right. The clearances weren't too bad to begin with, they tended to be only a few thou out.

 

Oh, and at work we export all our stuff to the states, so it's nice to be able to take advantage of the strong dollar every now and then (rather than the other way around).

[Wayne G]

http://cgi.ebay.com.au/Hella-Timing-Light-/230583029733?pt=AU_Car_Parts_Accessories&hash=item35afd1cfe5. Hella produce a nice strong light, are robust for being dropped etc, and has dwell angle, useful if it is points system. Also works well with DIS ignition coils.

 

May I politely suggest you take the colourtune with a pinch of salt and throw both over your shoulder?  You actually don't want your vehicle to idle at ideal air fuel ratio 14.7:1 or lambda 1, as it will be hard to start and slightly sluggish to accelerate, especially if it is slightly down on compression. It is probably as accurate to just breath in the aroma of the fumes, either at the tail pipe or inlet. If it burns it is lean if it smells of fuel it is rich. (old school way I was taught, just as scientific) The idle mixture fine tune with this type of tool is probably the last step, before road test, in a tune anyway.

 

[ozconnection]

What Wayne G wrote worries me.

 

Sniffing the exhaust isn't reliable enough. How can it be? Far from scientific. Leave it to the experienced 'old skoolers'.

 

I read the Colortune information on ebay. It provides a range of colours for different conditions, even for idle!! Perhaps the best way to use it is on a dyno so that different loads can be applied and the mixtures easily seen. Having said that, oxygen sensors that are put into the rear tailpipe can measure the mixtures more effectively and some might argue "What's the point of the colortune then?"  If you can't get to the dyno easily or regularly (cost), then there may be some merit in using colortune as a basic mixture set up tool.

 

As far as the timing light situation goes, that's what I mean by spending your cash wisely. The Hella unit might be good but the one I have gives all the same features plus it has a tachometer built in and you can see what the advance is doing at different engine revs, all displayed at the same time on the LCD screen. I plotted both of my 280zx dizzy's for revs vs degrees and could see exactly what was going on. The hella is good, sure, but is it good enough? If you want to tune your engine, then this timing light is the one I suggest you at least consider buying. Once you have it, all your mates will want to borrow it...its that sik mate!! 

[Wayne G]

I still have not figured out how to type sarcasm    Whilst I was taught the sniff method some time ago, please no one try it. There is some nasty junk coming out! I usually get headaches, probably from CO poisoning.

 

The 5568 is an impressive light, similar to my snap-on one, less than a third what I paid in the day too. I am merely suggesting something more in line with super cheap price but decent quality.

[ozconnection]

Thinking a little further on the idea of colortune is what happens when you've got two of them?

 

Put one in cylinder 2 and the other in cylinder 5 with a twin SU equipped engine.

 

Check mixture balance between the two carbs.

 

Unless you've got two oxygen sensors in the exhaust, can you check the mixtures like this any other way? Checking the plugs can give some insite but the results may not be so obvious.

 

The carb airflow checker, Unisyn I think I remember it being called, will balance airflow between the carbs but does it do mixtures?

 

On my Holley, set up as a dual plane with an Arizona 4 barrel manifold proved to me that the idle mixture curcuits were not sync'ed exactly the same. The idle mixture screws turned out one turn from seated didn't give the same response as each other at idle. (A manufacturing error perhaps?) Could two Colortune plugs (one in cylinder 2 and one in 5) give 'exact' carburettor syncronization?

 

Faaark...maybe yes! Even if one mixture screw is turned out 1.1 times and the other 1.3 times but the colour of the burn is the same for both cylinders and banks, then it's tuned correctly, right? How else could you get and check this kind of sync.?

 

Sorry to go off topic here but I think this is important enough to mention here.

 

Cheers.

 

[dazzed]

Have you checked the timing with a stroboscopic timing light? Do you know exactly how many degrees it's running at? Have all the tools handy that you need when doing this sort of thing..

excuse my ignorance but what is a srobostopic timing light wotchamacallit or whatever??