timing issues

[240zchevyv8]

Hello everybody not sure if any one will be able to help with this one, right my 240z has a 1962 327 cubic inch 5.4 litre chevy v8 installed in it, every thing is fine but the tick over is very rough, i was told it had lopy cams in it when i bought it so thought it was this, but wasnt sure so checked everything to do with the timing all ok, except that when i put the timing light on the car its as if it misses every few seconds (flashes correctly then stops for a mili-second or so then is normal again), ive got 2 timing lights and there both the same so rules out a faulty light, it does it on all the cylinders, have new leads fitted so dont htink it is that, thing is how do i tell if it is a faulty distrubutor or coil, one thing pointing to these is the car is smoking a bit but not burning oil, probably due to unburnt fuel in the bores when the engine misses, is it just a case put in a new distrubutor and coil and see what happens, the coil is a accel 8140 which says it does not need a resistor but car came with the 240z resistor and another one installed, i removed them because i read on a forum that cars with electronic ignition do not need resistors, but would this cause the fault i have, the car drives ok but stumbles on over run or while easing of the gas,

 

[grolls]

Check this tread for testing.


http://zclub.net/forum/anything-everything/3028-basic-electrics.html

"the car drives ok but stumbles on over run or while easing of the gas" of course you may also have an inlet manifold leak or wrong mixtures too.

 

[Wyn]

Does it have a manual choke
Does it need it to start? For how long?
What colour are the plugs?
If it starts without choke, runs lumpy on tickover and grey/black smokes it could be to rich?
Can you weaken the slow running mixture to rule it out ?

 

[sjcurtis]

I run a ballanced 4 bolt main 010 block 350 steel crank with 13.5 compression on straight lpg. I rely on a fireball ignition system and Coil though an optical mallory distributor. good electrical power supply and engine earthing are the key to success with these engine electrics.
Check ignition wiring set up confirm no loose connections check for spark at the end of every plug lead while cranking over. if you are not achieving the desired result (good strong spark) swap out the coil, you should not be running points with the number of breakerless systems around today it is really not a. huge cost,and a CDI type ignition enhancer should also be in your arsenal for use, this type of multi spark modules behind the primary are a good idea as it will ensure a cleaner burn and reduce fuel usage, a side benifite a successful low rpm idle down to about 550 if needed, sugest 650-700rpm may work better.

Give the idle screw an adjustment sounds like you need to invigerate your idle enough to sustain operation. Try about 15-17 degrees on the advance on the distributor with maybe 87- 89 plug gap, if the valve timiing is good you should get some sustainable idle in these numbers float level triming may also be a required once you get a strong idle established. get your advance set dial back the idle then see if it will run and not hunt up and down while idling.

are you running hyd or solid cam...


cheers
Steve

 

[240zchevyv8]

Cheers everyone for the suggestions, firstly car is running but idles roughly but does not stall, static timing is at about 15-17 degrees, cant get it any lower than this because it stalls, plug gap is set at .40 as recommended for chevy, it has a mallory 2548201 dual point electronic ignition distrubutor, these distrubutors do not have a vacuum advance on them, not sure whether i have hyd or solid cam cannot tell on these by looking, will test every plug later for spark, also car does not have a choke i find that by pumping the gas it starts quite easy even after standing a few weeks, will also check later for inlet manifold leaks using spray will let you know what i find.

 

[240zchevyv8]

Right first thing must get a bloody heater for the garage, i checked plugs they were wet with petrol, checked the spark on every plug all had a spark some were better than others, refitted the resistor in case this was causing a problem, fired up the engine still the same, turned down the fuel mixture this stopped the smoke comming out of the exhaust, checked for vacuum leaks with electrosolve (flammable) no increases in RPM so dont think ive got any vacuum leaks, but one thing i noticed if i increased the revs to around 1200-1500 rpm i could feel the engine missing more, is this itself a sign of some thing. plug gap still left at .40 could this be the problem.

 

[Rob Gaskin]

I know this seems like a cop-out but why not take it for a diagnostic check up? Could be money well spent.

 

[240zchevyv8]

I afraid im going to have to agree with you rob, ill never sort it out if i just keep swaping parts, i suspect its either a coil fault or distrubutor fault or both, will book car in tommorow.

 

[grolls]

I know this seems like a cop-out but why not take it for a diagnostic check up? Could be money well spent.

Nope, wont help as engine many years prior to diagnostics...its a work ya way through job... or take it to someone that knows exactly what they doing......

 

[Rob Gaskin]

Grolls I meant diagnostic in the loose sense of the word ie. something like a Crypton/Sun electronic tuner and use results to diagnose the fault.

 

[grolls]

Grolls I meant diagnostic in the loose sense of the word ie. something like a Crypton/Sun electronic tuner and use results to diagnose the fault.

I guessed that, but those machines still only give an out come and a guide, nowt better than to have an understanding and how to check the issue manually.... you may have guesed i have little faith in em.....as an example;

Engine misfire....the machine says its number 4 on pulse.
Ignition shows as ok.
Most ppl assume its a carb fault. (they dont think wider as a general rule)

1, it could be a faulty plug, ie crack.
2, it could be a sticking valve.
3, it could be a hairline leak on the head gasket to air, oil or water.

etc etc etc...


so we back to basics, start from the bottom each time is my view, learn n save a few squids at the same time.....

 

[240zchevyv8]

im afraid i have to agree with what grolls is saying about going back to basics OH AND SAVING MONEY, i spoke to a couple of guys at work about taking my car for a check up, and they both advised against it, they both had seperate engine troubles with modern cars, they ended up spended a lot of money for what turned out to be a simple fix but had no comeback to the supposed experts who spent there money on parts that were not faulty, im going to check the coil first chance i get, cannot do it at 4.30 after work because car is quite loud on tick over so will check it at the weekend, if coil is ok ill fit a new dissy with built in coil only around £100, i cannot think what else it could be everything else is new plugs, leads, carb, will keep you informed

 

[grolls]

if coil is ok ill fit a new dissy with built in coil only around £100, i cannot think what else it could be everything else is new plugs, leads, carb, will keep you informed

I take it the problem was there before fitting new plugs etc?....you can check the coil with a meter, you just need to visably check to coil tower for cracks.

 

[rhanagar]

Out of interest have you had an emissions test done while idling. It might lead to some further clues. Sounds as if your either running rich when at idle or your not getting enough air to mix with the fuel to get a clean burn. You have stated that you turned the fuel down and you lost the smoke ... did you check the plugs after doing this, in other words were they still soaked in petrol. I assume no adverse tapping noises or chatter so can we rule out sticky valves staying open and letting too much fuel in. A long time ago I had a similar issue with an old Yugo of mine that was running on a twin choke weber carb. I found that the idle solenoid was at fault as it was shorting and opening and closing when at idle making the revs jump. Obviously when picking up revs it cancelled it out but the first few rpm were quite rough.

Just a thought (from an amateur who is guessing really)

 

[240zchevyv8]

well i checked the coil tonight, coil is an accel 8140 primary resistance when new 1.2 ohms, mine read 1.6 ohms the secondary resistance was 9000 ohms which is fine, would the 1.6 primary resistance cause the problem im having, isnt it the higher the ohms the weaker the spark, or am i getting confused and only being 0.4 ohms out is nothing, any auto electricians out there know.

 

[grolls]

well i checked the coil tonight, coil is an accel 8140 primary resistance when new 1.2 ohms, mine read 1.6 ohms the secondary resistance was 9000 ohms which is fine, would the 1.6 primary resistance cause the problem im having, isnt it the higher the ohms the weaker the spark, or am i getting confused and only being 0.4 ohms out is nothing, any auto electricians out there know.

It is a little over but I would doubt is would cause such a problem, but bear in mind, its "over the tollerance" check with the supplier what they say it should be max.

 

[240zchevyv8]

Right now sorted, let me explain what was wrong bought new intermotor coil fitted it even worse?? F*&^$£%%G car, must be the dissy ill strip it down to see if its something simple, stripped it down cleaned it all then on the side of the engine module that is in the dissy a bit of writing that cannot be seen when installed, IMPORTANT THIS ARROW MUST POINT TO NUMBER 1 CYLINDER, ah i wonder put engine to top dead centre lined rotor with newly found arrow fitted leads fired engine nothing but accasional pop?? um i wonder if i had the TDC on exhaust instead of firing, whipped of rocker cover yes no wonder turned to TDC firing, checked dissy rotor facing opposite way to arrow, whipped out dissy turned 180 degrees put back together fitted leads turned the key and SWEET FRIGIN MUSIC YES YES YES

 

[rhanagar]

Well done my man. Amazing how simple some things can be. Now all we need is a video of it running

 

[grolls]

Well done my man. Amazing how simple some things can be. Now all we need is a video of it running

Echo that oh and a ride......well done!

 

[240zchevyv8]

once i get the handling sorted it will be comming out to play.