Easiest way to determine if car is firing on all 6.....
 

Hi,

What is the easiest way to determine if my car is firing on all 6.....

I am steadily losing power, and backfiring is getting more consistent and frequent, ie: going downhill, on any downshift.......




thanx,

SvK

Listen to it?

Tom

You should be able to hear whether it's running on all six. If it's running too rough to tell, one by one pull the ignition wires off the plugs. Each ignition wire being pulled off will cause the car to idle lower. When you pull one off that doesn't cause the idle to change, you've found your dead cylinder.

Well there are a couple of ways but one is to remove each plug wire one at a time while the engine is running. The engine should be noticably different with each one. If you remove one and have no difference then you may have the culprit.

thanx Rick....

emcon, i'm not sure HOW / what to listen for......

SvK

Ok.......guys

I just pulled ignition wire on each one AND....far left is dead. far right is also dead.....

now what?

SvK

So to make sure that my analysis is right....if during idle I pull ALL except the dead ones...the car should die right?

SvK

new wires, or make damn sure the wires plugged in correctly. you can use a spare spark plug, insert it into what you think is a dead wire and then hold it against a ground. make sure you wear heavy gloves, and start the engine...you should see a spark....if you do, the wire is fine, and its the plug...but I have rarely had a plug go bad...so make sure its seated correctly. BE CAREFULL< and I am not liable...

eh , it might die long before you find the dead one . the engine won't run on 2 cyllinders from 1 side for one thing

you pull #1 , if the idle get's worse
put it back in

proceed to #2
pull it , get's worse ? no
back in

#3 pull it , get's worse ? yes? that one isn't firing.

do continue with #4 5 and six
it might be more than one cyllinder, but probably not more than 2 , that would run really bad..

svandamme........should the idle be reduced by the SAME amount on each plug being pulled, using the above mentioned test?

svK

so....if I'm firing on 4 only........that explains my severe loss of power.......does it also explain my excessive back-firing?

SvK

Check that the tips of the plugs are still attached. One of mine fell off an caused wire to fall off. Then I was running on only 4 cyl. I mentioned this to someone else, and he said it was a common occurance. If this has happened to you; DO NOT REMOVE THE PLUG without retrieving the tip - too easy to slip into the cylender.

Yes, the backfiring would be explained by the non-firing cyl. The gas is dumped into the cyl and never ignites, rather igniting when it's squeezed out in the exhaust system.

VaSteve,

thanx ;-)

more or less, but at idle revs, it's hard to tell

yes that would explain backfiring
the cyllinders are sucking fuel from the carb
but it's not burning

that fuel goes in the exhaust unburned
and the output from the firing cyllinders will ignite it..

OK,

So since I have 2 dead cylinders, as opposed to just 1 dead cylinder.....what does that tell me as to what the cause is?

what i mean is, chances of 2 cylinders going dead at the same time are pretty slim, right?

SvK

You can also check for a cold header pipe off the head. You can do this various ways using fluid, infared laser and temperature crayons.

Pick up a sparkplug tester that simply goes between the distributor cap/spark plug and the wire. You can start it up and see if their is spark. This helps reduce the chance of getting shocked and is easy to spot while the engine should be running smooth.

If you need to comfirm the cylinder is dead, then remove the suspect plug and look at it. It should be obvious if its not firing.

you'de be surprised

bad wires
bad plugs
bad dizzy cap , may be dirty or something

check in that order

pull the bad ones
put a new, good plug in the boot , and hold it against a ground on your car
then check for spark

that tells you if you got current up to the wire

if you do ,then it's your plugs, or the little plug cap missing or something

if you don't
put another wire on the dizzy, check again


one more thing

2 cyllinders, you sure you haven't switched 2 wires on the dizzy??? do check

svandamme...all of you....you are all being very helpful....

checking Dizzy Cap 1st (since 2 cable/plugs going at same time is unlikely)

AND car is starting up.......so the olny thing between that is the Dizzy...RIght?

SOmeone tell me procedure for checking Dizzy, please...(thanx, this is the first time, I'm doing something my self).......

Oh .......is the dizzy cap easy to purchase? Not pep-boys thing is it.

SvK

the dizzy cap is cheap as piss, just don't skip any of te steps
do check the wires with a new plug externally ( just hold it against a ground , you'll see the spark , it's pretty easy to spot, at worst you get zapped, unless you have pacemaker, it's shocking not harmfull :)



might not need to replace the dizzy, just clean the contacts inside

No you have to get cap from someone with porsche parts.
Dealers carry them if you need to get it locally. Our host has them as well.

When you remove the cap, first look at the rotor button.

You will see where the top of it makes contact with the cap.

YOu should be able to see whether there is wear on the cap and the rotor.

If you replace one, you should go ahead and get the other at the same time.

OK....looked inside the cap.........the contact points at the top look black....how do I clean them? (rexpose the copper)

need shopping list.

SvK

Look at the center post inside the cap to see how far down it is worn. If not making proper contact with the rotor cleaning it will not help.

Also check the copper on top of the rotor. Make sure it is not worn thru.

These may or may not be causing your problem but they are not expensive and should probably be replaced anyway.

what grade sand-paper / file do I buy...

anyone?

SvK

dude, just scrap the dirt of the contacts, wirebrush or some metal sponge(you know , the kitching thing for old pots an pans) will do
if it doesn't help like that , buy another cap :D
it's 12 bucks or something

ok....when pulling / and replacing the 6 individual cables......the idle is NOT reduced by the same amount. In fact it varies wildly, depending on which ignition cable i pull....

What does that tell me?

SvK

the one with the most change is running the best
the one with the least change is not running at all or marginally

start troubleshooting on the latter

wire , plugs , ...

Stijn,

Thanx for your patience, and advice ;-)

I don't know if you know this, but TRE motorsports, just overhauled my car. They put a 3.0 in her and used my Weber's instead of CIS....All my spark-plugs are new and my Carbs were rebuilt by Dave @ TRE.

When I picked her up from TRE, she was hell on wheels, for about a week......now she sounds like a Tractor and has no power. Anyhow, I'm whining. Monday she goes straight back to TRE......



SvK

2 of these

http://www.marianitu.net/images/westmalle_triple.jpg

i'm mellow and patient as can be...
i'll try Westmalle Triple next time i'm troubleshooting mine.. i'm never patient enough when messing around with my own engine

I confirm spark plugs were ok to start with. New NGK BP5ES is a good hot plug for tuning carbs, etc. Flip them out later if they're to hot for your normal operation.

carbs will foul plugs very easily and the eyeball can easily be fooled. It's difficult to compare to a CIS as the carbs run rich at low rpms which may be disturbing the fuel mix big time.

I'm with RoninLB. You said "steadily losing power" and "switched to webers" in the same post. I'd check to see if your plugs are gradually fouling. As RoninLB said, try a nice hot plug like a B6-ES or even a B5-ES. I think a lot of people underestimate the importance of proper plugs. I know I did.


JA

Search the forum for weber*. You have yourself some plugged idle jets or sumthin'., I'm willing to wager your problems are not electrical.

Exactly..


if it misses w/new hot plugs use air to clean everything. Measure the idle screw turns before pulling them so you can replace same.

or your current turns could have caused this situation or have been a contributing factor.

Use an infared laser temp guage on each exhaust outlet... The cold one isn't firing. :)

Exactly

especially with carbs due to the low EGT's on a cold engine. If the carbs aren't right etc the plugs may never clean up with later proper operation. It don't take much to foul plugs.

I dialled in the idle circuit on my webers WAY too rich once during one of my first "attempts" to tune them. One or more of the plugs foulled realyl badly and this manifested as a distinct miss which went away when I got on the loud pedal. Once I leaned the carbs out the the plugs cleaned themselves up just fine. I had many miles of happy motoring on those same plugs after that.

If the carbs are in good shape (ie no plugged jets or passages), then 2 - 3 full turns out from dead bottom on each idle screw should be good enough to have the car run relatively straight. There's a bit more to it to set them up for real, but that's a good baseline I've found.

I also had to pull my idle jets one day because of a really bad miss. Turns out there was a piece of o-ring stuck in one of them. Many years later I had a power loss under load, and I found more o-ring in one of the main air jets and in an emulsion tube. The only o-rings on the car live on the idle mixture screws, so I took them all out and I'm having the smoothest idle I've ever had. The moral? - ou don't need o-rings to seal the idle mixture screws.

Good luck.

great story

Do you own a multimeter? Use the ohms function to test each end of each lead. Easier yet, fire it up, pull a plug wire (either end_ and touch it to ground it should zap with a fat blue spark repeatedly, if not, its a bad plug wire. Engines backfire especially on decelleration because the unburned fuel was too rich and it leans out into the combustible range as it hits the exhaust pipe and more oxygen is available to bring the mixture back into the explosive range.