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Do I need to replace my coil?

I have a 1975 2.0 914 w/ carbs. I just recently worked out enough kinks to go for a neighborhood drive! (At 1AM hope the neighbors didn't mind...) I drove it around and it seemed great until about 10-15 mins into the drive the motor died. It wouldn't start for about 3 mins. Then I was able to start it but not start driving. It would die whenever I let the clutch out in 1st regardless of rpm. After about 4 tries at this it just refused to start.

I towed it home and checked for spark, and fuel. The #1 spark plug was covered in soot indicating a rich mixture. Initially it didn't spark but after cleaning the soot off it sparked. I noticed the coil was lukewarm to the touch.

Is there a chance that my coil has a short that comes into play when it heats up? I checked the coil with a multimeter. I am not really sure how to do this but I got 0 ohms from the pos to neg terminal on the coil and 8.08 on the 20k setting of my multimeter when testing from the neg to the center of the coil.

What do these numbers mean? I know there is a spec but I don't know how to translate these numbers to test against that.

Will I need a new coil?

Thanks,

-Levi-
Old 03-28-2014, 12:48 PM
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Testing the coil and the readings depends on the coil. Some coils, like the Bosch blue coil have resistors built in.

There are write-ups on how to test your coil and what readings you should get... I don't remember where I found the write-up I used when I tested mine. It's probably right here on our host's BBS.

It seems like you are running way rich and I would start at the carbs. Turn all your air/fuel mixture screws all the way in gently, then back them out 2 turns but first count the turns it took to close them all the way so you know how far off you were. They should be 1.5 to 2.5 turns out from fully closed as I recall.

The 2 turns out will get you in the ball-park and allow the car to start and stay on. You need to dial them in (probably down) from there.

Good luck.
Old 03-28-2014, 02:50 PM
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The carbs I have are empi 40 and they only have one mixture screw per carb. Will this make any difference?
Old 03-28-2014, 07:10 PM
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Thanks for the advice it fixed my problem! I cleaned the spark plugs and leaned out the mixture. Apparently I had it completly backwards. After that it fired right up better then ever before.
Old 03-28-2014, 09:32 PM
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Normal for these coils to get warm or even hot to the touch. Ohm readings will be higher if the coil is hot when measured. the primary windings are very very low ohms, near zero, the secondary windings are higher resistance. Primary is a fat large diameter wire with few coils loops in it, hence it is short and not very resistive. The secondary coils is of a finer small diameter wire with many many loops in the coil, so it is a long wire, very resistive.

the ratio of coil loops between the primary and secondary determine the spark voltage for a given input voltage.

A primary with 50 loops in the coil, coupled to a secondary with 150,000 loops in its coil give a 1 to 3000 ratio. If 12 volts is supplied to the primary, the secondary will deliver...... 12 volts X 3000 = 36,000 volts.

the conductors do heat up from the internal resistance of the coils (and engine bay temperatures) and that is why the coils do get warm.

Many higher performance coils are filled with a non-conductive oil which circulates around the coil loops, this helps transfer the heat away from the coils to the metal outer can for cooling. other coils are simply filled with a tar like substance, that does not offer as much coiling.

a coil can leak tar or oil, at which point it should be replaced.

Ohm measurements can detect a bad coil, However some coils my ohm out like new when on the bench but still fail in use as heat and thermal expansion can move the coils around causing internal shorts that effectively lower the ratio of coils between primary and secondary, thus giving a lower spark voltage, causing poor performance.

eventually coils do breakdown and may leak or short internally, many times they don't totally fail, they simply degrade in the output voltage, causing running issues.
Old 03-29-2014, 11:29 AM
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Still running rich

I started it again this morning and let it run for awhile until it died yet again. I pulled the plugs and found they were covered in soot so I cleaned them, screwed both air/fuel mixture screws in all the way, and also a screw that I assume to be a fuel mixture screw near the side of the float bowl (picture). Despite these extreme adjustments the car still emits white smoke out of the exhaust when you push on the throttle.

I used a vacuum gauge to adjust the passenger side carb and it read about 15 inches but the driver side carb read less than 5. what could this mean?

Do I need different jets? What should I do?
Old 03-29-2014, 04:33 PM
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Could mean you need a valve adjustment. Could mean the rings on the one side are shot. Could mean vacuum leaks at or around the carb.

I think what you need to do is give yourself a very thorough education on carbs, and specifically on the type of carb you have on the car.

I'm not sure, but I think the Empi carbs might be knock-offs of the old Solex carbs. Try to find a manual for them if you can. And do read up on how carbs work, and what the various bits do.

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Old 03-29-2014, 07:03 PM
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Could it be the carb floats have sunk? That would certainly make the mixture very rich What is your fuel pressure? if not adjusted precisely then the float chamber may over fill, making things rich.

Of course check spark timing and valve adjust, maybe do a compression test too, make sure the basic engine health is good BEFORE proceeding to tune the carbs.

first off with the carbs is assure the fell pressure is correct and the fuel level in the float chambers are correct, adjust with pressure or with float adjustment.

Also make sure things are clean in the carbs and the fuel is filtered. Also make assure that there are no intake leaks, make sure the manifold gaskets seal, and such.

You will want to buy or borrow a carb syncrometer, to balance them.

You will need to set the throttle bar and levers to give the correct even opening of the butterflys, and then balance the flow using the syncrometer. then you adjust. if things are still out of range, then the next size bigger or smaller of jet may be required.

also make sure the air filter is not clogged, that will make the car run rich.
Old 03-30-2014, 04:03 PM
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Have read all replies and noted the answers,the following comments may help;
These carbs are made in China I believe they are a copy of the Kadrons,they have has mixed reviews,some say they aren't even close to being set-up "out of the box" tuning wise,the same has been noted with the Weber IDF copies.
Cabinetmakers comments on fuel pressure are spot on,what pump are you running for instance ? thats important,you may need to run a fuel pressure regulator as it sounds like thats an issue,best to google some forums such as the Samba,com for the correct pressure I don't have experience with the Kadrons on a T4 motor but NO carbs will run properly with excess pressure.
Go to aircoolednet as they have an excellent tech article on how carbs work,this will help you a lot,you can then start over and get the basics sorted.
Your vacuum problem indicates you may have one carb throat open @ idle or an air leak as mentioned.
Is your distributer set up to get vacuum from these carbs or are you running a 009 or 050? on the twin single barrel kits it is recommended to run vacuum from both carbs and a balance tube between the manifolds for a smoother idle.
Tune your engine first as mentioned,cap,rotor and leads( if you don't know how old they are),timing will need to be set for the ignition you are using...valve clearances ? you just have to do that on an aircooled motor
The linkage system used on this conversion takes some setting up and in IMO can be less than ideal compared to the top mounted bar type used on the Weber 34ICT conversions for example.
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Old 04-14-2014, 12:13 PM
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