1971 911T no fire on 1 and 4... head scratcher

[BCBarker]

Hi,

Purchased this 911T from Laneco, long time Pelican member. Car is great and i'm making good progress fixing all the little things, but recently I lost fire on 1 and 4. Decided to start with some maintenance items to ensure it's got strong spark. Did a new 123 Ignition dizzy, Coil, Wires and Plugs. Spark is very strong, but still no fire on 1 & 4. ordered carb kits to dive in and make sure they are clean and in good shape.

On a side note, the dizzy seems to be about 60º off. The old Bosch dizzy was about a plug off from where it was marked cyl 1 and the 123 is also about that much off. TDC on the crank pulley is actually TDC, (confirmed with a bore scope).

Car starts very easily and runs well on 4 cylinders, but i'm not driving it until I figure out why 1 and 4 are dead and fix it.

Any insight as to somewhere to look while I wait for the carb kits to get here?

[BCBarker]

Old Bosch. Orange paint on where TDC is marked on the dizzy. It’s marked on where 5 plugs in. This is how I got the car. I just marked the paint while setting valve clearances:



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[BCBarker]

123 Dizzy is spun to allow me to rotate it as the wire bung hits the fan housing, but it had to be rotated a good 60° to get it to run.



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[BCBarker]

And this is the car:



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[HarryD]

Dumb questions:
1-Are the wires seated on the cap.
2-Have you verified continuity in the wires.
3-If you move the #1 and 3 wires to other positions, do you get a spark?
4-If you move the other wires to the #1 and 3 positions, do they work?
5-If you put a noid (https://www.harborfreight.com/in-line-spark-checker-63590.html) on #1 or #3 does is show a spark?

[RSTarga]

After doing the above, try putting the old distributor on and see if the problem persists.

[RSTarga]

Originally Posted by HarryD

Dumb questions:
1-Are the wires seated on the cap.
2-Have you verified continuity in the wires.
3-If you move the #1 and 3 wires to other positions, do you get a spark?
4-If you move the other wires to the #1 and 3 positions, do they work?
5-If you put a noid (https://www.harborfreight.com/in-line-spark-checker-63590.html) on #1 or #3 does is show a spark?

How do you get that noid down the hole? Isn't it simpler to pull the plug and ground it to see if it fires?

[snbush67]

Quick review; 1 and 4 weren’t firing before you replaced the distributor and they still aren’t firing with the new 123 distributor. Is that correct?

You haven’t said how you have determined the plugs aren’t firing. Have you pulled the plugs? Have you checked spark at the plug?is it getting fuel in the cylinders that aren’t firing?

[HarryD]

Originally Posted by RSTarga

How do you get that noid down the hole? Isn't it simpler to pull the plug and ground it to see if it fires?

You are correct. Yep ways: pull the plug cones t to wire and ground or connect the wire to the Noid and ground the other side (if you do not want to pull the plugs).

[HarryD]

Originally Posted by RSTarga

After doing the above, try putting the old distributor on and see if the problem persists.

I had assumed (perhaps wrongly) the old dizzy was dead and gone. Otherwise, this would be a good test as well.

[snbush67]

Originally Posted by HarryD

I had assumed (perhaps wrongly) the old dizzy was dead and gone. Otherwise, this would be a good test as well.

I assumed the problem of no fire on 1 and 4 is why he replaced the old dizzy with the 123 distributor, new wires, etc.

[BCBarker]

Originally Posted by HarryD

You are correct. Yep ways: pull the plug cones t to wire and ground or connect the wire to the Noid and ground the other side (if you do not want to pull the plugs).

Tried the wires with the plugs I pulled. They were not terrible but I still replaced them to be sure. The old plugs tested with great spark on the new wires. I can’t imagine the new plugs would be bad.


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[BCBarker]

Originally Posted by snbush67

I assumed the problem of no fire on 1 and 4 is why he replaced the old dizzy with the 123 distributor, new wires, etc.

Yep. The old dizzy wasn’t rotating smoothly, so I figured best to replace it as it was close to worn out.


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[BCBarker]

Originally Posted by HarryD

I had assumed (perhaps wrongly) the old dizzy was dead and gone. Otherwise, this would be a good test as well.

I had the problem before the dizzy swap. The dizzy and new coil and wires have made other car run substantially better, but have not solved the dead cylinders on 1 and 4


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[BCBarker]

Originally Posted by snbush67

Quick review; 1 and 4 weren’t firing before you replaced the distributor and they still aren’t firing with the new 123 distributor. Is that correct?

You haven’t said how you have determined the plugs aren’t firing. Have you pulled the plugs? Have you checked spark at the plug?is it getting fuel in the cylinders that aren’t firing?

You are correct. I pulled the wires at the dizzy to confirm the dizzy is sending spark. It is. Then I pulled the wires at the plug and used an old spark plug to confirm the new wires are good. They are. Ive swapped plugs from cylinders that I know fire to the No firing cylinders and still no change. One thing is for sure, I have spark.


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[HarryD]

OK, you have spark.

Are you sure the 1 and 4 wires are not swapped? Check your firing order. Do not ask me why I ask this.

[BCBarker]

Someone removed the sticker, so I sharpie’d it into place so I wouldn’t have to keep looking it up.




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[BCBarker]

Only thing I can think it is now it fuel related.

I will say it was on the back of the transport truck when I got it, hanging at an angle. Then it ran out of gas on the way to get a tank, so maybe some sediment clogged up the back carbs? Do the rear float bowls of Zeniths only feed the back carbs?

Still wrapping my head around Zenith carbs. I’m used to CB350 Four, CB750 and old Ducati carbs with a float bowl for each carb.


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[snbush67]

Probably fuel then. I really can’t tell how you have determined that 1 and 4 aren’t firing?

[BCBarker]

The exhaust for 1 and 4 is stone cold when compared to the rest and I can pull the wires off the cap from 1 and 4 and nothing changes. It also idles like crap. I got 4 to idle for a brief moment tonight while Messing with the carbs. Do the rear float bowls only feed cylinders 1 & 4?


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