Author Topic: NO power in 2 & 3! Help! 78 550  (Read 1182 times)

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Offline BenjaminoLA

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NO power in 2 & 3! Help! 78 550
« on: October 07, 2018, 11:28:54 am »
Hey team

I have a 78 550 that ive been restoring for the last month!

Sent my carbs out to Mike Nixon and have driven 220 unproblematic miles

then all of a sudden cylinders 2&3 will not fire

Checked spark in all 4 looks good if anything could maybe be inconsistent


What should I be checking to figure this out!

Help meeeee




Offline 754

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Re: NO power in 2 & 3! Help! 78 550
« Reply #1 on: October 07, 2018, 11:40:50 am »
 Has to be ignition problem..
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Offline jgger

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Re: NO power in 2 & 3! Help! 78 550
« Reply #2 on: October 07, 2018, 11:44:40 am »
Points and condenser  are (place brand name here)?
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Offline calj737

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Re: NO power in 2 & 3! Help! 78 550
« Reply #3 on: October 07, 2018, 12:55:04 pm »
+2 on condensers.
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Offline Bankerdanny

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Re: NO power in 2 & 3! Help! 78 550
« Reply #4 on: October 07, 2018, 08:09:51 pm »
The coils fire in pairs 1-4 and 2-3, so as the others have said, if 2-3 aren't working then you have an ignition issue. Before I swapped the coil out I would first check the blue and yellow wires from the points where they plug into the wiring harness under the airbox right at the back of the engine and make sure both are firmly connected (I say both because I don't recall which color is the 2-3 points).
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Offline scottly

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Re: NO power in 2 & 3! Help! 78 550
« Reply #5 on: October 07, 2018, 09:04:15 pm »

Checked spark in all 4 looks good if anything could maybe be inconsistent

What do your spark plugs look like?
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Offline jakec

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Re: NO power in 2 & 3! Help! 78 550
« Reply #6 on: October 07, 2018, 10:30:24 pm »
I just started having this sameness problem on my 400. Spark on all 4 (plugs out) but when I run it it's cold on 2&3. Came out of nowhere after 700 unproblematic miles.
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Offline Don R

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Re: NO power in 2 & 3! Help! 78 550
« Reply #7 on: October 10, 2018, 09:08:53 am »
 Condenser, points, wiring all could cause a weak spark. A spark that will fire in air may not fire in wet compression. A fuel fouled cylinder will also repeatedly wet the spark pug. Maybe just leave the plugs out for a while and try after it's had a chance to dry out.  Good luck and keep us informed.
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Online Deltarider

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Re: NO power in 2 & 3! Help! 78 550
« Reply #8 on: October 10, 2018, 12:26:40 pm »
In case you have the stock ignition setup, I'd first check breakerpoints and condensers. Open the ignition cover. First check if breakerpointgap is still correct and also that the forked connectors at the back of the breakerpoints aren't accidently touching the plate. Breaker 2+3 in particular is prone do this as there's a crosshead dangerously near. Then, with engine running, see if there's excessive arcing at the breakerpoints. A tiny bit of sparking is normal, excessive sparking is not good. Check: 
In this vid left condensor (1+4) is bad, right condensor (2+3) is good. I'd also check plugcaps 2 + 3 and measure their resistance. Should be about 5 kΩ each. What plugs do you run?
« Last Edit: October 10, 2018, 12:48:28 pm by Deltarider »
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