NO SPARK AT #1 an 7 plug, engine will not start

[redz]

Hi, my name is David, my boat is a Thompson Daytona 250. Engine ser:# oc536754, model mcm 5.7 litre ,V8 Alpha one
thunderbolt ignition

things I have done thus for, which are; check tachometer lead, check terminal connection at distributor. new ignition sensor, an distributor cap, new ignition coil, new battery ,new spark plugs, also a new ignition module.
please help will not start, will turn over but no spark at one an seven plug. use spark plug tester an volt tester, have 12v at coil, at battery , 12v going to ignition module thanks any help out there

 

[thumpar]

Re: NO SPARK AT #1 an 7 plug, engine will not start

Even with 2 cylinders down it should start but not run great. Have you checked firing order and tested spark at the plug?

 

[Bondo]

Re: NO SPARK AT #1 an 7 plug, engine will not start

Ayuh,.... Welcome Aboard,... Is it gettin' any Gas,..??

 

[Bt Doctur]

Re: NO SPARK AT #1 an 7 plug, engine will not start

How experianced are you with the GM motor?
Was it running before all the work?
Could you have put a 6 cyl rotor plate in instead of a v8 one?
If you have spark on the other 6 leads and no spark on only 2 of then ,then check the spasrkplug wires
by swapping with a sparking cylinder.

 

[tazrig]

Re: NO SPARK AT #1 an 7 plug, engine will not start

Try switching 2 spark plug wires that you know are good, if you still aren't getting a spark on just those two then change your spark plug wires. Or you could have a cracked distributor cap... rare but I've seen them be bad right out of the box.

 

[NHGuy]

Re: NO SPARK AT #1 an 7 plug, engine will not start

Yes, swap the bad wires with known good. It does sound as if the wires are failed. BTW marine wires are longer that regular chevy ones. So if you find they are bad, or even if they are a bit old and brittle, get a set that's for your exact engine.
Then, for good measure, route them so they do not make contact with one another using ignition wire separators which are available at your auto parts store.
This eliminates cross firing and assures each pulse goes only to the right plug.

 

[Scott Danforth]

Re: NO SPARK AT #1 an 7 plug, engine will not start

welcome aboard

in your list you never mentioned wires. did you replace the wires?

even on 4 cylinders, a V8 will run. so if your not getting spark on only 2 wires, it should still fire.

how strong is the spark?

as Bondo asked, are you getting fuel?
what is your compression?

 

[redz]

Re: NO SPARK AT #1 an 7 plug, engine will not start

sorry I also replace all plug wires

 

[redz]

Re: NO SPARK AT #1 an 7 plug, engine will not start

yes getting gas

 

[redz]

Re: NO SPARK AT #1 an 7 plug, engine will not start

sparks are blue,purple

 

[MikDee]

Re: NO SPARK AT #1 an 7 plug, engine will not start

Is it possible you're talking about cylinders #1, & #6, they are the opposing cylinders on the small block chevy, both being on TDC at the same time, with the cam, & distributor determining which one fires when. So, has the distributor been out of this engine, and put back in the wrong spot? Out of phase, then when it's supposed to be firing on #1, it will actually be firing on #6, and if is supposed to be firing on #6, it's actually firing on #1, appearing as though there's no spark on #1, & #6, when actually it's firing on the alternate cylinder.

 

[NHGuy]

Re: NO SPARK AT #1 an 7 plug, engine will not start

Yup, good chance of MikDee having a finger on the issue. So recheck that #1 is firing when the #1 valves are closed on the compression stroke.

 

[Bt Doctur]

Re: NO SPARK AT #1 an 7 plug, engine will not start

spark will occur no matter what the valves are doing.

 

[MikDee]

Re: NO SPARK AT #1 an 7 plug, engine will not start

spark will occur no matter what the valves are doing.

Not if the distributor is in 1/2 a turn off, you'd get no spark at #1 at TDC, and have spark at #6. The next engine revolution, you'd have spark at TDC on #1, and no spark at #6. This would be out of phase/time with the camshaft, if someone put the distributor in wrong.

 

[Bt Doctur]

Re: NO SPARK AT #1 an 7 plug, engine will not start

No matter how you install a dist , you will have spark produced every time the points open or the cutout passes past the sensor. Says only #1 and #7 don't have spark. He never got back to answer the trigger wheel question either.
Plus he`s never responded to what work he had already done on the motor.

 

[thumpar]

Re: NO SPARK AT #1 an 7 plug, engine will not start

Not if the distributor is in 1/2 a turn off, you'd get no spark at #1 at TDC, and have spark at #6. The next engine revolution, you'd have spark at TDC on #1, and no spark at #6. This would be out of phase/time with the camshaft, if someone put the distributor in wrong.

It may not fire but it still would have spark.