lost spark in cylinder 1

[matt101590]

NOT to beat a dead horse but ill revive this a bit, its been over a year without a running driving ZR1

IM was tested by MH and came back good, Coils changed, Plugs and wires changed, Injectors are done.

Still nothing from Cylinder 1

anyone have any other suggestions cuz the cars turned into a very large poster sitting in my drive way that i love looking at and sometimes remember driving.

[-=Jeff=-]

How does the crank sensor physically look?

[matt101590]

Fine, nothing staring me in the face as messed with or wrong.

[rkreigh]

so we believe we have good DIS, coils, wires, spark plugs, but still no joy?? So within the electrical system likely we don't have a trigger for the coil to fire on the dead hole. This indeed takes a deeper approach to the "root cause" analysis to determine the source of the problem.


It's really hard to help remotely, can you get the car down to VA or up to Chicago?? I'm thinking that either wiring or something maybe in the ECM has gone south but indeed it takes a very methodical approach and testing to trace this type of problem. Parts swapping can be expensive and frustrating even when they are cheap.


Having lots of LT5 trouble shooting experience and spare parts lying around is a big help to pinpoint the problem. This one sounds like a tough one like a bad pin or wiring harness issue. Bet the old coil is fine too. Most times when they go both sides of the coil fail to spark and you lose 2 cyl. I have seen the corrosion on top of the coil towers get really bad too (*mostly on turbo buicks) which causes a weak spark to that cyl.


You've already tackled the "basics" so grab that Factory Service Manual!!! It's also a great help and has some nice trouble shooting trees. You can also reach out to Gordon K. for remote support.




I'd start with Mark H. and see what he advises as next step if you want to work this yourself. Consider compensating him for his remote trouble shooting time as it will save you several handfuls of hair and scuffed knuckles and is the right thing to do.



All else fails, drag it to a pro to get er dun.




Hope to help u!!!

[wfot]

I just want to go over some basic ideas again.

1) new parts do not mean that they are positively good. I know someone said that already.

2) The spark has to go from one tower thru the wire, jump the plug gap (from the center electrode to the ground electrode), travel thru the block to the other plug, jump the gap (from the ground electrode to the center electrode), thru the other plug wire, back to the other mating tower. this is the complete path that the spark needs to travel.

it fires BOTH plugs every rotation. one on the compression stroke and the other on the exhaust stroke.
knowing this, can you swap the #1 and #6 wires on the towers and see if the spark moves from the #6 plug to the #1 plug? not swapping wires, swapping towers #6 to #1- this will send the spark the opposite direction thru the same path. swapping the towers moves starting point of the spark from #6 to #1,



if #1 fires and #6 dies, this would indicate that the spark travel thru the block is poor/not getting to the other plug. the spark will ground to the nearest possible ground and not completing the whole circuit. for example: sparks starts in tower #6, it travels down the #6 plug wire and sparks the #6 plug, then somewhere that spark ground to the block/something else before it gets to the #1 plug, the #1 plug will never fire and you will have the symptoms you describe. If this is truly happening, swapping towers and sending the #6 spark to the #1 cylinder should spark the #1 plug and kill the #6 spark..... It is a weird scenario but what you have is weird so it might worth a try.

If the above starts firing the #1 and kills the #6, then looks for a bad block ground or a short of a plug wire somewhere along the entire path..

John


If that does not work take the #1 plug out and ensure that there is only ONE washer on the plug, and none down in the hole. if there are 2 washers in there, the grounding is compromised and the escaping cylinder pressure can push the plug wire off the plug as well... = dead cylinder/poor spark. ask me how I know that one...

[XfireZ51]

I didn't see this addressed previously in the thread, but I am assuming you have pulled plug #1 out and tried starting the motor to see if there is spark at the #1 plug. Is that correct? Or how do u know its not firing? Use an old style inductive timing light on #1?

[Subfixer]

Matt, you are not that far from me.
Maybe we can get together some weekend and I can help you sort this problem out.
Paul

[matt101590]

Originally Posted by XfireZ51

I didn't see this addressed previously in the thread, but I am assuming you have pulled plug #1 out and tried starting the motor to see if there is spark at the #1 plug. Is that correct? Or how do u know its not firing? Use an old style inductive timing light on #1?

yes tried to see if there was spark at #1


I really appreciate everyones responses and sharing of knowledge.

I am inching closer and closer hopefully to having a running driving ZR1 again soon