AussieVette

Ok I finally got a chance to have a look at the Corvette last night after yesterdays mini-disaster try to take the car for it's annual inspection. After limping the car home on 7 cyl's I was hoping for a quick and easy fix to get that 8th one firing again (of which I don't know which is the problem).

First thing I did last night was pull out all the spark plugs and inspect them, and they all seemed ok. I then made sure that all the spark plugs leads where on firmly, and after 3 more starting attempts the car is still running on only 7cyl's.

What should I be looking for now? I was thinking of testing the spark by pulling out one spark plug at a time, reconnectiong the plug lead to it, holding it against the block and turn the car over so I can see if it is actually sparking. Then do this for all 8. Is this a good idea?

If all goes well there, I guess I'm going to have to remove the valve covers to check and see if it's a problem of fuel not getting inside the head. Perhaps a sticking valve, or a push rod giving me problems?

I really want to solve this problem over this coming weekend so I can go for my annual inspection next week. I kind of have the pressure of time on me here...

Any advice appreciated.

jerryp58

Checking for spark at each plug wire is a good idea, but personally, I wouldn't hold the boot with my fingers. I've gotten hit with the spark going through those wires before and didn't like it :eek:

How have you narrowed it down to being a cylinder? Could it be something else like a loose distributor?

AussieVette

Jerry, so you can still get a very uncomfortable kick or shock even though you're holding the insulated boot? I might try holding it with a pair of pliers then for a little more protection.

I have heard the car run on 7cyl before after changing plugs one time and not connecting one of the leads properly. It currently sounds exactly like that again.

79 vette

Probably a bad sparkplug wire To check, with the engine off disconnect all the sparkplug wires from top of the distributor(pull the wire off one by one but leave them conected loosely to the disributor)after all wires are siting on top of the distributor loosely u can start the car and with a pair of insulated pliers u can disconnect and connect one wire at a time.As you are doing this u should notice a difference in the motor everytime u disconnect and connect a spark plug wire from the distributor.When u disconnect a wire and notice no change in your motor u now know that the problem is in that wire,plug,or cylinder.It will be a little easier if u have one of your trust worthy friends to put a slight load on the engine while u r doing this.I have an automatic so I would have one of my friends put it in reverse and with one foot on the brake and the other on the gas steadily hold the rpm around 1000 so it would be easier for me to notice the change in the motor when I disconnected and connected a wire.With a manual I would have a friend put on the emergency brake put it in reverse give it a little gas and slightly ease off the clutch but not entirely just to put a slight load on the motor.If u need more help u can e-mail me

dath

What 79 said would likely work (and probably is most likely to show you which cylinder isn't firing correctly), but I don't think I would have someone "put a load" on the engine if you have a manual. You're going to smoke your clutch and run the risk of them accidently letting out too far and... Loading is a good idea, I'd just not try it with a manual is all. Just me though.

-dath

LAvetteman

I would check each wire with an ohm meter.

ddecart

I've done more or less what '79 described. GO cylinder by cylinder pulling wires at the cap until you find one that has no effect on the engine rpm. Then you have your culprit.

Once you find the guilty cylinder, the fun is only beginning. Start with a plug outside the cylinder, frounded against the block to see if it sparks. If it does, then we're talkin mechanical issues and possibly a broken spring or the like.

Dave

AussieVette

Thanks for all the suggestions guys, although I haven't had a chance to try them yet as I need an extra pair of hands and the wife didn't get home from her 14 hour day until quite late last night.

I did however get hold of a multimeter and was able to test all the spark plug leads and the spark plugs themselves, all 8 tested ok. This was a bit disappointing as I was hoping it would be as easy as a bad lead. I will on the weekend try the idea of connecting up the plugs outside of the cylinder touching up against the block to watch them spark. Hopefully I'll find one that doesn't.

If I am getting spark to all cylinders what kind of mechanic fault could I possibly have? Broken spring, bend push rod, problems with the lifter? I guess the next step will be to pull the valve covers for a visual inspection.

I really hope I can figure this one out this weekend, I'm now down to about 20 days before my rego runs out and I have to present the car for inspection. I guess these things are may to try us :crazy:

427V8

If one cly is truely not fireing the header primary should be cold.
If it's not cold then it's just not fireing well!

If you have an inductive timing light clip the light to each wire and watch the flash pattern on your hand or something. If it's ignition based you'll see the light flash in time with the miss...( or not flash at all

LAvetteman

Time for a compression test. :confused: