One cylinder with no power

[b0mbtrack]

i have a 5.0 v8 volvo and the 8th cylinder is not firing. It has spark but when i pull the lead out the engine doesn't react at all where as when i pull out all the other plugs for each cylinder the engine gets week. what would cause that one cylinder to do nothing

 

[FreeBeeTony]

Re: One cylinder with no power

Could be lacking compression.........the cylinder won't "contribute" without compression even if it has spark.

I had a similar problem' but only showed up under load at higher RPM's.......

I would suggest a compression test to start.

 

[Haut Medoc]

Re: One cylinder with no power

Are you sure that particular wire is good?....
If so, then I agree with FBT......​

 

[Bt Doctur]

Re: One cylinder with no power

Might be a bad plug
bad dist lobe if a points unit
holed piston(no compression and a lot of blow-by)
valve burnt,tuliped,broken,bent
broken push rod,rocker arm

 

[b0mbtrack]

Re: One cylinder with no power

I will do a compression check first thing tomorrow.
If it turns out ok is there any other common areas i should look for? i will also try a different plug wire. I'm only asking in advance so when it comes time to work on it i don't have to stop looking at it to ask the question.

 

[Bt Doctur]

Re: One cylinder with no power

On the outside chance the head gasket is blown ,remove all the plugs on that bank and check all 4 cylinders,be wary if 2 adjacent cylinders show the same reading.

 

[b0mbtrack]

Re: One cylinder with no power

Here is the compression check, this is a ford engine by the way.
1=135 2=125 3=130 4=145 5=145 6=125 7=135 8=120
Cylinder 8 was the week cylinder but i don't think the compression is all that bad. Maybe a hung valve because the engine did sit for a few months. However it did overheat before it was sitting around for a few months so worse case would probably be the valve was tuliped. Anyone agree?

 

[Haut Medoc]

Re: One cylinder with no power

No, If the valve were tuliped, I think you would have zero compression.....
120 is still a decent#.......
Assuming that the plug wires are correct, you need to verify that the wire & spark plug are good & that you are getting spark all the way.....
You might want to look at the dist cap. for anything unusual.....
The dist cam lobe like BT Doc said.....
If you are positive that you are gettting spark all of the way to the plug & the wires are correct, then it would be time for a leakdown test......
​

 

[Don S]

Re: One cylinder with no power

A quick and easy test is to switch the spark plug with another one next to it and see if the problem changes holes. Do the same with the plug wire.
I've had brand new Champion spark plugs not work, right out of the box. That is why I don't use them anymore.

 

[Bt Doctur]

Re: One cylinder with no power

Knowing it`s a ford motor ,could it be using the wrong firing order?
302 vs 351?

 

[Gary H NC]

Re: One cylinder with no power

I have had new wires be bad also..Don hit that dead on about Champion plugs...AC's are all i use..