Dead#4 cyl on my L18

[paul rodriguez]

Greetings, I'm new to the forum so please bare with me . Today I noticed my 620 was running like S*#t . I checked the plug wires and saw that they were firing as they should. Then I pulled the valve cover off and noticed the small round seat that is on top of the valve had come off. I put it back on .still dead in #4. After that I thought the plug maybe fouled out so I replaced it .Still no luck. Any Ideas? Thanks!:

[Cuts metal like mad]

Had a bad injector in the wires car for a year... Replaced the injector still no go, checked the spark plug that was really bad, still no go... Took the car out for a hard romp and she started smoking real bad but firing on and off kept running it hard for a few miles and the smoke went away but still firing off and on... Told the wife to just drive it for a week to "clear it out" to see if it improves and it did, runs great now.

 

So carbon build up is a likely issue... Though it could be a worst case scenario... Good luck!

[datzenmike]

Greetings, I'm new to the forum so please bare with me . Today I noticed my 620 was running like S*#t . I checked the plug wires and saw that they were firing as they should. Then I pulled the valve cover off and noticed the small round seat that is on top of the valve had come off. I put it back on .still dead in #4. After that I thought the plug maybe fouled out so I replaced it .Still no luck. Any Ideas? Thanks!:

 

Did you check the rest of the valves for clearances? The clearance may have been loose for it to get away like that.

 

Stick an old plug in the plug wire and crank it over to check the spark. Try swapping the plug wire and see if the problem moves. Inspect the cap around the #4 wire inside and out.

 

If it looks like it has normal spark and both valves have clearance, do a compression check on that cylinder to check for a blown gasket.

[240ADAM]

If your valve clearance is too tight then the valves wont close and thus no compression. Stick your feeler gauge in there and see if there is correct clearance, intake .008 cold/.010 hot. exhaust .010cold/.012 hot. Good Luck!

[banzai510(hainz)]

Paul,

look like 240Adam has it right.

The lash pad(cap) fell out.

you need to reinstall and adjust the lash so it closes fully, otherwise the mixture just blows out in the exhaust and doesnt give you that bang your looking for.

 

More or less rotate the cam till the lobe points up. then get a 17mm and 14mm open end wrench and loosen the 17mm jam nut then adjust the 14mm POST up down till you get a feeler gauge up in there.then while feller gauge is still in there tighten the 17mm jam nut so it locks it. that should hopefully do it.

 

what I do( QUICK CK) is when I loose a cylinder is rotate the cam till the lobes points up, and you should be able to wiggle the roacker arm, than means you know the rocker is not pushing on the valve and is CLOSED all the way. then go to the next one pointing up till you got all of them. then if ones tight adjust that one and go on from there

[a.d._510_n_ok]

Had a bad injector in the wires car for a year... Replaced the injector still no go, checked the spark plug that was really bad, still no go... Took the car out for a hard romp and she started smoking real bad but firing on and off kept running it hard for a few miles and the smoke went away but still firing off and on... Told the wife to just drive it for a week to "clear it out" to see if it improves and it did, runs great now.

 

So carbon build up is a likely issue... Though it could be a worst case scenario... Good luck!

 

That's why I love reading the posts here.

 

I bought my '80 in September of this year and, after chasing down multiple vacuum leaks and changing the fuel filter, it's four banger ran like a little champ for several weeks.

 

One afternoon however two cylinders just flat freakin' quit. I called a bud who is a super mechanic and he told me to bring it out. I was about thirty five miles away from him and had to damned near floor the thing to get 40mph.

 

About twenty miles into the deal it started to run a bit better and by the time I pulled into his yard both cylinders had come back to life and it was running like a brand new one.

 

Now I add a bottle of Marvel Mystery Oil to every fill up and haven't had any trouble since.