out of ideas 76 124 spider 1800

[RAD]

I'm a new and third owner of a 1976 124 spider 1800, the last owner had it for 10 months and did a lot of stuff too it but still couldn't get it running right. right now it runs like a three legged dog. it runs like number 3 cylinder is not firing and no vacuum (5#). what I have done is check ignition timing check the dwell check the valve timing the belt looks new and corrected valve clearance, check compression all cylinders had 150 pounds each. having low vacuum just for fun I replace the intake manifold gasket. the last owners had the exhaust valve clearance way to tight. it has new plugs new plug wires cap rotor points and condenser. while it running pull plug wires to find a one doesn't making a difference that would be number 3. last weekend I thought I had it figured out by having a shared key on the crankshaft or cam they where fine. Can I have a burnt valve with good compression? what to do next?

[chrisfiat]

swap plugs from #3 and another cylinder, this will tell you if you have a bad plug
then swap wires, check the cap and rotor
check for vacuum leaks around the carb base, the intake manifold and all vac lines and vac ports. do this with an aerosol can of choke/carb cleaner ,
re check compression to be are you sure did you do a dry/wet test ?
how about a cylinder leak down test

report back

[RAD]

the plugs and plug wires swap I've done problem stayed with number 3, vacuum leak check I've done had everything dripping wet didn't find anything, check the brake booster no problem check the hose for the brake booster no problem. compression check was done dry with throttle wide open, have not done the leak down yet i can do it this weekend. I made a device to do this years ago now if I can find it. how much leakage is tolerable?

[So Cal Mark]

remove the cam covers and inspect the lobes on #3

[MrJD]

remove the cam covers and inspect the lobes on #3

i was thinking the same thing. if you have spark, compression, and fuel... gotta be a cam issue. If someone runs the wrong weird oil --> problems.

Oh, and I'd tripple check the timing... and even that the spark plug wires are in the right orientation.

[RAD]

when I adjusted the valve clearance I didn't notice anything wrong with the lobes but I was concentrating on valve clearance. I do believe one of my manuals have dimensions on the cam. the previous owners messed with exhaust valve clearance and adjusted down to .005 on # 1 and #4 was at .010 the other two was off but not as bad I adjusted them all to .019. that's why I'm worried about a burnt valve. the speedometer shows 81,000 but its pretty good chance 181,000. tonight I'll check the lobe dimensions and compare them to my manual.

[majicwrench]

Save your time, if you want to check cam lobes just look at them, you will see if they are wiped out. And I really doubt is that is your issue, esp since you have been in there adjusting valve clearance.
If you have good compression you do not have a burnt valve.

[131]

Have you tried another distributor cap, from reading through your posts you've tried everything except that? Or at least measure the resistances through the cap with a multi-meter. Are you getting spark at the plug on No 3?

[RAD]

I had not replaced the distributor cap because the previous owners had it replaced and while checking plug wires it was obviously firing on all including number 3. I also have a new coil. Next I may have to pull the head. not looking forward to that running out of options.

[RAD]

I had not replaced the distributor cap because the previous owners had it replaced and while checking plug wires it was obviously firing on all including number 3. I also have a new coil. Next I may have to pull the head. not looking forward to that running out of options.

[majicwrench]

Why would you pull the head???????? if cylinder has compression no reason to pull head. You are missing something. Does #3 have a vacuum port on it's intake runner??

[So Cal Mark]

It would be odd for the owner to set only two valves at a much tighter clearance. You may have a valve that is pounded into the seat. Despite magicwench's clairvoyance, I'd inspect the cams first. It only takes a few minutes to get the covers off

[seabeelt]

I would go back to step one. Are you relying on the fact that the previous owner told you he "did a tune up" and replaced plugs, wires, cap and rotor, or have you done these things yourself. Based upon the valve tolerances you found I am skeptical as to what else was done and in what quality fashion. I'm kinda slow sometimes, but IF you have good compression, that would seem to rule out valve seal in the seats and piston rings ( at 150 psi). So the symptom is that number three seems to lack power or indicate a malfunction. Pull all of the plugs and look at the color. Replace plugs except #3, ground plug and check for spark at #3. No spark, swap plug or replace, check again. Still no spark, swap wire or replace, still no spark, replace cap and rotor,. Out of curiosity, what do the lobes on the distributor look like, all four the same? Eliminate the spark problem first. How about the intake, could the tube to number three be plugged, did you look at it when you had the manifold off to replace the gasket? You indicate that there are no vacuum leaks and that all gaskets are tight but How about the manifold itself? Any cracks or open port holes? Top or bottom? How are the wire connections in the dizzy? All clean and tight and no shorts anywhere?
Process of elimination of all of the small basic stuff first.

Are the cams and timing marks where they are supposed to be with respect to the timing marks, what about overall timing. Number 4 at TDC and crank pully aligned with the belt cover mark? Cams still indicating correct position with respect to the timing marks? Do you have the correct cam pulleys one with the lip on the inside and one with the lip on the outside ( I forget which is which with respect to intake and exhaust, but you should have one of each and both should be of the same material (metal)) not mis matched I hope.

After that I would consider cams, pistons, rings, head gasket and so forth, but if your compression numbers are accurate, I would be skeptical that you difficulties lie in this area. I'm no expert, nor do I claim to have the years of experience of a lot of the good folks here. Just trying to sort through the symptoms with some sort of logic.
R/

[majicwrench]

I always tell people I'm a Magician not a Fortune teller.

Lots of things just take a minute, sure look at the cams if you want, don't bother measuring them. When I see engines w bad lobes, they always take some metal off the lifter/shim as well, so when you go to check clearance it is too big. If you have already check clearance, and none of them were excessive, odds of cam issue very slim.

I do this for a living, and can't afford to waste too many minutes chasing guesses.

Dang, I just wasted a couple writing this!!!! Back to work I go..........

Keith

[racydave]

Everyone has a lot of good ideas and intentions. Here's mine. Get her good and hot. Get #3 on TDC with the valves closed. Take rad cap off. Put compressed air in the cyl and see where it comes from, exhaust, intake or cooling system. I have seen vaccum leaks make one cyl dead, but you have done your homework. I did not read everything, but you have confirmed a spark yes? A bad head gasket could have good compression. Make sure you don't have a broken valve spring too.