One cylinder is gone

[Cuno]

Hi, i have a problem with my R4 - the 2nd cylinder is dead. There seems to be ignition, and the spark plug looks like the ones in the other cylinders. Still no power. I can disconnect the spark plug and nothing happens, the engine still rattles on regardless if it's connected or not. I have no compression meter, i think i'll buy one next week. Is this a typical case of burned valve guides? Will low a compression reading proof that?

Also, there's collecting brass filings inside the distributor, so i have a hope that it's a case of unbalanced centrifugal regulator (thanks Clementine for giving me that to hope for I read about it in your Florence story). Could that be the case? The engine is pretty weak, especially on low revs.

Any ideas?

 

[Steve Hennessey]

Hello Cuno,

Use the 'poor man's compression tester' - your thumb or finger!! Remove all the plugs, remove the distributor cap and leads (note where the leads go), disconnect the coil + or - wire. Disconnect the wire going to the starter solenoid (the small wire).

Connect a piece of wire into the wire that goes to the solenoid. If you touch the other end onto the + battery connection, the starter will operate. Place a brick or something similar to hold the accelerator pedal open. Place your finger or thumb over each plug hole whilst operating the starter for 3 seconds. You will then be able to guage how No 2 cylinder feels in relation to the other 3 cylinders.

If there is a significant difference, remove the rocker cover to check the valve clearances on No 2 cylinder. If they are OK then you'll need to remove the head and do a top end overhaul.

If there is plenty of compression on No 2, it could be a faulty plug or lead. Re-connect the coil wire, replace the distributor cap and put the original No 2 plug in the correct lead, lay the plug on the engine so it earths, turn on the ignition and operate the starter. See if the plug sparks. If not, substitute with another plug. If that sparks you have your answer. If not, it could be the No 2 lead or a cracked distributor cap.

Brass filings in the distributor often mean that the top bearing in the distributor body is worn causing the rotor arm to rub on the contacts in the cap. Just wiggle the shaft to check for any play. If it is bad, you'll need another distributor or see if you can get it overhauled.

Let us know how you get on.

Steve

 

[Chris H]

easy way to see if its a lead is to swap the leads over. if it moves cylinder leads duff.

Open the bonnet with it runnign at night, if you see any blue sparks from the leads/plugs then replace them.

Might be top end might be the bottom end. Chances are if its running ok then the top ends probably burnt a valve. May have some seat damage, should be able to get it recut if its not to bad.

 

[Cuno]

Thanks guys!

I'll try the manual compression test Hopefully my girlfriend can assist me so i don't have to do the rewiring. The leads are new, sorry should have mentioned that. I just assumed that it was a faulty lead, and since they all looked ugly i changed them all. And the spark plugs. So i guess it's the valve.

So i'm looking at either engine overhaul or finding a replacement engine. It's the 782 cc engine (R1126), so i wouldn't mind getting at least the big block 845 cc in there The engine has had a hard life, it's in constant need of attention and the crank shaft bearings don't sound too nice, etc.

Thanks for tip on the distributor bearing. I'll fix that pronto, and hope that the engine lasts through the winter at that. Maybe i'll look at the valve too, it sure would be nice to get all cylinders in there.

 

[Cuno]

Ok, i bought a compression tester. All cylinders checked out ok, although #4 was a little lower. I switched ignition lead, spark plugs, and adjusted the valve clearances. No change (ok, some change - the clicking of the valves disappeared). There's ignition on the 2nd cyl. The ignition timing is correct and everything. I'm baffled...

Could it be that the distributor bearings are so worn down that the timing on the 2nd is way off? Maybe together with an imbalance that pulls the rotor away from the distributor for the 2nd cyl, maybe making the ignition weaker?

The sparks are pretty weak, but they are the same on all cylinders. So it seems there should be at least some life in the 2nd.

I'll continue tomorrow, and i'll keep you posted!

 

[Steve Hennessey]

I hope you did the test with the acclerator fully open. If there is a 10% difference between the cylinders, that's OK.

Logically, you have a spark, you have compression. Have you checked the points gap? If one of the lobes on the distributor cam is worn, the points won't fully open (a long shot). Next thing is fuel. Check for a leaking manifold gasket. If the gasket is split on No 2 port, it will suck plenty of air in and give the symptoms previously described. Dribble some oil/WD40 etc around the manifold gasket and see if it get sucked in. The engine may falter as well. Similarly, dribble some oil around the carb to manifold joint for good measure and observe.

Steve

 

[Cuno]

Thanks for your reply Steve!

The points gap is ok, and the lobes on the distributor cam looks ok. The only things i haven't switched in the ignition line is the capacitor and the ignition coil. So all that should be ok. I have a new capacitor, so i'll install that tomorrow. Just to be sure...

You're probably right about the gasket. There is a sucking noise on idle, i assumed it came from the carb using some other port on idle. I'll take the car to a french car parts dealer tomorrow - he is a real R4 enthusiast, so he should hear what kind of noise it is. Hopefully he has got a new gasket and rotor bearings.

Edit: Couldn't worn rotor bearings/imbalance in centrifugal regulator have the same effect as a worn cam lobe? I would guess so. Oh well, we'll see tomorrow.

 

[Cuno]

Solved! Your guess was right Steve, it was the manifold gasket. Apparently that is a standard issue. I learned something today

Thanks again Steve and Chris

 

[Steve Hennessey]

Glad it's sorted now. It's great to hear that a problem has been solved as a result of long distance diagnosing.
I first came across this same problem on a Fiat 124 way back in 1977, but it's one of those things you don't forget.

Steve