Thread: Ignition timing woes. Help please

I must say it is beginning to look a bit like the timing chain skipped a tooth - this would throw out both ignition and valve timing, but ignition timing would be more critical. (Do you know whether the timing chain has ever been off? Just possible it has been out for a long time.)

Also, the crankshaft chainwheel is keyed onto the crankshaft, and it is not impossible that the key has sheared, especially if the nut on the end is loose.

John

John,
I am also suspecting that the timing chain has skipped some teeth. We have not disturbed the timing chain and as far as I know it has not been removed from the engine. I find it odd that the engine just suddenly became difficult to start after a long period of operating perfectly well. The problems all seemed to start when we had the vehicle nose down in the gully. I believe the timing chain tensioner is hydraulically operated and I am wondering if a lack of oil pressure could have caused it to slacken the chain? I will be doing some more diagnostic tests, probably tomorrow, but if it looks like a timing chain problem then I am guessing we will have a lot of work to do.

Regards,
Preso

Mine is spring loaded, on my 902******

whitehillbillies

Yes.
That is what it looks like in the workshop manual. I thought it was hydraulic. Now I am wondering how it could have allowed the chain to slacken enough to lose synchronization?
Regards
Preso

It is hydraulic, but there is a ratchet and spring to stop it going more slack when there is no oil pressure. However, I can see how it could slacked if the ratchet had worn and was not holding. And if you used high rpm with no or little oil pressure due to the nose down bit - well, that is the slack side of the chain, and it would be flapping with an inoperative tensioner and only a fairly light spring, so yes, I can see how it could slip.

John

The slipper ( right ) on this motor I rebuilt, was worn down to the steel. The chain would then wear.
Also one ( bottom one )of the 2 small bolts holding it had let go, and sitting at the bottom of the housing.
If you take the cover off, another small Mod is to drill out the rivits, holding the 'mud cover' that protects the crank seal.
Tap out the holes and put screw in.
If the seal ever needs replacing, the 'Mud cover' can be removed and the seal prised forward and changed.
With the cover riveted, the seal must be changed after removing the cover.

whitehillbilly

Today I worked on my friend's rover. We took out all the spark plugs and set the timing mark on the engine pulley against the prongs on the timing cover. We made sure we had #1 piston at TDC on the compression stroke. We then put the old distributor back (the one with points) and then rotated the distributor back and forward until we got a spark on #1 spark plug. Inexplicably, the distributor was exactly where it should have been and not rotated 30 degrees clockwise as it had been previously. We locked the distributor down and put all the plugs back and lo and behold the engine started and ran well. We replaced the old distributor with the new Accuspark unit and the engine again started and ran well. We checked the timing with a dynamic timing light and found that it is about 10 degrees out when it is running and starting well and any attempt to move the timing mark to where it should be results in the engine slowing and running rough. So, we decided to cut our losses and accept that we weren't likely to get the marks perfectly aligned. The vehicle is not going to be road registered and will only be used off road on the property so it is not ever going to be driving more that a few kilometeres a month so this is no big deal. I cannot explain what had changed and it appears that the timing chain had not slipped a few links as I had suspected.
Thanks to those of you who posted replies. We were growing so desperate that any and all suggestions were gratefully received. However, no sooner were we slapping ourselves on the back than a new issue arose. It appears the alternator is now SNAFU and it has been removed and on the bench for some testing. Oh well; it keeps us off the streets anyway.

Over and out.
Regards,
Preso

You do realise that the timing specification is for static timing (i.e. with neither the centrifugal nor vacuum advance changing the timing)? I would expect the timing to be different if the engine is running as it will be if you check it with a timing light.

John