Timing jumped a tooth?

BrenG · Post by **BrenG** » Fri Jul 06, 2012 1:58 pm

I posted a thread in the electrical section regarding non start on my SD1 VDP EFi- - suffice to say it still is'nt going.

I spoke with somebody who has experience with these engines, he explained that a combination of a slack timing chain and a back fire may cause the chain to jump on the sprockets - he said he has personal experience of this. Obviously you then have a situation where the engine will not run.

So I will take a look inside the front cover at some point over the weekend to see if anything has moved. Has anybody else had experience of this?

As an aside, the engine has 107k on the clock but was very sweet, quiet with good oil pressure.However, if I am opening it up I was thinking of replacing the timing gear anyway, but then you think while it is open should I consider a new cam / lifters / valve springs?

It actually crossed my mind that maybe I should break it for spares, however I have done so much welding on it it would be a shame to strip it then send it over the bridge.

Any advice and opinions, as always, are appreciated.

topcatcustom · Post by **topcatcustom** » Fri Jul 06, 2012 2:33 pm

Replacing the timing set wouldn't be a bad idea, even for a simplex set (single chain) as the originals become so slack they let the timing out anyway.

If it's the original cam then it's probably due a change, but as you said when you start doing that then where do you stop and it can become economically non-viable!

At least you can do the timing set change easily, replacing cam means an 80% strip down of the whole engine, maybe do the timing and see how it runs.

DaveEFI · Post by **DaveEFI** » Fri Jul 06, 2012 3:29 pm

Very unlikely it has jumped a tooth especially at such low mileage. And even if it had, it would still start. If it jumped more than a tooth or two, the valves would hit the pistons...

Depending on use and servicing, the cam could be worn at this sort of mileage. But won't suddenly have stopped it running.

richardpope50 · Post by **richardpope50** » Fri Jul 06, 2012 5:26 pm

My Pinto engine did just that. I was in M25 traffic and the engine got hot then a big backfire. Engine started again but lack of power above 3,000rpm. I changed all electrics and it took me about a year to find the problem. OK, Pinto is a rubber timing belt but ...

DaveEFI · Post by **DaveEFI** » Fri Jul 06, 2012 5:40 pm

It's also an OHC, so a long belt. The SD1 chain is as short as they come. It would also IHMO maker a lot of noise if so worn it could jump a tooth.

harvey · Post by **harvey** » Fri Jul 06, 2012 6:26 pm

DaveEFI wrote:It's also an OHC, so a long belt. The SD1 chain is as short as they come. It would also IHMO maker a lot of noise if so worn it could jump a tooth.

I've had Rover V8's jump one or two teeth and keep running (badly, but better after a timing adjustment) and I've had them jump mulitple teeth and bend the valves. (Zero compression on 5 out of 8 on the last one....) Not noticably noisy beforehand on the last one either, well according to the owner anyway.

JSF55 · Post by **JSF55** » Fri Jul 06, 2012 7:43 pm

Would this engine have the old type nylon ? timing wheel ? it's possible for them too jump !

mgbv8 · Post by **mgbv8** » Fri Jul 06, 2012 8:38 pm

The nylon cog can possibly jump a tooth. But also a knacked dissy drive can jump a tooth ??

DaveEFI · Post by **DaveEFI** » Fri Jul 06, 2012 9:50 pm

No need to strip things down - it it has jumped a tooth the ignition timing will have shifted too - so check with a timing light.

JP. · Post by **JP.** » Sat Jul 07, 2012 6:35 am

DaveEFI wrote:No need to strip things down - it it has jumped a tooth the ignition timing will have shifted too - so check with a timing light.

BrenG wrote:I posted a thread in the electrical section regarding non start on my SD1 VDP EFi- - suffice to say it still is'nt going.
.

Please Dave, explaine how to do so on a non runner.....

DaveEFI · Post by **DaveEFI** » Sat Jul 07, 2012 8:07 am

A timing light will work when cranking. But if it's actually a tooth out you'd see that with a static check - looking at the sensor or points. Assuming you know what the timing was before.

Did you check out my further reply to your original thread?

ian.stewart · Post by **ian.stewart** » Sat Jul 07, 2012 9:03 am

Definitely can happen, this happend to me a few years ago when the chain jumped a tooth, mind that was a 7k burnout, lifted off and it jumped, broke a tooth off and split the timing gear,
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DaveEFI · Post by **DaveEFI** » Sat Jul 07, 2012 9:23 am

Well, yes. But an SD1 EFI won't rev to 7k.

I know the cam/dizzy/oil pump drive is a weakness on a 'tuned' engine. It doesn't commonly give trouble on a standard one.

As I've said on the other thread about this car I reckon it's a red herring - the speedo acting strangely is a clue as the sensor is fed from the same circuit as the ignition. So as in all fault finding, check the simple things first before looking at the unusual.