Timing Belt Replacement On Golf Mk3

[mac100]

I want to replace the timing belt in my Golf Ryder 1993 Mk3 1391cc ABD engine.
Haynes Service and Repair manual recommends that before starting work the engine and vehicle should be immobilised as follows:
“(a) Disable the ignition system by removing the distributor centre HT lead and grounding it on the cylinder block using a jumper wire.
(b) Disable the fuel system by removing the fuel pump relay from its socket
[I am not sure where the relay is located , I understand that the pump is immersed in fuel tank]
(c) Unplug the electric wiring from the starter solenoid –“

IS IT REALLY NECESSARY TO CARRY OUT THE ABOVE PROCEEDURES.?
WOULD DISCONNECTING THE BATTERY NEGATIVE CABLE NOT BE SUFFICIENT? IF SO THAT IS ALL I WOULD INTEND TO DO.

One further query.

On searching the web for information on replacing timing belt I came across the following.

“If the marks don't line up exactly, but are only off by half a tooth, use some chalk to mark the positions. If the marks don't line up and are off by a full tooth or more, your timing belt may have slipped. If this is the case, you may want to seek professional advice before continuing. (If the car was running fine, the belt most likely didn't slip and the marks are simply off for some other reason. If the car was running like crap, then the belt probably did slip.) “
Might this be a problem?. I don’t understand how the marks could be off by half a tooth unless the belt had stretched.
Are minor inaccuracies to be expected and if so would they be sufficient to upset the ignition timing which cannot be adjusted manually without access to dedicated electronic equipment.? Not a DIY job.

Advice on these matters would be appreciated.

Thank you
MAC100

[boschmann]

I'm not that familiar with the engine, but the first list is a bit of overkill, just remove the battery negative cable. Sometimes you cannot get the marks to align perfectly no matter which sprocket cog you put the belt on, that is what they mean by 1/2 tooth off. On one cog it's 1/2 tooth advanced, on the other it's 1/2 tooth retarded. As long as I don't notice any spark knocking I'd leave it on the 1/2 advanced position.

[mac100]

Originally Posted by boschmann

I'm not that familiar with the engine, but the first list is a bit of overkill, just remove the battery negative cable. Sometimes you cannot get the marks to align perfectly no matter which sprocket cog you put the belt on, that is what they mean by 1/2 tooth off. On one cog it's 1/2 tooth advanced, on the other it's 1/2 tooth retarded. As long as I don't notice any spark knocking I'd leave it on the 1/2 advanced position.

Many thanks. Your reply has been helpful and has given me some reassurance. My main concern has centred on the risk of upsetting the ignition timing when replacing the timing belt. I had purchased a new timing belt and then went to my local library to consult a workshop manual. The manual recommends that on completion I should check the ignition timing and adjust it if necessary. However, when I refer to the section dealing with ignition checking and adjustment I am told “The ignition timing is under the control of the engine management system ECU and is not manually adjustable without access to dedicated electronic test equipment. A basic setting cannot be quoted because the ignition timing is constantly being altered to control the engine idle speed.”

I am sure that timing belts are being replaced up and down the country in garages, other than VAG dealers, without the dedicated electronic equipment. I conclude that alteration to the ignition timing is not normally required following the replacement of the timing belt and intend to proceed accordingly. If I get a good alignment or if I have to fit the belt 1/2 tooth advanced but don’t notice any spark knocking that is OK but if I do notice knocking do I leave the belt in the advanced position and take the car to a VAG dealer to have the ignition adjusted or should I refit the belt in the ½ tooth retarded position before taking the car to the VAG dealer.? Your further advice would be welcomed.
Maybe I am making too much of this.

MAC100