EFI If I have this on my 92 2.4td, why is pump timing so critical or is it?

[ro80rob]

Was thinking about changing the timing belt on my 92 2.4TD for good measure (and I don't know the belts history), and I read a lot about making sure to get the timing marks, including the pump set properly for the new belt. My engine says 'EFI'. Why is it important to set the timing of a pump if this is the case. Surely in this instance, the pump is just that and provides pressure that the EFI distributes to the injectors. Am I missing something, or is changing the timing belt going to be an old pig?.
Also, can't I just Tippexx up the old belt and toothed wheels, then transfer these marks to the new belt and put it on relative to the marks?.

Any enlightened souls who can tell me what I'm missing here? and any tips on belt changing?

Cheers... Rob.

[MattF]

http://www.toyotasurf.asn.au/techsite/timingbelt.htm

[TonyN]

The pump needs timing to fire at the right injector at the right time, the EFI bit just alters the fuel load depending on engine revs and load.

Changing the belt isn't a pig, just getting to it is.

[NiftyNev]

The pump needs timing to fire at the right injector at the right time, the EFI bit just alters the fuel load depending on engine revs and load.

Just to add to Tony's comments. The Pump and injectors are mechanical. The pump pressure and timing determine when the injectors open. The electronic components on the pump along with other sensors connected to the ECU determine the amount of fuel the engine receives.

Direct injection has electronically controlled injectors and an electronic pump which maintains a constant pressure. The ECU in these engines determines when and how long the injectors remain open. These are usually a common rail system and the Surf has a seperate fuel line for each injector.

Nev

[ro80rob]

Think I'm with it now. Its kind of a coarse and fine system. The pump provides the coarse high pressures, and switches the fuel in turn appropriately to each injector nozzle, whilst the electronics fine controls the actual dose. Quite a simple system. Not quite as elegant or reliable as the BOSCH K Jetronic CIS petrol injection, but simple enough, almost state of the art I guess before the common rail system.

No comments on the painting the belts/wheels approach to cam belt replacement, or is it as I think OK to just rely on the alignment technique?.

Thanks for the www link anyway.

Cheers... Rob.

[MattF]

Just rely on aligning after replacing the belt.

[Gazbo]

Just highlight the marks when you time it up! Its not worth doing it your way unless the 2.4 is safe? But to be honest, there is no hardship in linning the marks up anyway?