Croma Turbo ie - Ignition Timing Problem

[Rik]

I have a 1991 Croma Turbo ie fitted with standard Bosch Le2 Jetronic ignition, I have recently fitted a 130TC inlet cam and uprated fuel pressure regulator, the engine is essentially otherwise standard (cam timing is standard).

When checking the timing with a timing lamp connected to no.1 plug and idling at 800rpm my timing mark is as shown by the white line on the picture, (very advanced) however it should be between the red lines. I understand the timing is ECU controlled on this engine and moving the distributor through its full range of movement makes no difference whatsoever to either the timing or the running of the engine (that I can notice).

I've checked and double checked my cam belt is deffinately not out by any teeth and the distributor is in the identical position on the inlet cam as it was on the standard cam.

Can anyone tell me whats wrong and/or what I can do to rectify this?

Many Thanks, Rik

[Guy Croft]

On this engine the timing is a 3D map and thus when you say 'it's over-advanced' in fact it is more likely that the adv at that speed is just preset at a higher level than, say, you'd be used to on an engine with conventional distributor (eg: 10 deg).

The only way to check the timing is make sure the lug on the front pulley aligns accurately with the centre of the sensor, you have to leave the rest to the ECU..

I think I got that right, don't have the Croma manual in front of me.

GC

[Rik]

Ah that would explain it, I'll check the sensor lines up ok tonight.

thanks Guy, appreciated.

[SteveNZ]

As long as everything is bolted on as it should be the ignition timing will be correct, regardless of the cam timing. As you can see the front pully is bolted on with 3 bolts. If it were wrong the engine would most likely not run. Remove the vacuum line to the Microplex and you should see the timing drop back.

By the way, this engine has a Magneti Marelli Microplex ignition system.

[Guy Croft]

Microplex, thanks Steve, not an ECU as such.

This system (and Digiplex too) has a 3D map of ignition presets with vacuum/pressure sensor to enable the control unit to select the right advance/retard settings at rpm.

GC