Occasional bachfire when starting.

[DaveEFI]

In my one make car club (Rover SD1) two members with a similar setup to me (EDIS and MS2 batch fire) are having backfire problems sometimes when starting. My own car has never done this.
Both engines are 4.6 units, while mine is the standard 3.5, so not possible to just get them to try my tune. Both have standard cams, though, and run well otherwise.
Any tips on what to tell them to look for?

[slow_hemi6]

Are they basic trigger instals?

[grom_e30]

have you tried more fuel when cranking?

[DaveEFI]

Are they basic trigger instals?

Not quite sure what you mean? Two use the opto input (including mine) and the other the VR input for PIP. Non have a cam sensor.

[slow_hemi6]

Basic is one tooth per cylinder tach in, usually distributor based. Not a wheel decoder type input.
This cylinder (50+ trigger angle) without a trigger return often have a hard time calculating cranking ignition timing on engines with good compression or poor starters. The slowing of cranking rpm up to peak compression and then speeding up away from peak compression causes this and you can definitely get the odd backfire from it. One of the main things that pushed me to get a 36-1 crank trigger.

[DaveEFI]

Basic is one tooth per cylinder tach in, usually distributor based. Not a wheel decoder type input.
This cylinder (50+ trigger angle) without a trigger return often have a hard time calculating cranking ignition timing on engines with good compression or poor starters. The slowing of cranking rpm up to peak compression and then speeding up away from peak compression causes this and you can definitely get the odd backfire from it. One of the main things that pushed me to get a 36-1 crank trigger.

All the engines use EDIS. Which all use a 36-1 trigger wheel.

[rickb794]

If I am not mistaken EDIS is the same as TFI and the MS has no control of the spark at less than 10°.

The EDIS controls all sparks at 10° until the MS syncs and can command spark.

You can prove this by removing the spout connector and starting the motor.

And if it then still Bach fires you will know that the problem lies with the EDIS system.

Is it possible that the reluctor wheel is no aligned per EDIS specs?

With the spout disconnected you should see fixed 10°? with a light.

[DaveEFI]

First thing I thought of. Both cars are showing 10 BTDC with SAW disconnected. Using a timing light.

[rickb794]

So does it still pop when starting with the spout unplugged?

[DaveEFI]

So does it still pop when starting with the spout unplugged?

You've lost me there - don't know what the spout is.

[rickb794]

Spout is Fords term for the diagnostic jumper in the saw circuit.

Does it still pop with the saw disconnected?

[jsmcortina]

On TFI the control signal wire is called SPOUT. (SPark OUTput.)

On EDIS the control signal wire is called SAW (Spark Advance Word.)

Disconnecting either will run the engine at base/limp timing.

James

[DaveEFI]

Spout is Fords term for the diagnostic jumper in the saw circuit.

Does it still pop with the saw disconnected?

Not sure about that. But both cars are showing the correct timing when cranking with SAW connected.

[rickb794]

Does it still pop with the saw disconnected? This will determine if the problem lies with MS or EDIS.