Positive wire while engine running

[nick9one1]

Thanks for the offer but The alternator signal wire works fine. As mentioned previously it's grounded when not charging and only produces 12v when the engine has started. (300rpm cranking speed isn't enough to generate any voltage through it.)

I'm in the process of improving the starting.. already taken the wires off the back of the starter, and cleaned them up until nice and shiny with wet and dry. Re -attached nice and tight then covered in vaseline.
Next I'm going to replace the battery negative earth strap. Then look at the body to engine block earth strap (if there is one!).

 

[barks944]

ORIGINAL: nick9one1

Thanks for the offer but The alternator signal wire works fine. As mentioned previously it's grounded when not charging and only produces 12v when the engine has started.

Ah right missed that. Useful to know. Good idea to check all the earth straps and wiring, I've had a few probs with poor connections like that.

 

[peanut]

ORIGINAL: nick9one1

Thanks for the suggestion, but not sure if that will work either. As I presume the fuel pump needs to be live before the engine fires?

no that isn't the case actually. The 12v+ supply to the fuel pump is supplied via half of the DME relay which is in turn energised by the ECU.

I don't think you will be able to use the pump supply wire because when you turn the ignition on the ECU energises the fuel pump for a split second which fully pressurizes the fuel system then it de-energises the DME relay cutting off the fuel pump supply.
When the key is turned to the cranking position and the engine turns over at 20rpm+ the ECU re-energises the DME relay supplying the fuel pump continuously until the engine stops turning.
The ECU uses the voltage from the crank position sensor to tell it when the engine is turning over or running.

 

[peanut]

ORIGINAL: nick9one1


' Then look at the body to engine block earth strap (if there is one!). '

it should be at the back of the cyl head to the bulkhead . If you suspect a high resistance, poor earth to the transmission try bridging a jump lead from the negative battery terminal to the engine block and see if the starter turns over quicker

 

[peanut]

ORIGINAL: nick9one1



I can understand exactly where your coming from, although..

As the 944's aren't great starters it doesn't usually fire on the first attempt, its 2nd or 3rd.

possible reasons for a slow or hesitant cold starter is poor earthing connections ,loss of fuel pressure. (You may have a leaky FPR valve, fuel pump non return valve or leaky injector/s ) and non functioning cold start mechanism

 

[nick9one1]

Mine seems to always start first time, although its on the 3rd or 4th rotation of the engine. And is the same if hot or cold.

Will try to check the points you have mentioned though.
Thanks

 

[barks944]

The 944 will always need a few rotations to get it started. Firstly there is a delay before the crank sensors generate a sufficient voltage to trigger the speed/ref circuits in the DME and then there is a delay of up to one rotation after that before the TDC tooth passes the reference sensor and the DME knows the position of the engine in its rotation. You can't fire the ignition before this point.