36 replies to this topic

[egg]

Hows the Fuel Filter?

[colc]

This may sound bizarre.....but I once had this fault on a V8 Jag...turned out the oil was old, and didn't have the viscosity to pump the hydraulic tappets...........changed the oil, fired first turn.........

[garethj]

The test light on the injectors might not be telling you the whole story, if the voltage isn’t high enough they won’t fire. My ancient K-Jetronic needed 9.6V to fire them which you couldn’t tell from a light, only from an oscilloscope or by pulling the injector out and watching it spray over your shoes.

I think you might have to bite the bullet and pull the rail or one of the individual injectors out.

If it’s not that, it could be that the spark isn’t strong enough which is probably going to cost money to fix

[Barry Cade.]

Easyest way of telling a duff crank sensor- usually- is watch the rev counter when spinning over on the starter- it should register as the ECU usually gets its RPM signal from it. Older cars can have the sparks triggered from the crank sensor, and the injectors triggered from the cam sensor, not familiar with this motor though. Honda's were notorious for the igniter chip going down on the dizzy and having these issues, symptoms for weeks before was the rev counter going apeshit.

[wuvvum]

 

The test light on the injectors might not be telling you the whole story, if the voltage isn’t high enough they won’t fire. My ancient K-Jetronic needed 9.6V to fire them which you couldn’t tell from a light, only from an oscilloscope or by pulling the injector out and watching it spray over your shoes.

I think you might have to bite the bullet and pull the rail or one of the individual injectors out.

If it’s not that, it could be that the spark isn’t strong enough which is probably going to cost money to fix

Sparks looked OK when I connected a lead to a spare spark plug.  The plugs in the engine could be completely shagged, but I'm going to replace those so will hopefully rule that out.

 

Insufficient voltage to the injectors is a possibility - they only seem to be getting 6-8v according to the multimeter.  What would be causing that though?

 

 

Hows the Fuel Filter?

Dunno - not sure where it is (it's not under the bonnet).  It can't be too blocked up though as there's plenty of fuel getting through to the engine bay.

 

 

This may sound bizarre.....but I once had this fault on a V8 Jag...turned out the oil was old, and didn't have the viscosity to pump the hydraulic tappets...........changed the oil, fired first turn.........

That's an interesting one - would it not be the oil being too thick and keeping the tappets pumped up though?  I had that on my old Rover 400 once after revving the engine too hard right after a cold start, but that then resulted in no compression (which was evident from the noise the engine made when turning over).  I'd be surprised if the oil was too thin, especially with a cold engine and sub-zero ambient temperature.

[Barry Cade.]

OK, looks like cam sensor does control injector pulse..

 

[Zelandeth]

How's the engine earth?

Big volt drop there during cranking could cause all sorts of electronic gremlins.

I'd try it with a decent jump lead from a solid bit of metalwork on the engine straight to the battery negative terminal and see if there's any difference.