[ROVERNET - UK] OT Volvo 740 Turbo

[Anders Hedelund Larsen]

All this sensor and cranking reminds me of a fault I had with a Rover SD1.

Our son called home one saturday afternoon: His motor bike had a flat 
tyre on the motorway. Rescue service had hauled off to their station, 
but all too expensive for him to be taken all the way back home. Would 
nice old Daddy come to pick him, girlfriend and machine up? Sure, 
everything for the family.

So I took the SD1, auto trailer behind, tools in the trunk and off I 
went. Some ten kilometers from the target the ngine died. Lots of tools 
there, so roadside fault finding. No fuel supply.
 
Suddenly a voice: "Can I help"? Alas behind me stood a guy from that 
exact rescue service. Well, he tried, but still no success.

"So where were you heading?" "You won't believe it: To your station in 
Køge". "Exactly as me". "And I am a subscriber for your service". "Then 
I'll haul you for free". "No, not so good with the automatic". "Sure". 
"If only there'd been a trailer hook on that nifty Toyota Land Cruiser 
of yours". "Oh, but I can put one on. Only used very irregularly".

End of chapter one: We arrived with the Rover behind up on its own 
trailer. Son looked really bewildered. Now two dead vehicles.

Everybody tried for a couple of hours, but still no success: Rover would 
not supply fuel.

So another - larger - vehicle took us in the cabin, Rover on the back 
and trailer with motorcycle behind. Home for free.

Sunday I started severe fault finding. Found the electrical petrol pump 
somewhere below/behind the rear seat. It was not running and  - 
lo-and-behold - the power supply was not only 0, it was steadily 
grounded. Wire from battery directly to it momentarily brought 
everything to life. 

So where was the fault: Electrical diagram scrutinized.

It turned out that the SD1 engine oil pressure lamp switch is not an 
on/off, but a real A/B switch: Low oil pressure allows voltage to lamp, 
high to petrol pump.

So how can the thing ever start? There is no oil pressure initially 
while cranking, right?

There is also a connection via the starter motor positive side. When 
starting this is 12V, when running this is - via hefty starter motor 
windings - as good as a steady ground.

Oil pressure switch was dead, steady at low pressure => Only fuel supply 
while cranking.

So, disconnected the oil pressure switch, and a short wire between the 
cable ends for voltage supply and petrol pump brought the vehicle to 
life. A new switch a couple of days later also brought the low oil 
pressure lamp to function.

Yup, a nice Rovering weekend.   

Have a glorious weekend, whether Rovering or not.

...Anders, Copenhagen Denmark