1988 RRC staring problem

[trevauk]

Hi All

Badly need some help with a problem with my RRC. It is a 1988 3.5 EFI Auto.

It has developed a starting fault that I just cannot fathom.

The engine will start fine first time from cold and then cut out after just a couple of minutes. From then on again it starts first time but dies within 15 seconds if no power is put on.

However, once started, if I immediately unplug the temperature coolant sensor plug the engine will continue to run albeit slightly lumpy on idle. It will not start at all with the plug disconnected.

Thinking the sensor was faulty I got a new one but the problem is still the same.

I am at a loss to know what the fault is and, not being in any way a mechanic, I do not know what to look at next.

Help and guidance would be much appreciated.

Trevor.

[Rossko]

There's another temp sensitive component, the Thermotime switch, which controls cold starts and can play up.  There's ways to test these, diagnostics for the 3.5 Lucas 'flap' style EFI are around on the web.

The ECUs running these are very old-fashioned, and by now, very old.   They are completely non-digital and havea bunch of individual transistor circuits, each dealing with one facet of the fuelling strategy, like temperature compensation, or demand changes, etc etc.   The upshot is that a single component or joint failure can have an odd impact like that described, rather than dropping dead or flashing lights like a digital unit.  Suggestion to try swapping ECU with known good one.

cheers, Ross K

[trevauk]

Thanks Ross,

I have a spare thermotime so I will swap that over and see if that makes a difference. If not then I will get hold of an ECU and try that to see if it improves things.

Trevor.

[Rossko]

Another thought ... if the fuel rail pressure is too high, it runs over-rich.  This won't matter on a cold start but will have a worse effect as it warms up.
Pulling the temp sensor will make the ECU think the engine is red-hot and lean it off a bit, so could partially correct for an issue like that.   At least check the vacuum pipe to the regulator, if thats okay, put the regulator on your suspects list.