Starting Problem when hot

If I had any hair left, I’d be tearing it out!!!


The ECU has been changed. Coolant temp sensor changed. Engine speed reference relay checked. There is pressure in the fuel lines when it won't start. When being cranked over there is a spark of at least 1/4”.

Oh, and its probably a red herring – but the rev counter has just stopped working (it worked fine up until about an hour ago, this problem has been around for a couple of months)

Anyone got any further suggestions – or a match!!!

Have a look at the fuel over run shut off relay, it can be found under the bonnet near the air flow meter, all by it’s self, sometimes because of wear it sits the terminals get grubby, pull it out and give the socket a squirt of wd40, if that does no good it may well be the over run fuel shut off valve these can after some years of use become sticky when hot. The valve is fitted at the back of the plenum, I may be wrong but Advice is knowledge

pvmw said:

Oh, and its probably a red herring – but the rev counter has just stopped working (it worked fine up until about an hour ago, this problem has been around for a couple of months)

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I'm assuming you have a 3.5 Efi Flapper system.

The signal that tells the ECU the engine is running is also used to drive the tacho.

If the signal source (coil negative) connectors or wiring is dodgy this could be the reason.

Check the integrity of all the wiring and any relays in the circuit before the signal wire gets to pin 1 of the ECU and the tacho..

Your circuits will be similar to the system on my car so you may find the following links useful.

Rover SD1 Efi Trigger Resistor

Also the temporary image on this page

Rover SD1 Efi Main Circuit Diagram

If you still have problems then you may find other component information on my site useful.

Have a look at this its a good read

http://www.landyzone.co.uk/lz/f10/diesel-hot-starting-fault-p38-21995.html?highlight=hot+start

Dopey said:

Have a look at this its a good read

http://www.landyzone.co.uk/lz/f10/diesel-hot-starting-fault-p38-21995.html?highlight=hot+start

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pvmw is running an efi v8 3.5 I think you'll find your link is in connrection with diesel

ironhorse said:

Have a look at the fuel over run shut off relay, it can be found under the bonnet near the air flow meter, all by it’s self, sometimes because of wear it sits the terminals get grubby, pull it out and give the socket a squirt of wd40, if that does no good it may well be the over run fuel shut off valve these can after some years of use become sticky when hot. The valve is fitted at the back of the plenum, I may be wrong but Advice is knowledge

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I'm afraid I haven't gone away, I just had other things to repair.......

It hasn't got better. However, I've found and checked the relay. I then tried to get to what I think is the shut off valve. Initially I found a couple of spade terminals behind the back of the head. Disconnecting a wire caused the engine to stop immediately. After removing a couple of hoses and some skin I've reached the fuel regulator (which I initially thought was the valve) to which is attached what I assume is the valve. I am at a loss to understand how (if) it works tho'. It is "teed" into a vacuum pipe going from the plenum chamber to the regulator and has an electrical connection. If the pipe is detatched from the plenum the engine continues to run (albeit the revs go up as it runs leaner)

I've taken it off and measured the impedence - a few hundred Ohms. I then tried it on a battery - nothing! Put it back on car and engine no longer starts. Tested the impedance again and now it appears to be open cct.

So, after all the above rambling the questions are actually easily answered (I hope).....

1) what is it
2) how does it work
3) is it broken

Try by-passing the relay that is steered by the over run fuel cut off valve. It's on the AFM pedestal. Just remove the relay and fit a jumper wire between the wires coming from coil -ve and the wire going to the EFI-loom. Should your car work - faulty valve. It is actually there only for slight improvement in fuel economy when "braking" with the engine.

The tacho is driven by the w-connector at the alternator NOT by the -ve from coil. Should your tacho have problems check connectors at alternator.

I think I've reasoned this out.......

The "Fuel Cut-off valve" has two electrical terminals, and a vacuum pipe connected to the inlet plenum. It is actually a sensor, not a valve, detecting inlet manifold depression, switching when there is a high vacuum and signalling the ECU to turn off the injectors to save fuel.

The vacuum pipe is also attached to the back of the fuel pressure regulator, presumably to allow for increased(?) fuel pressure when the engine is under load and there is no manifold depression.

Therefore, if this thing is "sticky" when hot as suggested, when the engine is turned off hot it switches off, but then won't switch back on until it has cooled down a bit. So, if I short out the wires that go to it, I am simulating the switch closing and the ECU will energise the injectors.

Is my reasoning correct????