Flapper, swapping ECUs, RR classic

Fed_up_Stag-owner · Post by **Fed_up_Stag-owner** » Sun Feb 23, 2014 12:07 pm

Still working through this nearly-starter. Car sat outside for a couple of years as a non-starter. so plenty of corrosion on various connections, fuelling initially appeared to be very intermittent, (plugs generally remained dry), now have lots of fuel in the combustion chambers, initially starts then cuts out, plugs now flood. Have fitted 4 off HT lead test indicators (flashing plug caps), so can clearly see that spark is consistent. Firing order is correct from dizzy cap to plugs, need to check that ignition timing is correct though.

Can get a semi-start (fires on several cylinders but doesn't pick-up) for a few seconds by pulling the fuel pump relay, so clearly flooding. Cold start injector now disconnected in case faulty, coolant temp sensor to test (looks like fun to access that, might check resistance value of the sensor at the ECU connection as an alternative).

I have access to a known good flapper ECU, I'm probably moving towards swapping ECUs but I'm concerned that there might be a fault on the RR that will fry the known good ECU, is this a possibility?

ChrisJC · Post by **ChrisJC** » Sun Feb 23, 2014 4:34 pm

A couple of tests you can do:
1. Push the flap - the fuel pump should run.
2. Rapidly open the throttle. You should hear all the injectors pulse.
3. Check that the coil -ve is connected to the ECU (pin 1 I think). If this connection is missing, the ECU will not realise the engine is turning, and so won't do anything.

Download this:
http://www.cowdery.org.uk/downloads/Fla ... ual.tar.gz
It is the Land Rover fault finding guide for the flapper system.

Check the temp sensor is reading OK by probing it at the ECU connector. Same for flapper, and air temp sensor.

Chris.

Fed_up_Stag-owner · Post by **Fed_up_Stag-owner** » Sun Feb 23, 2014 6:32 pm

Thanks Chris, the pump does indeed run when the AFM flap is operated. It also runs when the engine is cranked. I've temporarily bridged the contacts on the fuel pump relay so that it runs as soon as the ignition is on, still only firing but not really starting.

I tried the TPS test a few days ago, but no injectors audible, although this was probably when fuelling was very poor (dry plugs), since then I've cleaned the multi-plug connectors for the power resistors and for the ECU, now have too much fuel so should probably repeat the test! Spark plugs might be old, so buying new. Dizzy cap and rotor look OK, have sprayed with contact cleaner and wiped, spark looks OK.

I have the Flapper manual, but can't open it. Will have to ask a young person for assistance.

Any thoughts on the risk of frying a known good ECU if I swap it for the existing?

ChrisJC · Post by **ChrisJC** » Sun Feb 23, 2014 9:45 pm

In my experience, the ECU's are very hard to fry.

Chris.

DaveEFI · Post by **DaveEFI** » Mon Feb 24, 2014 9:48 am

Most of the problems on the flapper are caused by external components rather than the ECU itself (although it can be faulty). They can be checked individually off the car - but this doesn't take into account the connectors and wiring. The best way is to remove the cover from the ECU connector and measure the return voltages from the various sensors with the system powered up. If you get someone to move the flapper and throttle, you should see a smooth change in the voltage output from these - they are all analogue.

The most likely thing to cause over-fuelling is the coolant temperature sensor - it's easy to measure its resistance against a chart at a given temp.

Don't forget to check the fuel pressure. Remove the hose to the cold start injector and connect a gauge. (It's possible to adapt a tyre pressure one)
You should see about 36 psi with the vacuum disconnected, about 28 psi vacuum connected engine idling.

If the ECU is faulty, it's often a dry joint. Simply re-flowing the entire thing is worth doing - it does take some time, but is quite easy since it is not densely packed. But still requires a skilled solderer.

The snag with checking things by substitution is actually knowing the 'new' parts are good. Everything is getting on for 40 years old.

Ramon Alban has produced a manual which incorporates factory data and later tips and fault finding. You can also read most of it on his site.

http://www.vintagemodelairplane.com/pag ... ual03.html

Fed_up_Stag-owner · Post by **Fed_up_Stag-owner** » Tue Feb 25, 2014 9:39 pm

Thanks Chris/Dave

I'm not at the swapping ECU stage, but not far away! I don't think the long rest did any of the electrical connections any good, but it has that feel of "nearly there". Coolant temp sensor is next, if the connector is anything like the others in the engine bay then removing the green deposits would be a good start.

I can blow through the idle air valve, so I've assumed that's OK, but might be best to spray it with carb cleaner.

ChrisJC · Post by **ChrisJC** » Wed Feb 26, 2014 6:53 pm

Those engines start from cold on fuel from the cold start injector. This remains on whilst the thermotime switch determines that the engine is cold. Without it, it is unlikely to start when cold.

In fact, because the thermotime and cold start are not controlled by the ECU at all, if you have fuel, spark and power (but unplug the ECU entirely!), the engine will fire, but not 'catch'

The ECU basically takes over once the engine has fired.

So it's worth getting it connected, and checking that it works.

Chris.

DaveEFI · Post by **DaveEFI** » Wed Feb 26, 2014 11:05 pm

Just to clarify, the thermotime unit stops the cold start injector operating after a maximum of 12 seconds - earlier if the engine starts, as it is energised by the starter circuit.

In most parts of the UK, a flapper engine will still start from cold with the cold start injector disconnected. Just takes a bit more cranking.

bodger · Post by **bodger** » Thu Feb 27, 2014 7:01 pm

Hi guys , have you tried the terminals on the resistor pack ....?
Thats the small silver box ... in my experiance the termial connection needs to be really good and tight for it to fire the injectors properly ...

Fed_up_Stag-owner · Post by **Fed_up_Stag-owner** » Thu Mar 06, 2014 5:33 pm

It lives!

Thanks for all your help with this chaps, non-running was due to a combination of poor electrical connections to various multi-plugs in the EFi system (car had been resting outside for a couple of years), LT connections at ignition coil, connections at fuel pump relay, sticking idle air control valve and old plugs (although they looked OK).

For my own reference if I have to come back to this (!), the coolant temp sensor is the 2nd sensor from the front of the engine, the resistance can be measured by pulling back the insulating sleeve at the top of the sensor and probing.