Hi guys not sure if anyone can help me on this i have a 3.5 efi r/r classic which will fire up but will not run for more than a second or two any advise please

is a flapper or hot wire EFI?

last time i had one that done that it had run low on petrol,

and what checks have you done?

theres plenty of fuel its a flapper changed plugs ht leads and coil

is there very good fuel pressure? you need more than you think!

the fuel is running very well

At the ECU take off the cover on the big plug. Find the black and white cable. this is the signal cable which runs to the coil and tells the ECU when there is a spark and in turn fires an injector. so if there is a brake in the cable to the ECU signal no fuel.

Also at the coil end trace black and white cable back and there is a small resistor. remove it and try and start it.

Also check the relay thats on the side of the Air flow meater as this is the over run relay whch basically cuts stops the signal going to the ECU (and in turn fuel to the engine) when going down hills or when the engine is over running to save fuel. if its Fooked you can either replace the relay or cut the fooking thing out and join the signal cable to geather.
As said before the fuel pressure is important and there should be around 30psi of fuel (I think) so even though you thing the fule pump is ok you need to either swap it or test the pressure.

At the moment the engine fires up for a second then this might be due to the 9th injector. There very prone to dripping inside of the plenum chamber and its this dripping of fuel that will be running your engine for a few seconds. once you have go your engine running unplug the 9th injector & block the pipe off. the 9th injector only works in thmps of -19* so its no neededin the Uk.

If all fails then there is a bigger problem. I have the Land Rover EFI manual that tells ya all you need to know about the flapper EFI system and how to test everything.
I also have a new inline fuel pump that cost me £80. you can have it for £20 if you do need it .

hope all this helps. PM me if you do want to know more

Sounds like you could have an air leak in the inlet side of the system. An air leak would have the effect of letting the engine start and run but it would die after 3 or 4 seconds.

I would suggest strip and clean plenum, check/set throttle disc, clean/replace air filter. On reassembly ensure all joints/mating faces are clean, tight and properly sealed.