3.9 V8 running rich...?

Right guys....

Got the 3.9 V8 in my 101 with a 14CUX Efi setup and 3.5 ECU. It's got (new) lambdas too as the setup was originally on a 4.2 LSE (tried the 4.2 ecu with same results but it drains the battery)

Done about 1000 miles since fitting but getting fairly poor economy, black exhaust and it stinks at idle.

Changed the temp sender, tested AFM (okay) and today checked the fuel rail pressure. Getting just over 2.5bar when the pump primes and about 2bar at idle. Not holding pressure when the pump is stopped though - drops 1bar in about 60 sec. I takes this means leaky injector(s)?

Would that affect fuel economy and running badly? If so what do I do? New ones or send the existing ones off for cleaning?

Help.

Jock.

temp sender or sensor they are different ?injectors are easy to pull out and check

Temp sender in the plenum (for the ECU)....injectors, no idea how they come out but what would I do if I took the out?

Not got time to write a proper reply,but one thing you could check is that the fuel rail temp plug hasnt been swopped for the coolant temp sensor plug - gives very rich running.

did you test the afm with a multimeter?

Yepo' I did......

....but, tonight I've been out with a multimeter again and was checking the lambda wiring. All seemed okay till I turned on the ignition when the feed went to zero volts - so.

It turns out that the relay fitted to this part of the loom is the wrong type and that it was an "or" type rather than "and" giving 2 terminals a feed at once.

The result of this was that the lambdas were getting 12v all the time when the engine was not running, and ignition off (it's got a battery cut off).

So that's fixed, it's running much nicer now but not taken it out yet so time will tell - ill post back.

Thanks for everyone's help so far.

Jock

jockscotland said:

Yepo' I did......

....but, tonight I've been out with a multimeter again and was checking the lambda wiring. All seemed okay till I turned on the ignition when the feed went to zero volts - so.

It turns out that the relay fitted to this part of the loom is the wrong type and that it was an "or" type rather than "and" giving 2 terminals a feed at once.

The result of this was that the lambdas were getting 12v all the time when the engine was not running, and ignition off (it's got a battery cut off).

So that's fixed, it's running much nicer now but not taken it out yet so time will tell - ill post back.

Thanks for everyone's help so far.

Jock

Click to expand...

Glad its sorted,the oxy sensors need that feed to heat them or they wont switch at idle/light load conditions. I saw exactly the same problem on a Morgan Plus 8 where a garage had fitted the wrong relay.They offered me a test drive in it after I fixed it..... I declined,I dont think I could have fitted in it without breaking several bones.

You can fit a tune revisited which will allow you to ditch the lambdas this wil help and leave a open loop injection system and allow you to set and adjust the emission