There's always a first time :-(

[duncscz]

Having enjoyed several years of trouble free motoring in 2 TVRs, my latest beast (1987 390SE)has let me down .. middle of a roundabout, the engine died ... and then the further embarrasment of trailer home.
Made the usual checks (fuses, relays) and all seemed well .. but she just wouldn't fire. Have changed plugs, ht leads, rotor arm, dizzy cap and coil .. all to no avail. Have checked the various sensors (it's a flapper) ... throttle pot, coolant temp., thermotime switch etc ... all seem ok.

So have now decided it's an over-fuelling problem and to prove the point (ie. excess fuel needs more air), I disconnected the pipe on the rear of the plenum (from the aux air valve) and hey presto, she started first time ... but at about 2500 RPM and with plently of bangs and crackles from the exhaust ... and as it's stuck in the garage, I can't run it for long !!

But now I'm puzzled ? What could be triggering the excess fueling ?

Anyone had a similar problem ?

It's got a LUCAS 4CU fuel control unit.

TIA

[Wedg1e]

Classic case of ECU-dryjointitis. Fine one minute, kaput the next. Try clouting the ECU with a shoe and see if the fault disappears (and reappears with another shoeing )
When mine went this way, I found I could actually drive it quite well with half the injectors unplugged. Sounded like a Subaru mind...

[duncscz]

Decided the shoe approach was a bit drastic, but had a good look at the ECU pcbs with a magnifying glass .. nothing obvious. Will probably need to resolder each joint to be sure.

Is there any information out there in web-land which would list the various signals the ECU needs to receive to actually increase fuelling, so I can try and isolate which one(s) are being/not being received correctly ?

[rev-erend]

The ECU and AFM both give this symptom. Easiest way to be sure it's the problem is to swap the offending item - either with a mate with the same model or there is a spare part pool in the sticky section at the top of the forum.

http://www.pistonheads.co.uk/gassing/topic.asp?h=0...

Edited by rev-erend on Thursday 25th February 09:41

[duncscz]

Thanks .. excellent. Let's hope there's a spare 4CU out there ?

Cheers,
Duncan

[adam quantrill]

Engine temp sensor is a classic too for this. Make sure you also check it at the ECU multiplug, as a break in the wiring or bad connector will knacker it up, too.

If you suspect overfuelling you can also try pulling the fuel pump fuse while cranking, it will run really well for a few seconds as the fuel pressure drops away. This can get you out of trouble on roundabouts, too, if you can lean over that far ;^)

[matt-man]

have you tried the fuel pump? Note that it only pumps on the flapper when the engine is cranking.

I had this on mine

[grahamw48]

Brittle wiring in that very hot engine bay can cause similar problems...happened on my last Wedge.

[duncscz]

Think I've sorted it It was the coolant temperature sensor after all. Intermittent bu@@er ! When tested with the engine off, it seemed fine. However, with the engine running (only possible with the aux. air flow pipe removed from the plenum), it must have been faulty, as I replaced it with a 220 ohm resistor across the connector and she fired up first time. Have since replaced the sensor and all seems well.

Had I spotted a thread on a land-rover forum earlier, which recommends that at 'any' hint of fueling problems, this sensor should be replaced first .. I may have saved some time ... and as it's just a few pounds, it almost justifies being a major service item. Live and learn.

And I certainly know a lot more about the start-up components of the engine than I did a couple of weeks ago

[Wedg1e]

You'll be a Wedge injection expert before you know it