Hi! Welcome aboard :-)

So while the new mixer and vapouriser on my 4.0 have seriously improved things, it would appear that both my lambda sensors are knackered! Neither of them are switching although judging by the performance things like the MPG on the trip computer dropping from 18mpg to 14mpg, the one that drives the gas system was probably okay the other night.

With the laptop plugged into the gas system I can see it's pegged fully lean with the stepper trying to open as far as it can go. Normally at all speeds (even at idle) it hovers right around the 90 mark with the odd excursion up or down under acceleration and lifting off. Would it be reasonably safe to just set the stepper values to lock it to 90 until I get some lambda sensors delivered? I figure that would make it work pretty much the same as a fixed power valve.

XYZ switch? Check the obvious - make sure the dashboard indicates it is in park or neutral. IIRC Thor engines won't turn over if they're immobilised, but GEMS will.

Can you jumper across the starter solenoid relay in the fusebox to get it to turn over?

Have you checked the maxifuse for the compressor and starter solenoid?

Here's a nice wee project for someone...

dhallworth wrote:

Is that a recent rule? I was thinking of booking it again so had best change my of vehicle for the trip it if it.

You need to run a wee self-test on your sarcasmometer ;-)

no10chris wrote:

I’m actually amazed it still works, ive had a few with a phone system, I’ve always just ripped them out. My one now has a roof Aerial from a phone system, I’m going to use the hole to fit a better radio aerial..

I used mine for a VHF aerial, since it's got a standard Panorama base. I just swapped out the little 900MHz rubber duck for a 145MHz whip.

They're not even that hard to do. I've replaced pretty much everything apart from the ECU in my single-point system in the four years I've owned mine.

If I'd started from a completely uninstalled GEMS vehicle I reckon I could have fitted the whole thing in a long day (or split it over two, at this time of year).

oil leak is from oil filter area, took off, cleaned but cannot drive it too far to prove its fixed !

Relief valve O rings, all day long.

If the injector solenoids were shagged and not actually allowing enough gas through, would that cause the differential pressure to be too high?

Certainly seems to be. I now know the tappets are pretty dished (you could serve soup out of the back four) and a new camshaft is on the cards, but it doesn't need to be particularly soon.

Are the reducers adjustable? The single-point ones seem to have a locknut and screw in the high-pressure side that resembles the adjustment in a normal (old fashioned, not crimped together) gas regulator.

It really does have a lot more poke between 2000 and 3000 revs. That blow between pots must have been actually pretty severe!

After much faffing and resetting of adaptives and poking and prodding I crawled underneath and hosed some IPA into the sensor connector and the plug on the lead, which seemed a bit damp. I managed to get some water out, so I flushed it with some more isopropyl and stuck it back together and lo and behold! Off it goes, right up to the rev limiter!

David mentioned that his dads exhibited similar behaviour when the flywheel sensor was on the way out, so possibly the signal was only clean enough at low revs or something. While he was here he reset the adaptives and I moved the throttle pot back to a sane position, so it's a lot smoother pulling away on both petrol and gas although I suspect I need to tweak the gas settings a little. It also looks like one of the lambda sensors is on the way out.

We had a quick look at his VSE too, while we had Testbook on in the shed. It's weird, it seems to be looking for downstream lambda sensors but they are not fitted. I wonder if someone's been fiddling?

I wonder if it's possible the connector is full of crud? With the crank sensor unplugged it won't start at all. I did have that cable unplugged to move the wiring loom out of the way of the head.

So after doing the head gasket my 4.0 GEMS idles beautifully and actually performs not too badly - up to about 2500rpm, at which point it start spluttering and generally won't rev beyond that. It's the same on petrol or gas. There's a fault code stored for the camshaft sensor according to my cheapy ELM327, but when I look at the appropriate pin with the sillyscope I can see the correct two short two long squarewave pulses, looking just like the picture in the manual.

One of the lambda sensors seems a bit lazy, but it was like that before I started working on the engine.

What have I missed here?

That's kind of what I'm hoping. I didn't get a chance to look at it yesterday (bit of a bugger since for the first time in the whole project the weather was perfect!) but I'll look tonight.

It's absolutely silky smooth up to about 2000rpm, even under a considerable load. The blow between pots must have been worse than I thought.

Okay, so it appears I have a fault code for a camshaft position sensor.

Reconnecting the gas just gives me bigger louder pops, so that suggests an ignition problem :-/

Okay, it won't rev particularly high on petrol, sounds like it's being starved of fuel. What obvious thing have I got wrong?