2.1 MV with LPG - Running rich?

[Walrus]

Just got back from having the tank out, new straps, new fuel lines & loads of other jobs done by a reputable garage.

At the garage I was chatting with the mechanic who did the work and he mentioned that it was unusual for it to start on LPG without starting on petrol first, so might be running a bit rich - I should get it checked out.

Set off ok (on gas) and thought I'd fill up with petrol and drive on petrol all the way home. I got about 15 miles and it started 'hiccuping' - losing power, even stalled a couple of times, then wouldn't restart for 5 mins. I thought it might be a result of having the fuel lines changed (maybe air in the system?) but as I was low on LPG I put up with this for 50 miles; filled up with gas as soon as I could and once I switched back to LPG it runs fine.

Other things I noticed - on petrol the temp gauge barely gets out of the white box, but on LPG it sits just under the LED. Also the tail pipe is full of black soot.

So does this sound like the symptoms for running rich? If so, is it something I can fix at home? I've never twiddled with the fuel system (as I've never had a problem with it before).

[kevtherev]

Really?
You never had an issue untill this garage messed about with the fuel delivery.
Reads like a temp sender is missing a connector
Hmmm

[Aidan]

Beakers lpg system was set up so that, if set to gas, it starts on petrol and switches to gas at 2+k rpm, and because the engine was new and the starter motor good it would reach the trigger point pretty much as it turns over hence it 'starts on gas'. Sounds like something has happened to the petrol delivery/return system or you have a stuck injector as it runs fine on lpg when the ecu thinks it's adjusting the timing and the fuel according to what it reads from the lambda but obviously on gas it can't adjust the fuel that's just sucked in by the engine. If you don't use petrol much then I'd check the spigot for the vacuum feed to the fuel pressure regulator is clear it may be blocked by deposits inside the plenum chamber so the fuel pressure regulator doesn't relieve the pressure as it should so it over delivers and the ecu can't back off the fuelling enough to run clean, check the return pipework to the tank hasn't been compromised, check the tank vents ok and isn't under pressure. Or take it back to where the work was done and get them to sort it if it was fine before the tank work was done, though from what you say I don't think they really understand it

[Walrus]

I rarely run it on petrol - when the tank came out he said the fuel that was in it was an interesting colour (yellow/scummy). I run it on LPG for long journeys as its much cheaper than petrol; the symptoms didn't show up until I'd gone >15 miles so I doubt the garage would have realised anything was wrong as they only ran it to an MoT garage & back. It passed it's emission test ok. 15 miles gets me to town and back so I never noticed anything wrong either - it may have been like this for months.

The idle has been high for a while; I put this down to a broken throttle return spring (replaced) but now realise it may be an indication of something else. I changed the plugs (& other ignition stuff) early last year and at the time they were a normal colour; I'll have a look this weekend but I suspect they'll be carboned up now.

Going to read up on LPG/fuel setup to see what can be tested/tweaked - like I said, I've never had a problem with it before so I've never had to do anything beyond service stuff.

[Walrus]

It seems I may have a dodgy Idle Control Valve.. I read it is supposed to 'vibrate & hum' - mine sounded rather loud (I could hear it over starting the engine) with the engine cover off - gave it a tap with the handle of a screwdriver and the idle settled right down - been running on petrol all weekend and no problems so far.