Losing power on LPG

[JumboBeef]

Hello all,

Lovin' our RRC, which we have now had for a couple of months.  Runs perfectly on petrol and LPG: until today. 

Driving along on LPG, and lost power: switched to petrol and all was well.  Filled up the LPG thinking it must be empty, but it was already half full 

Started it up on petrol, but everytime I switch to gas, it has no power.  On tickover, or VERY slight throttle (0-30mph in a couple of minutes) all is well, but put your foot down, and it loses all power.

Am I right in guessing that it is plugs/leads which need changing?  Which plugs would be best?

PS: no back/misfires at all.
PPS: thanks!

[jay2578]

plugs, leads and dizzy cap are probably your starting point..... as to which ones to use...... someone will be along shortly im sure 

[Rossko]

Also consider clagged LPG filter, failed LPG solenoid valve or vaporiser, vacuum leak, jammed catflap backfire arrestor ... and check the radiator water level (seriously)

[JumboBeef]

and check the radiator water level (seriously)

I topped up the water this morning.  What does it mean if I am losing water?

[Rossko]

If the LPG vaporiser is mounted high up, and engine coolant gets low, vaporiser wiil ice up in use - harder its pushed, the quicker it freezes.   Generally accompanied by a big stink as well as power loss.   Usual effect is you can start off fine from cold but it all goes wrong within a mile or two.  If your LPG problems are still there immediately from a cold start, its something else behind them.

That's a symptom, and the LPG system may not have anything to do with the cause of water loss, although rarely vaporisers can leak water internally.

[JumboBeef]

Right, thanks.  The thing is it did a 300 mile run the day before, without problem.  Today, I had been driving it for 20 miles or more before the sudden loss of power (sudden, just like running out of gas).

We did have a loss of power once before, a few weeks ago.  However that time, I kept driving (it had just enough power to keep going) and after a few miles the power came back.

The water level might be a red herring as it is the first time I have topped the water up since buying it, and it might have been a bit low anyway.

[jay2578]

Definitely check for leaks, i burst a hose on my old rrc v8, repaired it and the vapouriser kept freezing up, so i forced water through the cooling system with a hosepipe which pushed out the offending airlock

[Range Rover Blues]

Strip the vapouriser and check for sludge, the LPG system will need cleaning eventualy.  Also check the LPG liquid phase filter, I found mine to be full of metal fillings :shock:

[JumboBeef]

I can see from the history that the plugs were last changed about six months ago (don't know what sort are in there) so I will fit new ones.  Are NGK BP6ES the ones to go for?

Nothing in the history to say when the leads were last changed, so I will change them too.

The history tells me that, six months ago: 'wire in and fit new LPG switch, adjust emissions, find several LPG leaks and repair' (cost: £148) so I'm hoping that the LPG system is OK and that the problem is simply leads and/or plugs.

[Range Rover Blues]

BP6ES are the fellas, close the gap to 27 thou and make sure the tips are screwedon tight (I crimp mine with plyers too).

Decne tleads might help, as will checking the dizszy cap and arm.  Also check the state of the coil.  Ours was running badly 'till the coil finally let go, once fixed it was more powerful, faster and more conomical.

[JumboBeef]

Thanks!  How can I tell if the coil is on the way out?

[Range Rover Blues]

a) Gunson't flashtester
b) try a spare one for a few days

[JumboBeef]

Ok, thanks.  I will try plugs and leads first (they always seem to be the trouble makers!)

[JumboBeef]

This is what happened today.

Changed the leads: took it out for a drive, no difference.  Would not pull away but would tickover and rev.

Changed the plugs: took it out for a drive, no difference.  However, I limped a bit further.  After a couple of minutes, I could drive up to 2,000 revs before it would loose power.  Another couple of minutes, I could get it up to 3,000.  Long story short, after about 15 minutes of stop/starting/hard driving, it cleared and now drives as it should.

 

One of the plugs that came out was brown and looked old and dry, the others were normal black(ish) and slightly oily.  They were the wrong type (with an R).  It has always driven OK on petrol.

So, it is sorted.  But will it stay sorted? 

[Range Rover Blues]

Sounds like a blockage then.  The 'R'simply means resisted, to supress radio interference.  You don't need it with good silicone leads and the resister just saps a little spark power.

A car that runs well should be ok with resisted plugs but if you are having trouble then fit non-resisted.

I use Iridium plugs and have no choice about the resister.

[jay2578]

Have you checked the coolant system for air-locks? It almost sounds like you forced air out of the vapouriser which helped it run properly.
If it starts playing up again have a check under the bonnet and see if the vapourisers getting frosty

[JumboBeef]

Thanks for the replies.

Just travelled >50 miles today: all OK.  Fingers crossed!

[Bigjohn]

Hi I run a P38 on a Prinz injection gas system, had a few problems especially with water loss possibly the dreaded 4.0/4.6 liner movement but have found a slightly cooler plug runs well.

[JumboBeef]

Also check the LPG liquid phase filter, I found mine to be full of metal fillings :shock:

Damn problem has come back.  Where do I find this filter/what does it look like?

[JumboBeef]

OK, so after looking on here and other websites, I decide to take my vapouriser apart/clean it out.  I have noticed there is oily gunk beneath it, so I was guessing that a PO had already emptied it out before and that was all there was to this problem.

An hour later, and two knackered hands later, I remove the plug at the bottom......and nothing comes out.  So I remake all the joins again, fire it up and go for a drive.

Considering I hadn't actually achieved anything, I wasn't excepting much: however, it is (currently) running beautifully on both gas and petrol 

....but how long will it continue?

[JumboBeef]

....but how long will it continue?

Answer: not very long! 

I still have the problem and it is DRIVING ME NUTS 

To re-cap:

RRC 1991 auto. We have owned it for about two months.  Fine until a couple of weeks ago (start of this thread).  Runs fine on petrol, no issues at all.

On gas, sometimes it runs fine, other times it feels like someone has fitted a remote control rev limiter.

This evening, I took it out for a drive (covered about 25 miles, town and country).  First five miles or so (NSL roads), no problem, freely reved to over 4,000.  Then, suddenly, it will not rev over 3,000 (approx).  Try to rev it over this, and the engine dies (but does not stall, just drops back to tickover).  Take your foot off a bit, and it will rev up to (but not above) the 'limit'.

Then it will clear and rev freely, then it will not rev over 2,000 revs, then OK, then not over 4,000, then fine, then not over 1,500 rev.  And so on.  And on.

If you stop when it will not rev, put it into netrual, it will rev as high as you want, no problem.  Back into D, then you have a rev limiter again.

I'm no expert, but I don't feel there is a LPG blockage: surely the problem wouldn't come and go like this?  Remember, if I cannot rev it above 1,000 in D, if I drop it into N, I can rev it freely to any rev speed.

New leads and plugs fitted last week .  Haven't touched the cap, arm or coil yet.  I even put LPG from a different station to my usual one in the tank tonight to see if that was the problem (no difference).  I am losing some water (not a lot) but this might just be a red herring.

This.Is.Driving.Me.Nuts.

[JumboBeef]

Help!  Anyone, please?! I need to get this sorted asap.

[Rossko]

Have you looked to see if there is a catflap yet, is it free ?
Looked at the mixer, make sure it hasn't come loose inside ?
Will you tell us what kind of LPG system you have, is it closed loop (with a stepper motor) ? Stepper motors stick.
Have you stripped the front solenoid & cleaned, to make sure that doesn't stick ?
Made sure front and rear solenoid electrical connections are good ?
LPG system earthing good (no wire under self-tapper arrangements) ?
Considered taking it to an LPG pro (could pay for itself in a few tankfuls) ?

[JumboBeef]

Thanks for the reply.  The answer is, I just don't know enough about LPG to sort this issue.  So:

Considered taking it to an LPG pro (could pay for itself in a few tankfuls) ?

....this is what I will be doing next Wednesday!

[jay2578]

Really sounds like the problem i had with mine..... air in the coolant system

[JumboBeef]

Really sounds like the problem i had with mine..... air in the coolant system

Interesting.  How did you get the air out?

[jay2578]

Undone a nut and forced water in with a hose.... solved my grief

[JumboBeef]

Well, it is now fixed, but I am more confused  :-.

The garage only took one hour to fix it, and they (as relayed through the receptionist as the engineer had gone home) removed "something from within the vapouriser, as the rubber seal was blocking something else on acceleration"   "It's working now, but you need a new vapouriser".

What did this thing do, if the car runs fine without it?  Why do I need a new vapouriser if it is running fine now?  :-.

Photo of "thing removed" attached.

[Rossko]

It looks like the innards of a solenoid operated shutoff valve - the gas on/off tap effectively.

It still works because there is a shutoff at the tank as well, but ought to be fixed on safety grounds (the amount of liquid in the pipe from tank to front is significant and at the moment at risk of spills in an accident).

Some shutoffs are seperately serviceable/replaceable, some are built-in to the vaporiser.    Vaporisers have a useful life anyway, often seems to be 3-4 years or 60,000 miles ish, so renewal of the whole shebang now may in fact save more grief next month/year.

[JumboBeef]

OK, thanks. I understand what it does now!

If I buy a new vaporiser, do I need a certain one, or will any 'off the shelf' one do?  Where can I get one from?

Thanks.