Call to LPG powered XJ's!!

Hi,

I made LPG conversion (actually shop made it) recently, and altrough it is running fine when driving, it is having some problems when idling, and especially when idling in (D) with brakes on.

In such cases (idle in (D), brakes on) it seems that engine has no power to run, but it still runs, has regular RPM's (around 800-900) but shaking really bad. I don't like the feeling. But as soon as I start driving, everything is ok. Highway speed is great, I can hardly see any loss of power then.

Did anyone else with LPG conversion experienced similar/same problems ? And what did you do to fix it ?

Btw, I made at least 30 visits to the shop, to 'adjust' it, 'fix' it.. but they are clueless. They apparently tracked it down to bad vacuum connection at air filter box, and it ran fine for a day.. or less. I tried to change that L fitting with one that is even more tight, and it didn't help.. Maybe it is leaking somewhere else.

Btw2, I've changed O2 sensor, and cleaned throttle body. Filter is new, but unfortunately box is cracked a bit (I know, I need to fix it asap).. Does it matter very much ??

Thanks!!

Are you getting good water flow to the converter/regulator?
Look for signs of frost.

Hm, I don't know how could that be the case, it is all ok while driving. Temperature is just as it should be. Heater works also okay, there is enough fluid in system.

How can I check if they connected it to correct pipes ?

Like I said, look for frost on the line. I've seen it happen at idle when not enough water is flowing.
One other thing to check is the vacuum cutoff if it uses one.
How's your oil pressure at idle?
The electric cutoff valve uses oil pressure to controll fuel flow.

It's a long shot, but could a leaky brake booster be a cause? The loss in vacuum could cause screwy conditions.

Oil pressure seems to be in normal range, as far as I can see from this little bit tripped gauge. Not sure about numbers, but at idle, oil pressure needle stays at half, or just few mm below half. However, when driving, after it passes 3/4 of display, it jumps way beyond max mark. I suspect it is faulty oil pressure sender unit..
I'm not really into engine and LPG (I'm more into drivetrain so excuse me for maybe asking dumb question.. but, is there a way to check out for this cutoff valve type ?

Btw, what is the usual place on XJ to tap the coolant line for connecting to regulator ?? Can it be that they did it in the wrong way ? connected wrong line ?

@ncmerk,
Doesn't seems to be brake booster leak. It works just fine.

Btw, what is the usual place on XJ to tap the coolant line for connecting to regulator

Click to expand...

I don't know if there is a usual place but the heater lines would be easiest.

It seems that they connected it there.. to heater lines.
What kind of flow should be provided to regulator ? Does it have to be high flow, or its enough to just have something warm there.. ?

Re: Call to LPG powered XJs!!

mr_W said:

It seems that they connected it there.. to heater lines.
What kind of flow should be provided to regulator ? Does it have to be high flow, or its enough to just have something warm there.. ?

Click to expand...

It needs to be enough to vaporise the LPG if you don't see frost then move on to something else.
Any dirt or sludge will collect there.
Also the system is at least partially vacuum operated so check your vacuum at idle.

What system did you have fitted? Was it a Stako with Leonardo emulator? It might conceivably be some sort of electrical fault with the emulator/ faulty ground (earth). But don't take my word for it, coz I only drive the thing! I do know that everything has to be working 100% for LPG systems to behave, so another possible culprit could be a faulty sensor - as you have already checked out. I don't often make the reverse recommendation, but you'll find a lot of helpful people on Difflock.com - a British site with a specific LPG forum, and they might be able to help or put you in touch with an installer who could help. HTH

I have an old school non-computer controlled LPG system I am putting on my '84 J10 (with 4.6L stroker) till the motor is broken in, then I'll be injecting the fuel with the XJ harness and computer driving the system.

(oops!) Sounds like something is disrupting the idle mixture (manifold loose or bad gasket maybe?) and throwing of the idle. Most shops adjust in neutral and that is way wrong. I park against a wall, and put a brick on the brake pedal with the truck in gear (Ebrake set as well) then adjust the mix. Old school racer style (not the safest, but the best way unless you chain it to a VERY strong pole or something)

Hi guys,
I have yet to find solution, and thanks to everyone that recommended checking out various things..

I've tried checking vacuum hoses with wd40, but didn't found anything yet.

But, I've discovered something rather intereseting just 5 minutes ago. The idle changes for +200 rpms when I press brake pedal! It stays for 2-3 seconds, and then drops to same as before. If I keep pumping it, it idles better (at higher rpm, and also not that much rough).

So my guess is that it is definitly vacuum thing, as this is place where brake booster is engaged continously. It is also interesting that this also happens (+200 rpms at idle) when engine is running on petrol.

I'm puzzled with this.. Is this maybe normal behaviour ? Or possible lead to solution ?

Thanks.

Btw, it is Landi (or LandiRenzo ?) equipment.

You may want to check out the LP-Gas group on www.yahoogroups.com but the brake booster loses it's vacuum when you step on the brake which is why you get the RPM change. Try plugging the hose to the brake booster (don't drive it that way!Your brakes will be extremely poor!) and see if the motor runs better.