LPG Injection problem, need ideas to diagnose

[-Nemesis-]

So my LPG vapour injection has been playing up lately, get's a bad miss and won't put any power down etc etc.

Since trying to diagnose it the 1UZ has now got new leads, plugs, coils, caps and rotors, throttle posi sensor.... The works.


I've since noticed that when the engine and bay are cold, as in after first starting, it runs like a champ for the first 5min of driving. But 5 min down the road, as soon as everything (not just engine coolant) is up to normal temp, it burbles and farts and won't get enough fuel (that's what it feels like) to be driveable.


Assuming it's temperature related, anyone got any ideas as to what could affect it? The 1uz has intake air and engine temp sensors, but i've tried tricking these systems with no success.

[Tiny]

mate, I nont know much about lpg systems, but when my ftruck on lpg started couphing and mixing I found the mixer was freezing up, was blocked up, replaced and problem went away

[Jacked]

do injection systems still have convertors???

if so it sounds like its freezing up, when it happens pop the bonnet and look at it, will either be coated in ice or very very cold. check the coolant hoses into and leaving the convertor to make sure its getting hot water into it.

[-Nemesis-]

Yep they have a pretty small one. Interesting theory though, here's me thinking somethings getting too hot, where as it may not be getting enough heat.

My cooling system has been low alot lately because of a dodgey overflow, I wonder if it's got an air pocket in the heater hose or something...

In fact, I would say the converter is the highest point on the cooling system.

[-Nemesis-]

Just checked, coolant hose to it is dry


The converter is the highest point by far. That's a bad thing hey..... Wonder how I can bleed it from there.

[Jacked]

its the same as inside a/c systems and the like, when a liquified gas turns back into a gas it absorbs heat (for lack of a better term).

normally when i bleed systems i just leave the cap off and let them idle until the thermistat opens and keep topping it up. does take a while.

some systems dont like that.

if possible jack the front of the car up so the fill points the highest point.

[GUtripper]

Yeah, the converter needs to be lower than the top radiator tank or you will get an air lock in the converter and it will freeze over and start to block after a bit of gas has flowed through it.

However, if that doesnt solve it, how about this........
when you first start it it runs fine.
when it warms up (and hence the thermostat opens and coolant starts circulating through the system) then it runs shite.

Id then guess you have a coolant leak in the converter. Coolant is leaking through into the gas, then into the combustion chamber making it run rough. Try holding your hand over the zorst, is there condensation on your hand after a few seconds? Are you losing collant over a day or so?

Would perhaps also explain the dry coolant hose to the converter after shutdown. (if not the converter height issue)

I had an old OHG converter on a 351 that had corroded internally and the gasket had pooped out. These were the symptoms, the fix was a new (2nd hand) converter.

[-Nemesis-]

Thanks for the tips guys. I'm stuck at work for now so I won't be able to test it out till smoko (arvo shift)

Sounds promising though, because there's been once or twice where the gas has run great, even towed a rolled Hilux home from Stocko on gas. Then 2 days later it won't run (been like that since.)

Being so on and off and having dropped coolant from a broken overflow etc i'm getting pretty confident!

[Jacked]

should be apples,
the fact that it runs perfect before it freezes over gives it away

dont think it would be leaking water into the convertor because those systems arnt that old.... yet.

enjoy

[-Nemesis-]

Hmm I guess it's more complicated.

Coming home tonight it started to get a bit farty again and lose power after about 10 min hard driving. But when I got home I checked the converter and it's hot to touch, almost burnt me.

Bugger.

[Jacked]

you got water running through it???

maybe a bad batch of gas, it happens.

could be tuning, think might be time to go back to where you got it installed.

[Modified Toy]

Does is run fine when you switch it on to fuel when it is missing on gas if so this pretty much eliminates every thing on the Engine system besides the gas

[-Nemesis-]

Yep, runs great on petrol. Apart from not keeping up at high revs and boost lol.... (stocko petrol system atm)

[PGS 4WD]

I have seen a number of cases of injector faults, sticking and alike in vehicles that come in for tuning. In some software you can turn the injectors off one at a time from petrol to LPG making diagnostic easy.


Joel

[Yarno]

Hey Nemisis, Mico's 4runner was running like that, it was the cam angle sensor (from memory) , the serpentine belt had rubbed through the wire going to it. No idea if that's the same problem but maybe worth a check.

Yarno

Edit: he has the 1uz as well, if you didn't remember....

[-Nemesis-]

Thanks mate, it's worth a check I guess.