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slow acceleration, top speed 120km/h

 
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relaxed_diplomacy
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PostPosted: Thu May 08, 2008 9:49 pm    Post subject: slow acceleration, top speed 120km/h Reply with quote

I am running out of ideas as to what could be causing my LPG to not run properly. Acceleration is slow and top speed is 120km/h. If i bring the revs up at standstill it's rough between 2000 to 3000rpm, then after about 4500rpm it breaks down with more throttle equalling less revs.

the tank has gas
the manual valve is on
the first shut off is working, plunger is fine
can't see any dents in the line
filter has been removed
second shut off is working, plunger is fine
third shut off is working, plunger is fine
OMVL mixer has been refurbished, and rechecked
STEPPER VALVE NOT WORKING, but power valve does not fix problem
o2 sensor shows 0.4V, swapping in another old one made no difference
mixer is clean

dizzy contacts are clean
leads are spiral, contacts are good
plugs are near new
motor runs excellent on PULP
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ghia97
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PostPosted: Thu May 08, 2008 10:02 pm    Post subject: lpg Reply with quote

Replace stepper.
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basstrom_dave
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PostPosted: Thu May 08, 2008 10:55 pm    Post subject: Reply with quote

has it always done this? it sounds as if there is not enough gas getting into the engine, i know mine has various taps in the line and can adjust the amount of gas getting into the engine.
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relaxed_diplomacy
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PostPosted: Fri May 09, 2008 7:51 pm    Post subject: Re: lpg Reply with quote

ghia97 wrote:
Replace stepper.

Yes, i think i'll do this, quoted $120, but i'll see if i can test if the old one really is dead rather than it just not getting the right signal.

A gas man told me if you replace the stepper with a powervalve but leave the stepper's wires plugged in you should be able to see the stepper moving, but mine does not. I figure if i test a new one in this way and it works then i know the old stepper is dead.
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relaxed_diplomacy
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PostPosted: Fri May 09, 2008 8:05 pm    Post subject: Reply with quote

basstrom_dave wrote:
has it always done this? it sounds as if there is not enough gas getting into the engine, i know mine has various taps in the line and can adjust the amount of gas getting into the engine.

Unfortunately i don't know how it has run previously as when i bought it it hardly ran at all and i've never had it running properly. The system is 14 years old so you would think it has run properly, but i guess i shouldn't assume so. When i rebuilt the converter i found one of the old diaghrams had a small split.

The system had a filter and it was full of small metal particles, from the rolling of the tank i am told, but when i removed the filter and cleaned out the housing it didn't make any difference.

The only tap i am aware of on my system is the one on the tank, which i make sure is fully open. Some other systems have a tap called a "powervalve" in the low pressure intake line, but mine has an lpg ecu controlled stepper valve instead.
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elf100capri
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PostPosted: Fri May 09, 2008 8:21 pm    Post subject: Reply with quote

on the side of the convertor do you have a brass adjuster bolt? this adjusts the gas/air mixtures,screwing it in leans and screwing out makes it richer. just go half a turn out at a time and run it/test drive. sounds like its running lean to me.
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relaxed_diplomacy
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PostPosted: Mon May 12, 2008 6:32 pm    Post subject: Reply with quote

elf100capri wrote:
on the side of the convertor do you have a brass adjuster bolt? this adjusts the gas/air mixtures,screwing it in leans and screwing out makes it richer. just go half a turn out at a time and run it/test drive. sounds like its running lean to me.

The OMVL R90e has two bolts. I've tuned both as per the tuning suggestions in the main sticky, and i've mucked around heaps as well - including rich mixtures, but nothing i have done with them has made any real difference to the problem.
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relaxed_diplomacy
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PostPosted: Wed May 14, 2008 10:20 pm    Post subject: Re: lpg Reply with quote

relaxed_diplomacy wrote:
ghia97 wrote:
Replace stepper.

Yes, i think i'll do this, quoted $120, but i'll see if i can test if the old one really is dead rather than it just not getting the right signal.

A gas man told me if you replace the stepper with a powervalve but leave the stepper's wires plugged in you should be able to see the stepper moving, but mine does not. I figure if i test a new one in this way and it works then i know the old stepper is dead.

I tested a new stepper valve today as per above and it did not move. The engine was definitely running on lpg, i even gave it a rev, but still no movement. So my best guess is the o2 sensor, the lpg ecu, and/or the wiring is not working properly. Unfortunately even if this is so, solving it will not solve the main problem, considering it won't run properly using the powervalve.


I had an idea that with the filter being clogged-up the way it was maybe the line before it is also clogged, especially considering it spirals. But a gas man tells me this is very unlikely.

One thing i haven't done is tune in the powervalve as best as possible then retune the converter. I don't think this will work but it's an option.

Another option is to fit another converter that has been lent to me to see how the system goes then.

One more thing i will mention is that when i removed all the shut off plungers a small amount of gas trickled through the converter into the intake, enough to frost the outside of the converter and stop the engine from running on petrol. Considering one of the adjusting screws on the converter is called the "bypass screw", my best guess is that this is normal under these conditions?
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relaxed_diplomacy
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PostPosted: Tue Jun 03, 2008 8:36 pm    Post subject: Reply with quote

Breakthrough . . . ! ! !

Firstly, i decided to replace the vapour hose. This is the low pressure LPG hose between the converter and mixer. There was engine roughness between say 1500 to 2500rpm and replacing the vapour hose fixed this (but not the main problem).

Secondly, i fitted a borrowed converter and without even adjusting the idle and with only minor adjustment to the powervalve the engine ran just as hard on LPG as it does on petrol. My timing is advanced.

Now i just need to work out what is wrong with my converter, and why the stepper motor is not operating.
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Mechan1k
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PostPosted: Tue Jun 17, 2008 11:30 pm    Post subject: Reply with quote

Converter internals can get old and worn over time.

I just replaced my Vialle converter on my AUII EGAS ute ... and after the change it was like chalk and cheese ... I puled the old converter down and it look really good internally ... I couldn't see an issue with it really.

I had issues starting for so long .. and nothing fixed it until i bit the bullet and replaced the converter.

Seeing as your system is 14 years old ... you probably just had a tired old converter that was on the way out really.

You might just need a rebuild on your old converter and it might be perfectly fine again.
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Epitome
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PostPosted: Wed Jun 18, 2008 6:27 pm    Post subject: Reply with quote

My apologies, I haven't read the whole thread. So ignore this if already done.

I had a similar problem with my EL a while ago.

It turned out to be running WAY lean and the reason was a split in the intake hose between the mixer ring and the throttle body. That combined with a bent component inside the converter.

I'd had a backfire a few weeks before that and it slowly got worse.
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relaxed_diplomacy
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PostPosted: Wed Jun 18, 2008 6:30 pm    Post subject: Reply with quote

Thanks for the suggestion, but if you read back further, i mention rebuilding the converter, and it didn't work properly. I am still to examine why. One bloke said something about bending a tab. I plan to go back to him and see what we can learn, but any suggestions would be appreciated.

The stepper motor still isn't working either, i talk about that and some tests i have done earlier in the thread too.
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Epitome
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PostPosted: Thu Jun 19, 2008 1:57 pm    Post subject: Reply with quote

Epitome wrote:
My apologies, I haven't read the whole thread. So ignore this if already done.


That's why I wrote this^^^.

I can't remember which part it was but the guy who fixed my car said that some metal thing inside the converter had been bent. He straightenned it out and replaced all the seals in the converter.
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relaxed_diplomacy
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PostPosted: Thu Jun 19, 2008 10:05 pm    Post subject: Reply with quote

What a mixer-up! Epitome, your first comment slipped in while i was writing my response to Mechanik1.

My mixer is clamped directly to my log manifold inlet, and i haven't noticed any problems there, plus its working fine now, so seems good.

Thankfully for me i haven't had any backfires.

As for the metal tab, is yours an OMVL? If so, did he show you where and what to do? (mine is an OMVL).
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