Bl--dy Typical

[rob99]

Morning Chaps

The Shogun has been running fine on gas until I decide to take the caravan away for a few days then it starts playing up.

Had to come away on petrol (forgot how expensive it is)

Started losing power and dropping cylinders when cruising around 2000 rpm. Swapped plugs coils and leads to my spare set which seemed to cure it for a bit.

Towing the van yesterday it just got worse, same fault missing and dropping on to what seemed a couple of cylinders. Switch to petrol and it ran fine.

Kept switching back to gas but it just got worse until it started beeping and flashing the led's.

Give up at this point and left it on petrol, didn't want to knacker the engine.

Feels more like it's losing gas not ignition but can't see anything on my laptop. The ecu did not log any fault in the diagnosis page.

It's a Zavoli Alisei with Zeta S running at 1.4 bar with Matrix injectors.

Any Ideas

Rob

[rossko]

Coolant flow issues? "going off" in the cruise feels like the regulator is chilling down.

[rob99]

Hi Rossko

I checked the regulator and it was hot to the touch and when I had the laptop connected the temp never changed, on the other hand it didn't play up when I had it connected. I connected up this morning and from cold the reg temp rose slowly to operating temp as normal.

One thing I noticed which I don't think is was like this before was the gas pressure did not seem as stable as usual. It was around 1.4 at idle but dropped to around 1.25 when driving. It also rose to 3.9 when running on petrol.

[rossko]

It also rose to 3.9 when running on petrol.

This is a Bad Thing. If it isn't frozen, the regulator internal valve is seized up, contaminated, or more likely rubbers stuffed. Unusual for a zeta.

[Gilbertd]

I'll second a coolant flow problem. I had exactly the same happen on the latest Range Rover when it had a slight water leak. It was fine running around town but the first longish journey I did in it and it started to misfire and drop cylinders. Switching back to petrol and it was fine (or at least it was until the extra pressure in the cooling system forced the slight leak to become a more substantial leak and the temperature gauge started creeping towards the red bit.....).

[Tubbs]

Easter and the summer holidays. You can bet it's going to stuff up on you !
Sounds like a coolant issue.

[Gilbertd]

That's 3 for a coolant issue then......

[rob99]

Morning Chaps

Got the Shogun and van back home yesterday, was still losing power and cylinders every time I switched to gas. Not many petrol stations in the Peak District so it was fun watching the gauge go down with only a 5 gallon tank . Isn't very economical with a 1.8 ton van on the back! Got back home and unloaded the van and connected up the laptop and took the van back to storage thinking I'll get to the bottom of the issue. Well the bloody thing ran faultlessly no missing or losing power. I ran the acquisition and driving I saw the gas pressure varying from a low of 1.1 at about 5000 rpm to a high of 2.5 on a long over run. The reducer temp went from high 70's to around 92. The graph shows slightly less extremes but I am not sure how accurate the acquisition is.

I then unplugged the laptop to go down the supermarket and it started to play up again!!!

Looking at some old acquisitions the gas pressure stayed pretty constant for all rpm and loads. The reducer temp varied pretty much the same.

Should a Zeta S keep the gas pressure constant at the set point on a 200 bhp V6?. One other thing is what should I be able to adjust the pressure down too? With the adjuster all the way out I can only get it down to just below 1.4 bar.

Could a dodgy pressure sensor give this kind of problem? It's a 9 month old 025.

Rob

[rossko]

... gas pressure varying from a low of 1.1 at about 5000 rpm to a high of 2.5 on a long over run.

Dunno how else to say this is a Bad Thing.
I doubt it is the sensor, overpressure on the overrun is consistent with regulator frozen or goosed. Freezing effects are usually quite dramatic though, so that leaves just one sensible deduction.

[rob99]

Hi Rosskp

Spoke to the guy at LPG Shop and he says they will replace it as it is only 9 months old. He also said he hadn't seen a Zeta S fail this early in it's life.

Good job I aren't taking the caravan away over the BH because I can't get one until late next week.

Could anything else cause this kind of issue?

I have 8mm Faro from the tank into the vaporizer via a 6 mm valtek type valve, would I gain anything by swapping this to the 8mm valtek 07 type? These are easier to connect to the Zeta directly.

Could a dodgy vaporizer cause my initial problems with a uneven idle?

Thanks for the advice

Rob

[LPGC]

I agree reducer issues do look likely to be the problem, either due to low coolant flow or a reducer internal problem.... I too would usually doubt the latter with this reducer, but as others have said these types of pressures can be seen if the reducer freezes up and liquid gas escapes into the vapour side.

One thing to bear in mind though... If the vehicle was driven at full load on gas (with zero manifold vacuum) at 2000rpm the gas vapour pressure might correctly be 2.2 bar absolute, then when switched to petrol and at idle map that pressure would show at around 1.9bar anyway, and then under bonnet heat could increase that pressure to way above 2 bar... Ideally if possible you could've switched off the engine, stopped quickly and hand checked the temp of the reducer immediately when it started acting up - the reducer might get hot ticking over under no load but there might not be enough flow to keep it hot under high load. At 2000rpm with open throttle the reducer should be working well within it's capabilities on a Shogun but this reducer may struggle at high rpm and WOT on that vehicle..

A Zavoli system fitted with Matrix injectors - replacement injectors then? Has it been re-mapped properly for open loop at high loads operation and has Matrix injector type been selected in the software?

Runs OK with the laptop connected but plays up when laptop disconnected? Have you checked the voltage to the map sensor? On older ECU's (which yours might be having had replacement injectors?) the ECU's regulated 5v signal for the sensors can go wrong, thereby causing the ECU to read incorrect pressures and temperatures. When a laptop is connected the 5v signal can be temporarily corrected because the laptop can provide the regulated 5v (I explained this on another thread a long time ago). If the 5v signal is incorrect with laptop disconnected you can use something like a 7805 voltage reg chip to again provide the correct 5v to the map sensor. If the ECU isn't mounted with a good chassis earth, also check for a voltage between the ECU chassis and vehicle earth - sometimes 5V signal issues can be corrected by properly earthing the ECU chassis on older ECU's, on such ECU's just having the main earthing wire connected isn't enough.

Simon
www.Lpgc.co.uk

[rob99]

Hi Simon

Thanks for the tips.

I'll check the 5v, I've got loads of regulators at work so I can fit one if incorrect. I haven't checked the earth to the ECU, I assumed the ground wire would be sufficient.

The LPG system came off a Shogun I bought off Ebay. The Matrix injectors were fitted, Matrix is selected in the software setup. I have stripped and cleaned them and they look ok.

It played up again yesterday and I had a play to see if I could get any more info. It seems to go wrong more often when I am accelerating gently up to around 2k rpm. It starts to miss and lose power. If I lift off the throttle it seems to clear and accelerate ok most of the time. If I thrash it goes fine and very rarely loses power.

I have attached an image of the acquisition screen below. It did not misfire when grabbing this.

[rob99]

Hi

Measured the %v at the map sensor and got 5.03v. ECU case to battery negative 0.02v

Drove around for half and hour with laptop connected and disconnected and the bloody thing ran faultlessly!!!!!!

Ran acquisition while driving (see below) and the indicated gas pressure is all over the place. Is this how it should be?

[rob99]

OK

Ran round this afternoon with the laptop connected and logging. Didn't miss a beat. Pulled the USB lead while driving and it started playing up. Without stopping plugged the USB lead back in and still got the problem. Opened the Zavoli software and the issue stopped.

Don't know whether it's a coincidence but it does seem as the problem goes away when the software is connected.

Do you think resetting the ECU and reloading the firmware may help?

Rob

[Brian_H]

OK

Ran round this afternoon with the laptop connected and logging. Didn't miss a beat. Pulled the USB lead while driving and it started playing up. Without stopping plugged the USB lead back in and still got the problem. Opened the Zavoli software and the issue stopped.

Don't know whether it's a coincidence but it does seem as the problem goes away when the software is connected.

Do you think resetting the ECU and reloading the firmware may help?

Rob

That sort of faults been seen before and solved by fixing a dodgy connection (between the battery and earth points to the lpg system). I'd check your connections to the battery and earth points before trying anything else.

[rob99]

Hi Brian

Thanks for the tip. I have checked the connections but I'll go through them all again and remake the connections.

Just been down the shop and it ran fine??

Thanks Rob

[LPGC]

On those aquisition screen shots the temp readings are fairly constant but the pressure rises to 4 bar whenever the engine is on over-run.

The above seems to rule out voltage faults caused by bad earths or the 5v rail being corrected when connected to the laptop... Also points strongly to a reducer fault - the pressure quickly rises to 4 bar on over-run.

Don't concentrate on this just yet, it isn't causing your current problem, but when you get the reducer problems sorted your system will need a retune because your gas injection times go up to 22ms... your petrol injection times only go up to 16ms to allow them time to open, meter fuel and close again in time for the next injection sequence. If your gas injectors run to 22ms the AEB system will switch back to petrol at high rpm with wide open throttle because it will calculate that the injectors don't have time to open, meter and close before they need to open again.

Simon
www.Lpgc.co.uk

[rob99]

Hi Simon

Thanks for the reply.

I had a play again this morning. I upped the idle gas pressure to 1.5 bar and autocalibrated and it seemed to hold the pressure better at high revs/load.

The gas pressure rises on the overrun when the system goes into cutoff mode. Is this correct or should it be able to regulate the pressure to the setpoint?

I also only go up to 20ms on the gas injector time, still probably to high as at 6000rpm it's only got 20ms to inject.

Thanks Rob

[LPGC]

Hi Rob,

You can see where I'm coming from with the long gas injector durations then, 20ms will allow higher rpm running than the 20+ you had before. As said though, that won't fix the problem you mentioned.

The gas pressure will be higher on over-run, but shouldn't go anywhere near as high as 4 bar, can only be a reducer problem I reckon.

Simon
www.Lpgc.co.uk

[rob99]

Hi Simon

Just gad a look at the acquisition I ran with it at 1.5 bar and the max pressure on the overrun was 3.2 bar.
Had a look at some previous saved graphs and the gas pressure stayed quite stable at all rpm, so it does look like the regulator is goosed.

What the minimum opening time for Matrix XJ injectors?

Thanks
Rob