BMW740i 4.4 M62tub44 with Zavoli N LPG rough when cold.

[Marcuspd]

Hi guys, first post.

I've had a good search about this problem on here and have a few pointers. I just wanted to ask a couple of questions if I could?

I bought a 740i 4.4 V8 with LPG last summer. It needed a bit of work on the engine so I took it off the road in September to replace the cam chains and guides. It took me until February to finish the work due to the weather and having to do the work on the drive.

The car switched over to LPG quite smoothly last summer with only a brief drop in revs. Now it's very lumpy on changeover unless the engine is properly warm. I have the cables and software for both the Zavoli LPG system and BMW OBDII system. The misfire codes recorded after a lumpy changeover to gas, all point to cyclinders 5,6,7 and 8. I have upped the changeover temperature to 45 degrees C and upped the revs to 1500rpm, this helped a little but is still bad enough when cold to light up the engine management light and record misfires.

Once the car is warm, the changeover is seemless and it runs fine on both petrol anf LPG. I'm not sure if I never saw this issue before due to it being warmer in the summer, or whether this is a result of it being sat for 5 months.

I have read on here about the injectors needing cleaning so plan of giving this a go as well as an inline filter change.
I Have a Zavoli Alesi N system split to run each bank of cylinders, so it has 2 seperate 4 way Matrix injector blocks, each fed through their own inline filter (still with Zavoli stickers on it) to their own vaporiser.

Could anyone give me a few pointers on cleaning the injectors and replacing the filters? My biggest concern is that I'm not sure where to isolate the gas before I start taking hoses off the injector blocks. There is a brass knob in the bit that's by the solenoid on the tank.

What should I clean the injectors with? I have a small ultrasonic cleaner which I could use.

Also, does anyone know where I can get the inline filters for the Zavoli?

Many thanks, Marcus

P.S. here are some photos of various bits to helpo identify the systems.

The filters...



One of the injectors..



The tank end...



The vaporisers...

[Tubbs]

Up the changeover to 65. And make sure 'tank soleniod with dedicated wire' is ticked. Sometimes the sequential fuel change over can cause problems so try it either way. Filters generally show up at high rpm. But too cold a change over can cause problems with sticky injectors first thing. Just monitor it first thing. What's the gas temp at when the coolant temp is at 45 ? I'm not saying you won't have to strip and clean them. But it's always worth a go by setting change over temp up to get it over the hump first thing.

[Marcuspd]

Thanks Tubbs,

I changed the switchover reducer temp to 65 degrees C, at which point the gas is about 24 degrees C. The engine had been used a couple of hours before though so wasn't stone cold.

It switched back to petrol a couple of times even though the reducer temp was still over 65 degrees, so I have backed it off to change over at 60 Degrees C for now and will give it a try when it's properly cold in the morning.

The temperature guage on the car was about normal and the reducers were nice and warm when it actually switched over.

I have found a couple of 10mm Bigas filters from Tinley Tech, which are apparently compatible with my Zavoli Matrix ones, so have ordered a couple. I still think I'll have a look at the injectors though as the BMW ECU always reports misfires on one bank when the gas fails to switch over smoothly.

Do you know if the solenoid is good enough on it's own to shut the gas off or is there a manual tap somewhere to isolate the gas before I disconnect the injectors? I've found a brass tap/knob on the fittings at the tank end, but wasn't sure if that's just some kind of pressure regulator.

Cheers, Marcus

[rossko]

Have a close look at the gas hosework. You seem to have two Zeta vaps; are they feeding seperate injector banks? Is there a balancing connection? Are they plumbed to water in series? Which one is doing the temperature sensing? I'm wondering if one is lazier pressure-wise or colder than t'other.

Are the Matrix laying flat? Wax is a possibility.

I doubt this is new enough to have "seperate tank wire" feature.

[Tubbs]

Sorry i actually meant gas electrovalves opened in advance. man flu this week, feel like @!##.

[Marcuspd]

Ah, thanks. I'm beginning to understand this a lot better now.
I hadn't realised the bigger rubber hoses where the feed from the car's water system, the thin rubber hoses were just vacuum/pressure pipes and the gas feed was just a thin copper pipe.

Yes, there are 2 X Zeta Vaps, no visible balancing connector for gas. Each VAP has one rubber gas hose, with one filter each, feeding it's own bank of 4 injectors.

The cooling as you guessed, is plumbed in serial and the Vap temp sensor is in the VAP feeding the bank which the OBD is NOT reporting as misfiring. So it's possible that the other Vap, without the sensor isn't quite up to temperature when the sensor thinks all is good to go. Tubbs suggestion to up the change over temp should definitely help then. It did feel a bit colder than the one with the temp sensor when I felt it.

The injector blocks are mounted horizontally so could be getting a build up of wax. I had read about this in other posts on here, but looking at it, it would be hard to mount them upright as the engine cover only just fits on top of the engine as is. If it's going to be a major issue, I might look at cutting a couple of holes in the top engine cover to re-mount the injectors vertically. I'd like to have a go at cleaning the injectors as they've probably not been done in a while. The previous owner has neglected the car for a while and I've ploughed through a huge list of jobs to get it back up to scratch over the last 6 months.

Once I've worked out how to shut off the gas, I'll look into doing this. Has anyone any tips for cleaning Matrix black box injectors? I'm guessing an mini ultrasonic cleaner won't damage them?

Once, I'd realised the gas feed was just the thin bore of copper pipe, I also then traced the solenoid shut off valve thing. This is the blue thing in the photo below, I'm guessing. Is this where I shut off the gas so I can disconnect the injectors then?

P.S. The Zavoli software I've got doesn't have the option for "seperate tank wire", so I couldn't change that.

Cheers for the help fellas..

[Tubbs]

If its easy enough, change the water temp probe over to the second reducer, or just up the temp as i said.
You have 2 things going on. From the tank to the reducer is a liquid 10 bar feed. Out of the reducer is a vapour running at 1 or so bar. If you disconnect the feed hose to the injector blocks you will loose a bit of gas. But its only vapour. And will go with a bit of a whoosh ! But not for long. If you want to change the liquid pase filter, turn off the tank and run it until it beeps, and then try again. You can do the same to get rid of any vapour i suppose. But we mostly dont bother as its only a bit. And the electronic solenoids turn off the gas as soon as the engine is stopped. As long as they are working and not had the guts removed. So its always good practice to turn the tank off. The gnurled nut you have already found on the tank by the way.

[Marcuspd]

Spot on. That's made it clear.

I'm going to see if the Vap with the temp sensor warms up first, which I suspect is does, then swap the sensor to the Vap which warms up a bit slower.

Thanks for that.

[Tubbs]

You want to be a bit careful, sometimes they snap off, so it may be safer to up the change over temp. If you have a way of measuring the water temp you can work out where you want to be, its only going to be a few hundred yards between 45 and 65 by the way.

[rossko]

no visible balancing connector for gas.

Check again, it may (should!) take the form of a smallbore hose linking the injector banks.

Any tendency to run cold will encourage wax trapping (like short journeys etc), be sure the engine thermostat is working properly.

[Marcuspd]

no visible balancing connector for gas.

Check again, it may (should!) take the form of a smallbore hose linking the injector banks.

Any tendency to run cold will encourage wax trapping (like short journeys etc), be sure the engine thermostat is working properly.

Yep, you're spot on. There's a small bore hose connecting the injector blocks together, which also T's off to a pressure sensor, which also has a hose to the inlet manifold.

I've just replaced the electronically controlled thermostat on the car as the heating element that the ECU uses to open the thermostat had rotted away under the connector. When this happens, the thermostat only opens like a standard mecahanical one and will open later than it would if the heater element was working. This has been fixed now and no more thermostat errors have shown up in the ECU error memory since. The car is generally used on longer journey's but has been laid up over winter whilst I did the camchains and guides etc.

It definitely sounds like it would be a good idea to clean out the injectors. I've seen the post a few down form this one about the Valtek injectors and there's a fairly good descriotion of taking the same MAtrix ones apart in there. I'll see if I've still got any carb cleaner and have a go at the weekend.

Thanks for all the help, guys.

[Marcuspd]

Up the changeover to 65. And make sure 'tank soleniod with dedicated wire' is ticked. Sometimes the sequential fuel change over can cause problems so try it either way. Filters generally show up at high rpm. But too cold a change over can cause problems with sticky injectors first thing. Just monitor it first thing. What's the gas temp at when the coolant temp is at 45 ? I'm not saying you won't have to strip and clean them. But it's always worth a go by setting change over temp up to get it over the hump first thing.

Cheers Tubbs!

After upping the changeover temperature to 60, the changeover is hardly noticable again.
When the weather perks up, I think I'll give the injectors a strip and clean too.

[Tubbs]

Good show ! Now go up to 65 and see if its not noticeable at all.

[Marcuspd]

I've upped the change over to 65 degrees and now even on a really cold morning there's only a momentary blip now.

I decided to give the Matrix injectors a clean, so followed some descriptions I found on here. I couldn't see any coil springs in mine though. When I took the outer plate off with nozzles, there were just the 4 X O rings between it and the valve body. When I removed the valve body, there was the rounded rubber strip stuck in the valve body, which pushed against the bottom of the paddles. Behind the paddles and inbetween them and the coils was the foil shim with the rounded tops for each paddle.

I gave it all a good clean, there were only slight bits of sticky oily goo, but maybe enough to cause the paddles to stick a bit when cold. I tried to be careful with the foil shims but managed to partially tear one horizontally at the bottom of one of the rounded parts during cleaning. I've put it back together and it seems to be runnng really well so I might just keep an eye on it. If it starts playing up I've seen a link on here to a German site who does the Matrix XJ repair kit for 55 Euro's, so will bear that in mind.

I also managed to pull one of the wires from the housing of the gas temp sensor. The orange wire has sheared off inside the hole in the brass collar. For now I've twisted the end of the wire up and poked it into the hole. I thought about dropping a bit of solder in there to join the wire ends together but am worried that the heat may melt the rubber in the hole enough to cause a leak. It works for now and I can still read gas temp with the Zavoli software.

Please could I ask if anyone knows where I can get an inline gas temp sensor from? The hose is a 10mm one.
Here's a pic. the orange wire is just poked into the hole in the sensor at the moment...



I also took a few of the injectors in bits so if anyone wants to see what's inside before opening. If so, let me know and I'll post them up.