Oddly, my factory Bi-fuel still burns Petrol

[Pete_c20]

Yes. No leaks at all. The difference in noise was likely down to wear and/or different amounts residue build up in. Twas only a note of interest and nothing to with this.
I don't know if the problem is fixed it's too early to tell, but having said that I haven't seen any fault with them yet to fix. I swapped the two sets of injectors over simply to see if doing so may fix something I've missed.

Originally Posted by CNGBiFuel

Progress for me: I've establised that the fuel-pump is in the tank and a right sod to get to. I understand there is a access hole in the boot. I'm still digging.

I'd start at the fusebox end looking for its supply wire. This may help
http://www.volvowiringdiagrams.com/?...ing%20Diagrams
Which engine management system do you have?

Only other loony thought that I've had was that the engine management system fired the petrol injectors intermittently whilst on LPG. I've not investigated that one yet. Or giving the rail a measured amount of fuel from another add-on tiny tank to see exactly what it did use and when. But this kind of stuff is further down the line and into the realms of rainy day play only for me.

[CNGBiFuel]

So, if I have thsi right you're persisting in the wind too!

Mine has a fuse that feeds more thatn just the pump so tracing a wire will be hard work. So i went to find the pump to attack it that end, but that failed because as far as I can make out the pump is accessed vai a cover in the V70's boot.
But... I run CNG and I have a stonking great tank where you won't have one (behind the rear passenger seat) , so i'm not ripping that out to get to it. But if I had LPG that woudl be my line of attack - you assume correctly, a CNG Volvo V70 is no antique-dealer car.

So i go back to my solenoid valve idea... I soldier on.

[CNGBiFuel]

Right hang it, I've jsut bought this on eblag. £20odd delivered, but I'm not sure how i'll wire it in yet. It operates as they all do so that powered-up is 'Open'. I was thinking to put it to the Cylinder solenoid so that it cuts the petrol as & when the cylinder solenoid fires to open, but the actual operation 'Open' is the reverse of that. I don't want to mess about with relay to reverse that, so I'll need to find a petrol output that opeartes it when on petrol but not gas. I'll have a look at teh wiring diagram.

If not a relay it is.

Trouble is even if I see how to do it on the diagram, then there's finding it buried in the car.

[CNGBiFuel]

I've been advised by wiser blokes thatn me that that the whole thing is a stupid idea. To shut off a volume of fuel in the rail could have safety impications and an interruption to petrol supply whilst running petrol, when the gas system pre-operates its solenoids to establish pressure would mean a lumpy transition, liveable but not desirable.

I paraphrase from Rossko on anotehr forum:

I have a single-ended fuel system. The mechanical regulator is incorporated with the pump at the tank. (later systems still have a pressure sensor on the rail and control pump drive effort electronically)

The "regulator" on the rail itself is just a fluctuation damper.

If you fit a lockoff to such a rail, the pressure will be trapped (unless it leaks out). Warning; you should make sure the shutoff used will bleed backwards under excess pressure, or you could make a hydrostatic lock and burst something as things warm and pressurise further. The damper might take care of that - or it could be the first casualty.

He also said: You really sure you don't want to find the fuel pump relay instead? Or buy a set of used injectors?

He was right! I have now fitted a dealy timer relay, a solenoid-vlave is not wise or as simple. I have found the pump relay and have fitted a delay realy to drop the pump relay. The delay relay is fired by the gas shut-off relay and after 15 odd secs drops the pump. Voila! it works. The dealy is needed to allow the smooth transition to each fuel.

[Pete_c20]

I've read many of Rossko's posts in the past and found them very helpful.

I've been holding off posting for a little while to wait and see what happened to my rail of swapped injectors. I've now done enough miles to get a feel if the petrol consumption was still a problem. The excess petrol consumption has actually got worse! At a rough guess it might of doubled. This is before I've played with the knock sensor, see next.

I have another issue at the moment which I think is a knock sensor failure. The chap at the independent volvo dealer informs me that failure of the original part is very rare but the code showing is likely a specific knock sensor failure. So this last weekend I whipped the inlet manifold off it and replaced the sensor with a secondhand part (£7 rather than £70 and working on the basis that failures are rare). This issue has been clouding some things and is hopefully cleared now.

So I'm back to wondering where the petrol is going.

Do let us know how you get on as will I.

[CNGBiFuel]

Thanks to classicswede, (that guy has had an unwarranted hard time on here) and Rossko I'm sorted. I think Lucas Claener (not Prince of Darkness Lucas, but Lucas USA) injecot cleaner palyaed a major part, but I put in a timer relay fired by the gas shut-off relay. This drops the fuel pump. We have a dead-end injector rail on our cars so there are none of he issues we first spoke of. A tiemr relay for £10.00 on ebay.

The relay woks. I don't burn any petrol unless I mean to. Job done.
Don't use a solenoid valve. Not wise and more complicated.

See:
http://www.lpgforum.co.uk/viewtopic.php?f=33&t=12616

[Pete_c20]

CNGBiFuel,
Hopefully you're sorted now, but a late thought while trying to figure out problems with mine.

Did you check to see if the Fuel pressure regulator at the end of the rail leaks Petrol? If the diaphragm in this is ruptured it'll leech petrol into the air intake whilst running on LPG. How long for I've no idea as I haven't looked to see if the petrol pump continues to run after engaging LPG.

To check the diaphragm pull the vacuum pipe off the reg and wait anything up to a couple of minutes for the reg's pipe to leak petrol.

Just a thought over a cuppa.

[CNGBiFuel]

The pump runs when on CNG/LPG which is why my relay now drops the pump relay. 103 in the Relay Box. Frankly you may be right, tha could be the issue but now I've dropped the pump I'll not worry. Fuel pressue and has been cut from the injector rail, so why worry. That diapram I don't think regulates pressure. It's a damper. [See other thread] Regulation is done tank-end.

[Pete_c20]

As I learn more about the car's systems, an update to this thread which scuppers most/all of my previous thoughts on the issue.

While troubleshooting other issues on the car today I was doing fuel pressure and flow tests on the petrol side.

When the car is running on LPG, in my S40 2002 bifuel the petrol fuel pump is turned off as part of its normal operation. ie the petrol rail is not pumped and no petrol could be vented from the rail when it was on LPG through the Schrader pressure test point.
The petrol rail sits at 45psi to start, runs at about 35psi on idle and climbs to 45psi under engine load. Switching over to LPG and momentarily venting the petrol rail releases a small amount of petrol, the rail drops to zero psi gauge pressure but the rail doesn't returned to pressure until petrol is engaged again.

So......if yours is the same as mine, and providing your fuel pressure reg membrane doesn't leak, you may find that your problem is still there. The outstanding issue on mine (hesitation under load, sometimes a rough idle, poor petrol & LPG fuel economy) may easily account for a doubling or tripling in petrol consumption even though its only burning it to startup.

Worth checking CNGBifuel.

[CNGBiFuel]

Nope, mine is defintely not wired that way. Pulling the fuel pump really is the only way to cut fuel rail pressure. I have a 1999 V70. My mod was to make it do as yours is already wired. ie drop the fuel pump when the gas relay is fired.