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-   -   Depressuring Necam CNG system [Volvo S60 2007] (

darjusp Aug 7th, 2020 07:32

Depressuring Necam CNG system [Volvo S60 2007]
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Hi guys,

My Volvo started to shutdown again randomly on gas, especially when RPMs drops to low. I've read the FAQ on cleaning distributor, i am planning to do it first by pouring STP injector cleaner into the hose from pressure reducer to distributor. Before i was emptying gas system just simply by pulling out the hose and letting the gas run. Not a very nice way especially when pressure regulator is faulty (big boom). So i tend to go with more intelligent way.

There is a first step in FAQ

"With the car running on gas disconnect the solenoid cable under the air box to purge the system of gas. Reconnect before you forget."

Does disconnecting the cable means the plug from the pic on pressure regulator?

Or it meant by other way, as some guys in other forum also suggests to pull some relays to close CNG tanks?

thanks in advance for the help

CNGBiFuel Aug 17th, 2020 17:37

To be honest, I don't bother. On a V70 P80 CNG, and V70 P2 LPG I pull the stepper, 2 x 3mm Hex/Allen. You'll get a slight whiff of gas. V.low pressures in the dizzy anyway (1.5 Bar or less). Never worked on a S60 CNG, but low-pressure side, assume it's the same. It's the otherside of the reducer where you see 6mm steel that you need to be more careful (200Bar). You're not going near that. As long as you're low-pressure hose side of the reducer, do what you like. And if you had 200Bar there now, you, and most of Helsinki would already know about this...

Just make sure the ignition is off, and chissakes, don't smoke!

If you do have to 'blow-down' the high-pressure side, this can be done too, but a different question.

darjusp Aug 21st, 2020 07:51

Thanks a lot for the detailed answer. Clear enough ;)

CNGBiFuel Aug 21st, 2020 13:47

Just work in an open space or in your workshop with all the doors open. Methane, unlike LPG, is lighter than air. It won't sit around in inspection-pits etc etc like LPG. Don't allow anyone to touch a workshop light-switch. Done.

darjusp Sep 15th, 2020 14:59

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Well, not the most pleasant activity, a bit more sound than i expected :confused_smile: next time will put earbuds
But i guess there is no other way to depressurizing that system :regular_smile:

Saw that main hose (from Regulator to distributor) was cracked, needed to replace it. As CNGbifuel somewhere mentioned its 16mm, I got it from here You also will need two clamps as original ones unusable after removal. Also they have 8mm ones, which I will need to replace it someday too.

To reach distributor you need to remove the fan. I attached pic and steps

Btw did anyone experienced leaks from CNG gas tanks? On the passanger (left hand drive) rear wheel i noticed some weak smell of gas after i got close to the wheel? any ideas which part is responsible for it? Can it be solenoids in gas tanks?

CNGBiFuel Sep 16th, 2020 10:25

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A leak? Highly unlikely to be the cylinders leaking. If in such a poor state that they leak, you'd know by now!

Joints perhaps. The CNG receptacle/filler valves sometimes weep, I use an auto centre-punch to 'seat' the non-return valve. This is a bodge but worked until I replaced it.

Find the leak quick. Steal SWMBO's atomizer, fill it with soapy-water and spray to find the leak.

darjusp Sep 16th, 2020 14:48

Thanks CNGBiFuel, that make sense. i do have that pen somewhere, now will need to try to find whether really that valve leaks.

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