S80 bifuel - now refuses to run on LPG

[Hewey]

One thing that could be disabling the gas drive is a faulty motor temperature sensor. The gas drive (I think this is true atleast with the factory made bi-fuel models) can only be activated when motor temperature exceeds 15'C, and if a faulty sensor should decide to transmit information of a lower than that motor temperature during gas driving, the car will then switch back to petrol.

[duncan_ellison]

Hewey,

I wondered that, so changed out the sensor and thermostat with no effect.

I notice that some of the earlier Volvo Bi-Fuels had a temp sensor on the vaporiser body for this purpose, but mine doesn't.

Managed to get a BSR / PPC fault code reader, but there's nothing significant showing up there either, just the usual Climate control AQS fault.

If anyone else is interested to know, I pulled the shield off the tank yesterday and found that you can easily change the solenoid without changing the entire tank valve (I suspected that this may be the issue). In my case the U shaped steel bracket around the solenoid woudn't budge so instead if pushing it too far, I just gently bent it with pliers and the grey plastic coil part slid off very easilly.

Be advised that Volvo only spares the entire tank valve at £575+ VAT (Trade) !!! but the solenoid is the same as the one on the front valve near the vapouriser at a much more reasonable £70. Others may find them even cheaper as they are a standard Italian gas part.

I also found that you can take the sender off the tank without de-gassing it. Just remove the two small screws (don't break them like I did !) and it will pop off with no force. You need to use a magnet on the back of the sender to set the current tank fill level (you'll need to guess at this unless you've just had a full fill up).

I suspected that the sender might be telling the ECU that the tank was empty, (long shot as the gague reads OK), I've ordered a new one and if tis fixes anything I'll let everyone know.

I just ordered yet another new stepper motor and I'll report when I've fitted it.

Duncan

[Bigcheese1]

Strange how many posts there are with endless lists of LPG component changes only for the fault to reappear after a short time. Could it be because the fault is actualy nothing to do with the LPG system? That was certainly the case with my S60 BiFuel.

[duncan_ellison]

Bigcheese1, help me out here.

What was it in the end that fixed your S60 ? ETM ? Coils ? Plugs ?

Duncan

[Bigcheese1]

In my case it was the ETM. Surprisingly, the fault was only apparent when switched to LPG though.

[duncan_ellison]

Bigcheese1, thanks for that input.

I've swapped everything else I can think of, so the only places I can go now are the :

ETM
ECU
Fuel valve on the tank (already replaced the solenoid)

This is very helpful, now I know that you were only experienceing problems on gas and others report no DTMs with the ETM as well, I'll go there next.

I'm already the thick end of £1,000 in parts for a vehicle that's probably only worth £2,000 and this is turning into a case of diminishing returns.

Duncan

[Bigcheese1]

I think the V70s manufactured between 1999 and 2002 had dodgy ETMs so you should get a discounted price if you decide to replace it. Try a few different main dealers if you don't get a good quote.

I hope I'm not pointing you in the wrong direction but I did read that Volvo predict a 94% failure rate for ETMs at 100k miles. As you say, it's always hard to know how much money to throw at these faults before you decide to just cut your losses.

[duncan_ellison]

Originally Posted by Bigcheese1

I think the V70s manufactured between 1999 and 2002 had dodgy ETMs so you should get a discounted price if you decide to replace it. Try a few different main dealers if you don't get a good quote.

I hope I'm not pointing you in the wrong direction but I did read that Volvo predict a 94% failure rate for ETMs at 100k miles. As you say, it's always hard to know how much money to throw at these faults before you decide to just cut your losses.

OK - I'm on the right track now. Thanks to Big Cheese's input I persisted in looking at the ETM. I forced an entire can of throttle cleaner into it especially into the spindle to try to get it into the carbon potentiometer tracks. Ran like a pig for a while whilst the cleaner dried out, but now much better. Still not starting properly on gas (could just need the pressures turning up a bit) but been to London and back now without a switch back to petrol or stalling on gas.

Not a single DTC to suggest problems with the ETM, but I did check the service history and found 3 Volvo software updates aimed at the ETM. My guess is that after Volvo's meddling, the ETM could burst into flames and the computer wouldn't report an error.

Hope this helps others.

Duncan

[John_C]

That's interesting, I know the software updates basically apply a smoothing algorithm to the output of the ETM so the effects of the damage to the tracks inside it aren't felt as badly i.e the sudden spikes in output which characterise the problem are removed so it still more or less works until it fails completely.

I wonder if these changes only apply to the petrol ECU and the gas ECU is still seeing the spikes, pooing itself as a result and switching back to petrol?

[petrov05]

Hi Duncan, I also have S60 factory Bi-Fuel on 150 000 miles. On petrol runs smootly but on LPG can't even run 2 miles. I did the trick with the injector cleaner but no efect. Then before I did anything else I spend endless nights on the net researching the problem. After reading lots of material I came to conclusion that the ETM is the most probable cause of the problem. http://home.comcast.net/~donwillson/...20America.html this is a link to a page where an english guy has taken Volvo and a Main Dealer to court and won free of charge change of the ETM. He has bought the car second hand and it broke down completely and the main stealers and Volvo refused to change the ETM and sort the problem even after they have recalled 10 000 cars with faulty ETM in America. He won!!!. I am just between jobs and I have plenty of free time. I'll be starting on Volvo and the dealers from tomorrow.
Thanks and I hope it is some help.