I've found the gauges to be relatively useless on mine :)

Full is full - great, I know its actually filled up and I haven't missed 70 litres of LPG pissing out.

Anywhere between 50-100 miles, it'll go from three lights to on the red over a distance of about 3 miles somewhere in that range. Then... sometime later I'll go back to one light. Where I might sit until about 200 miles, where it actually runs out and I go back to petrol :)

Today, after finally getting the bonnet open, I've replaced/ repaired all the engine compartment LPG grounds, adding in a direct ground to the LPG ECU case, all back to -ve battery terminal. No difference- still comes on if it feels like it. Can't road test cos no bonnet catches or cables until tomorrow if new cables arrive.
While I'm waiting for those I'll go right through the permanent +ve feed, replacing everything as close to LPG ECU connector as I can.
If time I'll pick up +ve ignition switched from a new location- again replace as close to ECU as I can get.
Cold and clocking off for the day.
EDIT- is it worth grounding the ground connection on the tank solenoid to the chassis?

Orangebean wrote:

EDIT- is it worth grounding the ground connection on the tank solenoid to the chassis?

I was advised to do so by an installer from Vogels, only reason I can think of it saves the ground all the way back to front.
It one of the grounds from/to the ecu though.

That's what I was thinking, or rather, what you prompted me to think about! Belt and braces can't hurt- as long as it's the right one that gets grounded.
Unless error detection in the ECU is very refined though, I can see a sluggish solenoid valve causing running (on lpg) problems, but not shutting down the whole ECU and selector switch.

It's better to ground everything back to the battery. Mine originally had the ground to the tank solenoid and gauge tied to the tank mounting bolt. The level gauge would give a different reading depending on whether the tank solenoid was pulled in or not due to a small voltage drop in the ground. Tying all the grounds together and bringing a single main ground back to the battery meant that they are all at the same potential. However, that's just best practice and isn't going to cure your intermittent problem which is almost certainly in one of the supplies, most likely the ignition switched.

There's no real error correction. If it gets power, it powers up, if a solenoid doesn't work because of a high resistance connection, a dead coil or even completely disconnected, a modern ECU will detect a problem and flag an error (and not allow it to try to energise) whereas an older one will just detect the lack of gas pressure and not switch (or not dewtect the lack of gas pressure and the engine stops).

That's the path I'm following Gilbertd. In my mind a failing or broken sensor link (pressure, temp etc) might shut down the gas side but not the petrol and certainly not the switch/ lights.
I now know the grounds are all good. Next comes the power. As I've got the kick panel off to do the bonnet cables I may as well pull the underpanel and binnacle cover and check continuity of switch cables back to ECU as well. It's marginally warmer with my head in the footwell too, which is nice.

Orangebean wrote:

It's marginally warmer with my head in the footwell too, which is nice.

Believe me, when my head works as a stove my temper is below zero :)

:) Tony
Ever the optimist, I've ordered up the vapour filter as recommended many pages ago, some gas pipe and cobra clips so that I can move things around for a more orderly, and accessible, installation.
I suspect water plumbing won't be too far behind. What I have seems to work and not leak and I dislike doing anything to do with the bulkhead heater pipes because of the potential effect on the O rings inside of pulling/ pushing on the pipes, but I like things tidy and set up so nothing will rub against anything else and it's not that yet!

Take care with those heaterpipes indeed, there is no support at all other than the O ring support. Are you plumbing them in series or parallel?
Parallel gives the neatest install (and can swap the matrix when needed and keep the LPG functional) but in series you are sure they both get heat.
Dilemma's. Find a place for the vap just below level of the overflowbottle.
Richard may have a point in bringing all grounds to one spot: the - terminal, my levelindicator is acting up weird. It keeps toggling between 2 and 3 leds, no matter the volume in the tank. Sometimes it shows 4 leds on a nearly empty tank. I'm going to change that.
Tony

The next step should probably be check main live feed and switched live voltages at the ECU when the switch fails to light.

Ferryman wrote:

Parallel gives the neatest install (and can swap the matrix when needed and keep the LPG functional) but in series you are sure they both get heat.

Parallel gives a messy looking engine bay with Tee pieces everywhere and reduced coolant flow through both the heater matrix and the reducer. Horrible bodge dating back to the days when heater temperature was controlled by a valve restricting the flow. On a P38 (and RR Classic) it wants to be series every time. How often do you need to change the matrix anyway?

Hopefully not often but I'm glad my reduced is plumbed in parallel right now - even if it's sodding freezing driving round with no heat in January!!

Mine will end up with whatever I can get in a hose size to fit heater matrix stubs and has suitable bends in it! At moment, it's parallel. Ideally will be series, but let's see.
Didn't do much LPG work today- just checked switch cable continuity as I had panels out to change bonnet release cable. Sidetracked by the usual broken top fasteners on binnacle cover. Another aluminium strip/ JB Weld masterpiece. Damn I'm getting good with that stuff!

Huh? Is your heater bypassed or just blanked off? When I picked up the SE it had the reducer in parallel but the heater matrix replaced with two 90 degree plumbing fittings. As there was no restriction for the coolant through the bypass, nothing was flowing through the reducer. It would get warm enough to switch over but then the chilling effect of the vaporisation would cool it down and it would start to run ridiculously rich after about 30 seconds as the reducer started to freeze. I stopped, folded the hose over on itself and put a tie wrap around it so all of the heater flow went through the reducer so I could drive it home on LPG (and 6 cylinders as one head gasket had blown between the middle two cylinders).

So if you have the heater matrix bypassed, I'm surprised it will even run on gas. I'm also not sure how you are driving it in this weather. You're a fair bit further north than me and I wouldn't want to drive mine at the moment with no heater!

Going to throw it out there - after finding my thermostat had a moulding defect in it causing the return from the heater core to be 90% blocked off, we decided to leave my LPG and heater in parallel, and I've had no issues with lack of heat at idle since or the LPG taking ages to switch over - it has been a bit longer in the last few days, but its been much colder too. The inlets on my OMVL reducer look seriously restricting, 16mm pipe is a loose fit, and the actual ID is tiny.

There are bits of my plumbing that could be neater, but that's mainly because of what we had available to put it back together at the time, and I'm not going to drop a load of coolant again just to tidy the last bits up until there is a more pressing reason.

I've gone back to parallel plumbing too. I swapped to series plumbing previously, and due to where my vapouriser is, either way I have pipework across the back of the engine to it - but figured that it would be better.

To make it neat, I used a solid metal 90 degree elbow, as the hose run would have just kinked it to get it around the back of the engine neatly. The result - a luke-warm cabin as there wasn't enough flow through the heater matrix.

Mine was plumbed in parallel when it was installed, back in 2008, and I never had an issue with it cooling off the vap. I finished off the LPG plumbing today so I can get it set up to run on gas again with the new engine, and the reducer was still warm when I touched it, about an hour after getting home - so I really don't think it's going to freeze over in my case.

I've done my plumbing so that the hoses run around the back of the engine and are lower than coolant tank. Also as most reducers are 16mm, and the RR hoses are 19mm if you use the 19-16-19 T pieces available, then you don't have any extra pipe reducers either.

I now have a nice hot cabin again :) (sorry Morat - not rubbing it in! - we'll have yours sorted soon!

I can see justification for all above points but it's still true that over 90% of P38s and most other LPG converted vehicles have reducer plumbed in parallel without issues.

Both the parallel method and the series method could mean the heater matrix and reducer each only get half the flow - for obvious reason with the parallel method, the series method can mean twice as much restriction in the same pipe so the total flow can only be as much as the part with the most restriction. Series wouldn't be great with a fairly clogged heater matrix, in fact I have seen certain factory converted Vauxhalls fail to run on LPG due to this problem and during summers have re-piped the reducer in parallel to allow running ob LPG until the owner had the matrix problem sorted (even following matrix repair, parallel can be left in place with no ill effect)..

Which method works best (keeps both reducer and matrix hot) will depend on aspects of the vehicle. Some heater circuits will be capable of flowing a large volume but without much of a head of pressure, others will have limited volume but with a high head of pressure while flow is limited. So, with parallel method and only half as much total restriction, some heater circuits will flow twice as much water in total, meaning a no compromise reducer or matrix flow situation. Other vehicles like some Mercs, intentionally restrict water flow under certain conditions such as engine above idle rpm, seemingly so heater water flow is consistent between idle and off idle, and where you can't tap into the un-metered side on such vehicles series is best. In all honesty as long as the reducer is low enough on a P38 it doesn't seem to make any difference.

Wouldn't want to pipe some reducers in series.. some such as old Bigas only have 10mm water pipe connections...

Simon

I'm only going on my own experience with two cars, both of which were plumbed in parallel when I first got them and both running single point so run on gas from a cold start. The Range Rover Classic would freeze the vaporiser within 300 yards if the ambient temperature was lower than about 5 degrees which made it flood the engine and die. The only way of getting it to restart was to switch to starting on gas, with the vaporiser solenoid disconnected and crank it over for ages with the throttle pedal on the floor. Once it had started and run on the gas that was still laying in there, I had to run on petrol until everything had thawed out. The P38 never suffered from freezing but the heater would drop to lukewarm when sitting in traffic at idle on a cold day. Not pleasant when sitting in a queue for a car park while trying to go to do my Christmas shopping!

So it seemed that on the Classic I was getting more flow through the heater but on the P38 more was going through the vaporiser. Changing both to series plumbing meant that both got full flow and cured both problems. I agree that if a vaporiser has restricted flow it could have an adverse affect on the heater but that hasn't been my experience on the 3 cars I've tried it on. I did the same on the SE with it's eGas multipoint and that definitely allowed the vaporiser (reducer) to warm up quicker so it would switch to gas sooner with still no adverse affect on the heater.

Bloody heater outlet pipes are 22mm! Never gonna get a 19mm on there!

Quick question for anyone passing through as not shown in system manual.
Gas temperature sensor should be placed:
A Upstream of gas filter
B Downstream of gas filter
C Doesn't matter
Ta!