Hope this isn't too far off-subject...

I recently bought an Launch X431 Diagun 5, it will do OBD2 and OBD1 stuff on a wide range of vehicles and communicate not just with the engine ECU but also with other ECU modules. I had a P38 here for LPG diagnostics repair only yesterday but didn't really have an excuse to connect the Launch because I diagnosed and fixed the LPG problem in no time but I'd have liked to have tried the Launch on the P38 to find it's capabilities on the P38, I doubt it will feature as much on a P38 as a Nanocam but it would be nice to know if it could do suspension level sensor learns etc. The 'fix' to get the LPG working again on this P38 turned out to be to open the manual shut-off valve on the old Ikom 30 degree tank (old enough to have a 12mm copper fill pipe) lol. But as soon as it pulled up I told the owner he probably had a knacked lambda sensor, I could smell the exhaust running rich. Turned out these 2 young lads run a P38 dismantlers/scrapyard and were already aware their P38 needed a lambda probe. I told them it was needed on bank2 and advised them to join this forum - could be good news for some of you too if they do join up (since they run a scrapyard for P38's).

On another make/model vehicle I recently attempted diagnosis of an intermittent misfire accompanied with error codes pointing to the crank sensor and sometimes cam sensors, the same codes occurred even with the cam sensors ruled out (running the engine in group injection mode with cam sensors unplugged a fault still occurred pointing to the crank sensor and the revcounter reading that is crank sensor driven fluctuated when the fault was occurring). Using my cheap digital oscilloscope I diagnosed this problem as one of a knacked flex plate, something related to massive crank thrust bearing problem or knacked rear main crank bearing... because when the fault occurred the crank sensor signal connected directly to the scope showed an occasional double width pulse (the flex plate teeth seemed in good order and the same results were repeatable with several different crank sensors). This conclusion seems a little far fetched even to me (I made the conclusion) but when you've ruled out everything else the remaining possibility(s) must be true and I can think of nothing else that could be true in this situation. The car has since been to another 'specialist' (vehicle dismantler rather than diagnostics master in reality) whom, like me, at first suspected a dodgy engine ECU. He swapped and recoded a replacement ECU but the problem remained. The same car will be going back to the scrapman in a few weeks and I'm quite certain that this specialist won't be connecting an oscilloscope... But I do expect he could fix the problem by fitting a replacement engine along with it's flex plate and he has easy opportunity to do that because he has plenty engines lying around. If he ends up fitting a replacement engine I reckon that either the flex plate will be the fix or the engine without mega excessive crank end float would be the fix... and I expect my unusual diagnosis conclusion to be correct.

I remember watching 'tomorrows world' on TV as a kid when the toilet roll oil filter would supposedly mean very clean engine oil for very high mileages between changes... but didn't mention the breakdown or use-up of additives in the oil during that time. Which is why I expect it never became popular and people still needed to do regular oil changes (additives and detergents). Still I don't worry about cleanliness of oil, running on LPG sees to it that oil remains much cleaner than running on petrol and especially cleaner than running on diesel. ;-)

Can do maybe 3 times the mileage for same oil colour change on LPG versus petrol, probably less important regards detergents etc. But not much will protect against ground off metal bits found in a filter except perhaps good engine design.

I'm surprised modern engines don't have a supplemental electric oil pump fitted to build oil pressure before the mechanical pump kicks in with the engine running... The electric pump could run from turning on the ignition through cranking the engine until rpm is well above cranking speed.

On vehicles where the oil filter isn't orientated with the fitting at the top I've often wondered if changing the filter if not needed does more harm than good... The old filter might have still been doing it's job properly, a new filter will take a short time to bleed up during which time the engine runs without oil pressure.

Still like most other people I change the oil filter with every oil change.

Can understand that a used oil filter might be more effective at filtering than a new filter... but maybe not if the same total amount of oil flow is squeezed through parts of filter that are less blocked than the more effective (at filtering) parts - maybe in this case some parts of the filter are effectively blocked to flow and there will be more pressure difference between none blocked parts and open parts so more crap can get through.

I don't do much general servicing (oil changes etc) on customer cars but when I have done them I've found that the most common types to have collapsed screens are the standalone (none cartridge) type as fitted on BMW's, Mercs and (particularly) Vauxhalls. These are normally very easy to access but probably because they can get very tight to remove and because the housing is plastic (an owner can't just knock a screwdriver through the side to use as a lever without breaking the housing) they often go unchanged for years.

In my post #625 above I should have written 'stops until cranking but obviously pumps during cranking'.

You can't force start most BRC gas systems on gas.

I don't think the potential for a leaking LPG injector or reducer has been mentioned? Run on gas and the gas system gets pressurised, turn the engine off and gas leaks into the manifold, try to start the engine and the engine gets petrol and gas instead of petrol and air until there's been enough cranking to pump the gas out of the manifold but by which point the plugs might then be wet with petrol.

At least worth ruling this out by driving on petrol for an hour before turning the engine off so if there is such leak gas will have been used with the engine running rather than displace air in the plenum?

Others will know better than me but iIrc the pump doesn't work on these until cranking, either that or it runs for a couple of seconds in pos2 then stops until cranking. 17 Seconds after stalling is probably about right?

A lot of engines give a really long 1 or 2 petrol injector pulses immediately on turning to the cranking position before reverting to normal pulse lengths for cranking which may be temperature dependent.

Great write-up!

That's what I would have presumed thanks Bri.

Gilbertd wrote:

They'd need a good excuse because you don't fall under the distance selling regs.

Thanks for that. What about 'cool-off period' ?

My mate in Liverpool deals in used motorhomes now, in the past he's been a used car dealer. In both cases he's had people buy one but come back just before a couple of weeks are up saying they want their money back having put over a 1000 miles on the clock. He told them he'd charge them a rental and cleaning fee, in some cases this has led to solicitors exchanging letters but as far as I know he came out on top.

I've never had it but I wonder how I would fare if I converted a vehicle to LPG for someone and a couple of weeks later they returned and asked for the system to be removed and their money back - I imagine I could charge them for the labour but have to refund the cost of components?

75 Litres is 16.48 gallons.

185 miles from 16.48 gallons is 11.23 mpg. Which could be right if driving is around the doors, or would be low for a 60mph constant steady cruise on the motorway.

Mpg much depends on the driving conditions. If you're stuck in a long traffic jam and leave the engine running the whole time you could achieve 0 mpg, if you drive at 120mph you might get 4mpg.

My first thoughts were along the lines of flaps like Brian said in post #2. I'm not familiar with heater box design on P38's but if flaps move sideways and have become free to swing (actuator broke or something) it would be easy to imagine turning causing them to swing sideways.

I have known heaters get hotter/colder when turning, going uphill/downhill or with changing engine rpm due to water flow aspects but usually when there's a problem with water flow or just not enough water in the system.

It runs on LPG so will have an LPG pressure reducer plumbed into the heater system. I've known cases where reducers have been plumbed in parallel and most water has gone through the reducer at the expense of flow through the matrix in some conditions but centrifugal force during turning can change the dynamics and pushed more hot water through the matrix. Or plumbed in series and overall flow has been restricted but centrifugal force has caused more overall water flow perhaps by seeing the reducer (if fitted at a high point) is more fully bled up.

Although the problem is described as occurring when the heater is being used, if AC is on it could be due to something that causes the AC clutch to disengage when turning right.

Cornering might imply body roll and/or a change in engine rpm.

Wouldn't want to go far and it completely break. If you're not going out much due to lockdown it could be the ideal time to arrange a date with insurance windscreen fitters, they might not be as busy as usual due to people not using their cars so much, or if they're busy (maybe they get busier with cracked screens this weather) and mess you about changing the date of an appointment you won't mind so much if you don't have any plans anyway due to lockdown. Any down sides to fitting a windscreen in cold damp conditions? If it's not an inconvenience it's a bonus... new completely pit free screen with fully working electric heating.

Would it help to take the plugs out? Thinking it will crank faster so oil light will go out quicker while there won't be as much weight on bearings in case there is no oil pressure.

A mate used to have a race spec engine from a 70's 3L Capri in a mk2 Escort, it had a manual oil pump he'd pump a few times before starting the engine. Could anything like that be plumbed to the oil pressure sensor port to get oil around the engine and speed up the time it takes for the oil light to go out next time you time cranking?

I used to rebuild my own alternators, there was a local firm called Start & Charge in Grimethorpe. He kept all the brushes and bearings in stock, if you turned up with your alternator would identify which bits you needed, sell you the bits for a couple of quid and tell you how to do the job. Don't know if they're still there.

Some will have heard my story about having an alternator fail on a bank holiday weekend when me and my son decided to go and explore Scotland? No chance I could get the alternator fixed or a replacement on the bank holiday and I knew I could fix it for a couple of quid back home... so I bought a generator, wired it's 12v output to a cig lighter socket and drove all the way home with the genny powering the car electrics, no heater or radio and only sidelights on.

Gilbertd wrote:

It's looking more like the figure given by OBD2 standard and displayed by the Nano, is calculated differently to how Land Rover calculate it.

I wouldn't be surprised at that. What diagnostic gear do Landrover use?

You'll have to remind me if this is Bosch or Gems, I probably don't fully remember intake ducting arrangement for Gems but all air including IAV passes through the MAF on Bosch(?) and I seem to remember (though now expect to be corrected) it does on Gems? Gas entering downstream from the MAF is still gas, doesn't detract from the air the engine needs.

On quite a few P38 LPG conversions, and in fact on quite a lot of other vehicles too, I have seen engine load decrease at idle running on LPG compared to petrol. Some of this can I'm sure often be attributed to new LPG injectors supplying more equal cylinder to cylinder mixture than old/worn petrol injectors but I think there's a bit more in it than that because the same happens on some engines even with petrol injectors known to flow exactly the same - I believe it's related to the difference in stochiometric ratio. Another advantage (in some cases) of a mixer over injection is that if there's any difference in airflow cylinder to cylinder (which can effect cylinder to cylinder mixture in the same way as worn injector flow rates) a mixer will see that each cylinder gets the same/correct mixture anyway.

Most metric live data readings use grams per second as the unit of measurement for airflow, 18Kg/hr equates to 5 grams per second which seems about right for a 4L engine.

Maybe if you lightly touch the throttle in D the load reading will increase, or maybe it will see you're on the throttle and load reading will change to an 'out of idle mode' (my term hehe).

For most intents and purposes P is the same as N except P brings in the parking pawl, same load on the engine anyway. But maybe passing R causes a momentary ignition timing retard that could see the load reading blip positive a little (idle is less efficient with retarded timing but could make for less harsh gear selection)?

For sure the engine isn't running at 28% of power producing or airflow/fuel using potential when it's just idling even in D with AC on and the alternator causing maximum drag. Doubt a normal calculated load reading would reach 28% even if it were a manual labouring the engine flat out at 1000rpm (e.g. high gear low speed uphill).

Load seems to be calculated differently by different vehicles/ECU's. It's often loosely related to the maximum expectation of pinj x rpm, or max expectation for airflow. This of course means that even at full throttle if rpms are below the torque peak calculated load will be less than 100%.

Most OBD systems on most vehicles reckon calculated load is about 3% or so at warm idle. Iirc (but I forget what OBD readers I've used for this) I've seen calculated load much higher than that 3% at idle on P38s.

The calculated load figure isn't a reading I'd normally take much notice of. A manifold pressure reading at idle is a much better pointer for idle efficiency etc. The Rover V8's do seem to idle with a bit more manifold pressure than the average engine, I put this down partly to the cam and valve gear setup compromising a bit of bottom end charge trapping ability to gain a bit more top end (rpm) charge trapping ability.

On some ECUs OBD readings seem to change to a different kind of mode at idle. Maybe the 25% reading reflects the engine could only shift 4 times as much air at idle rpm if the throttle were opened? Does the figure increase by a lot if you put it in drive and turn all the electrical gear on?

Happy New Year...
A strange time to be online but everyone's in bed and I'm bored with the TV, might as well set the ball rolling. Hope for less Covid this year.

Will it depend on whether the birthday is counted as midnight tonight or the time of 'birth' on the 29th?