LPG Discussion Forum

I'll have to check. 14 was on both. Not sure about the 16.5.

I'll have to check but as they are the ltft is takes a little bit of it to sort itself out once on petrol. The stfts looked OK.

I suspect another injector has failed which caused the misfire and lean code on one bank.

What injectors would you recommend? Can't do anything about where there plumbed in atm.

Cheers.

Simon can you have a look at these videos please.

Petrol from cold...

https://www.dropbox.com/scl/fi/w3x87pe6 ... 8ul7h&dl=0

LPG from cold...

https://www.dropbox.com/scl/fi/eqvac2xd ... uph4y&dl=0

LPG @ running temp...

https://www.dropbox.com/scl/fi/7tydby8a ... wfeqe&dl=0

I'm only getting issues from cold on LPG. It's perfect once up to temp or running on petrol.

Toby,

I've had a look at the videos. There's lots of info in them, can see calculated engine load but it would be better to be able to see rpm and pinj at the same time as the fuel trim info and if the sample speed was higher.

Like you say, no problem on petrol.

The running on LPG video starts with an engine temp of 23C at which it point won't have warmed up enough to have switched to LPG yet, making it difficult to know when it did switch. The LPG ECU will read slightly different coolant (reducer body) temp to the Rangerover coolant temp sensor (reducer will usually read a few degrees cooler than coolant temp), but I assume it switched to LPG at some point around when the Rangerover sensor reads 37C?

I've noticed that when running on LPG the fuel trims are generally more positive on bank 2 than on bank 1, especially during low load / deceleration type conditions and especially during warmup...
We can expect trims stft's to increase during deceleration but they seem far more likely to hit high figures or peak at +25% on bank 2 than on bank 1 when running on LPG.

'Especially During warmup' could point to LPG injector(s) on bank2 being slower to open than those on bank1 when they're cold, or could be due to the lambda sensor on bank2 getting towards the ends of it's days (at which point given same mixture on LPG as on petrol they're more likely to read lean mixture on LPG than on petrol).

'Especially during deceleration' could also point to LPG injectors being slower to open on bank2 than on bank1. LPG injectors can take time more time to open/close if worn or gunged up with sticky oily residues inside (which are thicker when cold). If we have 2 injectors (say A and B) both identical in terms of flow when fully open but injector B takes a little longer to open than injector A then the multiplier in the map (numbers in the table with the AEB system) would have to be higher at low pinj figures for B than for A, while at higher engine loads / pinj figures (where the difference in opening times is a smaller percentage of total injector pulse time pinj) the map could be the same for both injectors.

Difficult to say for sure what the problem is but I'd start by suspecting a problem on cylinder 4 since cyl4 is the cylinder that the misfire is reported on and it is on bank 2 (the bank that has the higher fuel trim especially during warmup), and I'd suspect the problem with #4 is the LPG injector on that cylinder... But isn't that the injector you've already replaced/rebuilt?

It might be worth swapping the injector rail positions around and run the same warmup test again with the rail that was fuelling (say) cylinders 1,3,5,7 now fuelling 2,4,6,8, see if the high fuel trims / misfire move with the injectors.

I used to fit OMVL SL injectors on these engines but you might get 2 OMVL SL rails that flow slightly differently to each other, OK if you're an installer and have plenty rails on shelf to mix and match until you've got a matched set but not OK if you're only buying 2 rails and the 2 rails flow differently. The SL's still wouldn't be a bad bet but these days I'd be more inclined to try Alex Baracuda 120's on it, which will all flow the same as each other. The only potential negative about Baracuda's on your setup is that the coils on them are a bit lower resistance at 1.9Ohms than the Valteks or SL's 3.0 Ohms and some installers noted issues using lower resistance (though 1.3Ohms not 1.9Ohms) coils on AEB based installs, I don't think there'll be a problem though.

Hi Simon the LPG switches over @ about 45c water temp.

It seams like I should just replace the injectors as that's basically the last part of the system apart from the ecu that's not new. I'd rather replace like for like as that will ease fitment and I should be much closer to the current settings etc. As it does run OK once warm on these injectors I'm sure they should work well in all conditions once they are new. I've only had the misfire on 2 occasions and only from cold. I never rebuilt or replaced that injector., I just cleaned them all.

If you think that will be ok, I'll order the new injectors tomorrow.

Cheers. Toby.

I would first swap the positions of the injectors to see if any future misfires follow the injector that fuelled the cylinder that misfires were reported on (an injector issue) or stay on the same cylinder (could be an ECU, ignition, compression, etc problem). An ECU fault is unlikely but there have been cases of ECU's having failed injector output driving circuitry, they drive injectors 'peak and hold' so send (say) the full battery voltage to the injector for long enough to get it open (say 3.5ms) then give the injector reduced electrical current (hold current) to keep the injector open. Not very common at all but an ECU can fail in a way in which either the peak or hold fails on one or more injector output channel, perhaps intermittently.

Ruling out all the unlikely things it does seem likely the fault is with injector(s) so you may prefer to change them without doing any further testing.

Not all injectors are equal, far from the case even when brand new. I've spent a lot of time and money researching which injectors have the most consistent performance over (e.g.) various temperatures, various nozzle sizes, various pressures, and which are most consistent in performance when compared to others of the same make from different batches. But 'consistency of performance' mostly concerns short pulse duration and isn't as critical on an engine like the Disco's (which doesn't really see pinj shorter than 3ms) than it is on a lot of more modern design engines and I'd expect most injectors including the V34's to be OK on the Disco engine over the ranging conditions... And there is sense in replacing injectors like for like, you won't need to adjust brackets etc.

So in summary, you seem to like the idea of fitting new V34's and I can see the sense in that, might as well do it.

Thanks for the reply Simon. I would normally do more tests but I'm just getting a bit fed up of my lpg system tbh. That's why I made the trip up to you. I need to get this sorted once and for all. Hopefully a new set will sort me out. I'll report back and let you know.