Rich Fuel Problem

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JX350
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Rich Fuel Problem

#1 Post by JX350 » Wed Jan 01, 2020 10:48 pm

Hi all,

I have just joined the forum as I have a problem with my car that I have been trying to find the cause of for a long time. Firstly happy new year and hopefully I'll be part of these forums for a while.

I have owned the car since 2017 and I purchased the car with a Landi Renzo system already installed.

My car is a 2003 Jaguar XJ8 (X350) 4.2 litre V8 NA.

The car ran great for a long time and then started to get an engine vibration at between 1300 and 1800 RPM. When looking at fuel trims for short and long it seems that the car is running too rich but not enough to raise any rich running fault codes.

I've done lots of things like clean the MAF, replace spark plugs, petrol fuel injectors etc.

I normally do most of the maintenance myself and I thought this problem was not related to the LPG system as it runs rich when running on both petrol and or on LPG.

As I have very little experience with maintaining LPG systems I have read that they need the filters changed etc which I was not aware of so I have not done this as normal maintenance. I've also been doing some research and I have found that leaking gaskets and orings in the vapouriser can cause issues such as rich running.

So I'm going to urgently replace the filters once I find out what size mine needs.

Can a leaking vapouriser really cause this rich running condition even when running just on petrol?

How can I tell if the vapouriser is leaking somehow? I have an IG1 located right at the front of the car so it's really nice and easy to get to. Also if I need to replace the gaskets inside the vapouriser do I need to remove it from the coolant system or do you know if I can do it in-situ?

My vapouriser has the vacuum hose running to the back of the throttle body which is located post MAF sensor. If the vapouriser is leaking, would it be leaking gas into that pipe and fuel is then entering that way unmetered?

Sorry for all the questions but I've run out of options so I think this rich running has to be being caused by the LPG system somehow.

Thanks,

Chris
Current car: 2003 Jaguar XJ8, 4.2 V8 NA with a Landi Renzo LPG system.
YouTube Channel: https://www.youtube.com/channel/UC-AcBg ... R_9ym1fuGA

JX350
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Posts: 12
Joined: Wed Jan 01, 2020 6:42 pm
Location: Cornwall, UK

Re: Rich Fuel Problem

#2 Post by JX350 » Wed Jan 01, 2020 10:57 pm

Hi all,

And here is a video I made of the rich running problem. I ran the car at full temperature and on LPG and rev'd the car stationary at differing RPMs. This may help.

https://www.youtube.com/watch?v=QOyGxI-_8Ug

Thanks,

Chris
Current car: 2003 Jaguar XJ8, 4.2 V8 NA with a Landi Renzo LPG system.
YouTube Channel: https://www.youtube.com/channel/UC-AcBg ... R_9ym1fuGA

Brian_H
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Location: Milton Keynes

Re: Rich Fuel Problem

#3 Post by Brian_H » Wed Jan 01, 2020 11:44 pm

JX350 wrote:
Wed Jan 01, 2020 10:48 pm
Hi all,

I have just joined the forum as I have a problem with my car that I have been trying to find the cause of for a long time. Firstly happy new year and hopefully I'll be part of these forums for a while.

I have owned the car since 2017 and I purchased the car with a Landi Renzo system already installed.

My car is a 2003 Jaguar XJ8 (X350) 4.2 litre V8 NA.

The car ran great for a long time and then started to get an engine vibration at between 1300 and 1800 RPM. When looking at fuel trims for short and long it seems that the car is running too rich but not enough to raise any rich running fault codes.

I've done lots of things like clean the MAF, replace spark plugs, petrol fuel injectors etc.

I normally do most of the maintenance myself and I thought this problem was not related to the LPG system as it runs rich when running on both petrol and or on LPG.

As I have very little experience with maintaining LPG systems I have read that they need the filters changed etc which I was not aware of so I have not done this as normal maintenance. I've also been doing some research and I have found that leaking gaskets and orings in the vapouriser can cause issues such as rich running.

So I'm going to urgently replace the filters once I find out what size mine needs.

Can a leaking vapouriser really cause this rich running condition even when running just on petrol?

How can I tell if the vapouriser is leaking somehow? I have an IG1 located right at the front of the car so it's really nice and easy to get to. Also if I need to replace the gaskets inside the vapouriser do I need to remove it from the coolant system or do you know if I can do it in-situ?

My vapouriser has the vacuum hose running to the back of the throttle body which is located post MAF sensor. If the vapouriser is leaking, would it be leaking gas into that pipe and fuel is then entering that way unmetered?

Sorry for all the questions but I've run out of options so I think this rich running has to be being caused by the LPG system somehow.

Thanks,

Chris
Easiest one first - yes the vapouriser might be leaking via the pipe you identified, equally it can leak via a leaky gas injector. But if its doing this, it should stop once the pressure in the gas system has gone (a few minutes of running on petrol should be enough). You can test if its leaking by removing the hose and putting the end of it into some water, watch for bubbles (disconnect from manifold end so the vapouriser is on one end of the hose, and the other in the water). They can also leak gas into the coolant or the other way round depending on whats going on.

You say its at the front - is it quite high up? they can become airlocked which limits their ability to control the pressure properly, particually if they are higher than the expansion bottle.

To replace diapgragms is a case of removing the unit from the car and unscrewing it until you get to the diaphrams and then reverse the process to put it back together. But you can usually minimise coolant loss by either connecting the two pipes to each other, or keeping them raised while disconnected.
Do you know which Landi system it is? Omegas possibly? And what injectors?

Filters won't be the cause of running rich, though changing them isn't a bad idea if your doing other work on it. there is typically 2, one on the feed to the vapouriser, the other on the feed from it to the injectors (you might have the other landi system that doesn't use injectors, IG system i think that is, but I'd expect a filter on the outlet from the vapouriser somewhere either way).

You mention the MAF - Is it fitted with a genuine branded MAF or does it look to be an aftermarket one? If someones been playing around trying to sort it and replaced the MAF, the cheap ones available can cause that sort of problem. Some cars seem fine with them, others really aren't. You might be able to diagnose that by unplugging the maf to see if the trims improve at all if you haven't already tried that.

JX350
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Joined: Wed Jan 01, 2020 6:42 pm
Location: Cornwall, UK

Re: Rich Fuel Problem

#4 Post by JX350 » Thu Jan 02, 2020 9:48 am

Hi Brian,

Many thanks for the quick reply. All very helpful. I'll get the vacuum pipe tested to see if it is leaking gas through it.

I have very little paperwork unfortunately but I do have a small manual for the system. It is a Landi Renzo LSI system. I am familiar with what items are installed in the car so I know there is a vapouriser, pressure sensor, valve saver kit and electronic delivery module, LPG ECU etc and injector harnesses of course.

I have also just found paperwork to suggest that the LPG system was last serviced in 2016 !

The kit does have two filters by the looks of it, as you state. One just on the side of the vapouriser and one in line post vapouriser.

My valve saver kit is also fitted into the top of the manifold and not part of the LPG injector rail or feed pipes and have separate stud into the manifold. Unfortunately the valve saver kit seems to be a 'no name' type and has now part numbers or manufacturer names on it. Although I need to check the electronic distribution module as that may have part numbers on it.

The kit was originally fitted and last serviced by Leicester Gas Services but I have tried to contact them and they never answer the phone or emails so I haven't been able to get any further details from them on what exactly was fitted.

I do know that the vapouriser is a Landi Renzo IG1 as I can see the model number on it.

The vapouriser is fitted at the front of the car, just behind the grill and is fitted just under the coolant expansion bottle so the vapouriser is definitely lower than it.

I have noticed in the past when I have done a petrol injector replacement that even with the car running and set to petrol that removing the LPG fuel delivery pipe that feeds the LPG injectors that the LPG pressure is still quite high. I have had this rich running problem since before removing the rails for this work so this has not caused this problem. Does the pressure mean that my LPG system keeps the LPG pressurised even when it's running on petrol? If so and I have the leak into the vacuum hose then that could explain why I am seeing rich running even on petrol.

The MAF is an original and has all the right marking and part numbers for my vehicle. It has a Denso MAF sensor which it should. I have tried to disconnect and clean the MAF before but cleaning makes little difference. In fact, if I unplug the MAF then the car throws a restricted performance and puts the car in limp mode and runs very rough.

Thanks,

Chris
Current car: 2003 Jaguar XJ8, 4.2 V8 NA with a Landi Renzo LPG system.
YouTube Channel: https://www.youtube.com/channel/UC-AcBg ... R_9ym1fuGA

JX350
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Posts: 12
Joined: Wed Jan 01, 2020 6:42 pm
Location: Cornwall, UK

Re: Rich Fuel Problem

#5 Post by JX350 » Thu Jan 02, 2020 9:01 pm

Hi all,

I don't know what filter size the vapouriser needs so I was going to disconnect and remove the solenoid but realised that I don't know where to isolate the gas in the feed pipe. Does anyone know how I can stop the gas from feeding the vapouriser so that I can get the filter out? Or is the gas fed electronically from the tank in the boot and therefore no need for a shut off valve of some kind.

Thanks,

Chris
Current car: 2003 Jaguar XJ8, 4.2 V8 NA with a Landi Renzo LPG system.
YouTube Channel: https://www.youtube.com/channel/UC-AcBg ... R_9ym1fuGA

Brian_H
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Posts: 1774
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: Rich Fuel Problem

#6 Post by Brian_H » Thu Jan 02, 2020 9:24 pm

There should be somewhere around 1-2 bar of pressure in the front end - not a lot, but enough to make a pop when the hose is undone if you don't depressurise it first. theres a couple of ways to depressurise it, the easiest is if your tank has a manual shut off that you can access (yellow lever or thumbscrew on the valve) to shut it, and run the engine till it switches back to petrol. If that isn't an option, unplug the solenoid coil (needs to be the rear one if you want to change the filter on the front solenoid). And same as above.

Be aware if someone has been messing around before, that the solenoids can be disabled by removing the internal post. So if you do the above, you know the gas is shutoff for sure!

Otherwise, its a case of slowly undo the connection and let the pressure escape, do that somewhere outside and with no low-lying areas the gas can collect in.

The typical landi filter is a 14mm one, and can be a pain to find replacement cartidges to replace it as its an odd size (at least the one I had was, though that wasn't LSI so yours might be something more normal). But it has a replaceable paper element so there are other options. Otherwise you need to look around for one with the matching internal diameter for the hose spigots.
I think this would be the one you might need - https://tinleytech.co.uk/shop/lpg-parts ... ed-fl-one/

The one on the vapouriser itself, will depend on the shutoff valve fitted, the usual one is shown on the photo on this listing https://tinleytech.co.uk/shop/lpg-parts ... vaporiser/

Would suggest once your at a point where filters would be a sensible thing (they won't be the current problem you have, but if your looking to rebuild vapouriser etc then replacing them at that point is more sensible) I'd suggest you ask the supplier for advice on the correct ones - Tinley are a good bet for that and will be able to assist you get the right bits.

Wouldn't be too concerned on the brand of valve saver system as long as its distributing the fluid at the correct rate and to all cylinders.

I've just watched your video (didn't have chance to do so yesterday) - Is it even likely the air intake temp shown is right, its showing 149F which would be around 65C? You have the data there also for the air intake rate, it would be useful to compare that to the expected rate if you can find that detail (will be specific to your car). It would also be more useful to look at the other two o2 sensors, you look to be monitoring the post-cat ones rather than the pre cat ones there.

JX350
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Posts: 12
Joined: Wed Jan 01, 2020 6:42 pm
Location: Cornwall, UK

Re: Rich Fuel Problem

#7 Post by JX350 » Thu Jan 02, 2020 10:08 pm

Thanks Brian. I've also managed to find filters but they all appear to be for my system but are different sizes. I will get them out, measure them and then speak to a supplier. I don't have a shut off valve on the tank etc and I can't find one anywhere between the tank and the vapouriser. So I will be doing the work out side anyway so I'll just undo the solenoid and let off the gas until it depressurises.

Yes in the video it does show the intake temp which comes from the MAF as the MAF in our cars is combined with the intake temp sensor - it's also why they are nearly £200 from Jag. It's mounted in the air intake pipe just pre the throttle housing. I'm not sure what the correct specs are for normal intake temps. I'll try to find them from the service manual.

I've tried to get the other pre cat O2 sensor readings but for some reason my odb reader always gets zero readings for them even though it can see them. I have no idea why. I will try again at some point.

All the readings in that video where taken stationary and with the car at full operating temp so the car was not fully under load when running these.

Thanks,

Chris
Current car: 2003 Jaguar XJ8, 4.2 V8 NA with a Landi Renzo LPG system.
YouTube Channel: https://www.youtube.com/channel/UC-AcBg ... R_9ym1fuGA

LPGC
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Re: Rich Fuel Problem

#8 Post by LPGC » Sat Jan 04, 2020 9:06 pm

V8 Jag (Ford) engines have one throttle body so if the reducer vac pipe connects to the manifold near the throttle body a reducer diaphragm leak would cause richer running on both cylinders banks.

First to make sure we're seeing correct info in the video - It shows OBD2 readings that aren't the best for diagnostics of your problems... Slow sample rate (won't show aspects such as stft's returning to zero when engine load changes). Post cat lambda readings rather than pre-cat, we're not so much interested in post cat readings as pre-cat readings, should set lambda readings to show S1 (sensor1 / pre-cat lambda) readings. Fuel trim bars only show between -15% and +15% - a figure rather than bars and on a scale not limited to +- 15% would be better. Some code readers/software need setting up differently to show trim/lambda readings between narrow band probes and wide band probes - be sure you set software settings for B2 readings (which seem minimum'd out at -15%) the same as for B1 readings (which seem to be working properly). Some code readers (connected to cars using certain OBD protocols) tend to give limited info if connected at the wrong moment or after a connection hiccup, in which case they may only show B1 info (or spurious info for B2). The high IAT reading could be incorrect because you set that up incorrectly, or if real could be because you tried cleaning the MAF and broke the IAT?

You'll need to see all the readings working properly and showing values that show a healthy running engine on petrol before you can do the same on LPG.

It's early to be guessing but if pushed for a guess (assuming it runs properly on petrol) I reckon there's likely something wrong with an injector on B2 or an LPG ECU problem (not disconnecting a petrol injector or an LPG injector driver circuit gone wrong, I've seen both on old Landi[renzo] ECUs).

Simon
Full time LPG installer
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2 miles A1, 8 miles M62,
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Brian_H
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Re: Rich Fuel Problem

#9 Post by Brian_H » Sat Jan 04, 2020 9:52 pm

JX350 wrote:
Thu Jan 02, 2020 10:08 pm
Thanks Brian. I've also managed to find filters but they all appear to be for my system but are different sizes. I will get them out, measure them and then speak to a supplier. I don't have a shut off valve on the tank etc and I can't find one anywhere between the tank and the vapouriser. So I will be doing the work out side anyway so I'll just undo the solenoid and let off the gas until it depressurises.

Yes in the video it does show the intake temp which comes from the MAF as the MAF in our cars is combined with the intake temp sensor - it's also why they are nearly £200 from Jag. It's mounted in the air intake pipe just pre the throttle housing. I'm not sure what the correct specs are for normal intake temps. I'll try to find them from the service manual.

I've tried to get the other pre cat O2 sensor readings but for some reason my odb reader always gets zero readings for them even though it can see them. I have no idea why. I will try again at some point.

All the readings in that video where taken stationary and with the car at full operating temp so the car was not fully under load when running these.

Thanks,

Chris
You've probabbly got a 4 hole tank then - which in some respects is better, but won't have a manual shutoff.

JX350
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Joined: Wed Jan 01, 2020 6:42 pm
Location: Cornwall, UK

Re: Rich Fuel Problem

#10 Post by JX350 » Sun Jan 05, 2020 12:13 am

Thanks Simon and Brian.

Simon - I will see if I can change the setup of the diagnostics software as you suggested. I have had this problem for a long time, and among other things, I have cleaned the MAF but the problem still persists. I had this problem before I first cleaned the MAF. I have found that when I do clean the MAF then the car runs much better but only for a few hours and is then back to the vibration at these revs. At Idle the revs bounce up and down by about 50 to 70 RPM. I do have this engine vibration (rich fuel) on both banks by the looks of it and it also does it on both LPG and Petrol. I'll see if I can get readings from the pre-cat O2's. I always plug in my reader before ignition on and then connect it when the ignition is on. Beginning to get very frustrated with this car as I've had lots of problems with it and this is pretty much the last thing to get it running properly.
Current car: 2003 Jaguar XJ8, 4.2 V8 NA with a Landi Renzo LPG system.
YouTube Channel: https://www.youtube.com/channel/UC-AcBg ... R_9ym1fuGA

JX350
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Posts: 12
Joined: Wed Jan 01, 2020 6:42 pm
Location: Cornwall, UK

Re: Rich Fuel Problem

#11 Post by JX350 » Tue Jan 14, 2020 10:17 am

Quick update. Car sat for almost three weeks and has driven really well thereafter but the last two days it's vibrating again in that rev range. It's also now surging again when cruising along at a steady speed in that rev range and also is hesitant under acceleration. I did a quick check and the vacuum hose from the vapouriser does not appear to be leaking fuel. Their is no pressure in there and I've put the end of the pipe in fluid and I don't see any bubbles. So I don't think it's leaking into the vacuum hose.

I've now managed to get some further readings from pre cat O2 sensors etc. I've done another video which I will upload later.
Current car: 2003 Jaguar XJ8, 4.2 V8 NA with a Landi Renzo LPG system.
YouTube Channel: https://www.youtube.com/channel/UC-AcBg ... R_9ym1fuGA

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