LPG MPG and lumpy running
#1
05-01-2016, 09:50 AM
LPG MPG and lumpy running
I am wondering what MPG those of you with LPG conversions typically achieve? I have a 1999 3.3L Grand Voyager which I bought with a (probably not very quality) multi-jet LPG installed.
When I got the car it was only firing on 5 cylinders and had a slight manifold leak, and unsurprisingly was getting great performance from the gas. But after fixing those issues it got worse, which is weird as it is heaps better on petrol. I get about 90 miles from a 40L tank (before 120miles) and now it cuts out and stalls, particularly when cold and has a really lumpy idle on gas. Tbh its probably beyond my abilities to repair so if anyone knows a good lpg specialist in east central scotland that would good!
When I got the car it was only firing on 5 cylinders and had a slight manifold leak, and unsurprisingly was getting great performance from the gas. But after fixing those issues it got worse, which is weird as it is heaps better on petrol. I get about 90 miles from a 40L tank (before 120miles) and now it cuts out and stalls, particularly when cold and has a really lumpy idle on gas. Tbh its probably beyond my abilities to repair so if anyone knows a good lpg specialist in east central scotland that would good!
#2
05-01-2016, 12:19 PM
Hi Nitro my 98 3.3 is on LPG and I see between around 125 when driving in the city to well over 160 miles on the motorway from my 40 litre tank, though remember that they don't hold 40 litres. I think mine is like 38 or something.
However, it sounds like something hasn't been put back correctly.
I did the valley intake and plenum gaskets on mine as they are a common problem on the V6's as I was having metering issues with mine, but in doing so I had to remove a large amount of the LPG system in-order to gain access. So I'm thinking maybe something has been missed on the re installation.
The only other thought is that on some cheaper systems the base-line emissions have to be set manually. Now if its been adjusted to run with an air leak, then now that its been repaired, it may still be duping lots of gas into a engine which no longer requires it!
However, it sounds like something hasn't been put back correctly.
I did the valley intake and plenum gaskets on mine as they are a common problem on the V6's as I was having metering issues with mine, but in doing so I had to remove a large amount of the LPG system in-order to gain access. So I'm thinking maybe something has been missed on the re installation.
The only other thought is that on some cheaper systems the base-line emissions have to be set manually. Now if its been adjusted to run with an air leak, then now that its been repaired, it may still be duping lots of gas into a engine which no longer requires it!
#3
05-02-2016, 04:59 AM
Hi Nitro my 98 3.3 is on LPG and I see between around 125 when driving in the city to well over 160 miles on the motorway from my 40 litre tank, though remember that they don't hold 40 litres. I think mine is like 38 or something.
However, it sounds like something hasn't been put back correctly.
I did the valley intake and plenum gaskets on mine as they are a common problem on the V6's as I was having metering issues with mine, but in doing so I had to remove a large amount of the LPG system in-order to gain access. So I'm thinking maybe something has been missed on the re installation.
The only other thought is that on some cheaper systems the base-line emissions have to be set manually. Now if its been adjusted to run with an air leak, then now that its been repaired, it may still be duping lots of gas into a engine which no longer requires it!
However, it sounds like something hasn't been put back correctly.
I did the valley intake and plenum gaskets on mine as they are a common problem on the V6's as I was having metering issues with mine, but in doing so I had to remove a large amount of the LPG system in-order to gain access. So I'm thinking maybe something has been missed on the re installation.
The only other thought is that on some cheaper systems the base-line emissions have to be set manually. Now if its been adjusted to run with an air leak, then now that its been repaired, it may still be duping lots of gas into a engine which no longer requires it!
I will have to do some research as to how it all ties together.
Edit: Been thinking about this. When I changed the plugs and leads I had the plenum chamber off and never replaced the gasket. (Though the cruise didn't work before either). Are there any good simple tests for checking for a leak? and anyone to recommend for a gasket kit?
Last edited by nitro_warrior; 05-02-2016 at 09:30 AM.
#4
05-03-2016, 08:44 AM
Yeah a vacuum issue will effect your cruise. Mine didn't work either but does now since I did all the gaskets, however, a vacuum check would help determine if there is a major leak. You can pick a vacuum pump with gauge for around £20 on eBay. Hand Held Brake & Clutch Bleeder Tester Set Bleed Kit Vacuum Pump Car Motorbike | eBay
Simply hook it up to a vacuum line on your van and take a reading. It should be pulling anywhere between 17 and 19 inches of vacuum at idle.
Gasket kits I actual brought one in the US because nobody had them in the UK. Felpro MS96042 has everything you need although you can buy the items individually.
Simply hook it up to a vacuum line on your van and take a reading. It should be pulling anywhere between 17 and 19 inches of vacuum at idle.
Gasket kits I actual brought one in the US because nobody had them in the UK. Felpro MS96042 has everything you need although you can buy the items individually.
#5
05-05-2016, 06:15 PM
Yeah a vacuum issue will effect your cruise. Mine didn't work either but does now since I did all the gaskets, however, a vacuum check would help determine if there is a major leak. You can pick a vacuum pump with gauge for around £20 on eBay. Hand Held Brake & Clutch Bleeder Tester Set Bleed Kit Vacuum Pump Car Motorbike | eBay
Simply hook it up to a vacuum line on your van and take a reading. It should be pulling anywhere between 17 and 19 inches of vacuum at idle.
Gasket kits I actual brought one in the US because nobody had them in the UK. Felpro MS96042 has everything you need although you can buy the items individually.
Simply hook it up to a vacuum line on your van and take a reading. It should be pulling anywhere between 17 and 19 inches of vacuum at idle.
Gasket kits I actual brought one in the US because nobody had them in the UK. Felpro MS96042 has everything you need although you can buy the items individually.
#6
05-06-2016, 06:35 AM
Yeah I buy a lot of my stuff from the US and in all honestly a lot of the smaller parts stores are great, much better service than I've had from thier counterparts here in the UK!
Last edited by Vonhofinvule; 05-09-2016 at 10:10 AM.
#7
05-08-2016, 12:42 PM
Some years back I had an XJ6 3.2ltr. with a simple "gas-ring" conversion, that is the gas went straight to the throttle area, no separate gas injectors. The petrol part was injection.
The MPG was the same as petrol, litre for litre, which financially meant it did 32MPG in town, and 42MPG on the motorway.
Tuning the gas was simplicity itself. There was an adjustment screw on the vaporizer for idle, and a "bulk" gas adjustment that altered the max amount of gas deliverable to the air intake throttle area. This was adjusted for best revs at speed.
The MOT tester said he couldn't measure the carbon monoxide at idle, it was too low to measure.
The car developed a running-on-petrol fault due to clogged injectors, but was fine on gas which used no injectors.
Something one should remember with LPG cars is the "emulator" which makes the control micro. assume the car is running normally on petrol when it isn't.
The fault described in above posting may not really be due to the gas conversion, so make sure it runs perfectly on petrol first. Then there may be a fault with any gas injection system fitted, of which there seem to be a few.
Leedsman.
The MPG was the same as petrol, litre for litre, which financially meant it did 32MPG in town, and 42MPG on the motorway.
Tuning the gas was simplicity itself. There was an adjustment screw on the vaporizer for idle, and a "bulk" gas adjustment that altered the max amount of gas deliverable to the air intake throttle area. This was adjusted for best revs at speed.
The MOT tester said he couldn't measure the carbon monoxide at idle, it was too low to measure.
The car developed a running-on-petrol fault due to clogged injectors, but was fine on gas which used no injectors.
Something one should remember with LPG cars is the "emulator" which makes the control micro. assume the car is running normally on petrol when it isn't.
The fault described in above posting may not really be due to the gas conversion, so make sure it runs perfectly on petrol first. Then there may be a fault with any gas injection system fitted, of which there seem to be a few.
Leedsman.
#8
05-16-2016, 07:38 AM
My new plenum gasket and injector seal kit has arrived, as has a vacuum pump tester. I should have maybe got the vacuum tester first but I am more convinced in a plenum leak as the idle is bad on gas too and often stalls, particularly in cold weather which from my research suggests a likely symptom. Anyway I still want to test the before and after vacuum.
My question is, I don't actually know where to attach the vacuum tester for the test... Don't suppose anyone has a few pics or knows of a video that shows the process on a 3.3i engine? Thanks
My question is, I don't actually know where to attach the vacuum tester for the test... Don't suppose anyone has a few pics or knows of a video that shows the process on a 3.3i engine? Thanks
#9
05-17-2016, 10:44 AM
Hi, I'm in the processes of making a video on that very subject. However, to quickly go over it, look at your throttle body and you will see several vacuum pipes leading to it. Pull one of these and connect it to the 'T' adapter that comes in the pump kit. Then take one of the pipes supplied in the kit and connect this to the location on the throttle body where you removed the vacuum pipe. Now connect this to the 'T' connector and then finally run another pipe from the kit between the pump and the 'T' connector.
Now you need to do this with the engine at working temp. But once connected star her up and leave it to idle for a few minutes just to let it all settle down and then take a reading off the gauge. anything below around 17 inches then you know there's a leak.
As for buying the gasket kit, honestly this appears to be a common problem with the 3.3 and 3.8 v6 so if I were to buy another V6 GV then I'd do the gaskets anyway!
Another thing you can do with the vacuum pump is check all of your rubber vacuum pipes. Its time consuming but I found it worthwhile.
Just remove one at a time and place it on the end of the pump. Then block the other end with a fingerer and pump away. Then watch it for a few moment to ensure it holds vacuum. Several of mine didn't so they were replaced when I was doing the gaskets.
Now you need to do this with the engine at working temp. But once connected star her up and leave it to idle for a few minutes just to let it all settle down and then take a reading off the gauge. anything below around 17 inches then you know there's a leak.
As for buying the gasket kit, honestly this appears to be a common problem with the 3.3 and 3.8 v6 so if I were to buy another V6 GV then I'd do the gaskets anyway!
Another thing you can do with the vacuum pump is check all of your rubber vacuum pipes. Its time consuming but I found it worthwhile.
Just remove one at a time and place it on the end of the pump. Then block the other end with a fingerer and pump away. Then watch it for a few moment to ensure it holds vacuum. Several of mine didn't so they were replaced when I was doing the gaskets.
Last edited by Vonhofinvule; 05-17-2016 at 10:47 AM.
#10
05-18-2016, 06:45 PM
Hi, I'm in the processes of making a video on that very subject. However, to quickly go over it, look at your throttle body and you will see several vacuum pipes leading to it. Pull one of these and connect it to the 'T' adapter that comes in the pump kit. Then take one of the pipes supplied in the kit and connect this to the location on the throttle body where you removed the vacuum pipe. Now connect this to the 'T' connector and then finally run another pipe from the kit between the pump and the 'T' connector.
Now you need to do this with the engine at working temp. But once connected star her up and leave it to idle for a few minutes just to let it all settle down and then take a reading off the gauge. anything below around 17 inches then you know there's a leak.
As for buying the gasket kit, honestly this appears to be a common problem with the 3.3 and 3.8 v6 so if I were to buy another V6 GV then I'd do the gaskets anyway!
Another thing you can do with the vacuum pump is check all of your rubber vacuum pipes. Its time consuming but I found it worthwhile.
Just remove one at a time and place it on the end of the pump. Then block the other end with a fingerer and pump away. Then watch it for a few moment to ensure it holds vacuum. Several of mine didn't so they were replaced when I was doing the gaskets.
Now you need to do this with the engine at working temp. But once connected star her up and leave it to idle for a few minutes just to let it all settle down and then take a reading off the gauge. anything below around 17 inches then you know there's a leak.
As for buying the gasket kit, honestly this appears to be a common problem with the 3.3 and 3.8 v6 so if I were to buy another V6 GV then I'd do the gaskets anyway!
Another thing you can do with the vacuum pump is check all of your rubber vacuum pipes. Its time consuming but I found it worthwhile.
Just remove one at a time and place it on the end of the pump. Then block the other end with a fingerer and pump away. Then watch it for a few moment to ensure it holds vacuum. Several of mine didn't so they were replaced when I was doing the gaskets.