Hi all. Is there any way to check if an injector is leaking without removing them all? It's not a job I want to hop into as it's not causing me running issues.

*I won't refer to the word gas as for me, gas is LPG, to most of you, it's petrol.*

The back story to this is I run on LPG and have an approximately 30-40L petrol tank. I have to top up on petrol every 2-3 months which doesn't sound much but it does when you do some numbers. The petrol is only used some days for less than 10 seconds of running in the whole day, others it may get a minute or so. Past that, if I need the extra power from petrol such as when towing up a hill, it'll get used until no longer required.

For numbers sake let's say it uses 30L in 3 months, that averages to 0.3l per day, even in 6 months, 0.15l per day is quite an average for how little the petrol is in use.

Now that I am thinking about it, I'm going to monitor my petrol usage over the next few months and only use it if I absolutely have to. This should hopefully give me an exact idea of how much it uses when it shouldn't be.

Thanks

 

Do you smell petrol in the engine compartment? You can do a lab test of the oil possibly, here in the states a lot of folks use Blackstone labs, but I don't know about the U.K. or shipping "hazardous fluids" internationally.

Leaking injectors is something I'd worry about since petrol in your motor oil will ruin your engine in short order.

 

I've never had any sort of petrol smell and on my last oil change, the oil certainly didn't have any notable quantity of petrol in it, not that "it looks good" means it is. I found a website pretty easily that sample oils so I'll certainly have a look into it. It is very possible that the LPG system isn't stopping the injectors properly 100% of the time or that it uses them part time (although there is a notable power difference between the 2 fuels so I doubt it).

 

Your in tank fuel pump isn't running when on LP, is it?

 

I'll have to check later to be sure. I believe it is but currently have no LPG as my gauge doesn't work, and I thought I had more in it. I shall report back later

 

There is a spec for fuel pressure leak down. Something like it should not drop below 25 lbs after 15 minutes, that is wrong but there is the spec somewhere. That usually points to the regulator but will also surely show an injector. Or in the case of my present XJ a leak in the line somewhere because I smell gas and have slow starts.

 

I just had a look and FSM says 31 PSI at idle then it should drop down to a maximum of 11 PSI within 30 minutes. So unless it lost a lot of fuel when turned off through an injector, this would be hard to chase without pulling parts which I don't want to do for the sake of saving a bit of fuel money.

I have checked and it does run while on LPG. My best guess is so when you want to run on petrol, it's instantly available.

I've put 15.5L in today so I'm going to keep track of how long it lasts until the fuel light comes on again. I'll also use petrol as little as possible so I shouldn't be using much at all. If it still seems suspicious, I may wire up a relay to cut the fuel pumps power when the LPG is running. It should be easy enough as there is a LPG relay next to both fuel tanks so a trigger feed will be easy to source.

 

Question; if you're running on LP and you shut it down, like to go into a store or something, does it stumble when you start it back up? That would be a sure sign of a leaking injector. Or do you need to start it on petrol even if it's warm? I know our industrial forklifts start on LP even when cold. Our local buses run on LNG and they don't need petrol to start.

 

I haven't noticed any stumble but I'll look out for it specifically in a fresh start and restart scenario. As for it starting up, the system automatically starts the engine on petrol regardless of anything, it then switches over when the engine hits around 1300-1500 RPM which it often does on every start (which I've always assumed to be normal, revs up then goes down to ~1000). I have an older system on mine where it has a gas (no longer liquid) ring before the throttle butterfly valve so it needs to get running to help pull the gas through first. I know I wasn't going to say gas but I couldn't avoid it here.

 

just had a look and FSM says 31 PSI at idle then it should drop down to a maximum of 11 PSI within 30 minutes. So unless it lost a lot of fuel when turned off through an injector, this would be hard to chase without pulling parts which I don't want to do for the sake of saving a bit of fuel money."

I think you mean Minimum.?
Am fresh out of other suggestions atm. Take them out and pressurize them and see? Other than that changing the O rings and cleaning the bore with a brass gun bore cleaner is always a good thing and easy enough to do.

 

I think I started wording it differently and was left with the wrong word there. Yep, minimum is what I meant.

 

Hi boxburn, I have a similar scenario on my 97. It does seem to use more petrol than I'd expect although I don't have numbers. I'll see if I can measure petrol use but I think it'll be difficult to get a consistent set of conditions between our two jeeps.

I have swapped out a couple of injectors which were leaking but I suspect there might be more. One day I'll get a full set of refurbed injectors but it hardly seems worth the cost right now.

Mine doesn't rev up on start, it goes straight to 750 rpm. On a hot start it will swith to lpg within a few seconds. The suspicious symptom on my jeep is the way it takes 2-3 seconds on the starter to fire up whenever I have shut down on LPG.
If I switch to petrol before shutting off it will fire right on the button at the next start. I suspect the long crank is due to too much fuel in the intake manifold due to residual lpg and leaked petrol. If the lpg has been switched off before shutdown the cylinders just get petrol and the mixture is ok.

I may be dead wrong!

But in any event, getting the fuel rail off and injectors out is no big deal even for a Muppet like me 😀

I think your lpg setup probably needs some adjustment though, there shouldn't be any noticeable difference in power between lpg and petrol. I'd get it checked in case you're running lean which will damage even a 4.0.

Edit: just re-read your post and realised you're on a single point system so yeah, you will lose a little power on LPG. But on the other hand you can often get a single point to start on LPG without any petrol - when warm at least. You still need heat in the reducer for cold starts as you know.

 

Hey guys! I've just found out LPG is about 102 octane! Great!

 

I tested today and found that it started up the same from cold and from warm after leaving it for a while. I do not get any variation in starting it up by turning off when on LPG or petrol. Strangely, it has never seemed to care about the evaporator being cold except for when we had the icey mornings over winter. I had to run on petrol for about a week when it really chilled down. Past that, it switched over within 5-10 seconds of starting and runs perfectly every time.

I don't know what set-up you have but mine (StarGas) was fitted at some point in the late 90's. The only place "locally" is an hour drive away from me and when I had him fit a new fill port for me, he said he wouldn't have had the kit to do anything with that system when it was new. So other than a complete replacement, I can't do anything to the system in terms of mixtures. I'll have to pop around to the MOT garage we use and use their gas analyser to get an idea of mixtures.

I'd be happy to hear your petrol usage finding though when you next need to fill up and how much you seem to have used.

 

Boxburn, have you tried www.lpgforum.co.uk ?