Fuel system problems.

[skip]

Here I go again :roll:  

I thought I'd post in the rangie section as there seem to be far more V8 lovers here :lol:

I've been having trouble with my dico running on petrol, missing and general poor/eratic performance. so I took it to my local man with a rovacom.

Here's what he came back with.

Code 34 injector fault bank A
Code 36 injector fault bank b
Code 23 fuel supply

I already replaced the fuel filter incase that was the cause so i've eliminated that but i'm wondering if the first two faults would be cause by a lack of fuel pressure?

Infact any advice of what is the most likley cause would be appreciated as I can't afford to pay anybody else to do the work for me.

Thanks

Pete.

[Range Rover Blues]

Perticulary if it's got Lambdas the ECU will figure out a missfire as being caused by 'something'

Mine reports a missfire on bank A that I can't even detect, thing is it won't tell you when it happened or if it's cleared up.

Here'a a tip, if you disconnect the battery then the ECU resets itself and clears the faults, so do this a few days before hooking up Rovacom and you will only see current faults.

As for the cause, could very likely be a fuel supply problem but the ECU can't measure fuel pressure so it's guessing that's the cause.

Get hold of the Range Rover Haynes manual, it has a comprehensive test section for the hot-wire, one of which is to check that all 8 injectors are still connected properly.  If you strip the engine you can also measure the output of the injectors, though I've never done this.

Also check the fuel supply pressure.

[skip]

Thanks RRB

The chap read the ecu twice, once when I took the Disco in and then after he did a reset. The reading before also reported that there was a fault on both lambda sensors, but I think that was caused by me running the gas to the very last minute and ending up with a very lean mix :oops:

I think the first thing is to get a range rover haynes comic then find somone who has a suitable equipment to test the fuel pressure, I'll get into more complex stuff after that if need be.

Thanks again

Pete.

[Range Rover Blues]

EFi fuelpressure is only about 23? PSi, so a Gunson's low guage should be able to do it, otherwise a fairly common pressure guage (like you find atop some tyre inflators) will do, the pressure is less than you put in your tyres IIRC.

My lambdas somethimnes sulk if my LPG system is playing up.  Do you have a single point/multipoint system with feedback or is it a drawthrough system?

You can dissable the lambda by swapping the tune select resistor.  All you need to know about that is in the comic too :)

[skip]

I've got a mixer system with lambda control, when I first go the disco it was running very lean but i since adjusted that and all has been well.

I think I have found a copy of the official land rover diagnostic manual,       [/url]                  http://www.g33.co.uk/images/PDFS/14cux_fuel_injection.pdf                     [url]

i'm going to try some of the procedeures provided, hopefully it'll shed some light on the situation.

BTW is there a test port on the fuel rail? i've not noticed one.

[skip]

Well i've got an update. I managed to get a pressure reading from the test port on the fuel rail (found it). it turns out to be about 29psi at idle and rises to around 35 under acceleration.

According to the info I have infront of me the pressure should be between 34-38psi, so that's a little low but i don't think it would be causing the symptoms the disco is suffering, what say you?

Also I've put a multimeter across the injectors on the off side bank, all came back with 16.5 ohms so all seems ok there but i've yet to test the near side bank and the wiring back to the ECU.

Having looked at the test procedeure for the wiring it looks as though the ecu fires off the whole bank of injectors at once as opposed to sequential injection, interesting :-k

[kjj0506]

Is the pressure I need for my 4.2 about the same? I am having trouble getting the data. Also , I am curious what the flow should be and if I use an aftermarket in line pump will the factory regulator handle the flow AND the pressure? Not meaning to hi-jack the thread but this is so close to the info I am looking for ..... thanks as always ! [/i]

[skip]

Hi kjj0506,

provided that your RRC runs the 14cux injection system then it will almost certainly be the same, especially as the injectors are interchangable with the 3.9 according to what I have read today.

[skip]

I've done the final round of tests, Damn that ecu is a PITA to get out!

Anyway it looks a though the injector for cylinder number 5 could be suspect as it's giving a slighly higher resistance than all the others.

I first did the testing from the ECU plug as it details in the instructions I found yesterday, bank B gave exactly 4.5 ohms, so within tollerance.

But bank A was giving a resistance of 4.9 ohms, so I whipped all the plugs off, gave them a clean and put them back together but still no difference. So then I took off each plug and measured the resistance each time. Number 5 gave the least change in resistance, about 6 ohms whereas all the others gave about 8 in total so that must be it.

unfortunatley I can't get the meter probes actually onto the injector plug pins as it's all hidden under the intake :roll: but the ones I have taken readings from have all been 16.5 ohms.

So i'm guessing now that it is really a compound problem of slightly low fuel pressure and an iffy injector :roll:

At least I know now, half way there it's just the expensive bit to come now :D

[Range Rover Blues]

The 4.2 is exactly the same as the 3.9 unless there was a specific need to modify anything, it even runs the same dizzy.  The small amount of extra fuel is supplied by a longer injector pulse.

It's not uncommon to see and EFi system of this age not being sequential, one of the benifits of non-sequential (I say benifits, sequential systems need to be programmed to do this also) is that the fuel hitting the back of the valve helps to cool it, but they are less fuel efficient.

My LSE has an aftermarket fuel pressure regulator on it, presumably to cope with the 5.0L of Blackpool Rock under the hood.

Skip, where did you find the pressure test port?

[skip]

I found the test port between injectors 4 and 6, it's a shrader valve thats been fitted onto the fuel rail, it's even got a normal valve cap on it :)  which I forgot to refit and is now rolling around on the road somwhere.

To test the pressure I just used a normal tyre pressure gauge, seems to work very well too, just got to watch out for a small release of petrol when pressing the guage onto the valve.

You make a good point about the valves being cooled by the fuel hitting the back of them.

[Range Rover Blues]

Just be careful as most rubber used in things like pressure guages is not fuel proof.

[skip]

Yeah I found out! I ruined my digtal one but was expecting it anyway. I've since bought another sacrificial one :lol:

[Dave Rogers]

What can cause a v8 to hunt, ie revs rise and fall, tried discnnecting the cold start switch, made no difference, no leaks, pressure seems ok.
Can see the flap valve moving in time as well, goes away if the mix is made more lean and the unburnt fuel smoke goes away, tried to set the mix but no difference!
Runs great on LPG, so confused!

[Range Rover Blues]

Is it the flapper then? don't know much about these but the flapper is moving becasue of the extra air drawn is as the engine speed rises.