I am currently trying to make my 1986 Range Rover 3.5 EFi run propperly on petrol after having run only on LPG for 2 years. I replaced the fuel lines which had rusted out as well as the fuel pump but despite then running on petrol it was very rough compared to opperation on LPG.
Today I have stripped down the fuel injection system and tested the fuel injectors, 7 of them were opperational but had bits of rust in. I pressure backflushed them and they now seem to opperate fine with what appears to be a normal spray pattern. The eigth injector however will not fire, it gets warm but the valve does not open so I assume the coil has shorted or it's ceased up.
Does anyone have an old single injector lying around they would be able to sell me to get the engine running again? As long as it opperational it should be suffiecient seeing as petrol will only be used for satrtup and when LPG is not available.
Another thing I noticed when removing the fuel system was that for as long as I have had the vehicle the "Extra Air Valve" towards the front of the inlet manifold has not been connected to the electrical connector (which was lying loose). What would be the consequence of this and could there be any reason it was disconnected?
If not connected, the cold idle speed will stay higher for longer as it's a combination of direct conducted heat via the mounting face and electric heating element that make the valve operate. It has no effect on mixture, only idle speed.
Thanks for the help, I forgot to mention I also noticed there was no vacuum tube linked to the fuel pressure regulator when I stripped the system down, should this be linked to the same point on the plenum chamber as the overrun vacuum valve? The overrun vacuum valve was mounted electrical connector side up, looking at haynes this should be mounted the opposite way up, does this make any difference?
Before I started to reconstruct the fuel system the LPG would sometimes fail to start or cut out if the vaccum got too low, when this occured there was a click as the LPG solenoids shut down causing the engine to stall. Which part of the LPG system detects the vacuum and is it variable? Do LPG systems have a timer when you start on petrol to activate the switch to LPG or is this based on the vacuum being detected or for example the extra air valve closing causing the vacuum to increase?
I suspect the extra air valve may have something to do with the LPG changeover because of this observation I made when I was having trouble starting on LPG; if the tube to or from the valve was pinched closed when it was having trouble starting or idle dropping causing a stall the engine suddeny started to run much more smoothly and the idle increased.
As you can probably tell this is my first EFi V8 and first LPG powered engine so I'm gradually figuring out how everything works (or rather doesn't) and why, there seem to be so many more bits to go wrong than on my Webber 4 barrel carbed v8 or the twin stromburgs on my 101 but hopefully it should be fairly reliable once everything is set as it should be.
Haven't came across one spare yet, but I'm sure I have some somewhere!
Vacuum switch orientation makes no difference, but fuel pressure regulator should be connected to same pipe. Check these vacuum pipes very carefully for splitting, something they are prone to. It will not run right on petrol if the fuel pressure isn't being regulated correctly.
There shouldn't be any vacuum connections having an effect on the gas side of things, the gas control is electric, switched by whatever control switch you have. On my own 110 the gas switch energises the gas relay which simultaneously energises the gas solenoids and "breaks" the connection at the vacuum valve. The vacuum valve's function is to kill the injection system under conditions of high vacuum (ie overrun) hence saving a bit of fuel and emissions. it does this by interrupting the rpm trigger feed from the negative side of the coil to the ecu, hence the ecu thinks the engine has stopped turning so kills the fuel. It's possible that you have vacuum level issues due to pipes not connected correctly etc, and these are interupting the ecu trigger. try disconnecting the wires from the vacuum valve and simply joining them together and see what it does on petrol then.
Cheers for having a look for a 3.5 injector for me, would be very useful if you could dig one out, everywhere only seems to sell reconditioned ones in a set of 8.
I'm not sure if my LPG system prehaps works a little different to others (it's a Stargas system, they went bust it seems so they're hard to get info on). Basically I have an electronic controlbox on the dashboard with a single button on which and a screen that displays: 4,3,2,1,E to indicate gas level when on LPG, on ignition on this can be set by pressing the button to display b (petrol) or C (dual fuel) or if the button is held on whilst the key is turned it displays H (this forces the system to gas only, holding this button for around 25secs prior to starting primes the system allowing it to start).
If the system is started on "C" (dual fuel) it starts up on petrol BUT I am not 100% sure what determines when it switches to gas (you can tell when it has switched to because the display starts giving the level readout and the relays click). It seems to me that this switchover is somehouw linked to the vacuum as pinching a vacuum pipe closed on the extra air circuit makes the system immediately switch to gas. Another component on the circuit that appears to determine this vacuum related switching is a variable valve with a thumbwheel on in the gas feed line just before the LPG sandwich plate at the airflow meter, the system is more likely to switch to gas if this valve is more towards fully closed than open? Obviously I'll have to set all these things up once it's running propperly on petrol but will need to know how the system is working first really.
One thing about the system that struck me as odd was the fact that the LPG enters the system before the air flow meter (probably why it takes such a long time to prime when starting on LPG), would it not make more sense to have the LPG enter the system as near the plenum intake as possible rather than out by the air filter?
"fergus.kendall" wrote in message news:J46Yc.200$ snipped-for-privacy@newsfe2-gui.ntli.net...
Ok, found one, bit of an unknown quantity but you're welcome to try it. If it works ok, we'll decide what it's worth, probably a fiver plus actual postage. That ok? (Actual cost from landrover for part no. ERC3620 as of Oct
2001 was £81.00 +vat! Should change their name to landrobber!!)
Right, here goes. The basic system is std star gas, the control and switching unit sounds like a DC101, it can be set up in various ways. Yours appears to be set to change over to gas at an rpm very close to that at which you are squeezing a vacuum pipe, the slight change in rpm triggering the change. They can be set to change over either on acceleration or deceleration, at a preset rpm of your choice. I'll assume that squeezing a pipe to the fast idle valve results in an rpm drop, therefore yours is set to change on decel, the factory default. The orange thingy is an "Economax" or "Economiser", I'm not sold on them. Although the theory of operation is sound, I've yet to meet anyone that's been happy with it. Idea is to disconnect it's vacuum lead and plug it, hold engine at 3000 rpm and adjust CO to around 2-4%, then reconnect it and adjust wheel on top to give CO at same rpm of about 0.5%. The theory is, that as you increase throttle from cruise (High vacuum, lower CO, good economy) to accelerate, the drop in vacuum is sensed and the unit richens up the mixture to give the extra power required. The reason for the gas mixer plate being upstream of the airflow meter is that the airflow meter's vane creates a vacuum level between it and the throttle plate that isn't a true representation of engine vacuum due simply to airflow. This would cause the engine to draw an excessively rich mixture were the gas mixer fitted at the throttle. You can fit a mixer at the throttle, but you have to fit an additional "holding-open device" at the airflow meter, to hold the flap fully open when running on gas. This does have the additional benefit of tending to save the airflow meters if a backfire occurs, a lot better than the std totally useless backfire valve which is nothing more than a rubber band around some holes! There's a lot of gas volume in a landy efi manifold if a backfire does happen, I've lost count of how many airflow meters I've replaced for people. Make sure the ignition system is up to scratch at all times, and only fit basic plugs (ie champion N9Y's) gapped at 25 thou. Send me your postal address off-list and I'll get the injector in the post to you. (Remove the obvious)
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