as stated it starts and then promptly stalls. so far i have removed and tested the TPS all good , removed maf cleaned and inspected removed idle bypass valve cleaned, appears to be working maybe ? also have good fuel pressure at all times. can you test idle bypass and maf with a multi meter if so how ?
this problem started as it would idle but not run , would brake down as you tried to rev the motor and then would go back to idle, now it will just starts and then stalls out and will restart and stall out again. i have used timing light to check that the spark is their all the time , sparks to the last turn so that indicates that it is most likely turning off the injectors . no alarms on the nano other than o2 sensor (yes it is a bit fumey) but was not a problem until now? dose the CPS turn off injection when faulty also can this be tested with multi meter. no alarms on dash or check engine light . it appears that my problem may be associated to something that turns off the fuel system. any help appreciated.
1998 4.0L GEMS
Cps would cause lack of sparks and fuel if it failed, though sometimes they start to play up before failing completely. Not sure if you'd get a fault code for it (other vehicles i've had typically don't throw a code when its failed, they just die or fail to start).
Have you checked for a decent flow of fuel coming though? Either a blocked up filter or a pump thats on its way out would be possible causes I'd think?
Might be worth trying without the MAF connected, Have you removed the throttle heater plate that likes to leak?
Would also be a good idea to confirm what "it" is - I'd guess from your posts a GEMS is what you have?
Mine was doing exactly that until I changed the plugs and wires.
It started with sometimes needing a second crank to get going on very cold days and ended up starting, stumbling and flooding enough to be a major pain.
Either way, it's got to be Spark or Fuel so check em both :)
having another go at the rover today , having convinced myself its an air leak in the system (it starts and stops exactly like the supercharger problem on the other side , it has a video for those that are interested ) i removed the plenum box to clean and reseal. this has been done before.
my question is how important is the water heater on the inlet manifold mine was clogged with some crap, most likely radiator clog your system up in a bottle , can i just do away with the heater.
i have not found anything that was obvious as a leak but i will put it back together with a little more care than previous repairers.
Heater comes into it's own when the temperature is around or slightly above freezing and the atmosphere is damp, think foggy mornings. The intake air accelerating through the throttle body lowers the temperature and with lots of moisture in the air it can form ice in the intake. If you take it off you will have air leaks as the mounting bolt holes go right through to the intake so they need to be plugged up.
I've bypassed mine, no issues so far. I simply removed the hoses and left the plate and bolts in place so it can be hooked up again later if I ever run into icing problems.
If you suspect an air leak it's an area to test but it won't have any effect on starting especially in this weather.
Morat wrote:
but it won't have any effect on starting especially in this weather.
But he's in Tasmania so approaching winter there.......
Good point but from a cold start everything is at ambient anyway so the heater plate isn't going to make a difference.
Morat wrote:
Good point but from a cold start everything is at ambient anyway so the heater plate isn't going to make a difference.
As long as the holes have been filled if its been removed. Aargon discovered that after removing his (as mentioned above by Richard, and the reason I mentioned it as well, as I remember it taking him ages to find the cause of his problem. If i remember correctly he only found it by filling the manifold with smoke to see where it leaked out)
I've worked on a P38 that wouldn't start with the MAF disconnected but wouldn't run with it connected (or vice/versa, I forget which way around it was). Certainly a duff MAF can cause inability to run (bet Gilbert would remind everyone except with an LPG mixer system ;)
There's fuel pressure... but is there fuel pressure when the engine is running? And is fuel pressure correct when the engine is running (pump isn't haphazard and the fuel pressure regulator backs of fuel pressure with rising manifold vacuum)? They run very rich initially during cranking and just after starting, especially when the engine is cold and in cold weather.
They could probably start and run for a brief period with half the fuel they normally get for cold start conditions but with half the fuel they wouldn't run for long before leaning out and stalling. Very low or (less likely) very high fuel pressure could give the symptoms.
Usually a naff crank sensor would hinder starting too - crank sensors can be affected by temperature but between a cold engine to start and the engine running for a moment before stalling the crank sensor temperature will be almost the same.
A vacuum leak could cause it but it would probably have to be quite severe...
Others will know more about whether there's some system that powers up the fuel pump during cranking but relies on an engine running signal from the ECU to keep the fuel pump powered up?
Even less likely, severely block cats could cause the symptom, probably unheard of on a P38?
hi all just a note on how its going , have removed all from the inlet side and resealed, as stated didn't find anything obvious . managed to get it started and reving about 2 3 grand and found the entire left bank dead ,no spark . replaced spark plugs on left side no change so its possibly leads but most likely coils, will have another go today .
have removed the coils either i am testing it wrong or all the coils are stuffed, is that a thing with these coils ,is their any difference between the cheap and expensive ones. any recommendations on types or brands
It seems a bit weird to lose spark on one whole bank as each coil fires one plug on each bank on a GEMs - assuming I'm reading this right:
I'm trying to think what else it could be that one whole bank has in common on the ignition side of things.
There's 4 coils but each fires two cylinders so one coil going down would cause you to lose 2 cylinders, but it would be one on each bank. They are paired as 2 and 3, 4 and 7, 5 and 8 and 1 and 6, so to lose a whole bank would mean all coils have gone down (in which case you'd lose the lot). If it was just a case of one bank not firing I would have been looking at the common power feed wire to each fuel injector which would result in no firing on that bank but it wouldn't affect the sparks.
so to test the coil you put the positive on the positive terminal and the negative in the coil output and you should get a reading around 13 k ohm, it shows nothing on the meter on any coil ,meter on 20k ohm positive to negative terminals results 1.0 1.2 on 200 ohms setting on meter
coil prices in aust are $112 from repco per coil , another 4x4 shop has them for $55 per coil. this is how ridiculous our prices are over here , you can't even buy the item as a piece, well i haven't found one yet but this the australian way, every item is a seperate item.
Must agree with Gilbert though.
I got a new coil pack complete from the UK, a lot less expensive than trying to deal locally. I think it came from LRSeries.co.uk £53 + postage.
it's a strange one at idle they all appeared to be working, it would idle fine , as soon as you touched the throttle it would just rev brake down and stop and restart fine again and sit their idling and then it would start and then stall in seconds. this made it hard to diagnose faults. the nano showed nothing only a bad o2 sensor , no misfires, nothing. i have checked everything i can with the multi meter, eg maff, stepper motor, tps, plugs even air leaks this is the only thing that shows a fault, it's just that all coils are faulty?
have found a coil pack (lucas brand ) for around $130Au delivered . are they any good . also need leads , have a set off NGK leads on now, they would slip over the plug very easy would be loose when fitted but would not come off even with multi grips on them , they have a small hi tensile ring holding them from spreading. i do not recommend these leads for any application ripped two ends off removing them , literally tore the metal ends apart, was expecting the plugs to brake, that's just ridiculous .
PS do i need to seperate the coils to test them ?
Lucas coils should be fine. If you're looking for a decent set of plug leads, try and source a set of Magnecor ones. They're expensive but are a fit and forget item whereas cheaper once can become an annual service item on these cars.