3.9 Series1 Discovery Stalling When Hot

Hi,
I've posted this in a local northwest4x4 forum as well, but thought I'd see if you guys could possibly help me out too.....

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Hi,

I'm hoping that someone here can help me with diagnosing the problem.
So it's a Series 1 1996 LandRover Discovery V8 3.9ltr Petrol Only, Automatic (with cruise control) .

Its run great for the last 3 years I've owned it.
In the last year it's had:
New Plugs
New Coil
New HT Leads
New Dizzy Cap

The week before last it started to cut out on me, to start with only when slowing down and the revs dropped, then more frequently when it was under load too.
I thought it might be an electrical issue, so changed the coil pack.
I used it 2 days last week driving too and from work about 25 miles each way. No problems at all.

Came to use it the other night to drive into Manchester. It started fine and ran fine for about 15miles. On the M56 the engine started to run rough and when the traffic slowed, the engine cut out. I dropped it into neutral and coasted to the hard shoulder. Got under the bonnet, checked all the leads, all seemed ok, got back in and it started. It ran for about another mile and then died again. Did the same, opened the bonnet, poked some bits, got back in and it ran for about 1/2 mile then died. After that it would intermittently run for shorter and shorted periods, getting rough first then dieing.
In the end it just stopped and wouldn't start.
So I called the AA out. I sat with the car off for about 20mins, and it started and ran again for 2-3 minutes, at first nice and smooth, and then getting rougher and eventually dieing.
It sat for an hour then waiting on the AA and when he showed up it once again ran perfectly for about 5 minutes this time, then just like before, got rough then died. AA man couldn’t figure it out. Checked for air lock in the tank, good spark from the coil etc etc.
So he left me and called for a recovery truck. While I was waiting, just to keep warm, I'd run it until it died then leave it 10-15mins and then repeat.
By the time I got home on the back of the truck it started first time, like usual, ran nice and smooth while we did the paperwork, I drove it onto the drive, left it running 2 more minutes and then it died again.

When it dies, you can give it some throttle and it makes no difference, it just judders, like its not running on all cylinders, then dies.

The AA man did have a quick listen and said he could hear the fuel pump running ok, but this was before it died, obviously.

I suppose the first question is does this sound more like an ignition issue or a fuelling issue? The main thing is that the longer you let it sit for, the longer it will then run for afterwards before dieing.

So, does anyone have any ideas?

Cheers

Jack

UPDATE FROM YESTERDAY:

OK, so yesterday I took the carpets up in the back, had a look at the top of the sender.
There is some corosion on there but it's not THAT bad. Certainly no holes or cracks and I put some spit on the pipes to see if there was anything coming in or going out. Nothing. The pump is running fine.

So after about 20mins of running on the drive with the bonnet open it was running fine. the revs started to rise a bit at idle, but that was about it.
So I shut the bonnet. Within about 2 minutes it started running rough and then died again.
Left the bonnet shut and it wouldn't start. Turned over but woudn't fire at all.
Left it another 5 minutes with the bonnet open and it started first time and ran for a few minutes again and then died.

There is DEFINITELY something heat related under the bonnet.

Can anyone recommend some (simple) things for me to try? I'm not a mechanic

Thanks

Jack

I would suggest first port of call would be to replace the water temp sensors at the front of the plenum mounted in the inlet manifold as one of these supplies info to the ECU and have been know to cause this kind of issue.

Yeah I mean the first thing really is to ascertain fuel or spark issue.

Could be a dizzy amp aswell, could be anything though.

Temp sensors are both possibilities.

14 cux will run with both sensors unplugged so I would try that first, plus measure the sensor outputs with multimeter as the car warms up.

I am the busiest person in the world right now but put your location in your profile and I can attempt to have a look in the next couple weeks if it becomes a serious issue

As I have found out in the past RRC days a gumed up crankcase breather and it's hose to the plenum can make the engine fade away after a few miles and stall, some inconvenience when driving an auto and says a lot for LR servicing.
Also my experiance in my Rover car days with a failing EFI ECU temp sensor is the engine just misfires after a few miles.
The other sensor is the fuel temp sensor of which I know nothing not even if a 3.9 has it

Thanks!

Mr Noisy, I'm in Chelford, not far from you. Problem is I dont know how far I can drive before it conks out. It "might" make it to Altrincham.
Could you explain where the water temp sensors are, please? What am I looking for?
I assume 14 cux is the ECU? Does this mean I can unplug the sensors and if it was them causing the problem it should run fine with them disconnected? Are there 1 or 2 Temp sensors on the plenum?

Whilst I was poking around today I took the coolant cap off an noticed the coolant was very low. I couldn't see any in the header tank at all! I put in about 1.8ltrs and that brough the level up. I thought this might somehow have been the issue, but after topping off and letting it run for 20 mins just standing on the drive it died again, just the same as before. At least I can replicate it on the drive, so I should be able to test a fix without the risk of it breaking down and leaving me stranded somewhere again.

The ignition amp is mounted on a plate next to the coil. The amp actually sits right near the radiator. Could this be a contributing factor? Why would getting the amp warm cause it to stop working?

Jack

There might be a fuel line touching the engine ,which could heat up the fuel and cause the stalling...

OK, so I've found the water temp sender and got one on order and I'm going to replace the ignition amplifier module as well, just in case.
Cheers
Jack

Jack Wood said:

OK, so I've found the water temp sender and got one on order and I'm going to replace the ignition amplifier module as well, just in case.
Cheers
Jack

Click to expand...

ECU coolent temp sensor has a black top and can be seen just behind the dizzi, if you had a problem with the amp starting would alsobe difficult, the position it's in now is standard and it's bolted to an alloy bracket/heat sink it was moved there from alongside the dizzy because of the perceived temp issues with heat in that location.

This link may or maynot help http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm

Hi jack

I got your email mate but thanks for copying it here, keeps all the info in one place.

Yeah mate if you wanted to shoot down to Altrincham one evening I'm happy to have a rummage but you might sort it yourself anyway!

That link that was posted is AWESOME for diagnosing 14cux issues, go through and check all sensors with a multimeter.

Let us know what you find pal

O.K. then, another odd stalling 3.9. As already said, temp thermistor is a common issue, see how you go once that has been changed.

I strongly suggest you pop the plenum off and give it all a good clean and do the breathers like Discool said.

Check the vac advance on the distributor is working, check for split/perished vac hoses. Check base idle and ignition timing.

Lastly, you say you changed plugs, leads and cap but not the rotor arm? Maybe a new rotor arm would be worthwhile but please make sure it is a Lucas arm, and if the cap is not a genuine part get one that is.

If you do a search you'll find lots of info on rough running, engine stalling, won't start etc.

Yep, the fact is that these engines run off the crankcase air, so if it isn't there they can stall.

I would strip every hose off the engine, remove the plenum top and rocker covers, clean every hose, poke every hole, scrape every surface - and rebuild.

This takes time!

Thanks again for all the advice, and thanks for the offer Mr Noisy.

I'll do the simple bits first, like the water temp sensor and the ignition amp and then take it from there.

Stripping all the hoses, plenum, covers, etc is going to be a bit beyond me with my limited mechanical skill and time. Fingers crossed its just a simple fix. Probably not going to be though, is it

Take a hose off, clean out out, poke out the hole in the engine, replace, do another.

Very simple, but you will find that if certain breathers are blocked (they usually are) it will not run properly!

Honestly mate if I had a little more time right now I would gladly shoot down and pull it part for you.

Cheers.

Hi again,

Well, replaced the water temp sensor and the ignition amp today.

No change. Exactly the same. Started on the button, first turn of the key, but after sat left running for 15-20mins it died and wouldn't restart. Left it for a couple of hours and it started first time again.

It's obviously not either of those 2 things.

Will start to pull hoses and clean them out this weekend.

Jack

Hmmm. Seems too odd that it would die after 20 minutes and not restart, that ain't a hose blockage issue as far as I can see.

Does the fuel pump run good?

Suspect an ECU fault?

Need to establish what happens when it dies, this is crucial.

Does it run out of fuel, spark, air, or a combination of the lot through bad timing.

Find out what gets taken out of the equation when it cuts out and you're on the right track to finding out where the problem lies.

Have you got a warm garage to work in?

This would seriously increase the chances of me coming down to have a look at it tomorrow evening!

Mr Noisy said:

Have you got a warm garage to work in?

This would seriously increase the chances of me coming down to have a look at it tomorrow evening!

Click to expand...

lol, no, unfortunately no garage. And I know what you mean. I was trying to fit the ignition module in the dark with a torch in my mouth! Couldn't feel my fingers after 2 minutes

After it dies, you can hear the pump priming when you turn the ignition on. It turns over fine. Very occasionally it will catch for a split second and then die. Then won't catch at all until you let it stand for a decent length of time. Every time, the longer you leave it, 20mins, 45mins, hour, 2 hours, it will run for longer before it ies again.

I haven't got a spare plug to see if there is a spark while it turns over after it's died. In fact, I haven't got a spare pair of hands to turn it over while I look at a sparkplug to see if it's sparking

Could a fuel filter cause this effect? With it being so heat dependant, and the filter being so far away from the engine, I can't see how it could be. But I certainly haven't changed it and the fittings on it look so corroded I can't see it being changed in the last 5 years.

EDIT: Someone on a local forum has suggested that he has seen this kind of issue with cutting out when hot before and it has always been a faulty crank sensor. My mechanic that works on my other car also mentioned the other day that he would look at the crank sensor first as they can break down when hot. But both qualified their thoughts by saying they had no experience of the crank sensor on a Landy V8. Any thoughts on that as a possible cause?

Jack

Are the connections on top of the coil clean and tight including the king lead. Have you cleaned the crankcase breather?.
You have a distrubtor, your mechanic must think you have a D2 V8 which don't have one but have a crank sensor instead.

if you can persuade me with cups of warm tea i may be persuaded into popping in tomorrow evening.

i have some tuning to do on mine so need to get out and drive it, thus i could drive it down to yours.

i can bring various items with me, strobe light to check the timing, a spare ecu, etc etc.

start persuading!

Right what we saying for tonight pal? I'm out and about in mine so can pop down if you like, will bring some spares/tools etc.

Let me know ASAP