3.9 v8 (very) poor starting

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
D

DV8

Member
Posts
11
Location
Birmingham
Hi all new dude here, hope this finds you all well and you’re not too stressed with Land Rover related problems :)

I have a starting issue with a 1996 discovery 1 3.9 v8 auto. I have owned it for coming up to 2 years now and it has had this problem since I bought it, but after so long it failed fault diagnosis I am reaching out to fellow green oval enthusiasts for help!

To cut to the chase... the issue is that it takes 10-15 seconds of cranking (sometimes longer) until it splutters into life. Once it’s starts it runs and revs fine with no loss of power, but does seem to run quite rich.

Now the peculiar bit... if it has just been running and I turn it off, it’ll fire back up immediately on the button with no cranking. It it’s left off for more than 30mins, it will need loads of cranking. If I start it the next morning after running the day before, it will need loads of cranking. But.. if it is left for 3 days or more, it’ll fire up immediately with no cranking at all!

In my ownership I have renewed the following:
-MAF sensor
-Dizzy cap
-Rotor arm
-HT leads
-Spark plugs
-Coil
-Ignition amp
-Coolant temp sensors
-Stepper motor
-Fuel pump+filter
-Fuel pressure regulator
-Injectors flushed
-Fuel relays
-Spider bypass
-Tried different ECU

I have checked:
fuel pressure (OK)
Battery (OK)
Timing (OK)
Rotor arm spring test (OK)
Compression test (OK)
Spark (OK)

Sorry for the long post but want to give as much info as I can.. and unlike some I promise to come back with the solution if it’s ever fixed! :(
 
Hi, when it cranks over and over without starting, have you pulled the plus to see if they are wet or dry?
What colour are the plugs normally?
 
kermit_rr said:
Hi, when it cranks over and over without starting, have you pulled the plus to see if they are wet or dry?
What colour are the plugs normally?
Click to expand...

Hi thanks for the reply. Last time I checked they where that bronzy colour that they go and were wet so all seemed fine?
 
Does the 3.9 have a cold-start injector (into the plenum) like the 3.5?
IF that's the case, disconnect the wire at the injector & run without it … my 3.5efi never needs it, even in the coldest months.
Having said that, the absence of the CSI won't cause the motor to run rich as it only activates when the engine is cranking.
 
norseman said:
Does the 3.9 have a cold-start injector (into the plenum) like the 3.5?
IF that's the case, disconnect the wire at the injector & run without it … my 3.5efi never needs it, even in the coldest months.
Having said that, the absence of the CSI won't cause the motor to run rich as it only activates when the engine is cranking.
Click to expand...

I don’t think the 3.9 has one? Unless it’s hidden away somewhere I don’t know about!
 
Ok thanks. The only things I can think of left to try are maybe the fuel temperature sensor and the dizzy itself that I’ve heard can potentially cause this kind of issue?

I haven’t changed the lamdas but I don’t think they would cause a problem on start up?
 
DV8 said:
Ok thanks. The only things I can think of left to try are maybe the fuel temperature sensor and the dizzy itself that I’ve heard can potentially cause this kind of issue?

I haven’t changed the lamdas but I don’t think they would cause a problem on start up?
Click to expand...
Once the engine starts it runs fine, so dizzy doubtful, fuel sensor maybe, very difficult as you have replace everything thing, were any of the items secondhand, the idle control valve can have a bearing on iffy cold starting, not if it new of course.
Even while cranking if there’s fuel and a spark the engine should at least cough an bit
 
discool said:
Once the engine starts it runs fine, so dizzy doubtful, fuel sensor maybe, very difficult as you have replace everything thing, were any of the items secondhand, the idle control valve can have a bearing on iffy cold starting, not if it new of course.
Even while cranking if there’s fuel and a spark the engine should at least cough an bit
Click to expand...

Yes it’s had me pulling my hair out! Well actually the only thing I haven’t bought directly from a parts shop is the idle control valve, but it worked on another vehicle so I’d dismissed it as a potential issue. I shall try a new one and report back
 
DV8 said:
Yes it’s had me pulling my hair out! Well actually the only thing I haven’t bought directly from a parts shop is the idle control valve, but it worked on another vehicle so I’d dismissed it as a potential issue. I shall try a new one and report back
Click to expand...
Hold fire, it operates or it doesn’t, but if it does it could be sticking and not closing fully or an air leak at its filings or the hose leading to it. There’s a few tests that can be done lots of info on the exact way the valve works and when.
Just one snippet of info I’ve found but there’s lots more.
https://www.pistonheads.com/gassing/topic.asp?h=0&f=8&t=1327100
 
discool said:
Hold fire, it operates or it doesn’t, but if it does it could be sticking and not closing fully or an air leak at its filings or the hose leading to it. There’s a few tests that can be done lots of info on the exact way the valve works and when.
Just one snippet of info I’ve found but there’s lots more.
https://www.pistonheads.com/gassing/topic.asp?h=0&f=8&t=1327100
Click to expand...

Brilliant thanks for that I shall have a look through and try it today.
 
So this weekend for peace of mind I fitted a new distributor and fuel temp sensor. Timed it and running sweet.

I read through that article piston heads article and inspected the stepper, trying what it said. I purchased a new stepper and on comparison to my old one the new one had a lot more travel in the solenoid and would retract further into the stepper body.

I checked for leaks etc and after fitting the new one on initial start up revs ran high for a few seconds but returned to normal and has been fine since.

However, starting issue remains! I now don’t think there is a single component in the fuel/ignition system that hasn’t been renewed/serviced so I’m totally stumped.

Anyone got a spare 4.6 lump they’d like to donate?!
 
Where do u go know? So running ok once the engine is started cold or hot, the issue is the starting when hot, lots of cranking and then it starts... is that correct?
If so, it should be simple fix, so a faulty ignition amp has been known to give difficulty with hot starting but also misfiring, is your amp positioned near the coil ? I have look in my books, and see what they say, incorrect fitted coil maybe but then then it’s a new replacement like the other stuff, seems u should be looking for something temperature sensitive.
You have the small resistor fitted near the coil, it’s a small square item and show in the wiring diagrams.





Sent from my iPad on a train
 
Yes that’s correct accept it does need cranking hot or cold. The only time it’ll start immediately is when it’s been left stood for a few days or more, or if it’s running and I turn it off and back on again pretty much straight away.

Yeah the amp has the relocation kit and is next to the coil. The original amp did fail on me about 8 months ago on the m40, so it was replaced and I now also carry a spare!

I did notice those resistors.. am I right in thinking a signal is sent via those to the injectors?
 
Aye Up,

I’ve been trying to follow the logic through on this one -

Discool, you might be correct that there is probably a heat issue but reading the OP suggests that there is also a time issue - it fires up immediately if turned off then back on, if left for thirty minutes it needs cranking, but left for much longer (I.e. 3 days) it fires up straight away.
Plus, whatever it is doesn’t cause the engine to cut out whilst running so why isn’t heat affecting it then?
Plus, it is running rich.

Is it possible that it is a fuel issue, e.g can’t flood if momentarily switched off and straight back on, floods over the 30 minute period but the fuel evaporates when left for days so then starts normally?
 
Had breeze through this quickly....... intriguing.
Have you watched the timing for a good few minutes -- does it wander? Is the idle speed rock steady?
The other thought I had was the ignition timing, what is it actually set to? Is the base idle correct.
An inlet air leak is possible but would expect more rough running rather than just odd starting. One last thing to check maybe is take off, clean and re-fit the main power lead to the starter motor, remove, check and clean the small wire to the starter and lastly, remove, clean and reconnect the main earth leads.That might sound odd but believe me I have had a poor lead connection cause some issues when cranking so maybe worth a look.

The last time I remember having odd starting issues it was a stuffed head gasket but you say compressions all look good. Only other thought is to look at O2 sensors but the ecu ignores these when cold but does look for them when hot, well, above 70 degrees IIRC.
Good luck!
 
I checked the timing last night and watched it.. 90% of the time the marks are spot on aligned but suddenly the pulley mark does seem to jump a couple of degrees above and below the pointer mark, what does this mean? There is no hunting in the revs but periodically there does seem to be a very slight miss.

Originally the timing was set around 5 BDTC but since putting the new dizzy on last weekend I’ve set it to nearer 9 as it runs sweeter.

I haven’t set the base idle myself.. but it idles around 650 once warm.

I shall check and clean all the earths you mentioned tonight.

One thing I have noticed.. when removing the petrol cap there is quite a large rush of air, I’m under the impression that this is normal but it also sometimes doesn’t do it. So it would appear that sometimes there is a vacuum in the tank and sometimes there isn’t.. is this normal?
classic kev said:
Had breeze through this quickly....... intriguing.
Have you watched the timing for a good few minutes -- does it wander? Is the idle speed rock steady?
The other thought I had was the ignition timing, what is it actually set to? Is the base idle correct.
An inlet air leak is possible but would expect more rough running rather than just odd starting. One last thing to check maybe is take off, clean and re-fit the main power lead to the starter motor, remove, check and clean the small wire to the starter and lastly, remove, clean and reconnect the main earth leads.That might sound odd but believe me I have had a poor lead connection cause some issues when cranking so maybe worth a look.

The last time I remember having odd starting issues it was a stuffed head gasket but you say compressions all look good. Only other thought is to look at O2 sensors but the ecu ignores these when cold but does look for them when hot, well, above 70 degrees IIRC.
Good luck!
Click to expand...
 
You must log in or register to reply here.

Similar threads

PieterLV
D2 V8 not starting
Replies
6
Views
446
PieterLV
PieterLV
B
Restored 1972 Series 2 Diesel not starting
Replies
16
Views
550
Shedload
S
J
Range Rover sport SDV6 NOT STARTING!
Replies
3
Views
1K
AllanWorms
AllanWorms
C
3.9 efi no fuel, wont start, tested injectors right bank 8 ohms.........
Replies
7
Views
2K
cljcars
C
cappers
3.5 hotwire efi won't start - solved, poor connection to coil -ve!
Replies
14
Views
2K
AllanWorms
AllanWorms
Back
Top