Defender 300tdi not starting unless battery fully charged

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

bojackhorse

New Member
Posts
6
Location
Austria
I need help diagnosing an issue where my 300tdi won't start unless my 100Ah battery is fully charged (12.8v).
Main points:
- Battery is under 2 years old
- Battery has 1000 CCA
- Battery SOC indicator is green
- Starter motor relay doesn't click like I would expect if the battery was dead
- I wait until the glow plug relay has switched off before turning ignition (I can see the battery voltage go back up indicating the glow plugs are no longer on, also the dash light goes out)
- If I remove the glow plug fuse (60A) the car will start even when my battery is at ~12.2v (but not good for cold weather). The same is true if I disconnect the whole glow plug relay.
- I have checked the negative cable from the transfer case to the chassis and the contact is good on both ends.
- Battery lead contacts are not corroded.
- Even with a battery jump starter (Noco Boost Plus 1000A) the car doesn't start unless the actual battery is full.
- If I manage to start it then drive around for 15 minutes it will start up again easily.

Any suggestions or tips for diagnosing would be very welcome, thanks!
 
Thanks for the reply.
Defender 300tdi as stated in the title of the thread.

I'm unsure how the heater plug circuit can be dragging the current after it's switched off. I hear it click off and see the voltage go back up indicating no load. I have not yet tried a new glow plug relay. Could it potentially be a problem with the ignition relay?
 
bojackhorse said:
I need help diagnosing an issue where my 300tdi won't start unless my 100Ah battery is fully charged (12.8v).
Main points:
- Battery is under 2 years old
- Battery has 1000 CCA
- Battery SOC indicator is green
- Starter motor relay doesn't click like I would expect if the battery was dead
- I wait until the glow plug relay has switched off before turning ignition (I can see the battery voltage go back up indicating the glow plugs are no longer on, also the dash light goes out)
- If I remove the glow plug fuse (60A) the car will start even when my battery is at ~12.2v (but not good for cold weather). The same is true if I disconnect the whole glow plug relay.
- I have checked the negative cable from the transfer case to the chassis and the contact is good on both ends.
- Battery lead contacts are not corroded.
- Even with a battery jump starter (Noco Boost Plus 1000A) the car doesn't start unless the actual battery is full.
- If I manage to start it then drive around for 15 minutes it will start up again easily.

Any suggestions or tips for diagnosing would be very welcome, thanks!
Click to expand...

Have you tried it with a jump lead from the battery negative side to the engine block ?
 
bojackhorse said:
bojackhorse said:
I need help diagnosing an issue where my 300tdi won't start unless my 100Ah battery is fully charged (12.8v).


Any suggestions or tips for diagnosing would be very welcome, thanks!
Click to expand...

I had a similar problem with my 1994 300 TDi as it would normally turn over slowly or worse still, fail to start. It seemed fine when the engine was warm. I am not a mechanic and initially convinced myself it was earthing or battery. I managed to rule the battery out, then when I had another job done the mechanic said the starter motor was on the way out. I bought another and fitted it myself in about 20 minutes. The result was perfect starting even when really cold.
Click to expand...
 
I had a starting issue last year which sounds similar to yours, my symptoms were either starter not spinning or spinning too slow unless i had a jump pack on but once it had started, it was find for a while while the engine had some heat in it.
I tried a different battery with no difference, I rebuilt the starter because i thought it was that sticking or dirty brushes and that made no difference, I cleaned up all the earths and again no difference then i saw someone say put a jump lead off the starter earth to battery earth and when i tried that, it fired straight away.
I probably did the wrong thing after that and rather then fixing the real earth problem, I made an extra earth lead to go from the starter to battery and its been fine every since.
This sounds a similar problem to yours so maybe try that with a jump lead?
 
You must log in or register to reply here.

Similar threads

ibizalandy
1986 110 ex military 2.5 n/a won't start.
Replies
2
Views
959
ibizalandy
ibizalandy
U
Battery health testing
Replies
8
Views
991
kermit_rr
kermit_rr
F
TD5 Fuel pump mystery
Replies
3
Views
359
Brown
Brown
B
300Tdi Defender won’t start when glow plugs are on
Replies
2
Views
712
boguing
boguing
HeywoodFloyd
Freelander 2 wont start, short crank
Replies
16
Views
713
Nodge68
Nodge68
Back
Top