mikegsxr

mikegsxr

Active Member
Hi, My Defender 110 TD5 misfires when driving in heavy rain. As soon as the rain eases the fault is gone! Sounds like an electrical gremlin to me. Does anyone have any ideas where to look? Warranty runs out in a couple of months, but the daler has already drawn a blank.
Cheers Mike.:confused:
 
What kind of misfire are you getting? fade or or lumpy running?
Theoretically a diesel can run without any electrics at all, but modern ones use a fuel cut off solenoid to stop the engine quickly, and many use an electric fuel pump to supply the injector pump too.
 
Hi, It is as though the engine is running out of fuel. Cutting out for a second or less then resuming as normal. Power between the cut outs is normal.:confused: Mike.
 
I would start with the fuel shutoff solenoid and related wiring 1st, not sure whether that is controlled by other elctronic gizmos on TD5 or straight from ignition switch / relay.

Sorry I can't be more help, hopefully someone else will be more familiar with it on a TD5 than I am.
 
I agree with l3on.

Find the fuel shutoff, unscrew it and pull out the plunger/ball baring, with this removed there is no way the fuel can be shut off, so if it runs normaly with this removed, then the fault lies within your shutoff or its wiring.

If you still have a problem then you will need to look into the next part of the system which is the electronics controlling the fuel system after the shutoff. I take it that the heavy rain effects it after it has driven in said rain and got the engine bay a bit wet?

Could a hose simulate the rain therefore to give you a good testing method? Spray some different parts untill it misfires.
 
Is your accelerator pedal assembly getting wet? Being fly-by-wire, the potentiometer looks fairly vulnerable down there - and it is directly related to engine speed...... funnily enough
 
Thanks for the replys,The TD5 has electronically controlled unit injectors which are enabled by the ECU. I was thinking that maybe one of the many sensors that feed the ECU (inlet tract air mass/temperature sensor?) might be the cause. I cannot replicate the fault with a hose, and the cab is finally leak tight (only took three years for the dealer to nearly fix this) so the throttle potentiometer is dry. Cheers Mike.
 
If any of the above mentioned items were to fail then the ecu should default to *basic* (low power) mapping that you would notice but be less severe than the symptoms you are describing, accompanied by dash warning lights.
Presumably you have tried the fuel solenoid test as suggested by Discomania in his reply and that the symptons persisted?
Sounds like this is going to be a proccess of elimination starting with the most obvious first, but as I posted before, not many things will result in the symptons you are getting without ecu warning lights on dash apart from........errr...god forbid.....the ecu...:D presumably the engine light comes on during normal starting to show its working?
 
give all the electric relays/solonoids etc a good dowsing with wd40. may cure it, and it wont do any harm either.
 
Hi,
Haven't yet looked at the fuel shut off, but that is next on my list. I get normal engine light when starting. No lights when the fault occurs. Perhaps I can convince the dealer to change the shut off valve for me for no charge! Booked in March 17th. Heres hoping.....
Mike.
 
Is your accelerator pedal assembly getting wet? Being fly-by-wire, the potentiometer looks fairly vulnerable down there - and it is directly related to engine speed...... funnily enough
Click to expand...

Td5 Disco's had this problem on early ones when the potentiometer got wet. But I think it was more like a total failure rather than as poster describes.
 
Try looking under the drivers seat , make sure the seat box is dry and no water is getting in the plugs of the ecu.

And there is no injector pump solonoid on a td5 it is all controled by the ecu. It dont have a injector pump the injectors are seperate pumps them selfs
 
Check around the fuel tank as well - the low pressure fuel pump may be shorting in the wet.
 
I know this is a very old thread but I have exactly the same fault on my 02 TD5 Defender. Did you ever get it solved? What was the cause?
 
bellautos said:
Try looking under the drivers seat , make sure the seat box is dry and no water is getting in the plugs of the ecu.

And there is no injector pump solonoid on a td5 it is all controled by the ecu. It dont have a injector pump the injectors are seperate pumps them selfs
Click to expand...
I had problems with water in there tried all sorts improvement came when I took out the sun roof and 're sealed it sounds mad but it worked.
 
Try unplugging the throttle sensor and cleaning the plug... it does sound like your maf is faulty though
 
Mine turned out to be water getting into the airbox. Probably via the ill fitting pipe work between the wing inlet and airbox.
There were tide marks inside the airbox! And I hadn't been wading either. Removed and binned all the crap OEM bits and replaced with
snorkel and properly sealed pipework. No problems since. Check inside airbox, under the filter for signs of water...
Mike.
 
I had this problem also on my TD5 110. Water had destroyed the air filter after heavy rain. Apart from checking the non return valve on the air intake and replacing the air filter l’ve not done anything else to it.
It was VERY heavy rain though, and l should maybe have slowed down from 65mph
 
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