Funonthefarm

Funonthefarm

Active Member
Hi all,

just finished the rebuild on the td5 and it’s developed a fault... Engine light comes on and then no throttle. Turn off and on and clears itself.

read it with a Delphi reader which is showing a over boost fault...
I’ve had the actuator off and tested it with vacuum pump, working fine...
Had map out and cleaned...
any thoughts on what it could be?
 
A Little update, I had cleaned the MAP before, but today cleaned MAP and MAF. I checked the MAF has power and it registering a low voltage at idle which it is.
I hooked the computer up and can see live data, all done static on idle, whilst watching it, I noticed a anomaly on the MAF presser, a short sudden drop on the pressure... see image. Not sure if this could cause the MAP to see a over boost fault... thoughts?

MAP was showing slight fluctuations at idle, and increasing when rev'd so I presume is working correctly.

I've had it out for a 40 mile trip with no problems or errors showing so far... but would like to get to the bottom of it...

Also to note, injector loom has been changed and all plugs cleaned.

Any suggestions welcome.
 

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Hi. You can't rely on OBD2 reader when it comes to Td5, it gives false codes and shows erratic data cos the Td5 diagnostic protocol is not OBD2 compliant.
Funonthefarm said:
Engine light comes on and then no throttle.
Click to expand...
then most likely the problem is with the TPS cos the engine management warning light can be triggered only by two sensors: TPS or CPS , nothing else
 
Good to know on all fronts, thank you.

TPS and cps, light only come on, i don’t mean to question, but is this 100 accurate, I had read a few posts about over boost, where engine light comes on? just want to check as it then narrows this right down.
 
Funonthefarm said:
TPS and cps, light only come on, i don’t mean to question, but is this 100 accurate,
Click to expand...
It is 100% accurate according to the Td5 engine management description and operation mode from the WSM while it's first time i hear about EML triggered by overboost but if others have seen this in real life i'm not going to contradict them. If it's Eu3 engine unplug the MAF and drive it that way and if the symptom goes away it's the so called "MAF cut-out" when the air flow exceeds 680 Kg/hr and the ECU cuts fuelling. The symptom is physically the same like overboost but the fault code should be ''air flow too high"
 
Super thanks, I’m not questioning it too much as I also read that engine light on and engine goes to anti stall then it’s probably tps... but the formula are full of contradicting info so it was good to hear your view. I can’t see how the Ecu could detect a overboost anyway as there is no sensors to my knowledge that give boost pressure only the map at inlet... and the def has no boost control other than the pressure activated waste gate... correct?

move cleaned the TPS also, and wiggles wires to try and recreate the issue if there was a short. Last time it happened it was backing off the throttle so I guess pointing to the TPS. It was in bits so wondered if the contacts had lightly oxidised... any more thoughts are greatly appreciated.
 
Funonthefarm said:
I can’t see how the Ecu could detect a overboost anyway as there is no sensors to my knowledge that give boost pressure only the map at inlet... and the def has no boost control other than the pressure activated waste gate... correct?
Click to expand...
The ECU calculates boost by extracting the ambient air pressure reading (AAP sensor in the airbox) from the MAP reading(boost = MAP - AAP) and the factory overboost limit is set to 1.42 bar(142 KPa) so when this limit is exceeded it goes to default with reduced fuelling and overboost fault code is stored... yes, on defender the boost is controlled through the wastegate valve
 
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Sorry to butt in, but the way it can detect over boost is by checking manifold pressure, when it goes too high the ECU goes to limp mode to protect the engine.

As you say it should be regulated by the waste gate actuator which is driven by tapping into the turbo discharge and using the pressure against a diaphragm to compress the sping until it hits a point where it opens the bypass gate on the exhaust side, opening point can be adjusted by the threaded rod on the linkage, not sure how you could test this with a vacuum pump, as it operates on positive pressure.
Have you tried teeing into the turbo discharge to check the actual pressure when it cuts out? This is the only real way to set it up.
I bought a pressure gauge, a short length of plastic tubing and a tee piece and fitted it into the actuator pipe.
 
sierrafery said:
The ECU calculates boost by extracting the ambient air pressure reading (AAP sensor in the airbox) from the MAP reading(boost = MAP - AAP) and the factory overboost limit is set to 1.42 bar(142 KPa) so when this limit is exceeded it goes to default with reduced fuelling and overboost fault code is tored... yes, on defender the boost is controlled through the wastegate valve
Click to expand...
Sorry I was typing while you were doing your reply
 
Ok so to recap the above:
-Boost is pure measured by the aap and map
- if over boost or pressure is exceed at the map then engine will go to limp mode... by which you mean anti stall.

Will this trigger the engine light? This is a key question, as when the problem occurs it does.

obd2 reader - is reliable for the defender Correct? It does seem to ready all the data outputs?

On the actuator, sorry I meant I applied pressure with a gun to see what it moved the arm at and appeared around 12-14psi

At the moment trying to isolate the issue, to focus attention on the right parts.

additinal thought, could a faulty egr cause the problem? Adding additional “air” to the system which the map and aap haven’t calculated for? Engine does seem to run well tho....
 
Funonthefarm said:
Ok so to recap the above:
-Boost is pure measured by the aap and map
- if over boost or pressure is exceed at the map then engine will go to limp mode... by which you mean anti stall.
Click to expand...
No, boost is CALCULATED by the ECU by extracting AAP from MAP and if the 1.42 bar limit in the fuel map is exceeded then it's overboost which is not supposed to trigger the EML at all
Funonthefarm said:
obd2 reader - is reliable for the defender Correct?
Click to expand...
Wrong, even if it shows data you can't 100% rely on it especially not when it comes to fault codes cos as i said before the Td5 is NOT OBD2 compliant
Funonthefarm said:
additinal thought, could a faulty egr cause the problem?
Click to expand...
faulty EGR would eventually cause power loss and black smoke due to lack of air for optimal combustion.
 
Yes, so as I said is purely calculated by the data from the aap and map... obviously the Ecu needs to calculate this as is a combination of the 2.

on the obd2 a sorry I meant to say isn’t reliable. The Delphi software does have all the correct info for the defender, what makes it not compliant?

so engine in limp mode and engine light.... triggered or not? This is the question? which seems to have conflicting answers...
 
About the EML depends what you rely on... on the official LR WSM according to which the EML is triggered ONLY by TPS or CPS related codes which in my experience is correct or on oppinions from various forums.
 
sierrafery said:
most likely the problem is with the TPS cos the engine management warning light can be triggered only by two sensors: TPS or CPS , nothing else
Click to expand...

I am not questioning the validity of the statement, this is a genuine question to improve my understanding.
Assuming EML and MIL are the same, all but one fault that throw up the M&S lights will also throw up the MIL light. What the the process that causes this?

It occurs to me that your statement on the TD5 EML/MIL might have been focused upon the OPs vehicle and therefore may not apply to the D2. If that is the case I'll shut up. :)
 
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Funonthefarm said:
What are m&s lights?
Click to expand...
Only associated with automatic transmission, so I very much doubt they affect you. In High range there is a Sport mode with an S light, in Low range there is a Manual mode with an M light. They both flash with certain gearbox faults, but also illuminate the MIL (Eng Management Light); hence why I was surprised that the engine management warning light can only be triggered by the TPS or CPS. But as I edited my post, I suspect that the statement was for your vehicle rather than all TD5s.
 
Think I might have found the problem, the blue "jumper" block on the black loom was corroded, so these wires were cut by a mechanic friend of mine and soldered together and heat wrapped up - after "fiddling" I think I have identified the white and purple wires hadn't soldered well and look to be causing the fault... when they were wiggled the engine light came on... I've done a temp fix with a chock block and it seems to have solved the problem... well in the garage at least, so will see how this goes and do a proper repair shortly...
 
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