TD5 Start-up problems

Hi folks,

I'm Andreas from Germany.

Just wanted to post the problems having with my 15P-TD5 engine in my MY2005 Defender:

- poor start-up (wobbling engine for a few seconds, sometimes attempting start up to 3 times)
note well: behaviour even @ "normal" temperatures, 15...20 degrees e.g.
sometimes masses of white smoke (smells definitely like unburnt Diesel fuel)
- when finally running rough and "stiff" engine with no proper power

By pure chance I found out: doing a start-up with unplugged sensors for coolant and fuel temperatur (ECT/FT) the engine starts instantly without problems running @ approx. 1000 revs/min.
When re-plugging both sensors revs decrease slightly to 740 per min as it is normal

Done so far:

- fuel pump and filter checked: 4 bar in fuel inlet flow at full stream (have a look into my garage - ;-)))
- complete injector overhaul
- new glow plugs (relais working!)
- new ECT and FT sensor
- having off cylinder head and checked for no cracks

BUT: no fault codes found (Hawkeye) except having sensors unplugged;-)

Any ideas? ECU failure??

Many thanks and regards,
Andreas

Have you checked for oil contamination in the injector loom (red plug on the ecu)?

Hi Ratty,

yes, I did so. There 's no oil in this part of the loom.

But due to a leaky pressure regulator (sensor loom was full of dirt and gasoil) this sensor loom was yet swapped.

I had this done as the engine had cutouts and no power. Additional two MAF (mass air flow sensors) have been renewed (fault detected as out of function).

After having this done the cutouts failed to appear again but still having this rough engine and the difficulties whilst start-up.

Maybe there's something happened to the ECU?

However - currently I'm trying to test another ECU.

Regards,
Andreas

Hello,

I met Ploughman yesterday and we installed a different ECU, a new NNN one, via my Nanocom.
But, on the buttomline, nothing changed.

A friend of mine owns another Td5, MY 2004 with similar problems, running very bad when it is cold.
But, if You disconnect the AAP-Sensor, the engine runs fine. The idling mixture turns are up for appr. 150 turns.
Perfect cylinder balance and so one.
If You put the plug back on the sensor the cylinder balance gets bad and the idling mixture turns are goin up and down a little.

Is this only a german appearance?

Many thanks for Help!

Regards

Horst

From what I understand the ECM uses the signal from the AAP sensor for the following functions:
1. To maintain manifold boost pressure.
2. To reduce exhaust smoke emissions while driving at high altitude.
3. Control of the EGR system.

The sensor also supplies a voltage between 0v and 5v proportional to ambient temperature. The ECM uses this signal for the following functions:


- Exhaust gas over temperature protection.-
- Turbocharger overspeed protection.

The ECM compares AAT with ECT. If both are within a tolerance of each other (usually 8 Degrees) then the ECM assumes a cold start procedure.

Your location is SELM and from the internet it is at about 111m above sea level, so the AAP shouldn't be that relevant, however I can’t guarantee that!!

I would do the following next:
· Clean and visually check the sensor.
· Check the connector
· Check as much wiring as possible for circuit integrity
· Clean/change the Air Filter
· Check vacuum pipes from the waste gate to the solenoid and from the solenoid to the inlet pipe for Leaks.
· Check your intercooler hoses for excessive oil contamination and internal collapsing
· Do a run with Nanocom attached and see what your AAT is doing.
o Is it reading the same as the ECT (within 8 Degrees)?
o Is your Turbo limiting to 1 bar?
· Check Ambient Air Pressure and Manifold Air Pressure are not significantly different with engine cold/off.

You could also swop your friends Filter box cover (with AAP) over and see if the Nanocom readings are different

I don't know if it will flag up any problems, but you will be more confident that your AAP is working!!

HTH

Chan

Mines doing the same. running better with aap sensor unplugged tried another used sensor was better for abit then back to same old tricks.. what was it in the end???

Hi Discodevon,

sorry for a late reply!

Got the issue sorted out as an air ingress issue in the fuel feeding system during cooling down.

With unplugged sensors for fuel and/or coolant temps the start injection quantity is based on the reserve value: the bores in the injectors are flooded and filled much quicker than with normal values.

Remedy: disposed the in-tank pump and fitted a simple BOSCH fuel feeding pump in combination with an in-line filter.

Working perfectly up to now for 8000 kms...