Technical Starting issue - Throttle valve

[Phillo]

Hi

I have a ducato 3.0 160 multijet.

I have had an issue were it struggles to start 1st time. I either have to hold the key abit longer or give the accelerator a tap which i know isnt a good thing to do.

So i have stripped the front end which took alot longer than i thought due to badly rusted bolts - that scuttle tray

Tonight i took the throttle valve off and cleaned. Pics show how it was.
My question is should the throttle case or the case that it is bolted to be really dirty as well and should i have taken it off to clean thatalso. I tried my best to clean were i could but not too sure what if i should strip it further?


Thanks

Phil

 

[Anthony489]

Hi Phil

I don't know how much you know about modern diesels, so ignore the following if already familiar. The main job of the throttle body (TB) is to alter the pressure in the inlet manifold under certain engine operating conditions, to encourage the flow of recirculated exhaust gas from the EGR valve, part of the emissions control process. Its secondary job is to close momentarily when you switch off the engine, to prevent judder. Unlike in a petrol engine, the TB plays NO part in regulating engine power, and is not connected to the driver's "throttle" pedal except very loosely via the engine management software. Engine power is controlled by the amount of fuel injected. When starting, the flap valve is supposed to be partially open, which allows more than enough airflow to allow startup and idle. I doubt if the engine management takes any notice of the position of the drivers throttle pedal while cranking.

The Wahler TBs were fitted up to about 2009, but proved unreliable and were changed in production to an improved type. Most will have failed by now due to gumming up or water ingress, so you are living on borrowed time. I suggest you replace yours with an aftermarket type e.g. by Marelli. This also needs a short adaptor harness, as the electrical connector is different, most suppliers include this harness. The new TB and harness used to be about £250 but may be more these days.

As for the oily soot, although this looks alarming the inlet passages are fairly generously sized, so the restriction to airflow probably isn't enough to make any difference. I wouldn't therefore recommend going to all the trouble of removing the inlet manifold unless it really is seriously coked up. Where the mischief starts is on fiddly things like the TB flap, which may get gummed up and stick in position. There is also a MAP sensor which pokes into the inlet manifold. It has a tiny hole to communicate manifold pressure to the sensor chip inside. This tiny hole can get blocked, so worth pulling out the sensor and carefully cleaning (avoid solvents).

Assuming your vehicle is pre 2009, it would be worth checking/replacing the engine to body earth strap if it hasn't already been done. These are notorious for corroding internally and the extra resistance causes slower cranking (= hard start) and other odd electrical effects. Its mounted low down on the passenger side (RHD) under the air filter.

 

[Phillo]

Thank you for the informative response. Much appreciated. Its a 2008 and still has the Wahler type so i will look at getting a new type. Youve pretty much answered my next questions with regards eathing strap and sensors to check so i will also check them out as well. I have had the battery on trickle charge over night as the voltage dropped to about 10.7ish on cranking. It started first time after cleaning the throttle body and charging. I need to sort the scuttle tray water leaks out.

Would you recommend anything else on a 2008 model?

Thanks again for the response. Its my first van and its a massive help when you get such detail

 

[Phillo]

I have just checked the earthing strap. Looks like theres rust around were it is secured so i will replace it.

Anyone have any idea what the connector in the image is for. It is to the rightof the starter motor going into the bottom of the engine. As my hand brushed padt it it fell off. It pushes back on but unsure if it is broken or not.

Thanks

 

[Anthony489]

Hi again Phil

Ducatos sometimes have unused connectors dangling out of the wiring loom. The loom has provision for all options, so if something isn't fitted there will be a spare connector. If there is no obvious mating half then don't worry. The connector pairs usually have some form of retaining clip, so they can't just fall off - often the problem is the opposite i.e. getting the little devils to come apart when you want them to !

On my van I made the following modifications to reduce excessive water on the engine:

Seal the seam at the centre where the two halves of the scuttle tray join - use black silicone
Add a worm drive hose clip to the factory 40 mm drain pipe on the driver's side, so it doesn't keep falling off
Add an extra drain hose to the passenger side. I used rubber hose of about 10 mm bore, plus one of those plastic stiffener inserts (see pic) used for push-fit plumbing to keep pipes from collapsing. Drill an appropriate sized hole in the bottom of the tray, pop the insert in from the top with the shallow flange uppermost, then push the hose up onto it from below to keep it all in place. Then route the hose down and away past the back of the gearbox and tywrap in place.

 

[Phillo]

Sounds like a plan. Thanks.

The connector is sticking i to the engine but fell off as i brushed past it checking the cable. Could it be a sensor that i may need to replace if its fell off. I have pushed it back on for now but unsure what it does

If you looked straight at the starter it is to the right hand side and up a little bit.

Any ideas?.

Thanks again