Turbo Diesel – Excessive black smoke

[Phil Grimsey]

Hi guys,

Now, not all of you will have heard of the vehicle, but hopefully the problem is generic enough to get away with a question here.

I have a 2006 Fiat Doblo Cargo. It’s a small-ish sized van (similar to the Ford Connect) which is powered by a 1.9 litre (116ci?) 8 valve Single cam Turbo – intercooled diesel engine that (by books) makes 105bhp with 150lbft of torque. Now, the problem I am experiencing is thus.

I have noticed recently a steadily increasing level of black smoke from the exhaust when pulling away from a stand-still which seems to be accompanied by a more pronounced hesitation on the uptake. It will also throw out a cloud of smoke when changing down a gear to accelerate to overtake or maintain progress going uphill.It’s been bugging me what the cause is and whilst queueing in the bank today, I had (for me) a eureka moment.

What I was wondering is this;

Could it be a boost leak?

My thinking is that the boost is leaking away somewhere(hence the deteriorating performance) and thus leaving the engine running slightly rich (hence the smoke and also the performance issue again possibly).

What I have come to thinking is how do I test if that’s the case? It’s obviously impractical to sit on the engine at 70mph and look for bulging hoses ( 😉 )so would a visual inspection suffice? Would the engine generate enough load/pressure if revved while stationary to cause the hoses to bulge?

Also, I was wondering if the intercooler could have a pinhole in it that’s leaking boost? This is located low down on the front of the vehicle, so would be fairly prone to stone/other detritus hitting it and potentially puncturing it. For that, I wondered about removing the intercooler and filling it with something like paraffin and looking for any damp areas where the fluid is leaking out, which to me would indicate an area of potential loss of boost, especially if it’s leaking out at atmospheric pressure as I’d imagine any weakness to open up under positive boost.

In keeping with my ethos of preventative maintenance, the vehicle is well serviced, and has been all its life. I use the correct grade of oil (Morris Oils 5w/30 c2 fully synthetic) high quality filters (i’m a swine for good filtration, given my trade as a pool man) of which all 3 have been changed (fuel filter approx 5-6k ago, air and oil in the last 1,000 miles)

It is also run exclusively on Shell Diesel ( primarily as | have a fuel card, but also as it’s good quality).

Once over the initial pick up issue, it does still feel a little “blunted” but certainly does pull well and returns an average of 45MPG imperial, somtimes more (currently sat at 52mpg with 1 gallon = 4.54 litres, here).

Also relevant is the fact that I don’t always drive sedately and am a great believer in the “Italian tune up” i.e go out and give it a good, hard drive.

I assume it will have some sort of EGR system on it, too, but given the price of a door handle for it (£110+tax @20%) and Fiat’s tendancy to change whole parts (wiper linkage bushes wear and you have to replace the whole assembly @ £135+tax) I’d probably be charged about £3,000,000 and/or have to buy a whole new engine or something, so I’d like to try simple bolt on/off issues before delving deeper into the van and looking at things like that.

Any thoughts? I’d appreciate techie input on this as I’d like to sort it as it’s fairly embarrassing and I feel like people will think I don’t look after it, which I do!

Thanks

Phil

Topic

[JD JawDroppin]

As far as I’m aware – when it comes to Diesels (1st year apprentice) – black smoke is a sign of over-fuelling (running rich). What sort of injection does this engine use? Common Rail or Direct? Id be checking how much Diesel spray they are pumping out and you may find it is too much…

Hope this helps…

JD 😉

[Phil Grimsey]

hey mate.

Excess fuel, yes. That could be as a result of boost loss though as the ECU will be fuelling as though it’s getting (for sake of argument) 0.8 bar but the engine is only getting 0.4 bar.

Does that make sense?

Phil

[college man]

Try cleaning the MAF sensor

[Bill]

Have you checked the air filter? Could be a collapsing intake hose from the air filter to the turbo somewhere.

[Phil Grimsey]

hi,

1) MAF sensor – great idea! Will look into doing that.

2) Air filter is only 1000 miles old and will never get to be more than 10,000 miles old, which is the service interval on the vehicle, but thanks for the thought.

Phil

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