Fiat Ducato keeps cutting out whilst driving

[sgreensides1]

Newbie - please forgive any lack of etiquette / rules / etc.

 

Lunar Moonstar 580 motorhome on Fiat Ducato chassis with x250 2.3 Diesel engine that keeps cutting out whilst we are driving.  Can be as little as 2 or 3 miles after starting, but is random and we have completed 20 miles without a problem.  Local non-fiat garage says error code u1701 and u1600 point to the MH not recognising the keys.  Tried all keys when it fails and all turn the engine over, but few or none start it.  Wait a while and some or all of the keys start it.  Took it to Fiat Dealership and they reprogrammed the keys and tested it (i.e. repeated starting) - no faults.  Took delivery after paying large bill and the engine still cuts out as before.  Returned to dealership, they have checked and there is no fault with the Fiat elements of the MH and they believe it to be the after market security which they want to cut the wires to.  Checked with the makers of the security alarm and they say that the alarm could not interfere with the engine whilst driving and the fact that you can turn the engine over points to the alarm working as it should.

 

Before this happened I replaced the number plate light unit with exactly the same cutting back corroded wire and soldering on new terminals with proper insulation over and replaced the ageing vehicle battery 520 CCA 95 AH with 900 CCA 110 AH.  Could it be something I have done and how do we cure it?

 

Steve.

[colin]

You say 'cutting out' can you expand on that? does it shut down or does the engine only stop.

One thing I always say is a quick easy check, is for mice in the filter.

[Tracker]

What do you have to do to get it to restart?

 

It's probably no help but many years ago I had a petrol Renault Scenic with the same problem but it always restarted eventually as long as you were not too heavy on the starter battery at eaxh attempt. The fault codes pointed to keys and Renault did lots of things including changing the keys all to no avail. In the end it turned out to be an intermittent faulty tdc sensor, but the unreliable nature of both the car and the dealers caused a lot of angst and irritation. As I say, may be of no help to you?

[Keithl]

Steve,

 

If you Google 'U1701' one of the first results is from the Fiat Forum and 'FiatTechSam' has posted that basically the error code is a red herring!

 

"A few people are having issues with this code and I thought I'd try an help, 99% percent of the time the only reason that error code appears is due to a fault with the engine, so as soon as the engine light comes on it shuts down the ABS ECU causing the u1701 fault to appear because the engine ecu can not communicate with the ABS ecu."

 

http://www.fiatforum.com/ducato/439080-u1701-ducato.html

 

So it may be that you are searching in entirely the wrong place for your fault.

 

Other suggestions for the fault come back as 'Rusty junction' behind the LH headlight, a chafed wiring harness in the same area or ECU connections.

 

Keith.

 

PS And welcome to the forum.

[sgreensides1]

Cutting out = as if the ignition was turned off / the engine dies suddenly and completely - no stuttering or hesitation or warning and the driver has to floor the clutch and free-wheel to the side of the road.  Whilst freewheeling I have noticed a different warning light flashing on each occasion or the temperature gauge going up off the scale.  Warning light includes what I think is the pre-heater coil light - looks like a horizontal spring.

[Tracker]

I'm no expert but multiple random faults suggest to me an earth continuity issue?

 

Do you have the extra earth strap from engine to chassis which has widely been suggested as a good idea?

 

There have also been issues with poor connections, water ingress into electics and other bad earth connections so a full research and investigation is liable to be long and arduous unless anyone has had the specific issue and knows the cure?

[euroserv]

Nice work Keith!

 

This is the whole point about diagnostics. Codes are clues, not answers.

 

What stops an engine from running while driving?

 

Lack of fuel.

 

I am not suggesting that you have run out of fuel but this is the only thing that will stop the engine from running. The question is; why no fuel?

 

If the low pressure pump in the fuel tank stops running, and you are doing anything more than an idle speed, the engine will stop because of a lack of fuel or fuel pressure.

 

If any condition arises within the engine compartment that the ECU believes may be harmful to the engine; it can reduce the power of the engine but not shut it down while the vehicle is in motion. It can prevent starting by not giving 'permission' to start but while in motion the only things that can stop the engine are lack of fuel and major sensor faults. At the time that the engine shuts down, there will be a number of sensors that suddenly find themselves with readings that they were not expecting; a lack of electricity or vacuum or exhaust gasses will do that. Some of these strange readings may be logged as faults but many won't because they need electricity to do so and they might not have any at that time.

 

So where to start?

 

A good diagnostic device will have a fault log where you can find out more about the conditions that were prevailing at the time of the fault such as fuel pressure, battery voltage, engine temperature.... There may be a clue here as to what happened. This is an easy place to start.

Next, you would check the charging of the battery to make sure that you don't have an earth problem. Then you check that the fuel pump is running and staying on beyond the initial 20 seconds that it runs even if you turn the ignition off. You should be able to see that there is at least 300bar of fuel pressure with diagnostics connected. Is there a problem with the ignition barrel? Is it staying connected?

Next, you need to get down and dirty with the electrics. Fiat have conveniently located most of their wiring faults in one area; mentioned above... The wiring underneath the fusebox is notorious for bad connections and shorted wires with the looms leaving the area under the nearside headlamp also harboring many a gremlin. One joint, blue in colour is affectionately known as 'rusty junction'.

 

If none of these turn up anything i would swap the crankshaft sensor and failing that; the camshaft sensor. You would hope that one of these failing would produce a fault code with the description 'cam/crank sensor-implausible' but they often don't. If the ECU believes that there is a problem with the relationship between cam and crank sensors it will switch off the fuel sharpish.

 

Any good mechanic (especially a Fiat dealership) would know that this is the process of elimination that you must go through. It takes time, and time costs money. I might give my time for free but if it helps folks to understand that diagnostics is a dark art and requires a lot of thought and investigation and that there must be a cost for this; my time is well spent.

 

Nick

[sgreensides1]

I am happy to add another earth strap and clean up the old one as soon as I get it back from Fiat Dealership, who still say that there is nothing wrong with the Fiat side of the MH.

[sgreensides1]

Thanks for the replies.  Here is my thinking:

 

That the problem is not fuel as the engines dies immediately and I filled the diesel tank at Tesco's supermarket the day problem started and have not heard of any other customers having problems.  Diesel tank quarter full before filling, so probably still running on the old diesel.  Also had new fuel pump / filter / sensor 5000 miles ago.

When the engine dies, you can still turn it over, but it will not start with all the keys or start with only one.  Waiting a while and you can start it with most or all the keys.  Since I do nothing whilst waiting, does this point to over-heating?  Continuous watching of the temperature gauge showed only normal readings.  Just cannot connect waiting (and possibly cooling down) with more of the keys being able to start the MH.  Have I missed anything?

Steve

[crocs]

Here's an off the wall reason for an engine cutting out. One of my classics started cutting out after 10-20 miles. I would sit at the side of the road and check fuel and electrics (not much else to check with a 1949 car) but, without any intervention, it would start again in 10-15 minutes.

 

It did this a few times and, on the final occasion on restart, it gave an almighty bang. The exhaust had blown a hole and it ran fine after that. Apparently, the mild steel exhaust was corroding from the inside causing a blockage and the gas build up suffocated the engine. On resting, the gas seeped out and you could restart. The hole on blowing gave the exhaust another outlet.

 

So, a lack of air can also cause an engine to stop.

[sgreensides1]

Apologies - senior moment - my summary - tell me if wrong.

Fuel is cut off by the ECU because it senses a problem and the engine dies. This is also shown in the ECU not recognising some or all of the keys.  Waiting a while and the ECU now recognises the keys and turns on the fuel pump.  ECU problem could be caused by a fault connection / earth / ignition switch connection / fuse box connections.

[euroserv]

After the engine has conked out and you try to start it again (with a diagnostic device connected) you would only see a message about keys not recognised if there was a problem with recognising the keys!

The ECU cannot give this message without there being a problem with either the keys, the receiver ring behind the steering cowl or the immobiliser itself which is a part of the main ECU, or at least believing there to be a problem! A short circuit would cause this.

 

I think you have either got a problem with the receiver ring (which is at the end of a loom) or you have a wiring fault close to the ECU connector for the interior loom. (There are two connector plugs; one for the engine and one for the interior.) I would be looking into the cable bundles under the fuse box. If the cables going into and out of the blue plug are ok, there will more than likely be a couple of cables that have rubbed together and are shorting out. You will have to carefully remove the binding around the bundles until you find the problem.

[Tracker]

sgreensides1 - 2017-08-07 4:07 PMWhen the engine dies, you can still turn it over, but it will not start with all the keys or start with only one.  Waiting a while and you can start it with most or all the keys.  Since I do nothing whilst waiting, does this point to over-heating?  Continuous watching of the temperature gauge showed only normal readings.  Just cannot connect waiting (and possibly cooling down) with more of the keys being able to start the MH.  Have I missed anything?

  Steve

This is exactly how my Scenic behaved and nothing it did or I did was ever enough to form a pattern. So maybe Nicks theory about camshaft and crankshaft sensors is worth following up? I don't know how much these cost or how difficult they are to fit but along with an extra earth strap, which is inexpensive, they might, if nothing else, help to rule out what it isn't?PS In case, being a newbie, you did not know, Nick (Euroserv) runs a big fleet and has huge practical experience of Ducatos and Fiat and their vaguaries and I would value his views above any others on here.

[AliB]

Steve, I had a similar problem except that when it cut out it would not restart.

 

Read the saga here:

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Engine-Immobiliser-Locked-Out/34382/

[sgreensides1]

Progress Report: The MH will now not start under any conditions.  Just turns over.  I presume that this is a positive as now we can just look for the break / bad connection.  Easier than finding the problem that comes and goes.  Hope that this optimism does not jinx it.

 

Thank you all for your help and assistance - I hope to be able to repay the advice, although it might be better to  limit the questions to computers as the MH is new to us. 

 

Will update this with what we find as help for the next :)

[Billggski]

If the Moho is new to you, check with the previous owner/dealer.

This may be a long standing problem.

[witzend]

I had exactly the same problem wait a while it started again some time after 10 mins sometimes a hr fault codes didn't indicate it but a AA man suggested cam sensor may have intermittent fault when it gets warm coil inside expands and breaks circuit cools and makes again. I changed it and all OK since.

The wiring harness below the ECU is worth checking for signs of friction on a mounting bar mine and many others have worn thru and given a lot of different faults worth wrapping a little anyway.

[sgreensides1]

Dealership (nearest where we broke down) has informed me that after 9 hours of investigation they have traced the problem to the ECU either outputting nothing or incorrect values.  All the wiring and connections have been checked and are ok.  Could I please let them have a deposit for the special order of a new ECU?  Any advice on how to make the new ECU last longer?

[euroserv]

I am glad that they have pinned the problem down but sorry for you that it's an expensive item to replace.

 

I still find this sort of thing surprising because we have never had to replace an ECU on any of our hundreds of Ducato's but it seems clear that because our vehicles are in use every day and motorhomes tend not to be; that the problem must, however unlikely it seems, be that water is getting onto and into the ECU casings.

 

I have an electrical 'proofing' spray that i use on exposed connections and things like number plate bulb holders and i would be inclined to spray a new ECU, or for that matter ANY motorhome ECU (RIGHT NOW!). You may have to remove the plastic cover that is in place over the top of the connectors to do it thoroughly but it seems a wise precaution. I still don't see how even a constant flow of water over this cover would allow water to enter the ECU but i guess moisture gets up to all kinds of tricks if it does not get thoroughly and regularly dried out.

 

N

[Tracker]

With that sort of diagnosis I would want evidence that it is a diagnostic and not a desperation decision to blame the ECU?

Also some sort of guarantee that if it does not cure the problem a refund, or part refund, or further cost free investigation, would be forthcoming?

For all we know just taking out and removing and replacing all the connections might cure the problem and it is not an ECU fault but a wiring fault in disguise?

Cynical? Me, you bet I am!!!!