Independent Renault Forums banner
1 - 20 of 36 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 ·
Hello! I have a laguna 3 2.0 DCI from 2008 that hasn't wanted to start in the cold. I press the start button and it cranks but never starts. When i plug my elecrical engine heater in for about an hour it starts again just fine. I have changed glow plugs and battery and my mechanic says the fuel system works great. He could not find anything wrong and no codes show.

Does anyone have any advice on what to check next? Glow plug relay maybe?
 

·
Super Moderator Technical Supremo Platinum Member
Joined
·
23,233 Posts
Given your location, your idea of cold is likely to be different to mine.
What temperatures are we talking about pls?
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #3 ·
Thank you for answering! Well we have had some weeks at -10 but i noticed the problem way back in december when it wasn't even below zero yet. It runs as it should once i've heated it so i have been able to live with it, but its becoming a nuciance since i somtimes need to drive somewhere unplanned.
 

·
Super Moderator Technical Supremo Platinum Member
Joined
·
23,233 Posts
Okay, nothing too drastic then on temperatures.

Given what you have said I'd be tempted to a little bit of parts darts and swap out the coolant temp sensor.
The engine uses this as part of the equation for fuel/air mix, colder temp, richer mix and easier start.
That you can pre-warm and it starts makes me wonder if it is this....cheap part and simple swap.

Ideally, I would want not just a diagnostic but a data logging scan of engine conditions, see if anything seems amiss at lower temps.
 

·
Premium Member
Grand Scenic 1.6 2007
Joined
·
6,096 Posts
Could this be fuel waxing up in the filter?
Might be worth taking a sample of fuel and seeing if it starts to go cloudy when cold?
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #6 ·
Thank you for the advice! Regarding the temp sensor, I've plugged my OBD2 reader and it said the coolant temperature was -7c (it was -3 outside at that moment) I had my heater in for two hours and it read 16c. I then went for a drive and got it to 77c after about 20 minutes of active driving. Are the numbers normal or are there any signs from these numbers that the sensor is defective?

Regarding the fuel filter, I haven't changed it during my year of ownership, but my mechanic said that the fuel system seems fine and that the filter should not be the issue. I have also had a broken and leaking return valve a couple of months earlier at a reputable mechanic. So the fuel system should be all right I think.
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,691 Posts
Its got to be compression of fuel quantity/quality related because that is all that's needed.

Since it starts when hot I would suggest looking at the injectors ............... will your scanner allow you to look at the individual injector adaptations? .......... what are those values for the individual cylinders? ............. should all be close to zero
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #8 ·
Its got to be compression of fuel quantity/quality related because that is all that's needed.

Since it starts when hot I would suggest looking at the injectors ............... will your scanner allow you to look at the individual injector adaptations? .......... what are those values for the individual cylinders? ............. should all be close to zero
Thank you for your input. I don't think it does . I have a cheap bluetooth one that i use with the app "torque".
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,691 Posts
You may be lucky and those PIDs are actually present as part of the EOBD abilities of Torque - I would check, else get a scanner or somebody to have a look-see at those numbers
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #10 ·
After checking several apps it doesn't seem like it. Seems like I might have to take it in to the local Renault dealership and let them troubleshoot the old thing. Guess I just have to accept that I don't have the tools, knowledge or time to tinker with it.

Really appreciate everyone's willingness to help though!
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #11 ·
Hello! I would like to try my luck and bump this thread again.

After taking it to the dealership and having renaults own mechanics troubleshoot it last year i got my glow plugs changed. That didn't solve the issue and so i was told it was the diesel filter that was in need of change.

At that point the weather had gotten better as spring as temperatures stopped going below zero and so it was difficult for me to know if it actually had solved the issue. Now that winter is coming iv'e alredy noticed that the cold start problem is still a thing and i am frustrated by this.

Since they charge a great deal of money just to troubleshoot the thing i hope that anyone here might be able to share their thougts of what might be the cause of the problem.

Thank you
 

·
Premium Member
Grand Scenic 1.6 2007
Joined
·
6,096 Posts
Poor cold starting can be a sign of injector leakage. It only takes one to leak to drop the rail pressure enough to prevent start. A proper scanner can read the rail pressure. If you don't have that a test is to measure the flow of fuel in the injector return lines into a set of bottles. Typical limits are about 40cc per minute at idle. A bad one is usually much more than that.
 

·
Technical Supremo.
Scenic II, 2004, K4MW761, DPO
Joined
·
6,691 Posts
Poor cold starting can be a sign of injector leakage. It only takes one to leak to drop the rail pressure enough to prevent start. A proper scanner can read the rail pressure. If you don't have that a test is to measure the flow of fuel in the injector return lines into a set of bottles. Typical limits are about 40cc per minute at idle. A bad one is usually much more than that.
Totally agree there with the reasoning, but beware:

This method of testing identifies a leaky injector to the return line - there is another injector failure mode where the injector leaks diesel directly into the cylinder through the pintle and it will not show up in this test above - if THAT is the case, symptoms are exactly the same but not detectable unless you have a scanner that monitors fuel pressure or physically have the injector on the bench to visually inspect the animal's behavior under pressure
 

·
Super Moderator Technical Supremo Platinum Member
Joined
·
23,233 Posts
I'm less certain about leaky injectors.
Not that they won't cause poor starting, they will.
But that it seems temperature dependent makes me doubt them as a cause?

I would have hoped that a dealership diagnostics would have picked up on low rail pressure?
But a little confused why they would blame filter?
 

·
Premium Member
Grand Scenic 1.6 2007
Joined
·
6,096 Posts
I'm less certain about leaky injectors.
Not that they won't cause poor starting, they will.
But that it seems temperature dependent makes me doubt them as a cause?

I would have hoped that a dealership diagnostics would have picked up on low rail pressure?
But a little confused why they would blame filter?
Was thinking the same.
You would assume that the pressure was checked.
However, many a ship has foundered on the rock of assumption :)
As for blaming the filter, it's a fairly safe shot to nothing.
I would have thought that if the filter was blocked the first sign would be under load and not at start,
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #17 ·
Thank you for your answers. Does anyone know where the coolant temperature sensor is located on the engine? Is it an easy part to reach an change? They seem to be quite inexpensive so it might be worth trying.

But should'nt a broken sensor cause problems even when it is not cold? Or can i see if it works with an obd2 scanner?
 

·
Super fantastic Mod Technical Supremo Nice Guy
Joined
·
37,575 Posts
Thought

THIS battery you had fitted, is it actually up to the job
Might seem ok , might be right size and everything
BUT

All the electrics on the car are now old and lazy
Is there a possibility you could get a friend to give you a jump start,
You know how the engine starts, just try a jump start, if it starts easier/quicker, think about getting a bigger amp battery fitted
 

·
Technical Supremo, Platinum Member
Joined
·
3,956 Posts
Battery should be man enough for the job. On this pathway though, are the connections clean and tight, including the earths and starter motor wires?
 
1 - 20 of 36 Posts
Top