GL350 2010 Cold Start Problems - Mercedes-Benz Forum
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post #1 of 1 (permalink) Old 11-03-2018, 12:58 PM Thread Starter
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Date registered: Nov 2018
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Exclamation GL350 2010 Cold Start Problems


I've been having a problem with my 2010 GL350 Bluetec engine. When it gets a bit cold the engine will go entire start cycle with no start, sometimes it takes 3 cycle sometimes it takes 10. As soon as the engine started once, then I have absolutely no problem, no smoke, no nothing. The performance is good, fuel economy also. I've been back and forth from Canada to Mexico (10,000 KM) in a month in the summer absolutely no problems. It never had any start problem as long as the temperature are above 10c (or 52F).

Finally it has no error code, no ECU failure or any kind. (Check with a MB Diagnostic tool)

First check, I checked the glow plug resistance all 6 of them show an healty 0.5 ohms.
Just for the try I did order a Glow plug controller to make sure it wasn't the error.

But then it still the same problem, I started to suspect 2 things either air in the fuel line or pressure in the rail to low.

I hooked up the reader, and while cranking I took the pressure reading from the Fuel Rail.
When it wasn't starting I was having about 100BAR, or 10,000PKA, or 1450PSI.

Continuing on... Found on the forums that the pressure at crank should be around 200 bar (I AM FAR under) and running about 300BAR (4400PSI)..
So here are my result:
Crank : 1450PSI - NO START
Crank : 1800PSI - Start
Idle: 4300 PSI
4000RPM: 13,000PSI.

So I think the pump is working good as soon as its getting enough RPM.

I found that 5 things could be causing low High Pressure
1 - Low Pressure Flow to the pump (Works fine all summer, no problem ever, no performance) don't think that could be fuel starvation
2 - Quantity control Valve, Typically OPEN on start. Could be but I can't think why only the first start of the day and only on cold days...
3 - Pressure Regulator (On the fuel rail) typically closed to hold pressure on start. Again start fine always just not the first time of the day.
4 - Leaking Injector, found that this would cause also bad start on hot engine since gas is thinner.
5 - High Pressure Pump Worn out or seal.

I found no apparent leaking of fuel anywhere not near the pump or near any injectors.

I'm still not absolutely sure. But it's difficult to have the right information about each vehicule even on the internet.
What should be the cranking pressure on the 2010GL350. I've read it should be around 2900PSI (I am well under that even when starting I am still at 1800PSI!)

The car has always started in a few more seconds that I would normaly expect but I bought it this way so there is no compare before and after!

This morning I tested the car (5C) outside temp:
Cranking Second 1 : 1500PSI - No Start
Cranking Second 2 : 1500PSI - No Start
Cranking Second 3 : 1500PSI - No Start
Cranking Second 4 : 1600PSI - No Start
Cranking Second 5 : 1800PSI - Started
Idle Second 6: 4300PSI - Running Idle.

Now could a worn up fuel pump give these symptoms? I've also read somewhere that some bolt might be comming loose on the other side of the fuel pump that could potentially get micro seal failure.

I also measured the day before, it took 10 start cycle, all of them steady on the fuel pressure at 1500PSI
1 Start 1500PSI all the way
2 Start 1500PSI all the way
3 Start 1500PSI all the way
9 Start 1500PSI all the way

Then just for the heck I took out and hair dryer out, blow directly at the fuel pump for like 60 second
10 Start, 1500... ish,... got to 1600-1700-1750, started 1 turn and stopped
Heat for another 60 second the HP pump
11 Start 1850PSI started after 3 second no fumes no nothing car runs fine.

The high pressure diesel fuel contains so many variable.

What do you think? Is there a fuel pump seal kit that exist so we can just take it off and change all seals and try it on?
Replace the complete pump? (that is still on the costly side!!!)
Also another little detail, even on warm days it never fails to start but it always take a few turns like 3-4 before engine start, and even on warm days I don't see the pressure going higher than 1850-1900 psi on cranking.

Any suggestion ideas would be appreciated!

Nface21 is offline  
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