I have been noticing a problem with my 2008 GL550, at times it is slow to start or "hesitates" for a few seconds, usually happens when I turn the engine off then try to restart shortly after (e.g waiting in line at the gas station, etc). it does not happen in the morning or if the car has been sitting for a while, but typically when I try to restart after a only a few minutes. what do you guys think? does it sound like a battery problem or something else?

 

You need a new battery.

 

Does it crank slow?

 

it cranks slow and takes a few seconds to start the engine. only in these situations I mentioned if I turn the engine off for less than a few minutes and try to restart.

 

If it is cranking noticeably slow, I second the battery.
Could be the charging system also, so have the running voltage checked.

 

Thanks for the info guys. how should I proceed from here? the car is out of warranty so I was thinking of taking it to my local MB mechanic. but should I get it checked out at one of the auto parts stores first (autozone, etc) or even just go ahead and change the battery myself?

 

In fact, most auto parts shops install batteries in most cars. Get Optima
they take deep discharges better than flooded lead-acid or run-of-the-mill AGM
batteries. Watch out for overpricing, as Optimas sold retail are well marked up.

 

Any good brand of AGM is fine.
Optima are good batteries, but your old AGM lived 5+ years, so I don't know how much it is worth going "better".

I would probably strat with a cheap and easy voltage check before removing the old battery.
Find out what the voltage is cold, running and hot/not running.
If the voltage is so/so when off cold, good when running but sags when of hot, you need a new battery.
If it is low when running you need to have the charging system looked at.

 

Thanks for the info. I appreciate it guys!

 

it's not the battery, it;s a wiring harness to the starter

 

Based on?

 

i replaced my battery... did not solve the problem. i then had the wiring harness replaced - that fixed the slow crank. MBZ has a new and improved wiring harness (an improvement on what came with your car). I also has my fuel pump replaced to solve the long crank problem (my old fuel pump was starving fuel at the initial start).

All done at South Bay Mercedes Benz in Torrance, CA. They ripped em off for sure, but it works like new.

 

total cost was approx $2,500. get the wiring harness done by the dealer as many independent MBZ mechanics don't have the equipment to work on this part near the ignition. Save money on the fuel pump by having an independent MBZ mechanic do it, one that you trust

 

other problems I had repaired: O2 sensors, power steering reservoir replaced (leaked), power steering gear head replaced. This is may last major repair that I will pay for..... I am dumping the car when the next big repair comes up. car only has 45k miles - it's my wife's and she barely drives

 

i'll post the part #s when i locate my repair order

 

This makes me a little concerned. The Battery, Starter, alternator wiring harness is nothing but a few pieces of heavy wire.


I think your dealer is selling you a bill of goods.

 

I've had this issue as well. 2 years ago my wife was having starting problems, usually at the worst time - at the store. Jump start would solve the problem. So it was a no-brainer that I needed a new battery. Right?

Replacing the battery with a brand new over-priced dealer equipped battery did in fact solve the problem of dead-battery. It did NOT solve the problem of hard cranking on a warm/hot engine. My guess is the original battery was okay, albeit a bit weak, but was getting excessive drained due to the hard turnovers.

A few months back, I took it to a new dealer who immediately advised the problem would be solved with a new battery. BS. After explaining the details (which they later pieced together after going through prior dealer notes) - they agreed it wasn't the battery. Left it an extra few days so they could "test ideas" on it. They changed the wiring harness as a "try", to no use.

There's enough incidence of this happening that surely MB knows about but is not passing the info down to dealers. I've heard two items which, due to heat expansion, could be the culprit:

- Vapor Lock (Cranking Exertion): Increasing kinetic energy required to crank engine during starting - more energy than cold cranking. Don't recall where this cause was though to be, perhaps in exhaust outlet ports?
- Vapor Lock (Fuel Deprivation): Fuel Pump related issue
- Camshaft Timing Sensor

Thoughts?

@hbush You changed so many things, not sure how you conclusively know it's the harness and not the fuel pump for example. Unless you are saying you changed only harness and it was fixed, then subsequently changed other components for other reasons.

 

It can be so many things.


A hot engine can be a little harder to turn because compression is closer to optimum than when cold.
(Of course it can be easier to turn do to being fleshly lubed (including cylinder walls))
A "hot" battery can be weaker than after it sits and cools, so a slightly overcharging electrical system can contribute to slow crank when hot.
A hot starter can be weaker then when cold.
I don't know if the cam timing shifts enough for a bad sensor to change compression enough to slow cranking? (anyone??)
"Vapor Lock" is a fuel supply problem and may prevent starting but typically does not affect cranking.


Put a good meeting on the car and get the voltage when cold, when running hot, when off hot, when cranking cold and when cranking hot.


Then maybe we can start chasing gremlins.

 

Doh on my overloading the term "vapor lock" to also speak to "hot engine" compression related concept. Any event, glad you clued in on my intended meaning.

As for voltage metering, I can hook up and log a continue session tracking voltage and/or current. I assume you are thinking to run test off jumper connect points under hood. Or do you have a better test point in mind?

 

I guess I would use the terminal under the hood as mid point between battery, starting and charging system.

 

MBZ part # 154-440-07-36 "A Cable Harness" car now cranks right up at the push of the button. It is the starter harness from starter to positive battery jump post.... the defective part had a fault causing the delayed, slow crank, $700 for part and repair at MBZ dealer

 

I don't know what all the parts were, but the four main cables should only add up to a (ridiculous) $450 or so.


Wires rarely go bad. Most likely there was a loose connection that got fixed, or at the outside a bad connector that could have been replaced leaving the cable in place.


You also seem to be assuming all similar symptoms have the same underlying problem. (Not a good assumption with something like a slow crank)

 

Oldish thread, but it was recently helpful for me even though some of the other guys in here talking about how it couldnt be a cable ripped on guys suggesting it based on actual experience & correction of the issue.

The most helpful post was the one with the actual part number, but I was given a different part #:

Part #164-440-07-36 "Cable Harness" @ $96.25 was diagnosed for me as well for this same issue. I was told this is now considered a very well known issue & that the cause is in that 2 Amps were being fed through this cable & starving the starter. Additionally, I was quoted $490 for labor all in all it will cost $674.18 for the work, but the good news is that it's covered under an extended warranty with a $50 deductible. (on a 2008 GL550).

 

Hi guys, thanks a lot! I have the exact same problem and decided to bite the bullet and buy this part online and then have someone install it.
BUT, apparently the code 154-440-07-36 doesn't exist and 164-440-07-36 belongs to an ML550.
I am pretty sure that works but just wanted to double check, does this ML part require any modifications or additional components to fit GL550 or are they 100% same?

Question number 2:
Its obviously not a DIY project but half grand sounds soo much for a cabling job, how hard is it really?

 

And while checking online, I came across these two (one for high capacity battery, the other one is for normal battery I guess):
https://mercedes-parts.benzelbusch.c...bC12OC1nYXM%3D

https://mercedes-parts.benzelbusch.c...bC12OC1nYXM%3D

So I'm not sure which one I need, alternator to starter cable harness OR battery to prefuse box cable harness. On GL catalogues online, none of them list the code you told me you have used to fix this problem so I wanted to make sure.