Dear all,

I have a 2007 GL450 x164 USA version, drive everyday withut problem, but after sat unused for about 1 month, it cranks but the engine doesn't start. Many times, charged up battery to 13.3 volts or jump start still the same. Scan but cannot find any error codes at all.

But when first found out sat unused and battery drained, I charged the battery with the battery charger without disconnected the Battery Negative Pole, therefore the battery charger was connected to the whole car circuits also, and the battery charger was once slowlly raised up to 14.6 volts, when batter was fully charged. I don't know if that 14.6volts damage any of car electronics at all? but no error codes scanned.

- during cranking, the RPM meter on the cluster display stay at zero, the engine scan tools shows speed 0 also.
- scan tool show there is no fuel pump control module FSCU installed, as I don't know if there was one in this car.

kindly regards
Adam


KeyFlog at Positioni 0:



KeyFlog at Positioni 1: battery voltage:12.5v



KeyFlog at Positioni 2:


KeyFlog touched Positioni 3: it start cranks, but engine does start. Battery Drop to 10.8v during cranking.

 

When you have an issue that might be electrical, the first step is always to diagnose the electrical system.

There are many hidden safeguards in place in the overall system. One is that the injectors (and maybe also the spark, idk) do not pulse unless the cranking speed is above a certain threshold. Thus you can have an engine that cranks but does not fire. At least, I have deduced this from the "no hot start" problem that arises when the starter begins to fail; starter performance is reduced when warm, so it falls below threshold and the motor won't start.

Place the battery on a trickle charger and come back in a day. Ideally use a AGM-compliant battery conditioner. Then check the battery's health with a load tester, not a volt meter.

Whenever you store the vehicle, place a trickle charger on the battery. If I think I will not be driving in the next day or so, this is what I do. The battery's life is measured in terms of electrons in and out, with a multiplier for depth of discharge. There is not insignificant standby drain on this vehicle. You would be wise to offset it. Or disconnect the battery, but that is a pain.

Your battery is probably at end of life, and it may have taken the alternator down with it. After establishing a good battery, check the charging performance of the alternator.

 

Sounds like the battery died. Install a new one.

 

the H8 battery at Sam's Club or Costco cost ~$200. and installation is not hard, just follow youtube videos.

 

here are the eletrical system scan readings:

 

Again, you need to do a load test on the battery after charging it.

 

Thoroughly check that your battery is OK. It sounds like it’s toast.
when you have that, then do a load test on the alternator. I’m not sure your scan tool will do that, but a Mercedes DAS clone will and is important so you don’t fry your new battery as well.

 

I just used that test the other day. Keeping the rpm in the correct band for over a minute isn't easy especially when you have to look down to turn on the rear window defogger mid-way. Took me a couple of attempts. Mine failed once I completed the test successfully. It was a Auto Zone rebuild so it is going back for a free replacement.

I also tried the compression test, but it didn't seem to work. Held the brake down and cranked, but it never starts registering anything.

 

I think you are supposed to hold the throttle down, not the brake. Since it is an electronic throttle, I do not understand why the test cannot do it on its own. Maybe it is a safety feature: The only thing that can instruct the throttle to open is the pedal being depressed.

It only measures relative compression, by the way, not absolute. For that you have to put at pressure gauge on each cylinder.

I found it useful in diagnosing which cylinder had a sticking valve when cold. Not that I made use of that info, as a few tanks of Regane Complete, and strict adherence to fresh gas, seems to have fixed it.

 

I'll try it again, but IIRC you're supposed to crank with the brake and gas depressed. I double checked the instructions when I tried it for the second time and it was still no go. I just did it out of curiosity when I saw it on the list after doing the alternator test. I have a real compression gauge but don't have reason to believe there I have any compression issues so I haven't broken that out.

I fixed a low compression problem on one cylinder years ago on a Mazda with BG 44K inhaled directly into a vacuum line followed by a quick shutoff to let it sit and do its thing for awhile. I attributed it to a ring that wasn't doing its job because of carbon buildup, but who knows. Compression went up 30-40 psi after the treatment, which resulted in a large black cloud behind the car for about 30 seconds after startup.

 

there’s a couple of prerequisites, mainly engine temperature that need to be met before you can run it. One of the telltale signs that your starter is going bad is that it will not run the compression test because it is too weak.

 

I ran it on a cold motor because I wanted to find out which valves were sticky with varnish.

Definitely if you want warm-engine results, you need to have a warm engine.

Good point.

 

OP says engine cranks over without starting even with a jumpstart. Also, battery voltage drops from 12.4V to 10.7V which seems normal so I doubt this problem is caused by a bad battery. It sounds more like fuel delivery issue based on the "scan tool show there is no fuel pump control module FSCU installed." A varmint chewed some wires while it was parked for extended period of time??

It's also possible that the immobilizer is engaged if the battery completed died for a long time and the key code is out of sync with EIS. I haven't seen this problem on a MB before but it's quite common on it's German cousin from Bavaria. Try a spare key if you have one.

 

Those are good points and good suggestions.

However, I do not think the voltage being at 12.4 no load, dropping to 10.7 while cranking is exactly normal. No-load voltage is no indicator of battery health, but voltage under load is. These vehicles have standby drain and lead-acid batteries do not like being depleted.

How it behaves with a "jump start" is also no sure indicator. The jump start could be from a good battery, or it could be a lame jump start battery pack which is already depleted by being connected to a dead battery.

The core point is that one must establish a baseline of electrical system health before additional, more complicated, steps are taken.

 

Actually a 2-3V drop during cranking is very normal so 10.7 V cranking voltage is perfectly fine. A good battery has about 0.25 Ohm internal resistance so a 100 Amp cranking current will easily drop 2V. I’d even venture to say nothing wrong with the battery if it only drops to 10.7 V although I’ve learned to never say never.

A weak battery has very clear telltale signs that the OP doesn’t describe: clicks or very slow and labored turnover. If it’s boosted and it cranks, it should start unless there is a problem other than battery startup voltage

My bet is still on fuel delivery problem. Spray some starting fluid to see if it starts up

 

0.25 ohm x 100A = 25V

But your point is well taken. I do not know what the internal resistance of a battery ought to be (actually around 0.02 ohm, as I found out); I do not know whether 10.7 V cranking is low, and most of all I do not know the condition of OP's battery. It still comes back to - he should gently charge the battery and have its condition tested before doing anything else. The fuel system on these vehicles is pretty robust, much more so than the electrical system, so one eliminates the most likely causes first.

And if it turns out to be fuel, I will buy you a Coke.

 

Hahaha… Back in my undergrad EE days my circuit analysis professor wasn’t quite lenient either with such slips; a 25V drop across a 12V battery will defy physics.

I hope it’s obvious that I meant to type 0.025 Ohm which equals 2.5V IR drop and hence why 10.7V cranking voltage is quite good. Anything under 30 milliohm internal resistance for lead acid battery is fine.

Regarding fuel system robustness, the ‘mileage may vary.’ For instance, my 13-year old original GL450 battery is still going strong to my astonishment. Given the age, it was the first thing I wanted to get rid of when I bought my GL used but it load tested OK so I’m waiting for it to actually die.

BTW: I’m a strong believer in Occam’s razor and it seems like you are too; it’s just that in this case I believe OP has disproven the simpler hypothesis already based on his battery voltage observations. I’ll be very interested in the final resolution myself even if it turns out to be battery problem.