Long crank/hanging idle on cold start
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Member
Joined: Oct 2017
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2014 E550
Long crank/hanging idle on cold start
I've got a couple starting issues on my 08 E550. I'm not sure if they are related, as sometimes I will get one, sometimes I'll get the other, and sometimes I'll get both.
First issue is extended cranking. Normally when I start it, it will crank and start in under a second. But occasionally (one in 10 cold starts) it will crank for 3-5 seconds before it starts.
Second issue is a high/hanging idle on cold start. Normally on a cold start it'll sit at 1500 for a couple seconds before slowly coming down. But now(most cold starts) it will start, hit 1500 for a moment, then go up to 1800-2000 and hang there for longer than normal, before coming down.
Car is at 120k. I did spark plugs and replaced a damaged coil at 110k, as well as the air filter. Don't have any pending or stored codes. I do have an OETuning tune on it, but I tried swapping back to the stock tune and it the issues have persisted. I did a visual inspection and I don't see anything obviously loose/disconnected/leaking. Any thoughts on where to start would be appreciated.
First issue is extended cranking. Normally when I start it, it will crank and start in under a second. But occasionally (one in 10 cold starts) it will crank for 3-5 seconds before it starts.
Second issue is a high/hanging idle on cold start. Normally on a cold start it'll sit at 1500 for a couple seconds before slowly coming down. But now(most cold starts) it will start, hit 1500 for a moment, then go up to 1800-2000 and hang there for longer than normal, before coming down.
Car is at 120k. I did spark plugs and replaced a damaged coil at 110k, as well as the air filter. Don't have any pending or stored codes. I do have an OETuning tune on it, but I tried swapping back to the stock tune and it the issues have persisted. I did a visual inspection and I don't see anything obviously loose/disconnected/leaking. Any thoughts on where to start would be appreciated.
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From: MA
2008 E350 4Matic, 2011 E350 4matic
It could be either the Crankshaft position sensor or a weak battery. You could have the battery load tested and also check the voltage on the display. Switch to the temperature display and hit the reset button three times with the car on, but without the engine running.
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From: Seattle
2006 CLS55 AMG
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W211
I've got a couple starting issues on my 08 E550. I'm not sure if they are related, as sometimes I will get one, sometimes I'll get the other, and sometimes I'll get both.
First issue is extended cranking. Normally when I start it, it will crank and start in under a second. But occasionally (one in 10 cold starts) it will crank for 3-5 seconds before it starts.
Second issue is a high/hanging idle on cold start. Normally on a cold start it'll sit at 1500 for a couple seconds before slowly coming down. But now(most cold starts) it will start, hit 1500 for a moment, then go up to 1800-2000 and hang there for longer than normal, before coming down.
Car is at 120k. I did spark plugs and replaced a damaged coil at 110k, as well as the air filter. Don't have any pending or stored codes. I do have an OETuning tune on it, but I tried swapping back to the stock tune and it the issues have persisted. I did a visual inspection and I don't see anything obviously loose/disconnected/leaking. Any thoughts on where to start would be appreciated.
First issue is extended cranking. Normally when I start it, it will crank and start in under a second. But occasionally (one in 10 cold starts) it will crank for 3-5 seconds before it starts.
Second issue is a high/hanging idle on cold start. Normally on a cold start it'll sit at 1500 for a couple seconds before slowly coming down. But now(most cold starts) it will start, hit 1500 for a moment, then go up to 1800-2000 and hang there for longer than normal, before coming down.
Car is at 120k. I did spark plugs and replaced a damaged coil at 110k, as well as the air filter. Don't have any pending or stored codes. I do have an OETuning tune on it, but I tried swapping back to the stock tune and it the issues have persisted. I did a visual inspection and I don't see anything obviously loose/disconnected/leaking. Any thoughts on where to start would be appreciated.
i have an 08 w211 I have extended crank majority of the time, but a few times it does start right away no issues. No codes are present, and car runs great, I have replaced, fuel pump, fuel sending unit, cam shaft sensors, crankshaft sensor, purge valve, Canister vent valve, spark plugs and all 6 coil packs.
And MAF sensor. Still have yet to solve issue. My battery is good about a year old and the CCA on the battery is good. I’m starting to lean towards my starter going bad, or camshaft magnets.
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Member
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From: Seattle
2006 CLS55 AMG
i have an 08 w211 I have extended crank majority of the time, but a few times it does start right away no issues. No codes are present, and car runs great, I have replaced, fuel pump, fuel sending unit, cam shaft sensors, crankshaft sensor, purge valve, Canister vent valve, spark plugs and all 6 coil packs.
And MAF sensor. Still have yet to solve issue. My battery is good about a year old and the CCA on the battery is good. I’m starting to lean towards my starter going bad, or camshaft magnets.
And MAF sensor. Still have yet to solve issue. My battery is good about a year old and the CCA on the battery is good. I’m starting to lean towards my starter going bad, or camshaft magnets.
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W211
Could be cam magnets but it’s probably the starter. When the starter on my E550 went out, I had symptoms for months and at least 10k miles prior, by extended cranking. Most of the time it would fire right up but right before the starter died it would take like 3 or 4 seconds to fire up, up until the starter finally went out.
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2006 e350 wagon 4matic
honestly I’m leaning more towards the Starter cause my car runs fine no issue, now I am planning on ordering the cheapest one available from rock auto cause I’ve already spent a lot of money trying to figure it out buying all OEM parts. I’m at 105k miles I’ve put 7k since the starter started acting up. I’ll post my results after I replace it. Thank you.
Any update on this? I'm precisely in same boat. I replaced same parts + the intake manifold and injector bottom seals/ O rings to address p0171 and P0174 lean codes.
Last edited by Nicu268; Aug 30, 2025 at 11:14 AM.
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
LONG ENGINE CRANK
READ YOUR RAIL PRESSURE!
Good chance your fuel filter is plugged up: slow pressure build up.
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2006 e350 wagon 4matic
Out Of Control!!
Joined: Apr 2019
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Likes: 6,775
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
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Joined: May 2025
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2006 e350 wagon 4matic
Newbie
Joined: May 2025
Posts: 10
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2006 e350 wagon 4matic
I’m dealing with a persistent low fuel pressure issue on my 2006 E350 4Matic Wagon. I connected a fuel pressure gauge to the rail and observed only 30 PSI while running, which is well below spec. When I shut the engine off, the pressure drops to 0 immediately. Cycling the ignition (key to position 2) builds pressure momentarily, but it drops quickly. While cranking, pressure slowly climbs, and the engine starts once it hits about 30 PSI (after ~3 seconds of cranking).
A few months ago, I replaced both the fuel pump and sending unit with an aftermarket kit from FCP Euro due to a fuel leak. The car ran fine for about 5,000 miles. Since then, I’ve been getting lean codes P0171 and P0174 (both banks) along with poor fuel economy (16–17 MPG) and occasional sluggish performance. I swapped the pump back to the original unit, but the low pressure remains.
I’m planning to reinstall the original sending unit next, in case the aftermarket one is affecting fuel transfer from the saddle tank. The car did die on the highway recently with 1/4 tank showing. A shop added fuel and it restarted; they said the right side (pump side) of the tank was empty, suggesting the siphon jet (in the left-side sending unit) may not be working.
I've also replaced:
- PCV system components
- MAF and related gaskets
- Y58/4 charcoal canister shutoff valve (after getting P2422 shortly after the sending unit install. Replacing the Y58/4 sensor did not fix the issue. I believe the sending unit somehow is casusing this fault.)
My main questions:
- Does the sending unit have a fuel pressure regulator built in?
- Is it possible the fuel rail is contributing to the problem?
- Any ideas before I keep swapping parts?
Last edited by Nicu268; Sep 5, 2025 at 08:17 PM.
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Great: this is all consistent with fuel supply issues.
You're attempted repair has not solved low rail pressure.
Your pressure regulator is likely located in the tank near filter.
You're attempted repair has not solved low rail pressure.
Your pressure regulator is likely located in the tank near filter.
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2006 e350 wagon 4matic
Hope this can help someone else with P0171 and P0174 codes and engine long cranks.
Out Of Control!!
Joined: Apr 2019
Posts: 11,922
Likes: 6,775
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
WELL DONE RIGHT
It WAS FUEL SENDER that caused the low pressure !!. I can't believe the unit died with less then 5k miles on it..... The Old unit i reinstalled puts pressure at 60 psi and stays there after the engine is shut off.
Hope this can help someone else with P0171 and P0174 codes and engine long cranks.
Hope this can help someone else with P0171 and P0174 codes and engine long cranks.
-- Originally your pump was the bad part +
-- In addition the failed FCP filter/sender/regularor afterwards.
You're a hero to have sorted through all this successfully. The simple fixes are often hard to come by: CONGRATS.
Whats the mfg. name of that junk part supplier?
Last edited by CaliBenzDriver; Sep 6, 2025 at 03:35 PM.
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Joined: May 2025
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2006 e350 wagon 4matic
Do I understand correctly your new FCP-Euro part was junk that lasted only 5k.Mi.
-- Originally your pump was the bad part +
-- In addition the failed FCP filter/sender/regularor afterwards.
You're a hero to have sorted through all this successfully. The simple fixes are often hard to come by: CONGRATS.
Whats the mfg. name of that junk part supplier?
-- Originally your pump was the bad part +
-- In addition the failed FCP filter/sender/regularor afterwards.
You're a hero to have sorted through all this successfully. The simple fixes are often hard to come by: CONGRATS.
Whats the mfg. name of that junk part supplier?
Original Mercedes sending unit was brittle and leaking but still worked. I replaced it with a Pierburg unit (FCP Euro part PIE-703794390), which failed after only ~5,000 miles. That part isn’t listed on FCP Euro anymore—wonder why???Is it quality issues???
I just ordered a genuine Mercedes sending unit for $440 from FCP Euro and will submit a warranty return on the failed part to get back what I originally paid. That refund will go toward the OEM replacement. I don’t blame FCP Euro—I’ve used them for years with good results.
In hindsight, I should’ve run a fuel pressure test before throwing parts at the car. But I was confident the fuel related partes were new and in good working order
P. S. Every single blog and YouTube video points to a fuel pump replacement when the fuel pressure is low. I haven't seen one to sugest the sending unit might be faulty. Hope this write-up will help somebody in the future.
Last edited by Nicu268; Sep 7, 2025 at 08:36 AM.
