C43 fuel pressure dropping low over a few hours
02-26-2017, 12:07 AM
#1
Senior Member
Thread Starter
C43 fuel pressure dropping low over a few hours
Hi all,
Got an issue ive been chasing for months on this car, never been able to find it.
The first start after sitting for a few hours will be a bit rough for a couple seconds, if you hold throttle open a bit when starting it makes this issue worse, so it is light on for fuel. The pressure is dropping over time.
After the engine starts, it will run rough for 1-3 seconds, then is perfect.
The injectors were removed and cleaned, but 5 failed the leak test, so i replaced all 8.
The fuel pump has been replaced with a genuine Pierberg.
The filter has been replaced twice, once with a Hengst, once with a Mann.
Turning key on you hear pump run for about 1 second. Id expect it should run longer than that, but anyway, its not long enough to get enough fuel up there for cold start.
If i start the engine, then shut it off after 3-4 seconds, then restart, it starts perfect. It always runs perfect too, never an issue. Its just that first start after a few hours sitting.
Im not sure where it would be losing pressure. Is there a non-return valve in the fuel line somewhere that could be allowing pressure to drop?
Cheers all
Got an issue ive been chasing for months on this car, never been able to find it.
The first start after sitting for a few hours will be a bit rough for a couple seconds, if you hold throttle open a bit when starting it makes this issue worse, so it is light on for fuel. The pressure is dropping over time.
After the engine starts, it will run rough for 1-3 seconds, then is perfect.
The injectors were removed and cleaned, but 5 failed the leak test, so i replaced all 8.
The fuel pump has been replaced with a genuine Pierberg.
The filter has been replaced twice, once with a Hengst, once with a Mann.
Turning key on you hear pump run for about 1 second. Id expect it should run longer than that, but anyway, its not long enough to get enough fuel up there for cold start.
If i start the engine, then shut it off after 3-4 seconds, then restart, it starts perfect. It always runs perfect too, never an issue. Its just that first start after a few hours sitting.
Im not sure where it would be losing pressure. Is there a non-return valve in the fuel line somewhere that could be allowing pressure to drop?
Cheers all
02-27-2017, 03:26 PM
#4
Out Of Control!!
Regrettably with your 113.944 mixture and fuel documentation suggest the use of Star to diagnose actual values with design to determine cause, therefore I can't add any more speculation to confuse you further.
02-27-2017, 05:50 PM
#5
Senior Member
Thread Starter
Youre unlikely to confuse me with anything you tell me, but thanks all tge same 
Its not a mixture issue, its a leakdown issue. No pressure in rails.
Its not a mixture issue, its a leakdown issue. No pressure in rails.
02-28-2017, 06:13 AM
#6
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12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG sold)
Have you tried connecting a pressure gauge in the fuel rail to monitor real data? I believe there is a port for this somewhere...
02-28-2017, 06:17 AM
#7
Senior Member
Thread Starter
If i press the valve within a couple minutes of shut off, plenty of pressure there, but after about 2 hrs, just a trickle.
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03-01-2017, 02:12 AM
#8
Senior Member
Thread Starter
Well i can add a bit to this, took it into a mate's workshop and threw his fuel gauge on it, started up for 10 seconds then left it sit for 30 minutes.
Fuel pressure stayed around 55psi even 30 minutes after shut down.
The shrader valve was not real tight, so that could be where the fuel pressure is leaking down.
Fuel pressure stayed around 55psi even 30 minutes after shut down.
The shrader valve was not real tight, so that could be where the fuel pressure is leaking down.
03-01-2017, 04:37 AM
#9
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12' W204 C63 AMG coupe "T-Rex", 12' W451 Smart Fortwo Pulse (99' W202 C43 AMG sold)
Well i can add a bit to this, took it into a mate's workshop and threw his fuel gauge on it, started up for 10 seconds then left it sit for 30 minutes.
Fuel pressure stayed around 55psi even 30 minutes after shut down.
The shrader valve was not real tight, so that could be where the fuel pressure is leaking down.
Fuel pressure stayed around 55psi even 30 minutes after shut down.
The shrader valve was not real tight, so that could be where the fuel pressure is leaking down.
Keep us posted please.
03-02-2017, 04:27 AM
#11
Senior Member
Thread Starter
Well im wondering if it was my EIS failing all along...
Im 850klms from home, none of my 3 keys work. Nothing. Dead. Battery fine, seats work.
Stopped to fuel up, wouldnt start after, and still does nothing 4 hours later.
Im 850klms from home, none of my 3 keys work. Nothing. Dead. Battery fine, seats work.
Stopped to fuel up, wouldnt start after, and still does nothing 4 hours later.
