Fuel pressure drop
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Cls55
Fuel pressure drop
Fuel pressure at idle is 80, what's the normal drop off after the car's been shut off? Somebody told me after 24 hours it should be in single digits? When the car is in position 2 it jumps back up to 80, I just want to know if there is a leaky injector possibly? Right now it's been off for 3 to 4 hours and it's reading 50 to 55 PSI.
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Joined: Jul 2005
Posts: 3,174
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From: London, UK
No longer stock '06 E55, A3 3.2 Quattro, GLE 400d, R107 280SL, Golf Polo
Doing my head in tbh…
Have evap codes and think the system blocked or some other fault as fuel tank pressure is offscale / shorted … maybe been overfilling gas tank? Thats got the canister to get blocked up (I think).
blocked the evap line to the engine side purge valve to see how the idle is … its “ok” but smooth running still all over the shop.
one other curious thing is the “self adaptations” would turn on and then off intermittently - as though car cannot resolve the adaptations properly. I am pulling the evap canister tomorrow and try and see whats going in there with the other codes PO446/P0453.
maybe some more miles on car with evap not going back to engine (line) blocked at engine side should eliminate any canister / purge valve issues - lets see!
Have evap codes and think the system blocked or some other fault as fuel tank pressure is offscale / shorted … maybe been overfilling gas tank? Thats got the canister to get blocked up (I think).
blocked the evap line to the engine side purge valve to see how the idle is … its “ok” but smooth running still all over the shop.
one other curious thing is the “self adaptations” would turn on and then off intermittently - as though car cannot resolve the adaptations properly. I am pulling the evap canister tomorrow and try and see whats going in there with the other codes PO446/P0453.
maybe some more miles on car with evap not going back to engine (line) blocked at engine side should eliminate any canister / purge valve issues - lets see!
MBWorld Fanatic!
Joined: Jul 2014
Posts: 3,327
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2005 e55 AMG
I have done that,just plugged off the line going back and eliminated any possible leaks. Codes stayed off so new it was in the rear area for sure then hunted it down. If you can smoke it going back that would really help you to find a leak.
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MBWorld Fanatic!
Joined: Jul 2005
Posts: 3,174
Likes: 19
From: London, UK
No longer stock '06 E55, A3 3.2 Quattro, GLE 400d, R107 280SL, Golf Polo
As it turns out my euro spec car does not have the charcoal canister check valve - so that check needs to be disabled in ECU config same with fuel tank pressure signal - not present in euro spec cars. So eliminated two codes - yay.
Now just need to run down the smooth running code P1999 for now. Tasos recommended forcing the car to run in open loop to see if the base line running is OK. Ill take a look at cylinder bores as well and do a comp test at same time. Just cover the basics first and then will check ECU . Tune ... all thats left tbh. I need to have exhaust checked for leaks .. I have done all I can to eliminate them but think might still have some issue on the flexi's... will swap in the straight pipes and see how that looks.
Now just need to run down the smooth running code P1999 for now. Tasos recommended forcing the car to run in open loop to see if the base line running is OK. Ill take a look at cylinder bores as well and do a comp test at same time. Just cover the basics first and then will check ECU . Tune ... all thats left tbh. I need to have exhaust checked for leaks .. I have done all I can to eliminate them but think might still have some issue on the flexi's... will swap in the straight pipes and see how that looks.
Last edited by stevebez; Dec 29, 2025 at 07:54 AM.
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