Hot engine hard start, stumped
#1
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Thread Starter
Hot engine hard start, stumped
Hey everyone! I have a CL63 2008 AMG 180k miles. I have a hot engine hard start problem I am looking for help. I have tried to give all the information I can so you can throughly understand my cars situation. I hope I didn't write too much lol
Every morning she starts great, cold or hot weather no hesitation everything is fine. I drive around doing errands.. turn off my car, go into the store for at least 30 mins sometimes it takes an hour or more.. come back and she is hesitant to start. It makes a sound like the engine is trying to catch but its missing something... it chokes a couple times then turns on fine, drives fine.
If I went into the same store.. turned off the car, went inside came back in 30 mins sometimes an hour or less, she would start great no problems.
Things I have noticed or taken note of:
Once started she has no problems doing 100+ mph
Weather does not seem to be an issue, long as the engine reaches operating temperature and take into account what I previously wrote at the top.
Navigation screen restarts, its only happened twice.. once was over 8 months ago and just the other day.. it happened after about 20 mins of driving.
Fuel pump clicks and I can hear it whirring when I turn ignition
I do get a light puff of white smoke from the tailpipes once in a while but not every time and ONLY when she is hesitant to start
Fuel pressure drops after shut off, I am not sure if this is normal.. The range drops from 96 PSI at shut off to 59 PSI after 15 mins to 46 PSI after 1 hour
Self adaptation in idle speed range, RIGHT bank is always double or a little more than the LEFT bank no matter when I check it.. cold, hot, after a short run or a long one.
My pre-cat/upstream o2 sensors voltage constantly runs +/- .05 of 1.46 v, but my post-cat sensors run in good range at their respectful positions.... when the car is cold and off they always show -1 v while the post-cat shows 0v
Everything under the hood looks connected and no visual damage to wiring, etc.
Fuel pressure on a cold start.. turn ignition without starting reading shows 90 psi, turn the engine over it shows 66 psi idling.
While driving on freeway no traffic giving her a steady light push she reaches 69-71.
Fuel pressure signal seems to be working within range.
Fuel pressure correction factor PWM signal is consistently within +/- .05 of -2.26%, not sure if this means anything?
I have replaced in the past year :
Both batteries starter front is Mercedes, main rear is Bosch
Alternator
Starter & Starter Relays
CPS (crank position sensor)
Idler Pulley
PCV
Fuel Pump
Fuel Filter ..(& Regulator, I believe it is attached to filter unit from what I have read or ?) Someone please clarify this for me, this could be my problem but I can't not seem to find the information anywhere
Fuel Rail Sensor
4 Camshaft Position Sensors
Intake Air Temperature Sensor
PreFuse Box as the live data showed the car had an electrical fault (f/32 prefuse box was faulty) however no CEL or code was ever thrown. I believe this failed from clicking the car over too many times trying to start?
Oil dipstick
Regular maintenance.. oil, oil filter, air filter, ignition coils, belts, brakes
Spark plugs were ultra sonic cleaned and tested before reinstallation
Any thoughts on what the problem could be, would be greatly appreciated. Sorry if this is a long post, this is my first time. Thanks in advance
EDIT: I have added a video to show the hard start.. this was after checking the fuel pressure drop.
Every morning she starts great, cold or hot weather no hesitation everything is fine. I drive around doing errands.. turn off my car, go into the store for at least 30 mins sometimes it takes an hour or more.. come back and she is hesitant to start. It makes a sound like the engine is trying to catch but its missing something... it chokes a couple times then turns on fine, drives fine.
If I went into the same store.. turned off the car, went inside came back in 30 mins sometimes an hour or less, she would start great no problems.
Things I have noticed or taken note of:
Once started she has no problems doing 100+ mph
Weather does not seem to be an issue, long as the engine reaches operating temperature and take into account what I previously wrote at the top.
Navigation screen restarts, its only happened twice.. once was over 8 months ago and just the other day.. it happened after about 20 mins of driving.
Fuel pump clicks and I can hear it whirring when I turn ignition
I do get a light puff of white smoke from the tailpipes once in a while but not every time and ONLY when she is hesitant to start
Fuel pressure drops after shut off, I am not sure if this is normal.. The range drops from 96 PSI at shut off to 59 PSI after 15 mins to 46 PSI after 1 hour
Self adaptation in idle speed range, RIGHT bank is always double or a little more than the LEFT bank no matter when I check it.. cold, hot, after a short run or a long one.
My pre-cat/upstream o2 sensors voltage constantly runs +/- .05 of 1.46 v, but my post-cat sensors run in good range at their respectful positions.... when the car is cold and off they always show -1 v while the post-cat shows 0v
Everything under the hood looks connected and no visual damage to wiring, etc.
Fuel pressure on a cold start.. turn ignition without starting reading shows 90 psi, turn the engine over it shows 66 psi idling.
While driving on freeway no traffic giving her a steady light push she reaches 69-71.
Fuel pressure signal seems to be working within range.
Fuel pressure correction factor PWM signal is consistently within +/- .05 of -2.26%, not sure if this means anything?
I have replaced in the past year :
Both batteries starter front is Mercedes, main rear is Bosch
Alternator
Starter & Starter Relays
CPS (crank position sensor)
Idler Pulley
PCV
Fuel Pump
Fuel Filter ..(& Regulator, I believe it is attached to filter unit from what I have read or ?) Someone please clarify this for me, this could be my problem but I can't not seem to find the information anywhere
Fuel Rail Sensor
4 Camshaft Position Sensors
Intake Air Temperature Sensor
PreFuse Box as the live data showed the car had an electrical fault (f/32 prefuse box was faulty) however no CEL or code was ever thrown. I believe this failed from clicking the car over too many times trying to start?
Oil dipstick
Regular maintenance.. oil, oil filter, air filter, ignition coils, belts, brakes
Spark plugs were ultra sonic cleaned and tested before reinstallation
Any thoughts on what the problem could be, would be greatly appreciated. Sorry if this is a long post, this is my first time. Thanks in advance
EDIT: I have added a video to show the hard start.. this was after checking the fuel pressure drop.
Last edited by SoCalCL; 11-16-2021 at 11:37 AM. Reason: Add video
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biker349 (11-16-2021)