'99 323i (E46), M52TU engine. 200K miles Trying to diagnose a hard start situation.
On a cold engine, engine fires right up.
At temperature, if I turn off engine, and go to restart within 10 minutes, engine fires right up.
However, if after driving, turn engine off, and after an hour or more, the engine cranks for 5-7 seconds before it catches and engine sluggishly comes to life.
No CEL, no stored codes.
I thought it might be a temperature sensor not reading correctly and sending incorrect info to the DME. Changed the water temp sensor (underneath the #1 intake runner), change the oil temp sensor (in the oil filter housing), changed the air temp sensor (in the intake manifold). Changed out the crank position sensor, intake and exhaust cam sensors..
None of these changed the situation.
Fuel pressure:
Key on, engine off: 42 psi.
Engine on, idle: 52 psi.
Turn engine off, fuel pressure gradually drops to 30psi over a period of 20 minutes.
Also, key on engine off, then clamp off the fuel rail feed and return lines: fuel pressure does not drop off.
Let me add that the fuel pump was changed at 180K miles (VDO brand, it was the original and I was doing it as preventative maintenance). Also about that time I had R&R'd the fuel injectors, had them cleaned and bench tested.
So...my conclusions thus far:
It seems like the fuel pressure is dropping off too quickly, but it's not leaking through any of the injectors.
The hard start problem seems to be temperature related.
Which... at this point, please tell me what I'm missing.
Past that point, I'm wondering about the 3/2 valve. I understand the operation of the 3/2 valve in the M52TU engine (ie "running losses") , except:
I'm wondering whether the solenoid in the 3/2 valve isn't functioning correctly. If the solenoid is not getting energized, and therefore not opening the return line for 20 seconds... could it be that there's enough heat sink in the fuel rail to cause a vapor lock condition?
Then again that wouldn't explain the fuel pressure drop after the ignition is turned off.
The BMW diagram states that the solenoid gets its power from the DME relay. So I changed that... no difference.
So anyone with a good working knowledge of the M52TU 3/2 valve, I'd appreciate any input.
Thanks,
Ed
On a cold engine, engine fires right up.
At temperature, if I turn off engine, and go to restart within 10 minutes, engine fires right up.
However, if after driving, turn engine off, and after an hour or more, the engine cranks for 5-7 seconds before it catches and engine sluggishly comes to life.
No CEL, no stored codes.
I thought it might be a temperature sensor not reading correctly and sending incorrect info to the DME. Changed the water temp sensor (underneath the #1 intake runner), change the oil temp sensor (in the oil filter housing), changed the air temp sensor (in the intake manifold). Changed out the crank position sensor, intake and exhaust cam sensors..
None of these changed the situation.
Fuel pressure:
Key on, engine off: 42 psi.
Engine on, idle: 52 psi.
Turn engine off, fuel pressure gradually drops to 30psi over a period of 20 minutes.
Also, key on engine off, then clamp off the fuel rail feed and return lines: fuel pressure does not drop off.
Let me add that the fuel pump was changed at 180K miles (VDO brand, it was the original and I was doing it as preventative maintenance). Also about that time I had R&R'd the fuel injectors, had them cleaned and bench tested.
So...my conclusions thus far:
It seems like the fuel pressure is dropping off too quickly, but it's not leaking through any of the injectors.
The hard start problem seems to be temperature related.
Which... at this point, please tell me what I'm missing.
Past that point, I'm wondering about the 3/2 valve. I understand the operation of the 3/2 valve in the M52TU engine (ie "running losses") , except:
I'm wondering whether the solenoid in the 3/2 valve isn't functioning correctly. If the solenoid is not getting energized, and therefore not opening the return line for 20 seconds... could it be that there's enough heat sink in the fuel rail to cause a vapor lock condition?
Then again that wouldn't explain the fuel pressure drop after the ignition is turned off.
The BMW diagram states that the solenoid gets its power from the DME relay. So I changed that... no difference.
So anyone with a good working knowledge of the M52TU 3/2 valve, I'd appreciate any input.
Thanks,
Ed
M52TU 3/2 valve
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