1974 450sl drowning in fuel - Page 2 - Mercedes-Benz Forum
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post #11 of 30 (permalink) Old 06-17-2019, 12:42 PM
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Quote:
Originally Posted by Neil W. Lareau View Post
...The timing is dead-on the marks at 5deg BTDC.
Iíve got a 74 450SL as well (just set timing short time ago) and just went out to garage and double checked, timing should be 5 deg. ATDC!
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post #12 of 30 (permalink) Old 06-17-2019, 02:27 PM
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Can you post some pictures of your engine intake area - curious about that work you did on the idle circuit by removing the AAV and what lies in its place. I am assuming you have blue Bosch Injectors. I am also curious about the placement of your fuel pressure gauge and resulting fuel circuit.

Don't give up - I think we can figure it out. I have gobs of spares to help you diagnose when we narrow it down.

Have you had a look at your pulse generator (trigger points) in the base of your distributor?
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post #13 of 30 (permalink) Old 06-18-2019, 04:33 AM Thread Starter
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Originally Posted by cushjbc View Post
Can you post some pictures of your engine intake area - curious about that work you did on the idle circuit by removing the AAV and what lies in its place. I am assuming you have blue Bosch Injectors. I am also curious about the placement of your fuel pressure gauge and resulting fuel circuit.

Don't give up - I think we can figure it out. I have gobs of spares to help you diagnose when we narrow it down.

Have you had a look at your pulse generator (trigger points) in the base of your distributor?
I'll post pictures of what I've done tonight.

The fuel injectors are what Rockauto.com sells Standard Motor Products FJ118, the other 4 are OEM that I rebuilt. (<- yes, that statement should make you suspicious).

I haven't put an oscilloscope on the trigger points, but I did put little fuel injector noid lights at the end of the cables and saw clear firing pulses. the Trigger Point contacts are clean.

As far as the fuel pressure gauge, it is plugged into the fuel line where the cold start injector used to be. I removed that injector because a) I wasn't having trouble starting the car cold, and b) as I was getting too much fuel I wanted to remove it as a possible source of the fuel.
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post #14 of 30 (permalink) Old 06-18-2019, 09:59 AM
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Why so many modifications?

Do you have a stock fuel pump?

Are you sure your pressure readings are correct?




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post #15 of 30 (permalink) Old 06-18-2019, 11:36 AM
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Standing by for pictures - can you also take some of the fuel pressure regulator and damper at the rear of the engine?
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post #16 of 30 (permalink) Old 06-18-2019, 06:41 PM
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Quote:
Originally Posted by Neil W. Lareau View Post
I'll post pictures of what I've done tonight.

The fuel injectors are what Rockauto.com sells Standard Motor Products FJ118, the other 4 are OEM that I rebuilt. (<- yes, that statement should make you suspicious).

I haven't put an oscilloscope on the trigger points, but I did put little fuel injector noid lights at the end of the cables and saw clear firing pulses. the Trigger Point contacts are clean.

As far as the fuel pressure gauge, it is plugged into the fuel line where the cold start injector used to be. I removed that injector because a) I wasn't having trouble starting the car cold, and b) as I was getting too much fuel I wanted to remove it as a possible source of the fuel.
If we are assuming that timing chain isnt stretched and fuel injectors arent sticking open (doubtful), it really seems like the pressure is too high. What kind of fuel pump is on it and have you tried reducing the pressure from the regulator?
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post #17 of 30 (permalink) Old 06-18-2019, 07:50 PM
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Vehicle: W114 280E 5 speed manual 1972, W123 280E 1983
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I had this problem on my Djet powered W114 280E. It was due to a failed engine temperature sensor. Open circuit equals infinite resistance equals infinite injector opening time. Check it with a multimeter when cold and warm. I can't remember exactly but I think cold it should be about 2kohm, at engine temperature it is about 600ohms, but check the manual. Make sure you check it when hot as mine didn't go open circuit until it warmed up.
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post #18 of 30 (permalink) Old 06-24-2019, 10:21 AM Thread Starter
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Originally Posted by lsmoz View Post
I had this problem on my Djet powered W114 280E. It was due to a failed engine temperature sensor. Open circuit equals infinite resistance equals infinite injector opening time. Check it with a multimeter when cold and warm. I can't remember exactly but I think cold it should be about 2kohm, at engine temperature it is about 600ohms, but check the manual. Make sure you check it when hot as mine didn't go open circuit until it warmed up.
This is the one on the back of the passenger side cylinder head?
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post #19 of 30 (permalink) Old 06-24-2019, 04:37 PM
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I don't know where it is on a V8, someone else will have to answer.
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post #20 of 30 (permalink) Old 06-24-2019, 06:03 PM
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Quote:
Originally Posted by RobbyH View Post
If we are assuming that timing chain isnt stretched and fuel injectors arent sticking open (doubtful), it really seems like the pressure is too high. What kind of fuel pump is on it and have you tried reducing the pressure from the regulator?
Just a side note. Trigger Points work (fire)(create a pulse) when they are closed not open. 110 - 115 deg. should be your target.
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