380SL 1984 Stalling when accelerating from standstill when engine hot. - Mercedes-Benz Forum
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post #1 of 26 (permalink) Old 04-10-2019, 06:12 AM Thread Starter
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380SL 1984 Stalling when accelerating from standstill when engine hot.

Hi, My 380SL from 1984 is running really nice and has only gone about 50.000 miles. It's untouched in mint condition and I've had it since it was new.

The only problem i have with it since the last 5 years or so is that once it warms up and you stop at an intersection or stoplight, when you hit the accelerator hard or just slightly it stalls. To keep it from stalling you have to have one foot on the brake and touch the accelerator pedal back and forth to stop it from going down to idle. It's also harder to start the engine when it's warm since it doesn't want to ignite, now whether that is because it gets to much or to little gas i don't know. Apart from this it runs beautifully on all cylinders and accelerates all the way up to the red mark on the tachometer.

During the last 5 years i've changed the sparkplugs, wires, rotor, distributor cap, injectors and seals. The injectors where changed since an old mechanic thought some might leak causing this issue. I've also ruled out that there would be some leakage on the intake side by spraying "start gas" (a can with some ignitable gas to help engines start) around the engine bay without any change in revs. Last week i rebuilt the AAV after reading about it here on this forum so that one closes nicely to. The idle adjust changes the revs nicely so that seems ok to.

Any ideas where i should continue looking?

One more thing that struck me, many years ago an aftermarket alarm system was mounted and the company said they have to disconnect the vacuumdriven locking of the doors since they mounted solenoids in the doors instead. I don't know how they did it and the company's not around anymore but the vacuumdriven locking of the gascap and trunk also stopped working after their intrusion into the vacuum system. Could this have anything to do with it?
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post #2 of 26 (permalink) Old 04-10-2019, 07:18 AM
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Since it idles okay and it runs okay, your timing is good and you have sufficient fuel pressure. The symptom is of fuel starvation but only initially, which maybe points to a minor clog somewhere in the delivery system. Is it getting worse or staying the same? Try a new fuel filter or check your return line. Is your emission system okay? A mal/non-functioning O2 sensor might cause it to flood. Miles-per-liter holding up?
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post #3 of 26 (permalink) Old 04-10-2019, 07:50 AM
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Don't rule out leaks on the intake system. There are a lot more components that live deeper in block valley that can leak. Spraying starter fluid won't reveal those leaks.

Start with a smoke test and then a fuel pressure test. Avoid the temptation to mess with the metering screw until these two systems are in spec.

Also, did swedish spec cars come with catalytic converters? I could have sworn it was NA, Aus, Jap, and Sweden that had detuned cat'd cars. Paging Dr @rowdie
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post #4 of 26 (permalink) Old 04-10-2019, 08:47 AM
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As far as I know only the US 107s had catalytic converters in 1984. Kind of iffy in Sweden. I thought it started in '85 there.

Hard warm start is a normal symptom of a failed accumulator.

An '84 380SL should have an electronically controlled idle valve (ICV) and not an AAV.
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post #5 of 26 (permalink) Old 04-10-2019, 06:46 PM
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Quote:
Originally Posted by rowdie View Post
Hard warm start is a normal symptom of a failed accumulator.
When I bought my 85 380sl cold starts and hot starts were great, but warm starts were stubborn, meaning I had to really crank it to get it started. Replacing the fuel accumulator solved this nicely.
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post #6 of 26 (permalink) Old 04-11-2019, 01:19 AM Thread Starter
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Thank you all for the many replies, I've posted on 2 Swedish Mercedes forums in the last couple of years with very limited feedback so i'm glad to see that this Mercedes forum seems to have a lot of knowledgeable people.

Quote:
Originally Posted by Weather Man View Post
Since it idles okay and it runs okay, your timing is good and you have sufficient fuel pressure. The symptom is of fuel starvation but only initially, which maybe points to a minor clog somewhere in the delivery system. Is it getting worse or staying the same? Try a new fuel filter or check your return line. Is your emission system okay? A mal/non-functioning O2 sensor might cause it to flood. Miles-per-liter holding up?
It's staying the same i would say.
I changed the fuel filter in 2001 but that's only about 12000 miles ago, I'll change it again, any special brand that is superior to others that you could recommend?
How exactly should I check the return line? Just disconnect it and put compressed air through it? Any picture where it's located under the hood?
The emissions have been within the allowed limit every time the state inspection has been done (once a year) but they only measure CO level since it doesn't have an O2 sensor, it runs on "leaded" fuel.
"Miles-per-liter holding up?" If you mean what mileage i get, it's been about the same during the years meaning somewhere between 11-15 liters/100 km depending on the drive conditions so 16-21 miles/gallon.

Quote:
Originally Posted by okyoureabeast View Post
Don't rule out leaks on the intake system. There are a lot more components that live deeper in block valley that can leak. Spraying starter fluid won't reveal those leaks.

Start with a smoke test and then a fuel pressure test. Avoid the temptation to mess with the metering screw until these two systems are in spec.

Also, did swedish spec cars come with catalytic converters? I could have sworn it was NA, Aus, Jap, and Sweden that had detuned cat'd cars. Paging Dr @rowdie
What's a smoke test? Same as emission test? They only measure CO on these old cars without the catalytic converters but the CO was 3,0 in 2013, 1,0 in 2015 and 1,1 in 2017 so it's lower now indicating leaner mixture?
Is there any instruction on how to do the pressure test on these cars?
Which metering screw do you mean?

Quote:
Originally Posted by rowdie View Post
As far as I know only the US 107s had catalytic converters in 1984. Kind of iffy in Sweden. I thought it started in '85 there.

Hard warm start is a normal symptom of a failed accumulator.

An '84 380SL should have an electronically controlled idle valve (ICV) and not an AAV.
Where is the accumulator located and does anybody have an OEM number for it? I've only done basic service on this car before so still have a lot to learn but I would say it's an AAV that i rebuilt, attaching pic.
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post #7 of 26 (permalink) Old 04-11-2019, 07:19 AM
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Not at all like an emissions test. A smoke test is when smoke (as in literal smoke) is piped into the intake to reveal leaks in the intake system.

Dollars to donuts, you probably have a leak deep down where the plenum connects to the upper block. There are rubber donuts that go bad down there. Especially at 50k miles, they may be original.

A smoke test would reveal those leaks by flooding the area and coming out.

I would replace everything you need to replace along the way since so much has to be removed.

Does your car have a catalytic converter?

Quote:
Originally Posted by ed9msi View Post
Thank you all for the many replies, I've posted on 2 Swedish Mercedes forums in the last couple of years with very limited feedback so i'm glad to see that this Mercedes forum seems to have a lot of knowledgeable people.

Quote:
Originally Posted by Weather Man View Post
Since it idles okay and it runs okay, your timing is good and you have sufficient fuel pressure. The symptom is of fuel starvation but only initially, which maybe points to a minor clog somewhere in the delivery system. Is it getting worse or staying the same? Try a new fuel filter or check your return line. Is your emission system okay? A mal/non-functioning O2 sensor might cause it to flood. Miles-per-liter holding up?
It's staying the same i would say.
I changed the fuel filter in 2001 but that's only about 12000 miles ago, I'll change it again, any special brand that is superior to others that you could recommend?
How exactly should I check the return line? Just disconnect it and put compressed air through it? Any picture where it's located under the hood?
The emissions have been within the allowed limit every time the state inspection has been done (once a year) but they only measure CO level since it doesn't have an O2 sensor, it runs on "leaded" fuel.
"Miles-per-liter holding up?" If you mean what mileage i get, it's been about the same during the years meaning somewhere between 11-15 liters/100 km depending on the drive conditions so 16-21 miles/gallon.

Quote:
Originally Posted by okyoureabeast View Post
Don't rule out leaks on the intake system. There are a lot more components that live deeper in block valley that can leak. Spraying starter fluid won't reveal those leaks.

Start with a smoke test and then a fuel pressure test. Avoid the temptation to mess with the metering screw until these two systems are in spec.

Also, did swedish spec cars come with catalytic converters? I could have sworn it was NA, Aus, Jap, and Sweden that had detuned cat'd cars. Paging Dr @rowdie
What's a smoke test? Same as emission test? They only measure CO on these old cars without the catalytic converters but the CO was 3,0 in 2013, 1,0 in 2015 and 1,1 in 2017 so it's lower now indicating leaner mixture?
Is there any instruction on how to do the pressure test on these cars?
Which metering screw do you mean?

Quote:
Originally Posted by rowdie View Post
As far as I know only the US 107s had catalytic converters in 1984. Kind of iffy in Sweden. I thought it started in '85 there.

Hard warm start is a normal symptom of a failed accumulator.

An '84 380SL should have an electronically controlled idle valve (ICV) and not an AAV.
Where is the accumulator located and does anybody have an OEM number for it? I've only done basic service on this car before so still have a lot to learn but I would say it's an AAV that i rebuilt, attaching pic.
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post #8 of 26 (permalink) Old 04-11-2019, 07:33 AM
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My goodness Ed, you're running leaded gas?! Fuel filters are everywhere, cheap too. Bosch, I think. Forget the return line because Beastie, I like your idea of a vac-leak near the intake. Press the gas and the motor twists a little, admitting air; it takes a moment for the electronic mixture control to overcome the sudden extra air and hence the hesitation.

Good luck!
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post #9 of 26 (permalink) Old 04-11-2019, 07:53 AM
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Quote:
Originally Posted by ed9msi View Post
Thank you all for the many replies, I've posted on 2 Swedish Mercedes forums in the last couple of years with very limited feedback so i'm glad to see that this Mercedes forum seems to have a lot of knowledgeable people.

Where is the accumulator located and does anybody have an OEM number for it? I've only done basic service on this car before so still have a lot to learn but I would say it's an AAV that i rebuilt, attaching pic.
The accumulator is above the fuel filter. Should be the same as the US model but verify number 000 476 04 21

That is an AAV. Has your engine or intake been changed sometime in the past?

Edit...Never mind. I read it is untouched and you have owned it since new. All the 380SLs I could find on EBay in Germany and the UK had the electronic idle control valve including 1981. The only 380SL/Cs I have heard of that had an AAV and idle adjustment screw are the first ones in 1980.
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post #10 of 26 (permalink) Old 04-11-2019, 12:08 PM
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I don't think these cars, even the high spec'd euro models, were designed to run on leaded gas.

That might be part of the issue right there.
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