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1983 380SL
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17 Posts
Discussion Starter · #1 ·
Hi All:

Thanks in advance to any help with this oddball problem. I recently bought an 83 380SL. It has the double roller conversion and 88,000 miles. Cherry car... except: Once the car is at operating temp it will sometimes begin to sputter and jerk while accelerating and lose power - eventually it will stall. It kinda' lunges then drops back while holding steady pressure on the pedal - acts like a fuel starvation problem. It has happened more frequently and sooner these past few days as the temps have risen in the northeast leading me to believe I'm in for a lousy summer driving experience. No predicting it either. It happens most often on the highway but it also does it at 30mph in town. Thing is... if I pull over, just stop the engine and restart, it all goes away... almost like something is "resetting". Recovery is immediate - no "cool-down" time is involved. Everything goes back to normal only to return again a while later. Everything else is normal and the car drives like new otherwise. I alternate adding a can of Ventil Sauber and Jectron once a month. Within the last 3,000 miles, the tank has been dropped, flushed and cleaned, it has a new fuel filter, air filters, wires, distributor cap, plugs and brand-spankin' new injectors.

Any ideas? Thanks!
 

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5 Posts
Interesting problem. do you notice any flooding or" Overloading" smell when this happens. It could be a small piece of trash( fuel filter paper,rust,etc) in the fuel line that wasn't removed with all the other efforts.Did any of your efforts lessen the problem?It could also be a coil with a short inside that will not rear it's ugly head except every so often.I'd lay off on the cleanong stuff too.
 

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1983 380SL
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17 Posts
Discussion Starter · #3 ·
No smells - no smoke - just no go. While I started thinking fuel, the restart solution now has me thinking electrical. I've been thinking the same thing about the additives. Maybe it's a little too clean! [;)] Thanks for your input!
 

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Outstanding Contributor , Bob's Your Uncle!
83 280 SL- 5 speed-The PIG
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32,298 Posts
Your EGR valve maybe stuck or have a hole in the diaphram which would give you a large vacuum leak at certain operating temps which might cause some of your symptons.
 

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1983 380SL
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17 Posts
Discussion Starter · #5 ·
Here's an interesting discovery in my problem: The stalling, sputtering no power problem completely disappears when I fill up the tank. As long as the tank is more than 1/4 full, I'm OK - runs like a dream. At about 1/4 it starts happenning infrequently but then as the gas level in the tank continues to drop, it gets really bad.

Now I know there is supposed to be a certain amount of tank vacuum produced by these MB closed systems. Every other car I have ever owned makes a "whoosh" sound when I open the gas cap - this car - nothing at all. When I got it, it had a generic vented gas cap. Now since I know MB isn't vented, I replaced it with the correct non-vented MB cap. Did I make the problem worse by doing that? Also, assuming this tank vacuum / gas level clue is meaningful, what does this tell me? Have I stumbled upon something here or is this ongoing intermittent fuel starvation issue finally driven me crazy? :eek:
 

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1983 380SL
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17 Posts
Discussion Starter · #6 ·
I've now confirmed that the fuel level is a direct clue on the problem. Three times since my last post I got the problem to start and become chronic as the gas ran down only to disappear when I re-filled the tank. I also tried using the old vented gas cap and using no cap at all and neither one had any effect. And no matter what the situation or circumstances, I NEVER hear a sound when I remove the gas cap.

It's difficult for me to explain this as an ignition problem anymore. I'm also not sure how the FPR impacts this anymore either, but I'd like to make sure by getting the problem to manifest itself and then jumpering the relay. What pins do I jumper to test the FPR once and for all?

Assuming the FPR checks out OK and that the FP and filter are new, where do we go? FP check valve, FT vent valve, accumulator, screen, damper, warmup (control pressure) regulator, fuel distibutor?

If this weren't such a PIA, I might actually be fun!

Thank you all for your excellent suggestions, time, and interest in my problem.
Ray
 

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1983 380SL
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17 Posts
Discussion Starter · #7 ·
I've now confirmed that the fuel level is a direct clue on the problem. Three times since my last post I got the problem to start and become chronic as the gas ran down only to disappear when I re-filled the tank. I also tried using the old vented gas cap and using no cap at all and neither one had any effect. And no matter what the situation or circumstances, I NEVER hear a sound when I remove the gas cap.

It's difficult for me to explain this as an ignition problem anymore. I'm also not sure how the FPR impacts this anymore either, but I'd like to make sure by getting the problem to manifest itself and then jumpering the relay. What pins do I jumper to test the FPR once and for all?

Assuming the FPR checks out OK and that the FP and filter are new, where do we go? FP check valve, FT vent valve, accumulator, screen, damper, warmup (control pressure) regulator, fuel distibutor?

If this weren't such a PIA, I might actually be fun!

Thank you all for your excellent suggestions, time, and interest in my problem.
Ray
 

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11 Posts
Hy, I have similar problem with my 560SL (1989); in fact when I push the accelerator pedal the car have no power; and the car is very hot in the shift wood;some pepole said that is the catalyst blocked; now I would like make a smog test before to change the exhaust system.Do you have chenged the catalyst?
 

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1969-280s, 2000 SL500, 1981 300D, 1980 450SL
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I just purchased a 1980 450Sl and it just dies when driving. Just like you said!!!
I have 1/4 tank of gas. I'm going to do the fill up and check routine. :) To me, it sounds like a fuel pump/pickup issue.. even though I've only had the car one day. Thanks for the theories.
 

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1977 450 SL
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175 Posts
This might be a long shot, but the filter that is screwed into your tank can clog. Maybe their is enough pressure, with the pressure of the gas, to supply the pump with enough fuel. just a thaught. that is why restarting lets it regain the pressure.

The only bitch is this envolves draining the tank. but it is only one hose to take off and unscrew the filter from the bottom of the tank.

first thing to do if you hav not already is to get a fuel filter (18-22$ us from GermanStar).. the one that goes in-line with your pump (not the one i was just talking about).

If you have more thatn a 1/2 tank and the problem goes away... you might be able to rule out the vaccuum issue.
 

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1977 450 SL
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175 Posts
You are looking at the bottom of the tank in theis picture

Here is the only picture i have of where the screen is. It is not the thing i am holding, that unscrews and the other brass-looking-thing in the tank (in the picture) that is the filter.
 

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