560SL high temp slow down and stop - Mercedes-Benz Forum

 
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post #1 of 8 (permalink) Old 04-17-2015, 08:29 AM Thread Starter
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560SL high temp slow down and stop

I inherited a 560sl that had been played with for two years by others. I have replaced or repaired most components. I have a small collection but the only other CSI system is on a Ferrari GTSi which is QUITE DIFERENT so I am stumped.
It starts cold well and will idle indefinitely but when on the road it gradually loses power and develops a miss starting at about 2000 rpm then progressing till it will not get above about 1200 and has so little power that we stop completely. Starts happening after about 5 miles.After sitting for about ten minutes it will start but still with a significant loss of power and rpms. The water temp never gets over the mid point and the distributer is cool to the touch. Nothing seems too hot but it is definitely temp related. Fuel pressure is 150 off the pump. ignition ok. new injectors. fuel system has been flushed. The only component I haven't fussed with is the fuel distributor.
Any Ideas?
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post #2 of 8 (permalink) Old 04-17-2015, 08:39 AM
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Try reposting this in the 107 forum...very active with great people willing to help.

R/C107 SL/SLC Class - Mercedes-Benz Forum
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post #3 of 8 (permalink) Old 04-17-2015, 05:12 PM
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Hi, seems your car has issues. First off the FI on your car is the same as other models of the same year. It is a 86 i presume and that was the first year so they had a few issues. From what you describe the fuel pressure is good at the pump but thats not where you measure it. You need to know what it is at the return port of the fuel distributor after the regulator than the real important issue is the volume. You could have pressure with insufficient volume and as your consumption is increased with engine speed and load the volume can fall short of what it takes to fire it. The CIS system delivers fuel based on differential pressure meaning a difference between the upper chamber pressure and the lower pressure chamber. That is controlled in the EHA which is the black box attached to the left side of the fuel distributor. This system is why I bought my first Fluke meter. An in line test should indicate a voltage that will vary with load requirements and go negative during deceleration as it goes into fuel shut off. .... CIS test and did I mention CIS test. Thats what's next as it may well indicate what the issue is but there is always the possibility of a restricted catalyst which you can check with a good manifold vacuum gauge. There are a lot of tests listed here in literature but it's OK as I know somewhere else it is listed. How old is your fuel filter? I did state something incorrect, the 110 motor was a little different but that doesn't really matter for you. As for being willing, I'm not all that willing just retired and enjoy going down memory lane from time to time. This could get expensive so one thing at a time.
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post #4 of 8 (permalink) Old 04-17-2015, 06:06 PM Thread Starter
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Bill, thanks
Found two things today; Pump # 1 does not seem to be working. Will have to get it in the air and do some draining to check for certain. The inlet gas hose is old and when I took it off to attach the pressure gauge fittings I found that the inside lining was deteriorated and was blocking as least some fuel flow. It seems that when the line got hot it also got softer and the lining caused more blocking. That coupled with only one pump working could have caused the problem. Tomorrow we will pull the pumps and bench test. Clzude
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post #5 of 8 (permalink) Old 04-17-2015, 06:42 PM
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Originally Posted by cvbaker View Post
Bill, thanks
Found two things today; Pump # 1 does not seem to be working. Will have to get it in the air and do some draining to check for certain. The inlet gas hose is old and when I took it off to attach the pressure gauge fittings I found that the inside lining was deteriorated and was blocking as least some fuel flow. It seems that when the line got hot it also got softer and the lining caused more blocking. That coupled with only one pump working could have caused the problem. Tomorrow we will pull the pumps and bench test. Clzude
If it's a 2 pump car if one works and one doesn't then depending on which pump it is the car will run with no power and the other and the car won't run. Repair the malfunction and the fuel hoses and it may well be resolved. They arn't cheap pumps but cheap ones don't really work well. The volume should be 1 liter in 30 seconds measured at the return fuel line at the fuel distributor. If this system had a lot of issues it is almost cheaper to install a late model digital system but thats a big job as well. There is also a filter screen in the inlet fitting at the fuel distributor as well. Have a good weekend, were going away until Sunday
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post #6 of 8 (permalink) Old 04-21-2015, 04:43 PM
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Also, classic symptoms of a rusty gas tank with a clogged tank strainer. If you find rust in the strainer, best to replace the tank.

Chuck Taylor
Falls Church VA
1998 SL500
1959 220S
1970 280SL
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post #7 of 8 (permalink) Old 05-01-2015, 08:59 AM
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If it's a 2 pump car if one works and one doesn't then depending on which pump it is the car will run with no power and the other and the car won't run.
On my 560SL, there was one good pump and one dead pump. Don't remember which was dead, but that car ran fine with no power loss that I could tell. So this rule evidently does not apply in all cases.
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post #8 of 8 (permalink) Old 05-02-2015, 05:28 PM
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you check the basic fuel pressure at the line that goes to the cold start valve [ no where else ].you should have 75 to 80 psi while driving if you can .you get in trouble when pressure goes bellow 60 .
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