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  #1  
Old 12-10-2010, 02:13 PM
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two problems: are they related? 1983 300sd

Hey, I am having two problems of late. The first is that the car starts poorly when it is warm, but great when it's cold. The second is that it is damn close to not shutting down when I turn the key off. Could there be a vacuum problem causing both, or are they unrelated?

Ted

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Old 12-10-2010, 02:21 PM
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Answer

Possible answer = failing shutoff valve.

If the diaphragm is damaged = the vacuum system sucks engine oil = check the vacuum line for oil.

Replace with a new shutoff valve if oil is in the vacuum line..






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  #3  
Old 12-10-2010, 02:41 PM
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I just replaced a shut off valve on one of ours a few months ago with a brand new bosch one, it has since failed and is leaking oil. Apparently they do not make much like they used to.
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  #4  
Old 12-10-2010, 03:07 PM
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I can't think of a connection between the two problems. Vacuum leaks or bad shut off diaphragm explains the shut off problems but not the other---UNLESS--wait I minute, I've got it!!! If there is a problem in the ignition switch causing vacuum NOT to be bled off the shut down circuit and NOT fed too the shut down circuit, both problems would be explained. If the vacuum is not completely bled off the shut down circuit, the car will be hard to start.

Test: Pull off the brown vacuum line at the shut off valve before you try to start it hot the next time. If it starts fine with the vacuum line removed, I've correctly identified the problem.
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  #5  
Old 12-10-2010, 07:48 PM
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apparently if u swapped the 2 vac line into the ignition kills valve it is going to be very hard start. For some reason the valve does have a check valve built in, 1 side allows the vac to hold vac another goes thru.

All u have to do is to swap the 2 vac lines see if it will start easy when hot.
As the vac retains there keep pulling the diaphragm to kill the engine.
i had one it was that way, i couldn't understand, soon as I disconnect the vac line that kills the engine at the end of the pump , the car starts in no time. As previous u feel like the engine had been flooded and keep cranking & cranking until the vac disappear then it will fir eup.
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Old 12-10-2010, 08:29 PM
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Occam's Razor..Rasor...Razer...Raiser?


You have a vacuum leak - its slow to shut off (or doesn't)
You have a worn out starter - does fine when cold...Hard to start when warm


Thats what happened to me...same symptoms as you...just my experience.
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  #7  
Old 12-10-2010, 09:33 PM
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There is also a Vacuum Valve located on the Steering Colum Lock that actuates the Shutoff Valve on the Fuel Injection Pump.
Not sure what issues it would cause of not working OK, It also has 2 Vacuum Hoses going to it that could get disconnected or cracked.
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Old 12-11-2010, 10:14 AM
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I didn't explain above why you would have hard starts when warm but not cold given my hypothesis. If the vacuum is not being bled off by the ignition switch, it will stop fuel getting to the IP when warm. However after the car has been sitting for a long while the vacuum can bleed off slowly so when the car is next ready to be started there is no vacuum in the shut off line.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #9  
Old 12-12-2010, 01:04 AM
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Typically

On high milage Chassis with Bosch Starters,the Dust from the Worn Brushes
exacerbates the "Heat Sink" type "No Hot Start" problems.

A dis-assembly and cleaning (New Brushes and mayhaps New Bushings) and
your'e good for another 100K.
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  #10  
Old 12-13-2010, 12:19 PM
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I have parts car, so I'll replace the vacuum pump (after testing) and the lines. Thanks for the help and I'll be back if that doesn't work.

Ted

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