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1992 400SE
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Discussion Starter #1
starts great cold. starts great hot.....but wait 15 or 20 minutes on a hot day after shutting down and it turns over perfectly and then shuts down. as it cools completely it ill start and idle roughly and stall. finally it will be fine. thoughts for the trenches?
 

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1992 400SE
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49 Posts
Discussion Starter #2
did i mention this only happens when it's hot outside?

thanks
 

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1973 mercedes benz 280 se 4.5
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10 Posts
i have the same exact car and the same exact problem and i know that it has to do with the temp. of course the engine gets hotter after its shut off. i usually have to baby the idle along until it cools down, or it will stall just like yours. if the temp gets any hotter than 180 or so it will run rough. maybe your aux. fan isn't operating properly. i was thinking of wiring my aux. fan so that it runs with the key out of the ignition until it gets to 175.
 

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1992 400SE
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49 Posts
Discussion Starter #4
thanks that sounds exactly.........

correct. a thermostaically controlled fan would probably do the trick. great
 

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1966 230sl-1969 280se cp-1971 280se 3.5 cp-1988 300ce cp -1958 356a cp. etc.
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34 Posts
roadrosen said:
starts great cold. starts great hot.....but wait 15 or 20 minutes on a hot day after shutting down and it turns over perfectly and then shuts down. as it cools completely it ill start and idle roughly and stall. finally it will be fine. thoughts for the trenches?
Two words: VAPOR LOCK, the current fuel must have a lower vapor point and the cars cant cope. New pumps, custom added fuel accumulators, fresh check valves,after run fans all help a little. But not enough. I have at least 30 towed in each of the last several summers and all of them run great when they get off the tow truck after cooling down for1-2 hours. Then act up again when good and hot. If anyone has solved this let us now! Keith
 

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1992 400SE
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49 Posts
Discussion Starter #7
locks

locks do not operate automatically. vacuum leak.
 

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1992 400SE
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49 Posts
Discussion Starter #8
fuel evaporation

after searching the web some have suggested thatthe early injected cars have a problem with the fuel evaporating in the lines so spraying some cool water on injector lines can help or turning the key a few time to move cooler ful in. check this link

http://mercedesshop.com/shopforum/showthread.php?t=5904

it will be hot here in ci this weekend and i'll test the proposition.

comments?
 

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That kind of problem would definitely get me twisted. I tend to go with the incoming fuel temp after the car has reached operating temp as being the likely culprit. Their should be a an in line air exchange cooler available through a performance parts company that could be plumbed in with relative ease that should alleviate the condition. Good luck, frank220-450.
 

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1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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1,830 Posts
Perhaps a combination of check valve(s), fuel pressure regulator leakage and bad solder joints in the fuel pump relay.
 

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89 Mercedes 300E, 91 Mercedes 300CE, 71 BMW turbo 2002, 73 BMW 2002tii, 85 BMW 635csi
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Residual pressure being lost like others have said due to check valve failure or/and leaking cold start injector.



More test for you guys with D Jet.. more at the w116 forum here stickied at the top under Bosch D and K Jet Troubleshooting.

Main relay;

1)There should be 12 volts at pin # 24 of the ECU.

2)If not,check for 12 volts at pin # 24 of the relay.

3)If 12 volts is not present at the relay but it clicks,replace with a new relay.

4)If there is 12 volts at pin # 24 of the relay,repair
# 24 wire between relay and ECU.

5)If the relay does not click,inspect the wire from the main relay pin # 45 to ground.

6)If the ground is good and 12 volts at relay pin # 38
when the engine is cranked,replace the main relay.


Trigger points;

1)With the engine not running and ECU harness disconnected from the ECU,check the resistance between
ECU harness 12 and 21,then from 12 to 22.One should show a low resistance and the other should show an open circuit.

2)Rotate the engine 360 degrees and check the resistance.They should have an opposite reading now.

3)If not,perform the same test at the trigger points themselves.This will tell you if it a component or wiring fault.


Temperature sensor 1

1)With the engine not running and the ECU harness
disconnected from the ECU,connect an ohmmeter between
ECU harness pin # 1 and 13.At an ambient temperature
the reading should be 200 ohms.

2)If the resistance is well above 200 ohms,check resistance at the sensor itself to determine if it is
a component or wiring fault.

3)Check resistance of all the terminals to chassis ground.There should always be an open circuit.


Temperature sensor 2

1)With the engine not running and the ECU harness
disconnected from the ECU,check the resistance between harness terminal 23 and ground.The resistance should be 2000 ohms at ambient temperature.

2)If the engine is near operating temperature,the resistance should be below 1000 ohms.


Throttle switch

1)Test the throttle switch with the key on,engine off.

2)Slowly open the throttle,and as it opens the injectors should alternately click.You should hear
20 evenly spaced clicks.

3)If this is not met,place a 0.016 in.(0.4mm)feeler
gauge between the throttle stop and throttle stop screw.Connect a voltmeter to terminal 17 of the throttle switch.The voltmeter should show voltage while the ignition key is in the on position.Remove the feeler gauge and the voltmeter should show no voltage now.

4)If this fails,loosen the screws and rotate the switch until it meets these requirements.

5)If they can not be met and voltage is always present no matter where you position,replace the throttle switch.

6)If the voltmeter reads no voltage,ensure voltage is
being supplied to the switch.If so,replace the throttle switch.

7)If no clicks are heard while performing test 1 and 2,check wire numbers 20,17,14 and 9 for continuity end
for end from the ECU to throttle switch.


Pressure sensor

1)With the engine not running and the ECU harness
disconnected from ECU,check the resistance from ECU
harness terminal # 7 to 15.Should be 90 ohms and then check the resistance between # 8 and 10.Should be
350 ohms.If this is not met,test the sensor itself.

2)on occasion,the sensor resistance will check out,but will not hold vacumm.Using a hand held vacumm pump perform this test again (step #1)


Injector circuit

1)With the engine not running and the ECU harness
disconnected from ECU,check resistance of ECU harness
pins # 3,4,5,and 6.All should have less than 25 ohms.

2)If the resistance is greatly higher or lower than
25 ohms,test the injector itself.

3)If the injectors pass,repair the wiring harness.
 

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1972 280 SE SEL 4.5's

Hot Start Problems On The Electronic Fuel Injected V-8's 3.5 And 4.5 Is Often Caused By A Malfunctioning Fuel Check Valve Located Inside Of The Fuel Pump. This Can Be Fixed By Unscrewing The Outlet Port Nipple On The Fuel Pump And Replacing It With A Early Lucas Jaguar Nipple Which Has A Built In Check Valve. Thus Saving You The Cost Of A New Fuel Pump. It Works Perfectly I Have Done It.
LOW FUEL PRESSURE CAUSED BY FAULTY CHECK VALVE CURE.
 
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