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  #1  
Old 08-12-2009, 11:36 AM
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DIESEL SWAP WIRING/VACUUM QUESTIONS- FORUM NEWBIE

http://www.cardomain.com/ride/3215663

NEW TO THE FORUM!!!

I have done a engine swap, and now I have a '78 300SD engine vs a gas one.
I have done all the rewiring of the car.

questions:
1- how is the diesel "pumped"? (electrical like the gas pump? or mechanically?) (I was told there is a pump on the rear of the car for diesels...is it inside the tank? or resides in engine compartment?

2- I see on the "control box" that there is one connector that powers up the 5 glow plugs, coolant sensor and temp (from the back of my head thinking) ---
the other connector pin seems to only need the #6 red thick cable to constant power, the thin red one to switched power, ground? is this correct?
my car does not have on the gauge panel temp light, etc... I used the blue/white wire for the glow plug warning light (installed remote location)---seems to work fine

3- Since my car was not diesel, I don't have a diesel shut down button/switch....any parts/advice....hard to find a shut-off button..or not looking in right places. (was also told i should change out the ignition switch housing for a diesel engine one.)---any tips/advice and how the vacuum is routed?

4- Will I need the Speed Control Sensor? I mean, is it necessary to have the car running properly or is it just so I can check the rpm on the car? apparently it senses TDC & rpm...just clarification.

thanks!!!

I was told you guys are the diesel experts.

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  #2  
Old 08-12-2009, 12:16 PM
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Answer RE: engine swap, 1978 300SD engine vs a gasser

Here is a link with further data on your questions.
Fast navigation Do It Yourself Links
Fast navigation Do It Yourself Links



questions:
1- how is the diesel "pumped"?

ANSWER:
* The fuel is gravity feed up to the mechanical lift pump.
* The mechanical lift pump is in the engine compartment (attached to the injection pump).

2- I see on the "control box" that there is one connector that powers up the 5 glow plugs, coolant sensor and temp (from the back of my head thinking) --- the other connector pin seems to only need the #6 red thick cable to constant power, the thin red one to switched power, ground? is this correct?
my car does not have on the gauge panel temp light, etc... I used the blue/white wire for the glow plug warning light (installed remote location)---seems to work fine

ANSWER:
I need to see pictures of what you have done with this circuit, the description sounds correct.

3- Since my car was not diesel, I don't have a diesel shut down button/switch....any parts/advice....hard to find a shut-off button..or not looking in right places. (was also told i should change out the ignition switch housing for a diesel engine one.)---any tips/advice and how the vacuum is routed?

ANSWER:
* The ignition SWITCH should be changed to a diesel shut down unit.
Vacuum Diagrams W123 and W126 models


4- Will I need the Speed Control Sensor? I mean, is it necessary to have the car running properly or is it just so I can check the rpm on the car? apparently it senses TDC & rpm...just clarification.

ANSWER:
* The tachometer is optional, but a very useful diagnostic tool.



Have a great day.
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  #3  
Old 08-12-2009, 12:34 PM
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#3:

The diesel shutdown on the ignition switch can be emulated by using a N.O. 12v solenoid (aka: Mercedes switchover valve) to pass vacuum to the shutdown valve when 12v to the solenoid is off (ignition switched power).

This is what I'm planning for my gas > diesel 124 conversion.
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  #4  
Old 08-13-2009, 10:08 AM
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U GUYS ARE AWESOME!

I really appreciate all the help! This clears up the rest. I will try the switchover valve method. Gotta look at these vacuum diagrams before I try cranking her up!

As for question #2, I dont have pics.. (loomed everything up already after the test)...
basically it goes like this:
#6 red at glow plug relay = Constant power (used pin 15 I believe on ign switch)-
small thin wires on 6 pin connector:
brown = grounded
blue/white = to remote warning light (since I dont have a glowplug light on car)
red= switched on power
violet = not used (RPM I believe...my guage panel doesnt have it)
green = not used (Temp light I believe...my car uses the copper line type) working modification... tips?

ANYONE KNOW:
a- where I can get a replacement line from engine to gauges for oil pressure?
b- good way to convert vise-versa: from electrical temp sending to my meachanical coolant temp guage?

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