SL/R107: hot start issue
Thread Starter
Newbie
Joined: Jul 2015
Posts: 8
Likes: 1
1972 450SL
hot start issue
I understand this is a common issue with this model and this fuel delivery type, so if anyone has found solutions, I will be very appreciative.
1972 450SL with the D-Jet fuel injector system. Engine recently overhauled, new fuel injectors, distributor with electronic points, new fuel pump, and rebuilt ECU wiring harness.
Engine starts and runs A-OK when cold. When temp gauge reaches 200+ and the engine is shut down, it still starts and runs A-OK immediately after shut down. However, after 15-20 minutes, it is very difficult to start, and takes repeated rapid accelerator pumping to get it going, then it runs very rough. After 2-3 minutes, it settles down and runs A-OK again. This also happens when the engine is slightly warm, but the outside temperature is 90+, and the car has sat in the heat for a while. In the garage it is A-OK.
I am assuming this is a vapor lock issue with the gasoline, but everything I have tried (timing adjustments, fuel pressure adjustments, etc.) has yielded no positive results.
Any advice appreciated, especially if you have experienced similar problems and found resolutions. Thanks.
1972 450SL with the D-Jet fuel injector system. Engine recently overhauled, new fuel injectors, distributor with electronic points, new fuel pump, and rebuilt ECU wiring harness.
Engine starts and runs A-OK when cold. When temp gauge reaches 200+ and the engine is shut down, it still starts and runs A-OK immediately after shut down. However, after 15-20 minutes, it is very difficult to start, and takes repeated rapid accelerator pumping to get it going, then it runs very rough. After 2-3 minutes, it settles down and runs A-OK again. This also happens when the engine is slightly warm, but the outside temperature is 90+, and the car has sat in the heat for a while. In the garage it is A-OK.
I am assuming this is a vapor lock issue with the gasoline, but everything I have tried (timing adjustments, fuel pressure adjustments, etc.) has yielded no positive results.
Any advice appreciated, especially if you have experienced similar problems and found resolutions. Thanks.
Super Member
Joined: Jul 2007
Posts: 882
Likes: 11
From: Oldsmar, FL
2005 E55 Wagon, 2017 C63S Cab, 1986 560SL
I have absolutely no idea what it is, but on my E55 and SL65, I had exactly the same problem and it was the crankshaft position sensor. I have no idea what that is or if a 72 450SL has one, but what they heck
Thread Starter
Newbie
Joined: Jul 2015
Posts: 8
Likes: 1
1972 450SL
72 450SL crank position sensor??
Anyone know more about this? Thanks.
Senior Member
Joined: Jan 2010
Posts: 330
Likes: 26
From: Middle of Nowhere, USA
450SL
No 107 prior to 1986 has a crank position sensor. Some '85 and older models have a TDC sensor but it has nothing to do with starting.
Yes this a common hard start issue on DJet engines. Some have increased the fuel pressure to 30-32 PSI. Another suggestion is to turn the ignition on and off a few times to fill injector lines.
Hope this helps.
Yes this a common hard start issue on DJet engines. Some have increased the fuel pressure to 30-32 PSI. Another suggestion is to turn the ignition on and off a few times to fill injector lines.
Hope this helps.
Thread Starter
Newbie
Joined: Jul 2015
Posts: 8
Likes: 1
1972 450SL
No 107 prior to 1986 has a crank position sensor. Some '85 and older models have a TDC sensor but it has nothing to do with starting.
Yes this a common hard start issue on DJet engines. Some have increased the fuel pressure to 30-32 PSI. Another suggestion is to turn the ignition on and off a few times to fill injector lines.
Hope this helps.
Yes this a common hard start issue on DJet engines. Some have increased the fuel pressure to 30-32 PSI. Another suggestion is to turn the ignition on and off a few times to fill injector lines.
Hope this helps.
Newbie
Joined: May 2017
Posts: 6
Likes: 0
2005 E320
Solution found?
Ron,
Have you found any solution for your problem? My 2005 E320 has the identical problem. Trust me I understand your embarrassment in parking lots. I have been looking for a solution for over a year. I have replaced: CPS, MAF, Fuel pump, fuel filter, vacuum lines, EGR valve and the valve cover gaskets. All these recommended by this forum or MB mechanics. None of them have worked. Let me know if you find anything. Thank you.
Have you found any solution for your problem? My 2005 E320 has the identical problem. Trust me I understand your embarrassment in parking lots. I have been looking for a solution for over a year. I have replaced: CPS, MAF, Fuel pump, fuel filter, vacuum lines, EGR valve and the valve cover gaskets. All these recommended by this forum or MB mechanics. None of them have worked. Let me know if you find anything. Thank you.
Thread Starter
Newbie
Joined: Jul 2015
Posts: 8
Likes: 1
1972 450SL
Still Searching
Ron,
Have you found any solution for your problem? My 2005 E320 has the identical problem. Trust me I understand your embarrassment in parking lots. I have been looking for a solution for over a year. I have replaced: CPS, MAF, Fuel pump, fuel filter, vacuum lines, EGR valve and the valve cover gaskets. All these recommended by this forum or MB mechanics. None of them have worked. Let me know if you find anything. Thank you.
Have you found any solution for your problem? My 2005 E320 has the identical problem. Trust me I understand your embarrassment in parking lots. I have been looking for a solution for over a year. I have replaced: CPS, MAF, Fuel pump, fuel filter, vacuum lines, EGR valve and the valve cover gaskets. All these recommended by this forum or MB mechanics. None of them have worked. Let me know if you find anything. Thank you.
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Newbie
Joined: Feb 2024
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Sl380
Sl380
I’m facing the same issue, I’ve changed the injectors and the fuel pump with no positive results.
I’ve read some comments says that it’s about the idle or the gasoline filter near the engine (black one)
let us know if you have a positive result
I’ve read some comments says that it’s about the idle or the gasoline filter near the engine (black one)
let us know if you have a positive result
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Newbie
Joined: Sep 2024
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72 350SL
Vapor Lock
Has anyone tried wrapping the fuel lines in a heat-protective "wrap"? The 73-74 Datsun Z cars were notorious for this and that was the solution, though in the day it was probably an asbestos derivative. there has to be something that would keep the fuel cool under the hood. I've gotten so frustrated with it that I only drive my '72 on "perfect weather" days and plan long stops....
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Joined: Jan 2010
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NGL450 w/EORP, S550
I understand this is a common issue with this model and this fuel delivery type, so if anyone has found solutions, I will be very appreciative.
1972 450SL with the D-Jet fuel injector system. Engine recently overhauled, new fuel injectors, distributor with electronic points, new fuel pump, and rebuilt ECU wiring harness.
Engine starts and runs A-OK when cold. When temp gauge reaches 200+ and the engine is shut down, it still starts and runs A-OK immediately after shut down. However, after 15-20 minutes, it is very difficult to start, and takes repeated rapid accelerator pumping to get it going, then it runs very rough. After 2-3 minutes, it settles down and runs A-OK again. This also happens when the engine is slightly warm, but the outside temperature is 90+, and the car has sat in the heat for a while. In the garage it is A-OK.
I am assuming this is a vapor lock issue with the gasoline, but everything I have tried (timing adjustments, fuel pressure adjustments, etc.) has yielded no positive results.
Any advice appreciated, especially if you have experienced similar problems and found resolutions. Thanks.
1972 450SL with the D-Jet fuel injector system. Engine recently overhauled, new fuel injectors, distributor with electronic points, new fuel pump, and rebuilt ECU wiring harness.
Engine starts and runs A-OK when cold. When temp gauge reaches 200+ and the engine is shut down, it still starts and runs A-OK immediately after shut down. However, after 15-20 minutes, it is very difficult to start, and takes repeated rapid accelerator pumping to get it going, then it runs very rough. After 2-3 minutes, it settles down and runs A-OK again. This also happens when the engine is slightly warm, but the outside temperature is 90+, and the car has sat in the heat for a while. In the garage it is A-OK.
I am assuming this is a vapor lock issue with the gasoline, but everything I have tried (timing adjustments, fuel pressure adjustments, etc.) has yielded no positive results.
Any advice appreciated, especially if you have experienced similar problems and found resolutions. Thanks.
