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1975 450SL
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Discussion Starter #1 (Edited)
1975 450SL had been running just fine and I did a spark plug and wire change started it and it ran until fuel was out of lines. It will start with a shot of starting fluid so the ignition system is working. I did some research that points to the fuel pump relay but before I go to that expense I would like to be more certain. I am getting no fuel. I can hear the fuel pump start and turn off as it hits pressure.I also read the fuel accumulator can cause problems but it seemed it was mostly hot starts. Could some one give me a list of things to check before I just start throwing money at it. How pron are the ignition control mod to failure?
Prior thanks to all that give suggestions.
 

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450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
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If the fuel pump is turning on when you turn the key, it sounds to me like your Fuel Pump Relay is OK. The Fuel pump should even be OK I would think.

Do you have gas? :)

To the others:
- Is it possible for the points under the dizzy to all break down at once?
- Does this sound more like an ECU type of thing that is causing the trigger points to not fire the injectors?

I am assuming the car is a 1975 D-jet, and I am assuming it is a lot like my 73 d-jet.
 

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450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
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1975 450SL had been running just fine and I did a spark plug and wire change started it and it ran until fuel was out of lines. It will start with a shot of starting fluid so the ignition system is working.
If that is what happened, then I agree that it sounds more like fuel delivery. Maybe my thoughts about ECU and trigger points is way off.
 

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Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
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Never heard of an ECU going bad on one of those. Start at the top, Stickies that is EGV-107.
 

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1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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Never heard of an ECU going bad on one of those. Start at the top, Stickies that is EGV-107.
I have. I can send you one. Actually didn't just go bad. The alternator shorted out.

Check your fuses. There is also a relay for the ECU.
 

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1984 500SL 000760
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Originally Posted by center valley
"It will start with a shot of starting fluid so the ignition system is working"

You anwsered your own question regarding the ignition and ECU, if it starts with a squirt of ether then you have a fuel delivery problem.

Do you have a fuel pressure guage you can hook up to the fuel line and check waht PSI you are getting?
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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Originally Posted by center valley
"It will start with a shot of starting fluid so the ignition system is working"

You anwsered your own question regarding the ignition and ECU, if it starts with a squirt of ether then you have a fuel delivery problem.

Do you have a fuel pressure guage you can hook up to the fuel line and check waht PSI you are getting?
Not true on a D-Jet. If the ECU is not sending a signal to the injectors they will not open.
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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I did some research that points to the fuel pump relay but before I go to that expense I would like to be more certain. I am getting no fuel. I can hear the fuel pump start and turn off as it hits pressure.
The fuel pump does not stop because it reaches pressure. It is designed to only run for a few seconds when the key is first turned on. ECU then shuts it off, until the starter is engaged and engine starts. Then it of course runs.

If you think you have no fuel, do a pressure test of the fuel rail. If you have pressure there, then perhaps do a flow test. This would entail jumpering the fuel pump relay, disconnect the fuel return line downstream of fuel pressure regulator/damper and measure how much fuel you get in 30sec. Should be 1L or thereabouts. (see the d-jet training manual I posted for details)

Even if the ECU is good, the injectors won't fire unless the trigger points initiate an injection pulse. The only way all 4 trigger points would be bad, would be a bad connection (the plug) or bad ground connections at back of motor. Going through the test procedure in the manual (07.4) is the best way to check all connections are good. It also gets you close and intimate with your car ;)

The fact that all this started with a change in ignition parts would lead me to look and see if something was disturbed or incorrectly re-connected. Ignition points gap especially.
 

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1978 450SL--117K
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I have. I can send you one. Actually didn't just go bad. The alternator shorted out.

Check your fuses. There is also a relay for the ECU.
The ECU relay sits with the other ones above the fuse box, right? Seems to me that there are two in that area that control fuel delivery to some degree. For my own part, given the bath scenario, I replaced them all at the same time.
 

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1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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Yes the ECU relay is above the fuse box with the others. All of the relays are the same. The relays are 1,3,5,7 on the left. 2,4,6,8 on the right. Not all spaces are used on all models. 1 is fuel pump relay on the D-Jet. In '73 I think 3 is the ECU relay.
 

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Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
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What do you mean "it ran untill the fuel was out of the lines" ? Did you run it out of gas, close a fuel line, disconnect something ?
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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same OP has another thread in which he said:

ballast
The resistor was bad replaced and all is good.
Thanks
Hard to see the connection, but if everything is now good, I guess this thread is dead?/
 

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Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
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same OP has another thread in which he said:



Hard to see the connection, but if everything is now good, I guess this thread is dead?/
Maybe I should put my head in gear and pay attention. :surrender:
 

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1975 450SL
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Discussion Starter #15
Sorry

sorry for not getting back gentleman. I am new to any kind of fuel injection and when I wrote the original post, I will say before investigating, that what it acted like that it ran out of fuel,sense I have read the pertinent parts of the manual posted here and with your assistance I now have a better understanding of the system.After a couple hours of testing fuel pressure and eliminating, I started on electronics and traced it to the 4 ohm resistor. Lesson learned go to manual before you start asking question. Thanks again for all your assistance
 
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