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Discussion Starter #1
The flex line going to the filter on my 92 300SL had a leak so I removed and replaced it. I had expected this to be an easy fix, but I can't get the car started. I thought maybe there was air trapped in the filter/lines, so I hotwired the fuel pumps and ran each of them a minute or so, but I can't get the car to fire. Any thoughts or suggestions? I've no idea where the fuel pump relay might be, just in case it needs to be swapped out.
I'm going back out now to give it another go, but I'm running out of ideas.
Thanks
Mark
 

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Discussion Starter #2
Its been a week and my car still isn't running. I need some assistance here. I've jumpered the pumps and both run, although one makes a little more noise than the other. I also pulled off the return line from the accumulator, the one by the pumps, and ran the pumps for a couple of minutes; I got no fuel out of the return side at all, so is that telling me the pumps are running, but just not putting out sufficient pressure? I checked and I do have spark, and the car will run on starting fluid, but that's it. I also cracked the fuel line connections at the FI unit and I get fuel spraying out, so I know some pressure is getting to the FI unit. I'm left with the option of replacing one of several expensive parts, which is not an appealing method of resolving this problem. Anyone with some experience in this area and an idea or two to help identify the problem would be very much appreciated!! I do not have a manual so I'm operating a bit in the blind.
thanks
Mark
 

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00 SL500 SOLD, 05 SL600 Sport, 09 Silverado 4x4 LTZ,SOLD '15Silverado LTZ 6.2 8Speed John Deere 318
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If you have fuel pressure at the pump, And spark is OK, I would have to GUESS that you should be able to get fuel back the return line. Is there any way to check and see if you are getting fuel to the injectors? (I bet your not) I just don't know why???? Also, Please fill out your PROFILE when you get a chance, Thanks!!!
 

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Greek God of the R129
SL500-500SEL-190E
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8,372 Posts
I don't know your car spec.
But I would start flushing the line from the connection by the engine, hose in a container prime the pumps, I suspect being stopped up at the fuel regulator/distributor there must be a screen in there.
Or I hope not, the screens on the injectors. ( more work)
All you did was to replace the hose and filter, right? and the car was running good before.
So the only thing possible thing is crap traveling up in the line.........
Regards.
aam.
 

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Discussion Starter #5
I have fuel, under some pressure, at the inlet and outlet of the injector module. What I am not getting is any fuel coming through the return accumulator by the pumps. At the moment, my thought is that one of the pumps has gone bad, so I do not have enough pressure for the injectors to function well. What would be the point of having a return on that accumulator if it wasn't to get rid of excess pressure produced by the pumps in low demand situations? Since I ran the pumps continuously for a couple of minutes that should have built up plenty of pressure. Maybe I'll try to buy a fuel pressure gage today. Any idea what the fuel system pressure is supposed to be?
 

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1990 500SL
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My 500 ran fine on one pump untill you really put your foot into it. There is a screen on the inlet to the fuel distributor and it is very fine. I would give that a look. Good luck!
 

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Discussion Starter #7
Problem solved. The "new" fuel line, the one I had made at a local shop so that I wouldn't have to wait for a mail order one, was blocked. When I checked for fuel pressure at the FI unit, I had cracked the line between the FI unit and the fuel pressure regulator, so it had fuel pressure there. I took the inlet line off, ran the pump, and then discovered that nothing was coming out of the fuel line. When I had checked at the pumps, I had cracked the line at the filter outlet, which had plenty of pressure.
 

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2007 CLS 550, 1998 Harley Road King, 2011 F-150 EcoBoost, '65 Shelby Cobra
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A good news ending. That is how the forum and our members work together. :thumbsup:
 

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Greek God of the R129
SL500-500SEL-190E
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8,372 Posts
Problem solved. The "new" fuel line, the one I had made at a local shop so that I wouldn't have to wait for a mail order one, was blocked. When I checked for fuel pressure at the FI unit, I had cracked the line between the FI unit and the fuel pressure regulator, so it had fuel pressure there. I took the inlet line off, ran the pump, and then discovered that nothing was coming out of the fuel line. When I had checked at the pumps, I had cracked the line at the filter outlet, which had plenty of pressure.
Ahaaaaaa.
You didn't say anything about that new crappy line.

Soooooo you wanted to run a test on us.
See if we do know our shit.

I am joking with you.
I am glad that you fixed it.

Regards.
aam.
 
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