Author Topic: Fuel issues, please help a newbie!  (Read 289 times)

RobParkerMB

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Fuel issues, please help a newbie!
« on: August 31, 2025, 15:56:04 »
Skipping most of the story, I have no fuel coming out of a couple of IP outlets. Can you see in this picture a stuck plunger, or do I have to remove more parts?

Out of the two with their fittings off, the left one was producing fuel, the one on the right was not. Yet both looks the same. And nothing moves when turning the engine by hand.

I'm a decent home mechanic but haven't worked on one of these before so I don't fully understand which bits are meant to move and not.

Any help greatly appreciated.
1964 230sl
1998 sl320
2003 e320
2010 e350

rwmastel

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Re: Fuel issues, please help a newbie!
« Reply #1 on: August 31, 2025, 19:22:13 »
I'm sure you'll get some good advice.

I'll say that I've been in this group since before we started a website 23 years ago. I'm a basic DIY mechanic who's brave enough to try new things.  I wouldn't touch the inside of the fuel injection pump without multiple experience people agreeing on the same advice and instructions. Tread lightly.
Rodd

Did you search the forum before asking?
2017 C43 AMG
2006 Wrangler Rubicon
1966 230SL auto "Italian"

RobParkerMB

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Re: Fuel issues, please help a newbie!
« Reply #2 on: August 31, 2025, 19:42:47 »
Well it already doesn't work so I have little to loose before forking out 3k for a refurbished one
1964 230sl
1998 sl320
2003 e320
2010 e350

Lori

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  • 1968 280SL (US)
Re: Fuel issues, please help a newbie!
« Reply #3 on: August 31, 2025, 20:39:00 »
There is more than 1 type of injection  pump in these cars so it would be helpful to get more information. 
Here is one thread that has a lot of info

https://www.sl113.org/forums/index.php?topic=886.0

Lori
1968 280SL (US)

rwmastel

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Re: Fuel issues, please help a newbie!
« Reply #4 on: August 31, 2025, 23:40:40 »
And, once you join as a full member:

https://www.sl113.org/wiki/Fuel/Injection
Rodd

Did you search the forum before asking?
2017 C43 AMG
2006 Wrangler Rubicon
1966 230SL auto "Italian"

ja17

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Re: Fuel issues, please help a newbie!
« Reply #5 on: September 01, 2025, 04:49:26 »
Your looking down on the check-valve assembly. It  threaded on the outside. Find a fitting to scew onto it so you can pull it out. Below you will fine a cylinder and plunger (piston). The pistons get stuck in the up position and then do not pump fuel and cause the rack to stick also. Use penetrant and a blunt soft metal or hardwood drift to knock the pistons downward. Turn the engine and repeat until the pistons return down on their own. Eventually you may be able to free them up. When the pistons become free the rack will move freely also! Re-install the check valves. Torgue the fittings in place to 21 ft/lbs. (important)







Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

RobParkerMB

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  • United Kingdom, England, Taunton
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Re: Fuel issues, please help a newbie!
« Reply #6 on: September 01, 2025, 06:01:19 »
Really helpful advice from everyone, thank you.
I have ordered what I think is the right thread to pull out the check valves, so will give that all a go.

I've just replaced all the fuel lines, electric pump and the tank itself, so I'm really hoping this will now get it going.
1964 230sl
1998 sl320
2003 e320
2010 e350

BobH

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Re: Fuel issues, please help a newbie!
« Reply #7 on: September 01, 2025, 08:22:00 »
Hello Rob, there are a couple of helpful links on here

https://www.sl113.org/forums/index.php?topic=39147.msg285761#msg285761
February 1965 230SL Automatic
UK delivered RHD
Papyrus white, blue hard top & hub caps
Blue soft top
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RobParkerMB

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  • United Kingdom, England, Taunton
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Re: Fuel issues, please help a newbie!
« Reply #8 on: September 01, 2025, 13:27:37 »
1964 230sl
1998 sl320
2003 e320
2010 e350

rwmastel

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Re: Fuel issues, please help a newbie!
« Reply #9 on: September 01, 2025, 21:33:35 »
The pistons get stuck in the up position and then do not pump fuel and cause the rack to stick also. Use penetrant and a blunt soft metal or hardwood drift to knock the pistons downward. Turn the engine and repeat until the pistons return down on their own.
How do these pistons normally return down?  Spring?  Vacuum below?  Fuel pressure above?
Rodd

Did you search the forum before asking?
2017 C43 AMG
2006 Wrangler Rubicon
1966 230SL auto "Italian"

ja17

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Re: Fuel issues, please help a newbie!
« Reply #10 on: Today at 04:23:01 »
They return back down from a spring below.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

 

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