Author Topic: Fuel Injector? Fuel Injection Pump?  (Read 5411 times)

vande17941

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Fuel Injector? Fuel Injection Pump?
« on: August 26, 2014, 04:51:34 »
I have a 230sl (1966) that is fouling one of the plugs consistently because that cylinder is running way too rich.

Is it possible or likely it could be a bad injector causing the rich condition in that cylinder? I'm worried that it could be the fuel injection pump....but could that cause only one cylinder to be rich?

I'd like to get some advice from some of the guys on here that have experience and know their stuff.

FYI- All the ignition components are in top shape, compression is 150-160, leakdown is about 17%.
Thanks.
'66 USA (1967 model Year) 230sl, 4-speed Manual, Driven Like a Real Car! Set up with KYB Stiffer Shocks, and Motor Mounts w Urethane Inserts Underneath, 3-point Belts, Headrests Installed 🚗

1986 560sl Cabernet & Palomino (not recommended)

2001 SLK320 Sport AMG Silver & Black

Jonny B

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Re: Fuel Injector? Fuel Injection Pump?
« Reply #1 on: August 26, 2014, 16:25:53 »
What cylinder is experiencing the fouling? Is this a new issue, just occurred, getting worse? Automatic? Original injectors? Inj pump ever rebuilt? A few more details will help the experts assist.
Jonny B
1967 250 SL Auto, DB 568
1970 280 SL Auto, DB 904
1966 Morris Mini Minor

vande17941

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Re: Fuel Injector? Fuel Injection Pump?
« Reply #2 on: August 27, 2014, 03:13:35 »
This is a 230sl with 52k original miles...has never had the head off, never had the injectors or pump off. I'm suspecting that it has disintegrated valve seals and I'm actually oil fouled in the cylinder. I went with a w9dc plug and it improved Once I get it hot and run it hard,...it runs awesome. Compression and leakdown are awesome.
I'm thinking I will test the injector for proper flow, and then consider a valve job that I need to do anyway.
'66 USA (1967 model Year) 230sl, 4-speed Manual, Driven Like a Real Car! Set up with KYB Stiffer Shocks, and Motor Mounts w Urethane Inserts Underneath, 3-point Belts, Headrests Installed 🚗

1986 560sl Cabernet & Palomino (not recommended)

2001 SLK320 Sport AMG Silver & Black

ja17

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Re: Fuel Injector? Fuel Injection Pump?
« Reply #3 on: August 27, 2014, 05:45:17 »
Yes, check the injector.  At 52K You should not need head work.  Maybe remove the valve cover and use a flashlight to see iif the valve seals on that cylinder are still seated on the valve guides.
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

garymand

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Re: Fuel Injector? Fuel Injection Pump?
« Reply #4 on: August 27, 2014, 20:57:05 »
Just one plug, huh?   ::)  Not too bad I think.  1st swap injectors.  If it doesn't follow the injector, take a look at the valve guide seals.  They can be replaced with the head inplace.
Gary
Early 250SL German version owned since 71, C320, R350, 89 Porsche 944 Turbo S

vande17941

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Re: Fuel Injector? Fuel Injection Pump?
« Reply #5 on: August 30, 2014, 06:45:44 »
Thanks everybody. I will pull it apart this weekend and check the valve seals and the injector
'66 USA (1967 model Year) 230sl, 4-speed Manual, Driven Like a Real Car! Set up with KYB Stiffer Shocks, and Motor Mounts w Urethane Inserts Underneath, 3-point Belts, Headrests Installed 🚗

1986 560sl Cabernet & Palomino (not recommended)

2001 SLK320 Sport AMG Silver & Black

vande17941

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Re: Fuel Injector? Fuel Injection Pump?
« Reply #6 on: September 28, 2014, 08:52:38 »
Figured it out...wasn't running rich. Pulled the head and saw the #4 cylinder exhaust valve was missing the stem seal. Also, the valve guide was slipping up/down acting as an oil pump into the cylinder. At the machine ahop...can't wait to get her back together.
'66 USA (1967 model Year) 230sl, 4-speed Manual, Driven Like a Real Car! Set up with KYB Stiffer Shocks, and Motor Mounts w Urethane Inserts Underneath, 3-point Belts, Headrests Installed 🚗

1986 560sl Cabernet & Palomino (not recommended)

2001 SLK320 Sport AMG Silver & Black

ja17

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Re: Fuel Injector? Fuel Injection Pump?
« Reply #7 on: September 29, 2014, 13:20:56 »
Yes you will have to order an oversize valve guide. Have the head checked for flatness since a loose valve guide is often caused by overheating. However, only mill the head as needed.
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

Shvegel

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Re: Fuel Injector? Fuel Injection Pump?
« Reply #8 on: October 09, 2014, 01:14:06 »
I second Joe's advice to not mill the head unless needed.  Also if I remember correctly the new valve guides are stepped at the top tp keep them from dropping into the cylinder head.  I would replace them all.