I am changing the fuel injector O rings on my 90 300 SEL and when the injector is out there is a black rubber seal I am going to call it. How do these things come off to put the new ones on? There is a black hard plastic clip that looks like it is made on the inj. but I have new ones so they must come off somehow. Any suggestions?

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1987 300 TDT
1990 300 SEL

Break it off...the new seal slides on. It's probably rock hard after a number of years of heat.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Ya I figured that out. I think she is leaking down on the seals and losing fuel pressure

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1987 300 TDT
1990 300 SEL

It won't lose fuel pressure -- it will be a vacuum leak though.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

OK, I have a question. I have the Inj. out and am changing the seal/o-rings. I decided to check the injectors so I hooked up to a line and rolled over. Nothing. No fuel sprays out of the injectors. I disconnected the fuel line in to the pump and there is fuel there, there is also fuel on the return line. Is there supposed to be spray from those inj when just hooked like that? I thought I could have a look at the pattern to see if the inj was good, crude I know but effective maybe. So what is wrong? what do I check next? I can safely say the F Pump is working and the filter is not plugged.

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1987 300 TDT
1990 300 SEL

You need to jump the fuel pump relay first. Pins 87 and 15, then turn on ignition. Depress throttle plate and it should flow.

I just did it a few days ago. Video here:
http://www.youtube.com/watch?v=NyqTNyl99ZQ

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Should I get just an initial spray when the ignition is cycled and the f pump kicks in momentarily?

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1987 300 TDT
1990 300 SEL

No, fuel pressure doesn't equal delivery, it must be metered through the fuel dist.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

OK, mine is a 90, it does not have a fuel relay. Where do I jump the pump?

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1987 300 TDT
1990 300 SEL

Isn't it combined with the Klima or MAS? Not sure...do a search on it.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

In front of the brake master cyl. there is a three pin connector on the firewall. Unplug it with the key on.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff