Power Loss - 560SEC - PeachParts Mercedes-Benz Forum

halman2228 · #1 12-21-2009, 02:47 PM

Alrighty Forumites...

I've searched (but maybe not deep enough) to find the same situation...

Started her up on a chilly morning (32 F) and tooled up the road 2 miles for a cup of joe. Leaving from a stop light halfway there, it seemed to have no power as in no acceleration except slow and steady to about 2000 rpm under load.

Got her home and tried to redline (in PARK) and it would only (and slowly) rev to about 4000..idle is normal, no stalling or hesitation or anything else to report.

New OVP, plugs, dizzy cap and wires; known good FPR.

Is the fuel filter the usual suspect or what else should I be thinking?

'86 560SEC with 96,400 miles; recent addition to my stable; probably the original filter (I will change regardless but looking for input RE: other possible causes); no maint records

Best regards,
Kevin

jhodg5ck · #2 12-21-2009, 03:32 PM

w/o being there to fiddle with things fuel pressure would be a good place to start... You can pull the lines, jumper the relay and see how much flow you get in 30 seconds. I forget the spec off hand, but it's in the service discs if you have them

How are engine temps?

Jonathan

halman2228 · #3 12-21-2009, 05:10 PM

I forgot about that.

Engine temp did not reach "normal" (usually reads right at 82C) - it got up to maybe 50C...

Ambient was about 35F following a cold night (low to maybe 30F).

Your flow test suggests you think a fuel pump nearing its end?

Regards,
Kevin

jhodg5ck · #4 12-21-2009, 05:21 PM

it's a good place to start!~ Also, if a temp sensor is out/KE not sending the correct signals power can be Severely limited.

Does it do the same thing, consistently?

Jonathan

halman2228 · #5 12-21-2009, 05:33 PM

It did it the rest of the way to the coffee stop, then the 2.2 miles home. Tried revving in park in the back yard the one time but couldn't get back to it the rest of the day.

I'll see what it does tonight.

Kevin

jhodg5ck · #6 12-21-2009, 06:05 PM

Yes, I was just curious if you had any further tests/drives to confirm it as a consistent problem, ideally I'd like the car to get up to 80C and see if it's still funky.

Jonathan

hookedon210s · #7 12-23-2009, 11:29 AM

Is the throttle opening fully? Plastic bushings (see link below) on the throttle linkage are known to fail which can prevent full throttle. Mark

http://catalog.peachparts.com/ShopByVehicle.epc?q=1986-Mercedes--Benz-560sec-Fuel--Injection&yearid=1986%40%401986&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6301%3AMBC%7C1546%3AED%7C10000060%40%40560SEC&catid=240621%40%40Fuel+Injection&subcatid=240696@@Throttle+Bushing&mode=PA

halman2228 · #8 01-01-2010, 11:30 AM

...holidays, out-of towners, etc.

Anyway, new fuel filter yesterday - no change. Temp got up to near normal (just short of 80c).

Still no power, won't downshift on pedal stomp. Tranny now shifts very early and vac gauge seemed to be further to the right...

If it gets warm enough today, I'll check and lube the throttle linkages, examine that/those plastic bits and see if I can do a flow test

Which temp sensor (and its location) is involved?

Happy & Healthy New Year to all!,
Kevin

halman2228 · #9 01-27-2010, 01:02 PM

.. in posting the results.

It sometimes is so simple you don't think to check...

Throttle linkage was binding up from crudded/dried up grease. Lubed 'er up as best I could in the cold and she's back to normal.

It needed a new fuel filter anyway at 100K ODO. Looks like I have to schedule a warm weather linkage clean up and adjust project.

Regards,
Kevin

Hit Man X · #10 01-27-2010, 11:39 PM

Ooooooo you own an R107 280SL AND 300SL, I am green with envy!

An older Asian lady near me owns an R107 300SL I desire. I put a note on the windshield that in the event she wishes to sell, I would like to have first right of refusal. Never heard back, sadly.

halman2228 · #11 01-28-2010, 09:45 AM

I have the a 500SL and 280 (both Euros).

I talked my brother into buying the '86 300Sl (Signal Ed, black softop 7 tan insides w/36K miles). The bonehead has put about 300 miles on it in 2 years.

Regards,
Kevin

tinypanzer · #12 01-29-2010, 06:05 PM

A couple of things that get overlooked - Inspect your gas pedal! The plastic nub at the top where it joins the pedal rod can and will break. When it does, you step on the pedal but almost nothing happens. Check that.

Also, if your engine isn't getting to temp, there's a possible stuck open thermostat. Usually that makes the car run rich, and power loss isn't what you get from that typically. If a temp sensor is bad, that can be a big issue.

Fuel delivery can be an issue. If the fuel pump and filter are good, sometimes the fuel accumulator will rupture internally causing fuel pressure loss. However, that typically presents with cold-start problems too since fuel pressure will bleed off completely overnight if the accumulator is ruptured.

I would start by making sure that your accelerator is actually opening the throttle plate. There are several linkages in that throttle setup and plenty of places for it to jam up.