Why does my SLC 5.0 have no power? - PeachParts Mercedes-Benz Forum

alabbasi · #1 02-22-2009, 05:42 PM

I’m a little stumped regarding my 450SLC 5.0. The car now runs smooth and idles well but does not seem to have much power. The idle mixture seems good and it revs without issues. I’ve gone through and cleaned the injectors and it has a new pump and filter. I also have replaced the coil, plug wires, plugs and rotor. It should have plenty of spark and plenty of fuel, yet it feels like it has very little. With the other SLC’s, I can smoke the tires at standstill. No chance with this one.

Any thoughts?

450slcguy · #2 02-22-2009, 05:55 PM

Quote:

Originally Posted by alabbasi

I’m a little stumped regarding my 450SLC 5.0. The car now runs smooth and idles well but does not seem to have much power. The idle mixture seems good and it revs without issues. I’ve gone through and cleaned the injectors and it has a new pump and filter. I also have replaced the coil, plug wires, plugs and rotor. It should have plenty of spark and plenty of fuel, yet it feels like it has very little. With the other SLC’s, I can smoke the tires at standstill. No chance with this one.

Any thoughts?

Advance your timing a few degrees, should see a noticable change. Perhaps-enrichen your mixture a bit. One or both will show results, re-adjust your idle afterwards if needed. Make sure you know where you started from on both so you can return if need be.

alabbasi · #3 02-22-2009, 05:59 PM

Quote:

Originally Posted by 450slcguy

Advance your timing a few degrees.

Yeah but i'm talking about a lot of power. It is seriously lacking.

450slcguy · #4 02-22-2009, 06:05 PM

Quote:

Originally Posted by alabbasi

Yeah but i'm talking about a lot of power. It is seriously lacking.

What's the recommeded timing? Have you checked it recently? Could make a BIG difference.

Tweek the enrichment up 1/4 CW, slowly. Could make a BIG difference.

Either way, both are 5 minute adjustments that cost nothing and could make a huge difference. If that don't help, nothing lost.

t walgamuth · #5 02-22-2009, 06:10 PM

I agree it sounds like a classic case of retarded timing.

450slcguy · #6 02-22-2009, 06:26 PM

Also check your ignition coil, could possibly be weak spark. Mine was the original when I got the car. Did the usual plugs, wires, cap, rotor, figured what the hell replace the coil too. If yours is original/old, replace it. Got the Bosch replacement for like $30 bucks, haven't looked back.

alabbasi · #7 02-22-2009, 06:30 PM

Thanks, Coil is new. I will check the timing though.

wolf_walker · #8 02-22-2009, 07:44 PM

Clogged cat will do that kinda thing too if you have one.

alabbasi · #9 02-22-2009, 09:20 PM

Thanks guys, I have a rubbish timing light at the shop but I will try to pick up another one with the advance feature so that I can check the timing.

250 Coupe · #10 02-23-2009, 12:06 AM

Coil polarity can also cause power loss. There is a test you can do with a pencil in the spark gap but you'd have to google it to be sure how to check it.

Michael

t walgamuth · #11 02-23-2009, 06:03 AM

Also It could have the static timing right on but lack normal advance function...

sjefke · #12 02-23-2009, 12:17 PM

If timing is not it, check for air leakage along gasket of inlet manifold (anywhere between throttle valve and engine body). Car will run well at idle, but as soon as you put power on it, mixture will get weakened by air sucked in. Not sure whether this is possible on your MB, but I had it with my MGC after restoring it. Ran smooth at idle, but drove without much power. Chased timing, etc., but got solved when I tightened the inlet manifold. If you have ever seen the factory MGC inlet-exhaust manifold set up, you know how easy this can happen...

Bert

alabbasi · #13 02-23-2009, 07:13 PM

I think the timing was too far advanced. I turned the distributor anti clockwise the the engine began to rev better. I took it for a spin and it definitely had more guts. I need to fine tune it. I have a cheapo timing light but I have ordered a better light online.

Anyone know what the timing specs are?

450slcguy · #14 02-23-2009, 07:52 PM

Quote:

Originally Posted by alabbasi

I think the timing was too far advanced. I turned the distributor anti clockwise the the engine began to rev better. I took it for a spin and it definitely had more guts. I need to fine tune it. I have a cheapo timing light but I have ordered a better light online.

Anyone know what the timing specs are?

I don't know what year your SLC is, but mine is a 1980 4.5 . Spec. is 10 btdc. Not sure waht the 5.0 SLC would be though.

250 Coupe · #15 02-24-2009, 01:09 AM

The spec should be listed on the radiator support. My 450SEL is supposed to be at 0 IIRC but I'm running at at least 10 BTDC to get it to idle well and have all the power a smogged '76 motor can have.

Michael