My 4.5 is running rough - PeachParts Mercedes-Benz Forum

Litton · #1 11-06-2004, 09:13 PM

Recently I moved to a new house, bought a 560SL and my poor 280 SEL has been taking a second fiddle to all the other activities. Ehen I bought the 560SL, my wife said 'ONLY ONE TOY" and the 280 must go. Like any dutiful husband I listed it and the response has been OK but the care has been starting hard since it got cold.......I thought the trigger points need to be cleaned so today I pulled the dizzy and removed the trigger point module. (It comes out the side) They looked really great so I just cleaned everything up an put it back togeather.

To make a long story short.....the car that was running perfectly is now a 7 cylinder and I have a chap coming out tomorrow to look at it. CRAP.

I can not remember where #1 cylinder is for timming. Is it on the passenger side or the driver side? I set the timing using the passenger side as that is where the wire goes that lines up with the mark on the dizzy. It starts and idles just fine, but doesn't run under load worth a hoot.

Any suggestions would be appreciated.

psfred · #2 11-06-2004, 11:24 PM

#1 is on the passenger side.

Sounds like you need to clean the trigger points again with some brake parts spray, and clean the ignition points with a new dollar bill.

Make sure the connector for the trigger points is all the way on.

Peter

Tomguy · #3 11-07-2004, 03:16 AM

I seriously hope you didnt clean them with anything abrasive, or you WILL need to buy new ones!

All your injecors firing? To check, listen through a screwdriver (hold it up against the injector base and listen to the handle, you can hear the tick if it fires). If any miss, which ones? remember they fire in pairs (1+5, 2+4, etc) so if you find 1 matching pair not firing it means either a bad ground or bad points/connection.

You set timing with the vac line connected right? If so, yank it off - does the idle speed jump noticably? If not, plug the line and set it at 7°BTDC instead.

Major vac leaks? Can you hear any air hissing around the engine at idle (with the air filter housing on)?

Litton · #4 11-07-2004, 09:38 AM

The trigger points look real clean, just a tiny bit of built up crud around the phonelic things that ride on the shaft. Can not get at the points very easy as the plastic cover get in the way. Cleaned the module with carb cleaner then followed up with contact cleaner. Lubed the pads with a bit of tranny fluid (they were nice and soft). Cleaned the connector with contact cleaner.

Ignition is Pertronix so that should not be an issue. Timing was set at ~5 ATDC with vac off.....goes to ~7 BTDC. Vacuum is good.

I will listen to the injectors in a bit. I usually wait until after 8:00AM on a Sunday before starting projects.

Tomguy · #5 11-07-2004, 10:33 PM

Quote:

Originally Posted by Litton

Timing was set at ~5 ATDC with vac off.....

hope that's a typo, otherwise, there's one of your problems. While you disconnect the vac on many American cars when setting the timing, you need to leave it connected when setting your 4.5!

Litton · #6 11-08-2004, 01:53 PM

Yep, it was a typo. Finally solved the problem.....it was a fouled plug in #3 cylinder. I can not for the life of me figure out why that happened when it was running great before I did the trigger points and wasn't afterwards. This should have been an unrelated issue.

All is well now and the guy didn't even come out an look at the car.....oh well, I told my wife I would sell it, I just didn't say when. It is such a joy to drive, I am in no hurry.

buch32 · #7 11-08-2004, 06:37 PM

Quote:

Originally Posted by Litton

Recently I moved to a new house, bought a 560SL and my poor 280 SEL has been taking a second fiddle to all the other activities. Ehen I bought the 560SL, my wife said 'ONLY ONE TOY" and the 280 must go. Like any dutiful husband I listed it and the response has been OK but the care has been starting hard since it got cold.......I thought the trigger points need to be cleaned so today I pulled the dizzy and removed the trigger point module. (It comes out the side) They looked really great so I just cleaned everything up an put it back togeather.

To make a long story short.....the car that was running perfectly is now a 7 cylinder and I have a chap coming out tomorrow to look at it. CRAP.

I can not remember where #1 cylinder is for timming. Is it on the passenger side or the driver side? I set the timing using the passenger side as that is where the wire goes that lines up with the mark on the dizzy. It starts and idles just fine, but doesn't run under load worth a hoot.

Any suggestions would be appreciated.

If you still have the car please advise the info a buyer would need. Thanks