1980 450SL - Mechanic says I need new fuel distributor - advice appreciated

[supercanuck]

So here's the 411:

My 1980 450sl has been running pretty poorly lately, with the following symptoms:

• Running sluggish
• Poor MPG
• Rough Idle
• White smoke and gas smell out of exhaust

So I gave in and took it to my local mechanic. After an hour inspection, they diagnosed it as the fuel distributor dumping too much fuel into the #8 cylinder, and told me that I need to get a new fuel distributor.

Before I do that, I wanted to get some feedback on a couple of questions I have:

1. Can it be repaired?
   Is there any way that the particular problem that it's having can be repaired without having to replace it with a new distributor? I don't know the full functionality of it yet (i'm researching it), but is it possible that the fact that it's only dumping fuel into one cylinder mean that the whole thing isn't busted and can be fixed?
   
2. Experience with re-manufactured units
   So I've also started researching what my best option is for replacing it, if that is what I need to do. Instead of $1,800 for a new one, I've seen re-manufactured units offered for the $400 - $500 range. Has anyone had any experience with these, or give me any advice for things to check out to make sure it's in good shape?
   
3. Can I do the replacement myself?
   My mechanic also told me that it would be about a 2 1/2 job to replace the distributor with the new one. Is this a job I can do myself at home, or does it require skill beyond those of your evening mechanic?

Thanks for your help!

[450slcguy]

When was the last time the O2 sensor was replaced? Try adjusting the air/fuel mixture a bit richer.

[Lexxani]

if you send me a PM I can snag one from the yards around here, they are plentiful, and in rather good shape. Cost+shipping (actual). . .

[supercanuck]

Originally Posted by 450slcguy

When was the last time the O2 sensor was replaced? Try adjusting the air/fuel mixture a bit richer.

To be honest, I'm not sure when if/it was ever replaced. The O2 light is on, but from what I had read before, that didn't mean too much after about 60,000.

Say it does need to be replaced...is that potentially something that could make the fuel distributor 'appear' to be faulty?

Thanks!

[sublettd]

My guess is this is a job you can do yourself--IF you can get the two screws that hold the FD to the throttle body busted loose. Get you a wide/thick blade screw-driver and see if you can break the screws loose. I watched my experienced MB mechanic wrestle the screws on mine for over a half hour before getting them broken loose. You'll learn what you need to install it by removing same.

However, the FD may not be the problem. On my car, the FD only does what it is told to do by the warm-up regulator (WUR). Don't know if yours has a warm-up regulator on it or not, but after replacing the FD, injectors, warm up regulator, fuel pump, fuel accumulator it turns out the rebuilt WUR that was put on the car was not holding pressure. Thus, causing the rich mixture. Have another WUR that was shipped today and hope that will finally put this problem to rest. It has been close to a year that we have been chasing the problem. But, boy have I learned a lot about this car!!!

I recommend John Hervey at http://www.specialtauto.com to you. His is a one-man operation, so you need to stay abreast of the transaction.

Finally, don't just take a FD or WUR off of any car. The FD has a number on the plate on the back of it and the WUR has a number stamped on the top of it. Try to replace the one on yours with the same number. You'll see the various part numbers on the SpecialTAuto website.

Good luck.

[450slcguy]

Originally Posted by supercanuck

To be honest, I'm not sure when if/it was ever replaced. The O2 light is on, but from what I had read before, that didn't mean too much after about 60,000.

Say it does need to be replaced...is that potentially something that could make the fuel distributor 'appear' to be faulty?

Thanks!

The O2 sensor can make a big difference. Bosch make one for $22 bucks.

[Gurunutkins]

Hi supercanuck
I would be a little wary of this one. generally speaking the FD will put out the same amount of fuel to all of the lines, so saying they are adjustable individually but generally if no one has messed with them the same amount goes to all. the injectors can let different amounts past if they are worn differently. the WUR is generally the biggest problem as it (mainly) controls the pressure that the FD runs at.

personally at this point I would however suspect other things as white smoke is not a indication of fuel burning but of either coolant in the combustion chamber or transmission fluid being sucked out of the transmission into the engine through a bad modulator. I would pull all of my plugs and report back on the colours and condition
cheers
Barri

[mbboy]

Originally Posted by supercanuck

To be honest, I'm not sure when if/it was ever replaced. The O2 light is on, but from what I had read before, that didn't mean too much after about 60,000.

Say it does need to be replaced...is that potentially something that could make the fuel distributor 'appear' to be faulty?

Thanks!

An experienced MB mechanic told me to disconnect the O2 light or remove the bulb after about 30k miles.

[KarTek]

Since I'm relatively unfamiliar with the FI systems on these cars all I can give is a general observation here. White smoke can be fuel boiling rather than burning. How's the ignition? Is it running on all 8? I'm sure the mech. thought about that though...

[450slcguy]

Originally Posted by mbboy

An experienced MB mechanic told me to disconnect the O2 light or remove the bulb after about 30k miles.

That does not mean you don't ever have to replace the O2 sensor. If the car has over 70,000 miles replace it. It's a major component for lambda control.

[Gurunutkins]

got to agree with 450slcguy the o2 sensor is a major part of the system and controls enrichment feedback when normal running. if your o2 sensor is bad it will slowly enrichen the mixture to defaults. most o2 sensors last about 60k miles and then start to be very slow to respond. all narrow band sensors work the same way and so long as you are able to splice wires you can replace them. I just bought 2, 4 wire o2 sensors for $10 off ebay, gm sensors for a suburban as i remember. put one in my jag and one in my mercedes 450sl (I have djet but use it to run an air fuel mix meter). they work just fine
cheers
Barri

[450slcya]

Not to discount all the 'replace the O2 sensor' advice...but in this particular case, according to his post the number eight cylinder is wet. This would not be a sensor issue.

Check the the spark plug at the suspect cylinder and confirm the fuel wet condition. Swap that injector to another cylinder. Run the engine. Check both spark plugs for fuel wet condition. If the wet plug follows the injector, replace the injector. If the wet plug remains at the number eight cylinder, the fuel distributor is suspect.

[supercanuck]

Thanks everyone for all of the advice.

Before I took the car into him, I had been told that the WUR was the most likely culprit, but I had also been told to have the cooling system pressure tested as well, to maybe account for the white smoke.

When I took it in I told him these things and specifically told him about the WUR - when they were done with all of the tests, he said it was only the FD and that everything else, even the WUR were working just fine.

But that's the reason I wanted to put this post up, to check and see what others thought. While I'm trying to get this worked out, I may go ahead and replace the 02 sensor AND WUR, just incase, and see what happens.

Now, another question. With all of this in mind, how bad is it to drive the car for a little while? I realize I'll be getting horrible MPG, but is that pretty much the only major problem, or will doing so cause more damage?

[supercanuck]

Another question...

Fellow forum Member Lexxani has offered to pull a Fuel Distributor from another car and send it to me, however it's from an earlier 450SL with a 117.982 engine.

Will this fit my 1980 450SL with the 117.985 engine, or is the FD specific to this engine?

[450slcguy]

Originally Posted by supercanuck

Another question...

Will this fit my 1980 450SL with the 117.985 engine, or is the FD specific to this engine?

FD is specific to this engine.