1968 280SE - Wierd MFI pump - PeachParts Mercedes-Benz Forum

Doc Vegas · #1 02-02-2013, 04:06 PM

Hello Folks:

I picked up a beautiful '68 280SE. Only issue right now is that it smokes pretty bad ONLY when accelerating. Even on a cold start after weeks of sitting, no smoke unless I hit the throttle. I realize it could be valve seals or rings, but I doubt this for several reasons (but could be...). My suspicion is that it is running rich. I have the shop manuals, did a search, and one member even tried to help. Odd thing is that the back of my MFI pump does not have the adjustment screw as shown in the shop manuals and described by others. This is the rear of the MFI (facing the firewall). Instead of the screw adjustment handle, mine just has what appears to be a large bolt head. Above that are two selenoids. The rest of the pump looks 100% identical to the manual. Any ideas?

Anything I can do to rule in/out the fuel injection being rich versus valve seats/seals? This car was LOVED by an enthusiast and it is hard to imagine that he left it with bad seals/rings considering the thousands that were spent elsewhere and the stacks of manuals, receipts, and other details. It did sit for a few years before I got it. Starts up instantly with no smoke, but hit the gas and a cloud comes out the back.

Thanks!

280SE Guy · #2 02-02-2013, 05:15 PM

Although this pump only has one solenoid the placement of the mixer knob would be the same as yours, it is below the solenoid pictured:

Don't turn the knob unless you know what you are doing.

Regards,

280SE Guy

Palolo · #3 02-02-2013, 10:49 PM

Any chance you can slither a phone in there and snap a pic?

I can think of two scenarios; someone backed it off so far that it came off, or they put on a blanking plate and the adjustment inside is full-rich.

The smoke you get is black, right?

Have you looked at plugs?

Cheers,

Pat

wbain5280 · #4 02-03-2013, 10:56 AM

Don't turn the knob especially when the engine is running. Don't adjust any stop screws, on the injection pump or venturi.

Please see Welcome - Mercedes Benz 230SL, 250SL, 280SL Pagoda Group. The injection systems are the same. There are instructions on properly setting the linkage rods. If you don't know what your doing, don't touch the injection system.

Doc Vegas · #5 02-03-2013, 11:21 PM

Thanks guys! I will do my reading tonight. Indeed I found the adjustment knob, it simply was not visible from my vantage point from the fender. I jacked up the car and could see it from underneath.

Let me do my homework, then report back.

Thank you!

Doc Vegas · #6 02-04-2013, 01:11 AM

Yes, these look odd. Like something is melting around them.... have a look.

Any ideas????????????

Doc Vegas · #7 02-04-2013, 01:12 AM

Lucky #6

mercmad6.3 · #8 02-04-2013, 04:23 AM

Normal color but those plugs have thousands of miles on them . Time for a change.
Check the Porsche archives here for MFi adjustments. it's mostly for the porker crowd but the system is adjusted identically on the mercedes systems.

Doc Vegas · #9 02-18-2013, 11:39 PM

Gentlemen:

Because I have only a week to pass smog before my temporary plate runs out, I decided to call in the pros. They told me it needs a new fuel injection pump and quote around $5000. For now, the leaned out the MFI and increased the air to get it lean enough to pass. Idles really high now and shuts down at stop lights. Sucks. Ran better before they messed around.

I looked over the service manual and I just do not get it. Complicated design, but what could failing to make too rich???

Any advice would be GREAT appreciated!!!

Thanks

mercmad6.3 · #10 02-19-2013, 12:36 AM

Never trust "experts!" There aren't too many of us left actually..

if it stalls at the lights it's too lean. If it is idling too high,it will be running lean because they have screwed the air by pass screw out too far. Screw it back in again .
If it is still stalling the nerxt step is a cheater move. The link to thev pjump itself can be shortned so the pump is slightly opened . This means that the throttle is closed but the pump is beginning to pump fuel. It will still idle ok but shouldn't stall as easily.
it's hard to diagnose a system after someone else in another country has messed with it .

mercmad6.3 · #11 02-19-2013, 12:41 AM

Never trust "experts!" There aren't too many of us left actually..

if it stalls at the lights it's too lean. If it is idling too high,it will be running lean because they have screwed the air by pass screw out too far. Screw it back in again .
If it is still stalling the nerxt step is a cheater move. The link to thev pjump itself can be shortned so the pump is slightly opened . This means that the throttle is closed but the pump is beginning to pump fuel. It will still idle ok but shouldn't stall as easily.
it's hard to diagnose a system after someone else in another country has messed with it .
As i mentiioned before,Pelican parts has a really data base of anything you would need to know. It does deal with the Mfi as bolted to Poerkers but it's exactly the same syastem as fitted to MFi mercedes engines. Same principles of repair apply.
Pelican Technical Article: Mechanical Fuel Injection Troubleshooting and Adjustment - 911 (1969-73) -

if your expert can find a pump for 5 grand I will take a few. Last time I got a price for the 8 plunger pump it was $48,000 .

Palolo · #12 02-19-2013, 02:37 AM

Quote:

Originally Posted by mercmad6.3

Never trust "experts!" There aren't too many of us left actually..

yeah, ain't that the truth. ASE Cert does not mean someone can experiment with my M130.

Quote:

Originally Posted by mercmad6.3

if your expert can find a pump for 5 grand I will take a few. Last time I got a price for the 8 plunger pump it was $48,000 .

Can't the M130's IP be "rebuilt" for less than $2000?

I think "280SE Guy" had his redone, and calibrated, too.

mercmad6.3 · #13 02-19-2013, 02:41 AM

yes, that is true. In fact i dont think I have ever heard of anyone buyiong a new pump . There are two places in the USA who rebuild them for around $2000 and often it's less if the pump only needs recalibrated.

Doc Vegas · #14 02-20-2013, 07:57 AM

Thanks again. Indeed the shop's leaning of the mixture (increasing the air and idle) did allow my beloved 280SE to pass emissions. Thus, I can go forward with finally getting a license plate. However, it ran horribly and continued to stall. I took it back to the shop and they returned the system to "normal" setting. It seems better but continues to blow smoke on "hard" acceleration or at high RPM. I love the car and hope to get to the bottom of the issue. Would you agree with the shop that the issue is not likely oil or coolant as I (we) originally suspected???

Thanks