1988 300sel Fuel Distributor Problems
 

This is my very first mesage here and would appreciate some help. I recently purchased a used 1988 300 sel MB 179,000miles that was running well until a mechanic decided to give it a tune up. All hell broke loose from there. I have ploughed in about $3000 thus far, trying to fix this old battle horse. My wife is not too happy about it. The problem is that it does not start when the temp gets cold and when it starts, it hesitates when I step on the gas pedal. Sometimes I feel like it need a " choke" or something to help the fuel delivery. I have changed the battery, fuel filter, fuel pump, fuel relay, bought a used fuel distributor (which we suspect is the main culprit), changed the plugs, trans mount, flex disc and idle arm. It is a beauty to drive when it starts but at times when it doesn't I have to repeatedly start or wait for a while before it kicks in. I need help before I consider purchasing a new fuel distributor which is rather pricy. Where can I get a refurbished fuel distributor? Best Regards.......EKOWBEE

Ref: 300sel fuel dist
 

There is a company in Arizona, German Star that sells rebuilt fuel distributors. Price range is about $400 to $500. I have not done business with them but maybe some of the other folks on the forum have given them a try.

The toll free number is 800 377 6598.

Good luck!

thoughts
 

Have you checked your fuel accumulator, idle control valve, and cold start valve? Also, I assume you have completely (and without question) fully verified your ignition system for correct and correctly operating components. Never jump to the fuel system until you have completely and thoroughly verified every aspect of the ignition system, I learned this the hard way.

In all likelihood, your fuel distributor doesn't need changing. If it worked before the tuneup, it's still working. I'd first try to undo whatever this "mechanic" did. Look for loose or broken vacuum lines & fittings. A spray of carb cleaner will cause an increase in idle speed if it hits an open vacuum line.

After that, two things to check right away: duty cycle and coolant temperature sensor.

Check duty cycle when idling warm with a DMM with duty cycle function, $30 at Sears for a Chinese cheapie. It should flicker up & down if everything's ok. If it's steady, there are error codes built into the readings. Caution here: MB uses % off as their numbers, my meter (Sears) uses % on. So 30% on my meter is 70% in the manual. YMMV.

The sensor is the B11/12 sensor all the way at the back of the cylinder head on the left hand side (driver's seat view). Each of the terminals should have some resistance to ground. Both sides are identical, one goes to the fuel computer, one to the ignition. If one side is open, try switching leads, the ignition is less sensitive to temp. A new sensor is about $40. If the open lead was on the fuel side, you'll get an error code instead of a duty cycle reading.

I've got some links with more complete info at home, but you can search on "duty cycle" or "temperature sensor" and find recent threads with these links imbedded. Another on adjusting the EHF has these links.

Jetronic adjustment

General info, ya gotta dig to find.

Try finding what the mechanic did before spending more big bucks. It ran well with the old parts.

Editing to add: Check the resistance of the distributor rotor, it should be about 1kohms. There are rumours of some failing right out of the box.

Best of luck,

I have a 1989 300SE and my problem is that there is a throttle response flat spot when the air temp is normal, 50 - 75 degrees. When it's colder out, I have good throttle response.

I did a search using these parms:

Search: Key Word(s): x11 ; Posts Made By: stevebfl ; Forum: Tech Help and child forums

or: http://www.peachparts.com/shopforum/search.php?searchid=63771

which gives some valuable info.

Since a 'tune up' was done, I'd look for loose connectors or vacuum lines. This FI system is really simple, it's a CIS system with a computer wrapped around it. Fuel pressure is modulated by the EHA, electro hydraulic adjustment valve with the O2 sensor providing feedback. The EHA valve is at the base of the fuel distributor with a connector attached, or maybe not in your case. The computer is inside the car behind the passenger kick panel not between the two firewalls in the middle. That's the ABS computer.