joe b

I have a 1997 E300D with a surging issue. I have spent thousands trying to fix the problem yet no resolve. I have replaced all aspiration, seals, electronics, etc. and the problem still exists. I was driving on the highway the other day and I noticed a consistency in the surging. At 65 mph, the car surges for about 8 seconds, then stops, then 18 seconds later surges again, this is a consistent behavior and it repeats itself in different time intervals at various speeds, yet there is a definite time period between surging. The local dealership had already charged me almost $5,000 in repairs and never fixed the problem, so I no longer take the car there for repairs.
I had been told by a race mechanic that the timing in the fuel pump sounded like the problem but according to the mechanics I have talked to, there is no way to retard the timing, all wanted to replace the fuel pump and that was over a thousand dollars with no guarantees it will resolve the problem. Is there a way to retard the timing of the pump? Is this a realistic fix? Has anyone heard of such an issue?

Carsy

Joe,

It must be an unusual problem as none of the experts of the forum can advise you !!

Thinking outside the box ,I wonder whether it is connected to valve timing ie worn chain or gearing. I had a car with OHV bevel gears which were worn & caused surging when lightly loaded ie driving on the flat. Under load it was OK. How is it under load?

The other thing that came to mind was whether it was your auto gearbox ?

Can't help you with the fuel pump except to say that if its drive is worn it could cause a change in timing.

Any other thoughts on the forum ?

fixbenz

you can adjust the timing of the injection pump, (its better to have the special timing light for this)i had a surge issue on my 97 similar to yours, mine also had a resistor added to the wiring to the pressure sensor, ( resistor was already installed, before i had surge issue) i adjusted the pump timing 1 degree or so and never had the surge come back, btw the resistor in the harness to the pressure sensor was one of the "unofficial fix" from MB, i talked to one of the higher ups on this issue. my surge was 55-70 mph zone only

fixbenz

btw an injection pump is about 3grand for a 1997, and way less on a 1998, i own both years,

joe b

Thanks for your input. I had talked with several race driver mechanics and every one of them said it was the fuel pump timing. Ironic since the "professionals" at the local Mercedes dealership wasted my money and my time even when I asked specifically to cjeck the fuel pump timing. I already had the timing chain replaced and that did not help ($900 later).
Question for Fixbenz: Is there a place, besides the Mercedes dealership, that can fix the timing pump? Is it an involved task?

fixbenz

adjusting the timing is not a big deal to do, you need the special timing light, 2 led's that light up when it is timed correctly, you can advance or retard the timing..i think i retarded the timing by 1degree or so when my surge issue started, it quit after that. you can try the mercedes doctor...
adjusting the timing isnt hard just tricky
as far as the injection pump goes i don't know what you want "fixed" on it. you are on your own on this, i simply do not want to get involved in this car. Nothing personal

keithfoco

try this ten cent repair. put a blue electrical butt connector in the egr vacuum hose. crimp it down a bit before to create a restriction, but not blocked off altogether. take the little, yellow vacuum hose connector out where it connects the egr hose to the solenoid 90 deg hose. put the butt connector where the little yellow vacuum line connector was. enjoy your benz. you can mail a thank you check to me at....
to explain. at cruising speed the vacuum going to the egr is too high at times. this makes the egr valve flutter. by restricting the flow to it, you are making it move more slowly. this will fix it. i just did it to a car today. had surging at 60-70mph. if you even touched the throttle it would go away and then come back when the speed leveled out.
Keith

06e320cdi

Also, check the vacuum hose on the top of the intake manifold, it goes to a sensor on the firewall. Mike was cracked. You also might want to put a pipe cleaner down and and clean the nipple.. Has anyone pulled the intake, EGR, and Intake Flaps for cleaning? Thats where my surging started. Its most likely vacuum related. Also, go to the other sites www.peachparts.com. and search the forums there. You will find alot regarding surging.