Hallo to all. New in your site.

I have a 89 300SE which in general give me no problem.
However, occationally the engine just die, as if out of fuel.
This have happened several times the last year.

I have changed the fuel filter & pump twice, the kick-down rele three times, installed new cables from kick-down rele to pump, but the problem always return after a week, or two months, (I never know). (Sparkplugs, cables and distr. cap is new).

I have also noticed that when driving at a higher constant speed, (160 to 180 km/h), and releasing the throttle followed by full throttle, the engine just die. Have to "jiggle" the throttle repeatlly to get it going again, as if the throttle "valve" in the intake get stuck in full open position, (booging, as on a Q-jet).

At the moment the car is parked on the high-way after my wife had a break-down. (She is not happy ).


Thanks, Per.

Did you change the fuel pump relay? The 88-89 models, at least the ones in the U. S. have a separate fuel pump relay, supposedly near the battery.

Thanks for reply.

Changed the kick-down rele, (again), and she started straight away.
I have a feeling that the pump must be drawing to much current, and that way it burns the rele.
(The pumps previously changed have been second hand, (out of wrecked cars), as only only bad copy pumps are sold locally.

What would be the amp reading for a good pump?

Per.

I seem to recall in an older post that MBDOC indicated 8 amps as being too much.

I pulled the fuel pump fuse on my 91 300-SEL from the main fuse box and hooked up an amp meter. I did this out of curiosity to see what amount of current was being drawn. The car was performing OK. I saw measurements from 3.5amps to right at 5amps.

Very good info, thanks a lot.

Per.

Help.

It happened again.
It stopped suddenly two times yesterday. After some cranking it starts again.
Checked the amp through the pump, and that seems within limits.

Any other suggestions?

Regards, Per.

You might see if the OVPR is okay..It has a 10 amp fuse under the plastic flip top cover.....MB updates these on a regular basis.

While your at it...run an a/c voltage check on the alternator at the Alt+ stud.
Over 0.05 vac seems to makes weired stuff happen.

Also found a few with badly burnt armature segments on the idle valve stepper motor....'corse, you have to break them open to see ! Then you definitely need a new one !

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Hi, Dkveuro!

I opened the OVPR, cleaned it as best as I could, measured the circuits with the Fluke and reinstalled. (Date stamp on the OVPR 13/04 89, so I recon that it has done job well in 16 years and 200 000 km).

Got a very stable idle, and seems to have sorted out the "low" speed/rpm issues I had.
Will get a new OVPR ASAP.

Thanks, Per.