At 50 -55 mph I am noticing a hesitation/surge in my 79 SD. With this weekend's oil change I included a dose of Power Service in fuel. I don't believe the hesitation was there before the PS, but I have had this car just a couple of months and can't say for sure. I have ordered new fuel filters and will install those before moving on to injectors. Any suggestions?

You may want to try loosening the filler cap and seeing if there is any change. When I first purchased my SD, it had a clogged vent and had the same problem. I was able to repair the vent and the surging was eliminated.

Tom
82 300 SD
86 300 SDL

Don't know if it was serendipidous or not, but about after 1 month of using Redline DFC, I noticed a slight loss in power on my 1977 300D. It might have been a bad tank of diesel as well. I changed both fuel filters and was amazed at the improvement in performance.

A good indicator is to get some light on the clear fuel filter, I can best see mine from under the car, and see if there is any sediment in it. I noticed mine while I was changing motor mounts. After this experience, I change my clear filter about every 1-2 months. It helps me keep track of what is going on.

Good luck,

PS, coming to the diesel meet?

Probably fuel filters. Replace one at a time starting with the one in the tank (which can be cleaned and doesn't have to replaced) and see if the problem is solved.

The Power Service may have loosened up some crud and that plugged a filter. I only replace fuel filters when they plug and not on a regular schedule. Why, If no dirt gets in the fuel the fiters, they last for years. If I get dirty fuel the filters will plug soon afterward. and even if I replaced the filter yesterday, it wouldn't help.

Actually, I clean the filters by putting gasoline in them and reverse blowing them out with compressed air. I know the technicians wouldn't do that because their hourly rate is more than the filters cost, but it works for me. MB used to have a fixture to clean the insert fuel filters in the old 190D and the primary filter had a lid that came off and the element could be easily cleaned. That was before shop rates became so ludicrous that the labor charge is much more than cost of the parts.

P E H

I should have the new filters tomorrow. If the roads are clear, I'll pop them in and give it a whirl. Thanks, PEH, I didn't even know that there was a filter in the tank. A closer perusal of the Haynes is obviously in order.

To take out the tank filter, drain the tank by disconnecting the fuel line and draining into a bucket or 2. Its easier to do if the tank is almost empty. In the bottom of the tank you will see a large recessed hex, about 23mm. This is the bottom of the filter, actually it is more of a screen. Screw it out after the tank is drained and clean if dirty, it doesn't have to be replaced. If you don't have an allen wrench that fits, you can use the head of a bolt and turn the bolt with a Vice Grip pliers.

Replace the filter, reconnect the fuel line and put the fuel back in the tank and you are finished.

I forgot to mention that this job is easier with the car up an a lift or over a pit. But it can be done by backing the car to where the rear end is hanging out over some type of drop off. If none of these are available backing onto ramps might work. You need enough clearance for the bucket.

P E H