I'm not a diesel guy, so help me out if you can. It feels like my '82 300dt is starved for fuel at higher speeds. At lower speeds, I get proper throttle response and good power. At speeds above 35mph, I feel like the throttle response is not appropriate to the amount of pressure I'm putting on the pedal. I think it may be a fuel related issue.

So far, I have replaced the fuel lines that go from injector to injector, replaced the primper pump with the newer style Bosch one, replaced the clear pre-filter and hose that connects it to the injection pump, and the fuel filter, but the problem still persists.

What else should I look into, fuel-wise, to rule out anything fuel related as being the cause of a loss of either power or throttle response at higher speeds?

there are 2 fuel filters and a screen in the tank.chec or change all 3...do the screen with very low fuel level in tank and lift car from right side so fuel does not run all over.also check throttle linkage is adjusted rite to give full open throttle good luck

Can you verify that you're getting proper boost? Clean out the banjo bolt and line to the switchover valve to start.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

When was the last time the air filter was changed?

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Yes, I'd say first check the air filter, then the tank screen. You can test the tank screen without actually removing it. Substitute a gallon of diesel in the engine compartment for the fuel tank. Run pick up and return lines into the plastic bottle thu holes cut in the lid. Take it for a drive. If the problem is solved, then the issue is upstream of the engine compartment in the fuel system, probably the tank screen.
I'd also check the flow on the lift pump. A weak lift pump could possibly produce the symptoms you describe but I wouldn't bother checking it before doing the boost system chekc, air filter and tank screen checks.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

good advice. does the fuel tank need to be removed in order to replace these screens and filter?

haha. the only banjo bolt i've ever had to deal with on an MB was the one that goes to the fuel filter on a w124 and w201. where is the banjo bolt on a w123? and how about the line to the switchover valve? i really don't know what these items are--very unfamiliar with these engines, when it comes to the details...

about a month ago, i changed to K&N filter. it's had about 100 miles since the filter was installed

that's an interesting idea. but isn't it dangerous to have a gallon of diesel in the engine bay? i think the only way i'd do this is by going to the junkyard and buying a spare washer bottle, plugging the hole for the washer pump, and substituting it for the stock bottle and putting diesel in there, to avoid any spillage or a fire.

could someone point me to the pick up and return lines? is this a safe thing that someone else would try themselves?

Everyone does it while purging. Fewer have probably driven around with this set up. But if the connections are tight and the jug of fuel fastened to something I don't think there's much danger.
Return line is the cigar hose. Input line goes into the primary fuel filter.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

OK, i know where the cigar hose is. the input line is the one that goes into the clear "pre-filter"--the one that connects directly to the back of the injection pump on turbo models, right? thanks kerry