My '87 SDL has developed a severe lack of power... to the point where the car is floored in drive with a cold engine, it won't move foward. The car is somewhat driveable after warming up for 5 to 10 minutes, but takes a long time to get from idle to 3000 RPM and it is not possible to start up hill. Power is at bit better past 3000 RPM and will go 70mph on a level highway, but it takes a long time to get to that 3000 RPM. (When cold, with the car in drive and floored, engine will not move past 900 RPM).

I've changed the both the inline and canister filters; lift pump delivers 9oz in 30 sec when measured via the return line. (spec is 5 oz). Car starts (both warm and cold) and idles w/o problem. I also bypassed the fuel T-stat with no change. Car has 93k miles. Also, this is likely the 1st time the car has ever seen temps below 30 F; not sure this is relevant. Problem came on over the course of a week driving 20 miles per day.

What should I look at next? I'm thinking fuel return valve at the injection pump. Other ideas? Thanks.

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as ever
Paul

1989 560SL
1987 300SDL
1987 300TD
1983 BMW 633CSi
1972 280SE 4.5

Well, I think my car has the same engine as you... I had some issues, and what was suggested to me was to Check the Turbo boost tube. Also I would check your air filter if you have not already. a Clogged one can bugger up a lot of things.

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

Check that the overboost protection switchover valve and its associated small plastic lines are not blocked with soot.

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Even if the overboost protection was malfunctioning, and the turbo was not working, the car should still easily move from a standing start, hot or cold. Sounds like a fueling issue, does the engine rev when in park in the situations where it won't move the car?

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'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Check for excessive backpressure by removing plug on exhaust manifold near #1 and #2 cylinders.

I'll check the exhaust backpressure today and report back.

Thanks

Paul

My thoughts as well. It doesn't appear to be lack of fuel.

What you describe is exactly what I had a while back.

Have a look at this - photos on post #29

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

Is one still fitted?

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James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
1996 Suburban K2500 (192k, 6.5 turbo diesel/4WD towmaster 10,000)
www.engineeringworks.biz
1987 300SDL junker 170k
1982 300SD junker, 265k

No trap on the car; just the catalyst thing installed with the recall.

Back pressure at 4000 RPM is about 18psi. Service manual seems to indicate 2 bar is OK, but that is in the manual section regarding the trap, so I don't know if that figure is relevant. 18PSI seems like it would be a problem to me. Thoughts?

Thanks
Paul

If the vehicle is in your driveway, in Park, and is producing 18 psi @ 4000 rpm, you absolutely have an exhaust restriction. Remove the downpipe from the manifold and take it for a drive (ignore the noise).

Ok. Exhaust is coming off tonight. Thanks.

Paul

I removed the exhaust downpipe; no change. Still can't get over 1000 RPM when the car is in drive. I also picked up some new fuel from a different station and pulled directly from the can w/o change. I'm stumped.

Pinch the fuel return line from the filter to the fuel tank.

Sixto
87 300D

Have you checked your throttle linkages?

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1982 240D, sold 9/17/2008
1987 300D TurboW124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
262,715 and counting