I've been having fuel delivery problems and in the course of diagnosing things I found that no fuel is flowing out of the cigar hose (disconnected at metal fuel return line) while the engine is running. However, when I shut the car down and manually pump the primer fuel does come out here quite well.

Does this seem to indicate my lift pump isn't functioning properly? Tank screen was checked yesterday and is clean. Sorry if this has been covered before...I just spent the last three hours searching and didn't find anything that addressed this.

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1983 300D

It sounds like you have a weak lift pump. Normally the 2 check valves are the problem. either they get a bit of crud under the disk, the spring fails or they fall to pieces. Its worth pulling it off the car & checking it out.

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Grumpy Old Diesel Owners Club group

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1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
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1968 Ford F750 truck. 6-354 diesel conversion.
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I pulled the lift pump from my spare engine and installed it on the car. Everything is running great now! Goodbye fuel starvation, hello power. So I guess my injection pump had been pulling fuel from the tank all this time (instead of the lift pump) and the car was not happy (i.e. low power, hesitations, lots of engine shaking, stalling occasionally). My car feels like a totally different car now that the lift pump is actually doing its job.

I'm not sure what the actual problem was with the old lift pump. I'll look at it closer at a later date to see if I can tell what failed.

If you've got power issues (esp. on hills and other situations where you're trying to get more fuel to the engine) then the next time you're parked simply pull the fuel return hose off of the hard metal line while the engine is running. If there is no fuel flowing, then you may have a lift pump issue.

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1983 300D

To make sure that you have enough pressure to overcome the relief valve either disconnect return again and check for flow. Or close off the return and power shouild be greater with a smoother idle.

You will not hurt anything with the test. The power with the return line closed off may suprise you if the lift pump is putting out what it should.

Really the base pressure in the injection pump should be checked with a gauge. The operating pressure is more important than people think and the relief valve spring can weaken with time lowering it. Yes the car will still run well but the base should have the recommended pressure or as high as 19 pounds. Certainly more than ten pounds.

If you use a regular Gauge to check your Supply/Lift Pump Pressure you will find the needle fluctuates too much. You need a Liquid Filled Gauge to dampen the Fuel Pump implulses.

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84 300D, 82 Volvo 244Gl Diesel