I've got an '85 300D and wanted to pull my glow plugs and bench test them. I can hardly get my hand down there to unscrew them. The only way I can figure to get them out is to remove the metal fuel lines from the top of the injection pump and the injectors. Is this the correct way to gain access? Do I need to be aware of anything before loosening the lines or do they come right off?

Thanks,

Scott

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Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

Although it is possible to remove the GPs with removing the metal fuel lines doing so makes this job a lot easier. Nothing to be aware of before loosening them but make sure you start them right when you put them back on. A cross thread won't seal and you will have to get new parts if this happens.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

Yes, I completely agree.

You can remove the hard lines in about 10 minutes with a 17mm open end wrench.

When putting them back on, first tighten all five fittings on the IP. This should go without any difficulty. Make sure that you start them all by hand.

The attach each line to it's respective injector. If the line is not lined up with the injector, use some brute force and bend the line until it's lined up. Then, force the line down to the injector and start the nut, by hand, and be sure that you have it on without a cross thread. Tighten it securely. Repeat for the other four injectors.

I strongly urge you to bend the hard line, as required, to ensure that it is aligned with the injector, before starting the nut. If you fail to do this, there is a better than 50% chance that you will cross thread it. Then, you're out of commisssion until you get another hard line from the dealer. Significant cost and a lengthy delay.

All I could add is, using a gear wrench helps.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Yes, even with the hard lines removed, a gear wrench is valuable for #4 and #5. Inaccessible with a socket.

I agree with everything above, but let me ask a dumb question. Why are you removing the GPs to bench test them? You can check their resistance in the car, which is a reliable method of making sure they are working. IMHO, it's not worth the trouble of removing them unless you are going to replace them. Just wondering.

"it's not worth the trouble of removing them unless you are going to replace them"

I've had bad GPs pass the resistance test (coulda been the tester ) I always pull em cause theres no mistaking if there good or bad when you put the juice to them on the bench, (not to be done with the old style plugs tho)

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

In general, I just check them if the car seems to miss when starting (The idiot light doesn't tell you until two GPs fail on my 300D). I check them with a multi-meter (from the relay plug) and just replace the one that fails. Takes about 5 minutes.