Just disconnect the fuel line to the lift pump. It can't pump fuel if it's not being fed fuel.

__________________
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

The rectangular piece is the jamb. Notice the slot? It's for a positive fit. Use Oak or similar hardwood. Aluminum or steel will do also but take longer to make than wood. Oh and do not disconnect fuel line as suggested . Not only will you still spray lot's of fuel out the holes from the fuel that's in the IP. You will then have to do more work to bleed the air out.



Jammed in place. Make it fit tight.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Have you confirmed that via experiment? The engine will shut down if running and the fuel line is disconnected, suggesting quite strongly that the IP cannot pump fuel if new fuel is not entering it.

__________________
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

Hmmm, that's kind of similar to what I did (I can snap a picture in a bit), though my linkage is a little different. The first attempt I had it up as far as it would go against the idle cable stop (which I know was enought to stop the engine before, but maybe it was not stopping the fuel entirely). After that try, I took the cable off and put the stop linkage all the way up, so the lever sat against the valve cover. I'm not sure if it was still delivering fuel at that point, but the first try would have been enough to lubricate the cylinder (and comes out the GP holes) on subsequent tries I guess.
I didn't think unplugging the fuel line into the IP would help because the fuel left in the IP would still enter the cylinders, wouldn't it? Even though it's not much, it would do the same thing that happened last night, and provide a little lubrication and give high readings.
I'm going to put it all back together and run it a bit to get out any fuel that may have sat in the cylinders overnight. Then I guess I will experiment. What happens if it fires on the cylinder you're testing? I know it won't start because the other cylinders can't fire, but wouldn't that be pretty damaging to at least the tester?

__________________
1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

It could be bye bye tester if you get ignition but that depends on the state of the engine and the tester - don't the really good testers have a pressure relief valve? Anyway according to the SAE OM617 development paper at idle the cylinder pressure is just under 40 bar - that's about 580 psi.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

no I have not. have you?
we know that every time the fuel system is opened, air gets in. what you are suggesting does not seem like a good idea.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

No, I haven't but there was a post on here a couple of years ago that definitely proved that if you disconnect the fuel line, the engine shuts down promptly and doesn't use up the fuel remaining in the filter/IP etc. It was in regards to the options available when the engine runs away after a faulty shut off valve install. That's why I suspect that that the IP won't pump fuel if there's no fuel arriving at the inlet because the lift pump isn't pumping fuel to the IP.

It would probably allow air to get sucked in which would need to be cleared out with the primer pump.

__________________
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

We talking about a compression test, not how to stop a runaway. A fuel connection has to be broken, air will get in. If a new washer is not available, the old washer may not seal, more problems. So, still not a good idea.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I thought if you unplugged the feed line to the IP, it would still burn the small amount of fuel left in the IP before it cut out? Maybe I'm misunderstanding the way it works.
I will stick with fiddling with the stop lever for now. I didn't have time to try anything today, since my dad needed some help moving stuff around, which is fair because he helps me all the time. I'm tempted to go out to the garage and work now, but I've learned a few times not to start a somewhat complex (to me) project late at night.

__________________
1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

Not sure what washer you are referring to. I said disconnect the fuel input line at the lift pump, the one coming from the tank.

The question as to whether the IP will continue to pump fuel with it disconnected is what is unclear in my mind. Evidence on this site so far is that it won't. Maybe it will still pump a small amount. It definitely won't pump the remaining fuel in the secondary filter and the lift pump based on what has been posted here in the past.

__________________
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

Cold compression test numbers are extremely inaccurate.

Heat expansion of the cylinder, rings, and piston can (depending upon engine condition) change individual readings by 200 PSI..

To prevent unwanted fuel entering the cylinders.
* Remove the steel injector lines from the injection pump and injectors.
* Cover the delivery valves and injectors with loose caps/condoms to prevent trash entering/damaging precision components.

IMO:

* It is easier to relieve cylinder pressure by removing the injectors, and a great excuse to visually inspect the nozzle condition.

* A wise owner keeps spare "NEW" heat shields on hand for injector work, and compression testing.

* You do not want to drain the injection pump, because diesel fuel is the only lubrication of the delivery valves + it will seriously increase the difficulty of restarting the engine after testing.

.

Well, I did determine both the shutoff valve and the shutoff lever easily stop the engine. But I decided to try doing it through the injectors anyway, since like whunter said, I could also inspect the injector nozzles. Everything went surprsingly smoothly until I actually went to do the test. As soon as the guage reaches 250 psi, the connector pops off. There's only one quick connector in the kit that fits the injector adapter, so I can't try another one to see if it's just a bum connector. That would be my guess. Naturally I got the cheap Harbor Freight tester. It worked fine with the glow plug adapter (it popped off once on that round but I assumed I had not seated it right, and it was fine every other time). Frustrating.
Also my injectors came out covered in oil, especially Nos. 1 and 2. Not an encouraging day.

__________________
1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

True for the VE pump and other fuel lubricated pumps, but not the inline Bosch pumps, which is lubricated by engine oil. Am I right or wrong?

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

It's popping at the quick coupler? That HF kit is not very good. The fittings are nickel plated brass (should be steel for such application) and tolerance is lousy. I did extensive work to my HF kit to make it work and leak free.

Post a pic of your injectors. Where is the oil coming from?

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

My fuel system is highly modified and not anything like a stock system. Maybe it's easy to disconnect the fuel input line at the lift pump on a stock system. I am not willing to try it on mine since it requires a lot of work. Can you try it on your car and report the results?

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked