I have been having lot's of fun in up-ing the fuel pressure by tweaking the IP fuel pressure relief valve in this thread and getting some positive results.

Fuel pressure.

I just made this adjustable pressure relief valve. On the right is the adjustment (a socket head cap screw), the blue nut is a nyloc lock nut, there's an o-ring to provide a positive seal. By turning the screw CW, fuel pressure is increased, CCW, pressure is decreased. I still have to test it to make sure it works well. I have confidence it will.

This poll is to see how many are interested in buying an adjustable fuel pressure relief valve and renting the test equipment to set the pressure. The test equipment will be a banjo bolt that has a quick disconnect fitting with a 6 ft nylon line to a pressure gauge so you can set the fuel pressure, like the setup in the thread I linked to above. There will be a core charge on your unmodified fuel pressure relief valve. I only have 3 of them currently and need your core so I can continue to make them. Price is TBD. I am just putting this poll out to see how much interest there is.

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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

Clearly there is a need for a Fuel Pump Pressure test Kit.

However, I think the 2 way shipping charge needed to rent one could better be used to buy one or what you need to make one.

I am sure there are some who would like an adjustable Pressure Relief Valve.

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84 300D, 82 Volvo 244Gl Diesel

D911, good point about offering a fuel pressure test kit instead of rental with the 2 way shipping.

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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

Maybe you cold factory preset them to the OEM pressure. People could then do their own extra adjustment. You should be able to give a starting point like say 3 turns out from the stop. There are probably some down sides to increasing the pressure by too much like diesel leakage into the oil.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

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
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

I could most definitely preset the pressure to whatever is desired.

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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 might be in but due to my current situation pricing would be the deciding factor.

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

I know a free solution; stretch the spring to 27mm like the factory tells you to and be done with it for good.

Attached Thumbnails

 

Yes, except the spring will slowly give and the fuel pressure will slowly drop. Looks like there is not much interest. That is good actually because I don't have a lot of time for another project.

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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 am interested in this - however I have to be honest and say that I haven't a clue about the fuel system on a OM617. I'm still trying to figure out exactly how the basic system works. I'm still quite new to this.

I guess this could be a reason why everyone has not been hammering down your door funola.

Can you direct me (and perhaps others) to some good diesel injection systems for newbies / dummies threads?

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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!

Would this work on cars such as mine with the non adjustable spring?

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----Adam

1985 300SD 322,000

Army, you're no newbie with all the work you've done. I don't have any links to good threads on the inline pump but a search should turn up a lot.

4the sporty, it is a direct replacement of the non adjustable. As a matter of fact, it is a modified non adjustable and I would need your's as core, if I was actually going to make them.on a continuing basis.

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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

Sending you a PM with links.


.

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ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

Thank you very much. For those who may want to know more Wikipedia gives a great overview

http://en.wikipedia.org/wiki/Diesel_engine#Early_fuel_injection_systems

The links that were kindly sent by whunter were:-

Fuel Delivery:
Diesel Fuel Delivery:

Diesel Injection:
Diesel Injection:

Run away diesel, why does it happen?
Run away diesel, why does it happen?

Engine blow-by test, Blow a bag of blow-by
Engine blow-by test, Blow a bag of blow-by

Blow-By curioisty questions
http://www.peachparts.com/shopforum/diesel-discussion/188320-blow-curioisty-questions-post1798266.html

Diesel TURBO issue Links thread
http://www.peachparts.com/shopforum/diy-links-parts-category/229542-diesel-turbo-issue-links-thread-post1929856.html

Engine oil cooler and hose/line issue, link thread
Engine oil cooler and hose/line issue, link thread

Valve adjustment OM615, 616, 617 FYI.
Valve adjustment OM615, 616, 617 FYI.


Sorry to go off on a tangent funola - I'll say no more!

__________________
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!

Don't understand why adjustability is required for anything other than spring fatigue over time.

Don't see the need to overpressure the fuel in the IP, either there is enough pressure to deliver the volume to the delivery valves, or not. So long as there is enough pressure, the valves are full and you get a full charge down the line.

Once the critical pressure is met, what does the extra pressure buy you? Nothing. It can't possibly increase the flow to the injectors. It can't possibly change your MPG or power.

To get the critical pressure, just replace the original spring, or stretch it a bit, as per FSM.

None of the poll options have what I'd vote for, so I didn't vote.

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Cheers!
Scott McPhee

1987 300D

I also do not understand how this would provide any benefit over a correctly adjusted IP.