Thanks to Barry12345 and Diesel911 for their help.....
Pressure @ idle = 11 psi but slowly goes back to zero....RPM @ 3000 pressure goes up to near 30 but returns to zero within 12 seconds while RPM remained @ 3000....TANK SCREEN WAS COVERED WITH WHAT LOOKED LIKE MUD.....Installed Stanadyne FM-100 5 micron filter between lift pump and prefilter...pressure now holds @ idle see photo's...

Liquid filed gauges installed in glove box....Barry12345 suggestion

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Not a good idea long term. Copper capillary tubes will eventually crack from vibration and leak and strand you not to mention the mess. If you must have fuel pressure gauges inside longterm, use elec pressure senders.

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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

The copper fatigue if it becomes an issue should occur in the area of highest vibration. That is closer to the engine in my opinion. Remember that failure of the oil sendors pressure line on the average 616 0r 617 is virtually unheard of.

At this moment I am not sure of the fluid filled tubes composition on the oil pressure gauge. Some have gone 500k or more by now . Supporting the tube in the areas of maximum vibrations also can reduce vibration fatigue problems.

Having the gauges is more important than that extreme possibility in my opinion anyways. I know you have at least one aftermarket gauge in your own system

Plastic feed lines could virtually eliminate any concern if used.. The nice additional bonus of the need for fluid filled mechanical gauges. If an internal gauge leak evolves it will in all probablity be confined to the sealed gauge. Unlike the mechaniucal oil presure gauges.

SUNPRO has both copper and nylon tubing available...their Engineering Dept. recommends the copper for longer life..they also said to form a 3 inch coil in the lines would help reduce vibration? Never heard that one before.

That is a standard operating procedure to keep a metal line from cracking. I have seen it on brake lines also.

I have also seen it with large diameter pipes. there is an area east of Reno, Nv along I-80 where there is some sort of plant that has these large pipe lines running along the Hwy. they have a few "S" turn in the pipes every so often. this is more for expantion I think.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Update...both gauges developed internal leaks mixing diesel with the liquid which put out a strong odor in the car...they were $26. each...Amazon refunded the money...I liked the idea and may try more expensive gauges later...

What brand gauges and approxamatly how many miles on them? There have been no known issues reported with the approximatly ten dollar chinese gauges from harbour freight unless yours are the first. There are at least a few in fairly long term service by now.

I just went back and studied the pictures. They look like the ten dollar chinese gauges. That is the two you show as installed not the earlier ones used for testing. Random defects almost seem out of the question as both failed.

You can get by well with just one gauge remember. That the internal leak overcame the sealed housing for the dampening fluid was also informative. I had suspected if there ever was an internal gauge leak occur it would have been contained. Unlike the mechanical oil pressure gauges on the 123 cars.

My last thought is on some of the installations a trapped air situation remained in the feed line on some perhaps. If this were the case no oil may have been in actual contact with the internal sensing mechanisim. I guess we wil just not know for some time about these gauges.

On the otherhand the same gauges with higher calibrations are meant for hydralic systems. The fluid is different would be the most likely variable. The prime suspect might also be inconsistant chinese quality but I am not certain of anything right now. It is a reasonable proposition that both gauges came from the same production batch as well.

I have also used the chinese gauges from our equivelant of harbour freight up here in Canada for other applications with no issues. That at the same time should not be considered an absolute defense of them. Funola for one runs with one in his cab I believe for quite some time now. Much longer than you have and I think he accumulates substantial miles.

Still sorry to hear of your experience yet thanks for posting it. Glad you liked the application though otherwise. To me it has always made sense. Why not blow the money for one cheap gauge from harbour freight and give it a test? If it develops an issue as well then it may need more investigation. The odds from what I have observed is it will not.

At the same time I am far from certain at the same time. If you still have the gauges in your possession we could compare the script of the backs of them.

This is meant to be funny. You could have gotten more expensive chinese copies of the cheap chinese gauges. Unfortunatly once again I suspect they are the same though.

No brand on them...PheumaticPlus is the supplier sold thru Amazon...You can review them on Amazon site...0--60 PSI; 2-1/2"; ANSE40.1 compliant; suitable for Air; Water; Oil & Gas....$24.35 each. I will take a look at the harbour gauges...

BIG thanks again for your help....car is doing much much better since the fuel pressure increase...

Well you want the 0-30 pound harbour freight model. Strikes me that it was a little larger but unsure. The closest gauge of that type I own unfortunatley is up the road so I cannot verify it today but will tomorrow. The gauge diameter of the harbour freight ones may also be in their site listing.

Why would you want fuel pressure gauges in the car after the problem is fixed? I can't see any reason why they would be that necessary.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

They just for starters inform you when the fuel filters should be changed out. Also great early warning indicators of things like the lift pump may be failing or some form of obstruction is forming up in the system somewhere. Greatly aid in troubleshooting issues as well.

Running with low fuel pressure reduces milage. Reduces the quality of the engine idle and increases engine noise especially on the highway.

It is my somewhat unproven belief constant low fuel pressure will take the first cylinders rod bearing out over time. Almost for certain on the 616 four cylinder engines. Less certan on the 617 five cylinder engine but still a probability. There are some reasons the 616 engine is more prone to this.

Pressure gauge installed permanently or not. You should at least know where your fuel pressure in the base of the injection pump is. The upside of this is far greater than the downside. It is still fairly safe to say the vast majority of members at this time have no knowledge if they have even adaquate fuel pressure as these engines will still run seemingly decent at very substandard pressures. In my opinion there is a price to be paid for doing so one way or another.

The high milage expert on our site is not talking much. Still i think the fuel pressure he is running at is beyond what I suspect the recommended maximum pressure is. It is only one of a host of modifications he has done.

I am starting to think what he is doing in this area of boosting the fuel pressure higher is safe but still cannot recommend it without certain tests I would have to do.

At about thirty two miles per gallon at fairly high speeds I thought there was no further room for improving his milage. Yet he was getting 35 or more miles per gallon just awhile ago steadily. Drives a thousand miles a week as well back and forth to work and his observations are reliable in my opinion. He also does not vend cars on ebay. This is one heavy old 617 type engined sled he is doing this with.

I forgot to mention that good pressure increases power as well. So there is absolutly no downside I can think of to actually knowing you have it. Anyways if you have the gauge is it really of better use sittting in your tool box even if just installed in the engine bay? You had to hook it up to use it anyways.

AFTER I CLEANED THE TANK SCREEN MY PRESSURE WAS STILL BELOW SPEC.
SINCE ADJUSTING THE RELIEF SPRING THE CAR IDLES MUCH BETTER AND HAS MUCH MORE POWER...THANKS AGAIN TO YOU AND DIESEL911

The reasons I like the gauges are listed in the 27 page post FUEL PRESSURE RELIEF VALVE ADJUSTMENT... APPRECIATE YOUR QUESTION

You could replace the Copper Tube with the Nylon Tubing that is typically used for that purpose.
If you used the Copper Tubing with the compression Fittings the Nylon Tube will directly replace it.

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84 300D, 82 Volvo 244Gl Diesel