I am still getting air in the fuel. I can see many tiny bubbles in the clear return line. Air is getting in some whereI have to find and fix the leak. If I block the IP return port and pressurize the IP at the inlet port, It should hold pressure right? I also need to pressure test the lift pump which could also be a source of air.

I said ealier that fuel pressure was the same on VO or diesel. After installing the shimmed relief valve, I noticed that fuel pressure is higher on diesel than VO by about 3 psi. I would have expected VO to have higher pressure because of it's higher viscosity. I am going to change both diesel and VO filters and see what the pressures are with new filters.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Since pressure is related to flow and volume it may be not as much of the thicker VO is moving through the system or passing through the filter fast enough.
Maybe the Spin-on/Secondary Filter is restricting the VO flow.

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84 300D, 82 Volvo 244Gl Diesel

It could be the length of the Hose and the Air trapped in the Hose helping with the dampening.
When I did mine my hose was less than 1 foot long because I did not plan to drive with it hooked up.

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84 300D, 82 Volvo 244Gl Diesel

I set mine at 30psi and never looked back.

I put in a thicker shim and tested it and it went up a little bit not as much as i wanted. The spring measured 20 mm. I stretched it a bit (forgot to measure) and left the thicker shim in and tested out a little higher than 30 psi (gauge only goes to 30).

Here is a video of it starting on diesel:

29 psi idle fuel pressure on diesel. CLICK TO PLAY!

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Just something to consider is if the lift pump is capable of producing a higher pressure than what the gauge reads in order to have a good amount of fuel flowing out the relief valve.

I had a ball valve in my return line so I could get max pressure that my 616 lift pump would put out, (it was 15psi), for about 3000 miles. This gave me very solid pressure, but no return flow. I monitored the IP temp and it didn't get any hotter than the engine oil temp, BUT, after installing a stronger spring, I am running 35 psi, (25psi at 4000rpm full power), have a boat load of return flow, and the IP is now cooler than it was with no return flow.

The test is easy, with the engine running at the desired test speed and load, pinch off the return hose and read the pressure gauge. If the pressure does not raise 15-20%, there may not be enough pressure difference to flow a reasonable amount of fuel when operating under highway or high power/load conditions.

Just a thought.

Good lift pump should make thirty pounds or more on most these engines with the injection pump return closed off.We do not know if there is any long term negative effect of running a base injection pump pressure higher than 19 pounds. Once a year routine output pressure test of the lift pump with a gauge installed unless some fuel supply fault is suspected .

I was also going to mention earlier it sounded like the air the thread originator is picking up is occuring before his lift pump.

He hopefully is now out enjoying the change in driving feel if he has shimmed up to 18 or 19 pounds base pressure. He has no time to post.

Here vid of it on VO stomping on the pedal at 2500 RPM. Fuel pressure never goes below 25 psi no matter how hard I mash the pedal. I thought spec for fuel pressure is not less than 11 psi at 3000 rpm? Do you think my pressure is set too high? Will there be any long term effect with with high fuel pressure? Seems to have more pep climbing hills with the higher pressure.

CLICK TO PLAY!

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Have an idea! I am gonna make an adjustable fuel pressure relief valve. Drill a hole in the relieve valve cap for a stainless set screw that pushes on the spring, cut a chamfer in the cap for an o-ring seat, add an o-ring and a nut to push on the o-ring and lock the set screw. I think it should seal and do the job.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I took out the 4 aluminum washers on the IP inlet and return banjos, with soap and water and a diamond stone, sanded them flat and reinstalled. The air leak seems to be much less now but I am not sure if it is totally gone. I will see in the morning if i get any air infiltration. I hope the thread boss in the return port of the IP is not cracked. A few months ago, while I tightened the nut on that banjo I heard a cracking sound. I have replaced that banjo but the leak is hard to stop there for some reason. Maybe it was I re-used the aluminum washers. The way I check for leaks is wash the area till dry, start engine and put a white tissue wrapped around the banjo. If I see any signs of wetness it is leaking.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Potential problems of running at higher than 19 pounds are really unknown. Running at high base pressure without overflow may be a problem long term or may not.

All I am aware of is there has to be temperature increase in the area where the fuel gets compressed inside the pump. The elements specifically. This has been reffered to as the core temperature.

Maybe the base engine oil circulating through the area can carry enough heat away and maybe not. So in my opinion it is still nice to have relief valve overflow present.

Now to the unknown. you are taking the injection pump perhaps into a new area where it's original calibration is perhaps being effected more than desired. Nobody probably knows at this point.

Too much pressure may rotate the condition into a type of engine imbalance. The same as what exists with too low of a base pressure but with power. Theoretically the pump should be recalibrated if it will alow it at whatever much higher pressure say 25 pounds is chosen. This I might consider safe.

Power corrupts I am well aware so it is a hard thing to remain at 19 pounds but that is considered safe at this time. Plus not stretching the injection pumps existing calibration profile beyond a known envelope.

As time moves forward it may prove just as safe to elevate the pressure further. The spring stretchers examples of using no refference pressure gauges scared me at first.

Also you want to keep an eye on your fuel milage while trying to drive the car in a simular fashion as when the pressure was lower. One individual claimed the milage was a small amount less at really elevated pressure. But the car was being driven much harder and faster than before so his fuel milage situation is anyones guess. Is this change something for nothing? Who knows?

An extremely good millivolt examination at various fuel pressures would indicate if any issues are occuring. All cylinders should remain at the same operational temperature. You never want any one cylinder hotter than another by much of a margin.

At least I am happy that some people are actually commiting to installing gauges. It has taken a long time.

Personally I believe in the permanent type of gauge installation. In a crude way it is like having a scan gauge hooked up to a gas car. Just it reads pressures instead of codes.

What barry said in Pose #25.
I used 1/4 inch rubber fuel hose; but as I said it was only about 1 foot long.
There also could be a differance in how the Gauges were made.
Stiff tubing or not you said you felt it pulsating.
What matters is you have a good setup.

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84 300D, 82 Volvo 244Gl Diesel

It matters more to me to understand why. I think the small diameter and longer length of my nylon line acts as a restriction to average out the pulses.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

What was your old pressure and how did you set it to 30 psi? Mine was sort of accidental by stretching the spring a little and an added shim.

Any difference you noticed with the higher fuel pressure?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

There are lots of things that should be quite noticeable at the higher 19 pound pressure. Smoother idle, engine efficiency is improved by the more balanced delivery of fuel to each cylinder. Probably the causitive for better fuel milage. Some sembalance of proper sequential timing has been restored or improved.

The out of sight out of mind equality of power sharing between cylinders and contribution to less apparent loading on the number one cylinder. I suspect this improves the life of the number one rod bearing. Low pressure inversly the reason for failure. Just a subjective belief of mine. Not too many followers of it yet or there would be more gauges. Quicker starting if all else is well.

Above 19 pounds base fuel pressure other undesirable effects are potentially present. Yet all the items listed are usually gained by going from say a 11 pound average pressure to 19 pounds pressure. Some of us are only too well aware of these improvements that have been mentioned by members many times. These are the reasons I have pushed and pushed for members to get gauges installed for quite a time now. There is absolutly no doubt the improvements are worth the effort.

If you want to operate above 19 pounds base pressure there are threads containing lots of information of a few members experiences. They are quite impressive. I would private message them since at least a year has gone by now. Asking just how things have worked out. Power corrupts is not an idle concept. Look up threads and posts by cervan in the archives for relevant information. There are also others to find.

I cannot recommend it as there may be unknowns there. I would not want to be held responsible for recommending it. That does not mean with some tests I might not eventually try a portion of it for myself. I have no proof it is going to damage anything either at this point.

There again is absolutly no doubt that the optimum injection base pressure of 19 pounds does improve many things. With no risk. This is an absolute. Higher than 19 pounds pressure will result in higher performance is known as well. At really high pressures burning rubber is apparently possible or the back end breaking loose on dry pavement. There are even videos by cervan.

I suggest operating at 19 pounds pressure for quite a period of time before entering the partially unknown if you are going there. You then have at least a baseline for comparison then. Right now all you are sure of is some more pressure is better than what you had.