Fuel pressure mod, how much is too much? - Ford Powerstroke Diesel Forum
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Old 11-01-2007, 05:12 PM
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Fuel pressure mod, how much is too much?

Can someone tell me how much fuel pressure is too much? I did the bb in the fuel pressure regulator mod on my truck. (95 F250, 7.3L, ext. cab, 4x4, E4OD). I don't remember exactly what the stock pressure was but it increased to about 60 psi @ idle. I was expecting 70 so I put another bb in it and the pressure increased to about 70.

Now, just to clarify, I am estimating these figures due to the fuel pressure gauge bouncing between numbers. These figures are midpoint readings.

I installed a 100 psi gauge and after a couple of days the gauge started leaking. The gauge was under the hood so I could not monitor it while driving.

Then I decided to do the DIY stage I injector rebuild, cat delete, and 3" downpipe plus a couple of other minor mods. During the rebuild I replaced all fuel lines in the valley of the engine and found the fuel pump leaking from the weep hole and I replaced it also.

After completing all this, I installed another 100 psi gauge and the reading was bouncing between 60 & 80 psi @ idle. That gauge lasted about200 miles and then it started leaking also.

Now, I have installed a 200 psi gauge onto a 4 ft. hydraulic hose and run it out onto the hood using a magnetic base and clamp. The needle is pretty steady now and reading 85 psi @ idle. 90 - 95 running 60 mph and the pressure increases whenever I let off the throttle and decreases to 80 or so when accelerating. I saw 150 psi momentarily with overdrive locked out and hard acceleration and then quickly backing off the accelerator.

I'm sorry this is so long but I wanted to make sure you could understand what is going on and what led to this.

Finally, here is my question! Can it take the pressure? Should I go back down to 70 psi @ idle or is it just personal preference to what pressure to run? Will this pressure harm any thing?

BTW, the truck starts and runs good but I haven't checked mileage yet.

Any info or comments are greatly appreciated. Just concerned whether any harm is being done.
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Old 11-01-2007, 10:10 PM
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Is anyone else running their fuel pressure this high?
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Old 11-01-2007, 10:19 PM
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Smile fuel

humm like to know myself.
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Old 11-01-2007, 11:37 PM
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that sounds kinda high to me... ill bump it up for you hopefully one of the number junkies will catch up with this one.
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Old 11-02-2007, 02:33 AM
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I wish I knew, I quit buying gauges afte I blew one on the dyno, but it wrapped the needle tip around the peg on a 100psi gauge and burst the cappilary. I'm gonna try a remote mount and a few other tricks to see if I can get the bounce out. Then I may be able to read the gauge.
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Old 11-02-2007, 09:17 AM
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I think adding the rubber hose takes the bounce out of the gauge. The needle was bent on the gauges I blew also.
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Old 11-02-2007, 04:46 PM
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Went for a drive down the interstate today and I'm pushing 100psi @ 70 mph. Mileage seems to be no better, maybe a little worse. I'm going to drop my pressure back to 70 @ idle and see how that works. I'd rather run @ 70 than have to worry about it all the time. Thanks for the bumps, guys.

Last edited by Glen95Stroker; 11-03-2007 at 01:37 PM.
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Old 11-03-2007, 01:38 PM
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I'm adding this reply to make a correction. I didn't put a second bb in the regulator. I put the first bb in and then I inserted a small phillips head screw into the outer end of the spring, the head was about 1/16" thick and the point on the nut sits right in the phillips head. Which actually I'm glad I did because I was afraid I wouldn't be able to get the bb out.

Anyway, I took the screw out and I'm ready to put it back together now and see what difference it makes.
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Old 11-03-2007, 03:47 PM
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"Oh what a difference a good screw makes." I took the screw out and left the bb in the regulator and now the needle is very stable and reading about 68 psi @ idle, took it for a drive and it registers about 65 @ 70 mph, drops to 60 when I accelerate, (mid 50s if I really get on it) but it only increases about 3-4 psi when I let off the pedal. (I think I got a defective bb, )

I went from 85 @ idle and 100 psi @ 70 mph to a pretty steady 65 - 68 anytime. I think it idles a little smoother now but it doesn't have the kick down that it had before. I wonder if there is a middle ground where I can get the best of both.

I think I'm going to drive it a couple days and see if the mileage might improve and then mic the screw, then machine it down to half and put it back in and see what kind of results I get.

Does anyone have an opinion on this and I would still like to know if 100 - 150 psi was doing any harm or is it just personal preference and trial and error until I get it the way I like?
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Old 11-03-2007, 07:03 PM
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62psi is opt pressure according to Jody at DP.

Bill
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