Fuel Pressure under load?

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OK you Diesel Gear Heads, I got a question for you all. Does anyone run a fuel pressure gauge in cab, and if so what are your pressure readings under load? My gauge runs 20/22 at cruise, and down to 8 when under hard acceleration. My filter is new, and my pressure is within spec 22 at idle and 30 on a throttle snap test. I was just curious what the pressure should regulate at under load. #ad

 

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If all is working well, I like to see no less than 15lbs under hard pull.

 

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18 psi is my lowest under load,otherwise 22 at all other times.

 

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DBR,

Are you noticing a problem under load? Where are you measuring?

 

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Truck is running fine…I think. I just got around to installing an electric fuel gauge I purchased over a year ago or so. I am taking the reading off of the fuel supply banjo fitting at the injection pump. When I had the #10 plate, BD gov spring Kit, and HX 40 on I was able to go 3 psi on a hard run. I am presently running the #11 plate, stock gov, HX35/16 and get the 8psi value. So before going overboard here, I think I need to install my mechanical gauge and compare values between the two gauges. The electric gauge may not have the right sender for this application.

For those of you who have gauges in cab, what type are you running, mechanical or electric, and what brand?

 

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I run an electric S-W 40 psi oil pressure gauge for my fuel pressure,sender is in the same location as yours. Some senders need to be upright in order to work correctly.

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95' 25004X4,AT,Driftwood,Banks Stinger,Warn fender flairs and running boards(Play truck)95 3500,5 speed,Driftwood,Banks&Phscotty,34,000 GCVW apple and tractor hauler(work truck)

 

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Thanks Guys, I went out today and purchased some brass fittings so that I could run both gauges at the same time and reference them against each other. I will also try to install the sending unit straight up. I believe the sender is a “Dayton?” Not sure, I need to find the sales receipt. I’ll have time tomorrow to check things out.

I did remove the pressure return valve and stretched the spring to increase the pressure. Well it did, to 32/35 idle and 20 under full throttle. The pressure differential is the same, just different base values. So what does that mean? I was thinking the seat or ball may be worn but it holds pressure consistently. I would think if the pump is capable of providing 20 psi under full throttle with the stretched spring, it’s not the pump. I’m going to buy a new pressure return valve regardless (especially after my last “precision” adjustment!). #ad


What are your thoughts?

 

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I think you need to send me your old valve. My '94 isn't "adjustable" and it sounds like the pressure is about perfect!
Actually, the pressure differential should be the same. You changed the preload against the spring but the RATE didn't change (unless you really stretch the snot out of it).
If you run a mechanical gauge, use an isolator so there is no fuel run into the cab. Nt as big an issue with diesel but...

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'94 3500 4x4, 204,000 miles, Never had a cat, Auto w/shift kit (thanks Dave G), 3. 54 Gears, TST #5 plate, 235-85-16s, Rancho 9000s w/remote, Isspro gauges inplace of cupholder & Amsoil Bumper to Bumper. NRA member. Blue Ribbon Coalition member.
"Warrantee? We don't need no stinking warrantee!"

 

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Installed a new overflow valve (78. 66$) this evening and all is well. I installed my miller mechanical gauge in parallel to my electric gauge and both reflect the same values. I also installed the electric sender in the upright position as illflem suggested. The pressure now read as follows: Idle 22psi, Full load 18/20psi, Cruise 23/25 psi. Thanks for the help folks! #ad


Extreme1,

That explains things very clearly, Thanks. I guess I was trying to make things more difficult than they were, as usual.

[This message has been edited by DBR (edited 11-28-2000). ]