Fuel Pressure Problem
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Lead Driver
Joined: Oct 2004
Posts: 7,413
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From: Columbia, MO
Fuel Pressure Problem
Last night I did the FPR shim kit. Next to largest shim gave 61psi, so I swapped in the largest one. Still 61psi. So, I put a post up on the forum, and came to the conclusion that the fuel pump was going out. I replaced the fuel pump today.
Started it up and pressue immediately jumped to 67-69psi, with the largest shim still in. Not as high as I figured it would be, but better. Thought there might be air in the line, so I took it for a 10-15 minute drive, got on it pretty hard a couple of times.
Pulled back home, up to the garage, and popped the hood to see what the pressure would be. I was again thinking it would be higher. Much to my dismay, it actually dropped after the drive.
Down to about 61-62psi. Exactly where I was at before I replaced the fuel pump.
I'm becoming rather frustrated.
I have no idea what's going on, and why the fuel pressure didn't increase more than a couple of pounds. Plus, I feel like I've just wasted money on a fuel pump that I didn't need.
What are everyone's thoughts and ideas of what's going on here? In 2 years, this is the first trouble my PSD has given me.
Started it up and pressue immediately jumped to 67-69psi, with the largest shim still in. Not as high as I figured it would be, but better. Thought there might be air in the line, so I took it for a 10-15 minute drive, got on it pretty hard a couple of times.
Pulled back home, up to the garage, and popped the hood to see what the pressure would be. I was again thinking it would be higher. Much to my dismay, it actually dropped after the drive.
Down to about 61-62psi. Exactly where I was at before I replaced the fuel pump.I'm becoming rather frustrated.
I have no idea what's going on, and why the fuel pressure didn't increase more than a couple of pounds. Plus, I feel like I've just wasted money on a fuel pump that I didn't need. What are everyone's thoughts and ideas of what's going on here? In 2 years, this is the first trouble my PSD has given me.
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Lead Driver
Joined: Oct 2004
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From: Columbia, MO
Any ideas? I'm guessing that a factory type fuel pump, even brand new, just can't support the flow necessary for more psi. I just don't understand why it would drop from 67 to 61 after a quick drive.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,112
From: Rio Rico, AZ.
Originally Posted by jtharvey
Any ideas? I'm guessing that a factory type fuel pump, even brand new, just can't support the flow necessary for more psi. I just don't understand why it would drop from 67 to 61 after a quick drive.
Does the pump sound like it's drawing a lot of air, making it sound like a mad bee?
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Lead Driver
Joined: Oct 2004
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From: Columbia, MO
Not that I can tell. First time I turned the key on, it souned a little odd for a second, but once it got fuel to it, it sounded ok to me. I'll double check it today though. May go buy some fuel line and get rid of the quick connects on the supply line.
Would air in the system caust low pressure?
Would air in the system caust low pressure?
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,112
From: Rio Rico, AZ.
Originally Posted by jtharvey
Not that I can tell. First time I turned the key on, it souned a little odd for a second, but once it got fuel to it, it sounded ok to me. I'll double check it today though. May go buy some fuel line and get rid of the quick connects on the supply line.
Would air in the system caust low pressure?
Would air in the system caust low pressure?
That aside, the fuel injectors simply don't work as well on foamy fuel as they do on pure liquid fuel. You'll be glad to get rid of the air in the fuel regardless of your pressure issues. Also the pressure that you are getting right now is IMO optimum for these engines. Not to high and not too low, just right.
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Lead Driver
Joined: Oct 2004
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From: Columbia, MO
Sounds good. I'll leave the FPR shim as is for now. I'll keep an eye on the pressure though. Do I need the fuel injection hose for tank to pump supply though? Since it's not under pressure, wouldn't a standard fuel hose work, as long as it's rated for diesel fuel? Also, I had bought some 5/16" hose to try it, but it's just a hair too big and doesn't fit snugly onto the fuel pump inlet. Would hose clamps tighten it down enough? I was thinking of going with 1/4" instead for a tighter fit. I don't want to have a chance that air will leak back into the system. I saw where someone used a 3/8" hose. Bigger than the 5/16". I'll probably wait until tomorrow to do this mod. I've got another thing in mind for today. Kiwkk, I'm sending you a PM to see what you think of it.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,112
From: Rio Rico, AZ.
Originally Posted by jtharvey
Sounds good. I'll leave the FPR shim as is for now. I'll keep an eye on the pressure though. Do I need the fuel injection hose for tank to pump supply though? Since it's not under pressure, wouldn't a standard fuel hose work, as long as it's rated for diesel fuel? Also, I had bought some 5/16" hose to try it, but it's just a hair too big and doesn't fit snugly onto the fuel pump inlet. Would hose clamps tighten it down enough? I was thinking of going with 1/4" instead for a tighter fit. I don't want to have a chance that air will leak back into the system. I saw where someone used a 3/8" hose. Bigger than the 5/16". I'll probably wait until tomorrow to do this mod. I've got another thing in mind for today. Kiwkk, I'm sending you a PM to see what you think of it.
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Postmaster
Joined: Jun 2005
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From: New Hampshire
Originally Posted by jtharvey
Since it's not under pressure, wouldn't a standard fuel hose work, as long as it's rated for diesel fuel? Also, I had bought some 5/16" hose to try it, but it's just a hair too big and doesn't fit snugly onto the fuel pump inlet. Would hose clamps tighten it down enough? I was thinking of going with 1/4" instead for a tighter fit. I don't want to have a chance that air will leak back into the system. I saw where someone used a 3/8" hose. Bigger than the 5/16". I'll probably wait until tomorrow to do this mod. I've got another thing in mind for today. Kiwkk, I'm sending you a PM to see what you think of it.
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Lead Driver
Joined: Oct 2004
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From: Columbia, MO
I just ran a pressure test on the 5/16" hose. Took the fitting from the old pump and clamped the hose on, using only one clamp (I plan to use 2 on the truck), just to expose any weaknesses. Capped the end of the old pump fitting, then put some air pressure to the open end of the fuel hose. I gave it around 80 psi of air pressure. Then, sprayed some soapy water around the fitting of the hose and old pump. No air bubbles!! 
I think the 5/16" will work fine once the clamps are on. Can't find 7mm anywere in town. I'm just concerned with going bigger, like 3/8", that the gap might let air in. I think the 5/16" will flow enough -- for now.
Only thing is for me, I have a 40 gallon tank, and I couldn't even see the supply that goes into the tank. I'm going to have to drop the tank to get this one done completely.
I can do the line at the fuel pump, but that tank supply is going to have to wait.
I think the 5/16" will work fine once the clamps are on. Can't find 7mm anywere in town. I'm just concerned with going bigger, like 3/8", that the gap might let air in. I think the 5/16" will flow enough -- for now.Only thing is for me, I have a 40 gallon tank, and I couldn't even see the supply that goes into the tank. I'm going to have to drop the tank to get this one done completely.
I can do the line at the fuel pump, but that tank supply is going to have to wait.
Postmaster
Joined: Oct 2004
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Originally Posted by jtharvey
I just ran a pressure test on the 5/16" hose. Took the fitting from the old pump and clamped the hose on, using only one clamp (I plan to use 2 on the truck), just to expose any weaknesses. Capped the end of the old pump fitting, then put some air pressure to the open end of the fuel hose. I gave it around 80 psi of air pressure. Then, sprayed some soapy water around the fitting of the hose and old pump. No air bubbles!! I think the 5/16" will work fine once the clamps are on. Can't find 7mm anywere in town. I'm just concerned with going bigger, like 3/8", that the gap might let air in. I think the 5/16" will flow enough -- for now.
Only thing is for me, I have a 40 gallon tank, and I couldn't even see the supply that goes into the tank. I'm going to have to drop the tank to get this one done completely. I can do the line at the fuel pump, but that tank supply is going to have to wait.
I think the 5/16" will work fine once the clamps are on. Can't find 7mm anywere in town. I'm just concerned with going bigger, like 3/8", that the gap might let air in. I think the 5/16" will flow enough -- for now.Only thing is for me, I have a 40 gallon tank, and I couldn't even see the supply that goes into the tank. I'm going to have to drop the tank to get this one done completely.
I can do the line at the fuel pump, but that tank supply is going to have to wait.
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Lead Driver
Joined: Oct 2004
Posts: 7,413
Likes: 1
From: Columbia, MO
Looks like I've got some driving to do before I can empty out the tank. That'll give me a chance to go test out the exhaut brake (using EBPV) and TC lockup that I'm finishing up this morning.