In-tank pump problems

m16ty

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I've got a strange issue that I can't seem to nail down. Truck will run fine for 5 minutes or so and then die. You can open the bleeder on top of the filters and get nothing but air bubbles. You have to leave the bleeder open for about a minute and then you'll finally clean fuel, it will start and run for another 5 minutes and the process starts all over again.

What I can't understand is how the pump is pumping air. There is plenty of fuel in the tank. I've had the pump out and everything looks fine. I've cracked the lines at the pump and primary filter and get air bubbles when it happens. What am I missing here?

I've got another spare pump at work that I don't know the condition of, I may get it tomorrow and see if it will work. I'm supposed to haul my daughter's cheer team in the Christmas parade Sun so I need to get this sorted out.
 

TsgtB

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Mine will splash fuel off the hood... (big stream) when the secondary vent is open.
The primary filter should push a nice stream if you vent it also.

Can you hear fuel recirculate back into the tank?
Your flex hose on the pump attached proper and in good shape?
Fuse connections good (getting power to the pump).?
I put in one of the Parker units (works great).
Fuel line under the radiator smashed?
after all that, checking fuel lines on top the IP/HH... best of luck.
 

winfred

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if you are getting air at the primary and fuel is not hitting the ground and you sure that the pump works you may have a issue in the tank, heard of a pump pick up coming apart, just installed a parker pump in my truck and when i removed the sender my hose was turning into jello
 

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m16ty

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I pulled the pump and took it apart, everything, including the hose, looks fine.

The thing that has me puzzled is it's still pumping when no fuel is coming out, it's just pumping air. You can see bubbles coming out of the bleeder. It's like the fuel level is below the intake but there is 3/4 in the tank. It got dark on me tonight, I'll just have to do more investigation tomorrow.
 

rustystud

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I pulled the pump and took it apart, everything, including the hose, looks fine.

The thing that has me puzzled is it's still pumping when no fuel is coming out, it's just pumping air. You can see bubbles coming out of the bleeder. It's like the fuel level is below the intake but there is 3/4 in the tank. It got dark on me tonight, I'll just have to do more investigation tomorrow.
Are you sure it's "pumping" air and not just "pulsating" ? Your intake line could be leaking so bad that it is just squirting back into the tank and causing a pulsation in the lines.
 

rosco

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The motor to the pump is a magnetic drive. Sometimes the drive fails, but the motor keeps running, as it should. Or the pump comes apart, and doesn't pump. I can't explain the bubbles. Mine has an 1/8NPT at the top of the pump - you can put a guage on it there. !st thing though, is to change all the filters.
 

frank8003

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The motor to the pump is a magnetic drive. Sometimes the drive fails, but the motor keeps running, as it should. Or the pump comes apart, and doesn't pump. I can't explain the bubbles. Mine has an 1/8NPT at the top of the pump - you can put a guage on it there. !st thing though, is to change all the filters.
yep, put a gauge on it, change all the filters
filterpumpjob IMG_0179.jpg
and a new pump and hose and be done with it.
pump lift one each 1400pph at 27VDC.jpg
The pumps are still 50 bucks and the special hose is about 12 bucks
the hose could be failing inside the hose.
 
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jamboly

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Disconnect lines going to the pump. Pull pump, leaving wire to pump assembly connected. Put the pump in a bucket with about 3-4 inches of diesel. Turn on the ignition and you will quickly find if it is a pump problem. If pump is working, you will have diesel spraying everywhere. A problem I have found is that with low sulfur diesel and biodiesel, your fuel will start forming what they are calling asphalteen. It is a tar looking substance. I had one pump that had the impeller stuck by that black goo, but the motor ran great,
 

jamboly

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Disconnect lines going to the pump. Pull pump, leaving wire to pump assembly connected. Put the pump in a bucket with about 3-4 inches of diesel. Turn on the ignition and you will quickly find if it is a pump problem. If pump is working, you will have diesel spraying everywhere. A problem I have found is that with low sulfur diesel and biodiesel, your fuel will start forming what they are calling asphalteen. It is a tar looking substance. I had one pump that had the impeller stuck by that black goo, but the motor ran great,
After posting this I realize I left out an important part. When you put the pump in a bucket, you need to run a grounding wire from the battery negative terminal to the pump (I usually attach it to the pump mounting plate screw holes.) All that being said, a quick check is to just disconnect the fuel output line on the pump while it is still mounted. The advantage of putting it in bucket is you will quickly find out if you have a problem with the rubber hose on the pump.
 

m16ty

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I've done the usual filters and inspected lines and everything. I'm pretty sure it's something inside the tank. I'll get a new pump but I need this thing going tomorrow. It just acts like it's sucking air through the intake.

I'm going to try my other spare pump and see if it works. Last resort is I installed a 24v in-line pump on my m715 when it's fuel pump took a dump, maybe I can rig it up somehow to get by.
 

M35A2-AZ

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I've done the usual filters and inspected lines and everything. I'm pretty sure it's something inside the tank. I'll get a new pump but I need this thing going tomorrow. It just acts like it's sucking air through the intake.

I'm going to try my other spare pump and see if it works. Last resort is I installed a 24v in-line pump on my m715 when it's fuel pump took a dump, maybe I can rig it up somehow to get by.
For now till you can check the rubber hose on the pump, fill the fuel tank all the way up and see if it stops sucking air.
 

TsgtB

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Mine buzzed (not the air buzzer), and sounded like it was doing something, but it wasn't.
The Parker pump is QUIET. All you can hear is the return fuel stream, pouring back in the tank.
I'd make sure the fuel level is at least above the metal bracket that is below the fuel cap...
 

3rdmdqm

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You probably have already checked this, but the bottoms of these pumps are notorious for falling off and the spacer plates that create the pump well drop out. When that happens the impellar spins but nothing is actually pumped through the line. Is the bottom still on the pump and the spacer plates still attached?
 

m16ty

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The old pump looked fine and on a bench test I could shine a light through the screen and see the impeller shaft turning.

I ended up putting in another pump I had and everything ran fine so it must have been the old pump. I'll tear it down when I get a chance and see if I can figure out what's going on.
 

gimpyrobb

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The old pump looked fine and on a bench test I could shine a light through the screen and see the impeller shaft turning.

I ended up putting in another pump I had and everything ran fine so it must have been the old pump. I'll tear it down when I get a chance and see if I can figure out what's going on.
Don't waste your time, its not worth it. Pull the power cord off and chuck the rest in the trash.
I'll take the old pump if you don't feel like pulling the old power cord off.

I've taken a bunch apart and never got them to run right. If you do tear into it, watch out for the BB that will fall out and never be seen again!
 
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