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Discussion Starter #42
74 degrees today started engine showing 0 psi

Installed inline electric fuel pump before the lift pump.

Rated 10-15psi. 35 gph

Applied 12v to pump without engine running, gauge showed 1 psi.
Started engine with electric pump running & still showing 1psi.
 

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Can you give us a picture of your fuel gauge setup?

Unplug your FSS and turn your ign key on with the electric pump running.
 

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When you say stock lift pump, is this the diaphragm or piston type?
 

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Think you may need to tap into the fuel filter area and check the pressure there.
Sounding like you have a restriction between the lift pump and the IP or a dodgy lift pump.

Are all the fuel lines standard?
Cheers Steve
 

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Are you going to give A picture of how you have your gauge installed?
 

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Discussion Starter #48
Can you give us a picture of your fuel gauge setup?

Unplug your FSS and turn your ign key on with the electric pump running.
Here is a pic of my fuel gauge setup.

This morning 57 degrees outside. Started engine, fuel pressure reads 4.75 psi. Added the electric pump before the mechanical pump and showing 5 psi.

Unplugged FSS, Applied 12v to electric pump, with the key in the run position. Showing 5 psi on my gauge.
 

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Everything looks ok as far as what I can see on your gauge.

I still think you need to try dumping cold water over your IP when the pressure drops to 2 PSI or lower to see it anything changes.
 

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Discussion Starter #51
Think you may need to tap into the fuel filter area and check the pressure there.
Sounding like you have a restriction between the lift pump and the IP or a dodgy lift pump.

Are all the fuel lines standard?
Cheers Steve
Steve,

All the fuel lines are stock standard.

Just moved my banjo bolt where the where the fuel pressure gauge is tapped into the fuel system from after the fuel filter to between the fuel filter and mechanical lift pump.

73 degrees out and at this location I'm showing 1 psi

Also with all hooked up as above I installied the electric fuel pump before the mechanical pump with engine not running showing 4.5 psi. As soon as I start the engine it drops to 1 psi

Thanks!
 

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On the return line coming of of the injection pump, the banjo bolt that connects that line should have a small orifice in it. If that banjo isn't there that may let your pressure run low.
 

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I was just reading back your first post, you said you had you IP rebuilt. Did this problem start after your IP was rebuilt and if so how long after?
 

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Okay,
I would take the lines off from the Lift pump to the filter and have a very good look for a blockage.

You could check the electric fuel pump to see just what pressure it is making before entering the engines fuel system.

With pressure before the engine starts and dropping after is a good sign of a restriction.

You will need to refresh my memory on whether there is a hose after the lift pump. My system bypasses all the stock setup.

Have seen hoses collapse internally and act like a check valve.
 

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My experience with fuel pressure gages

A few years back I tried a glycerine filled analog gage down stream from the filter but before the banjo fitting to the Bosch injection pump . The gage rotated between a reading of zero & 15psi like a windshield wiper on steroids; that means so fast it was worthless. My snubber couldnt reduce the flow from the lift pump to a steady flow w/o starving the engine. The lift pump is a positive discplacement pump so the output ranges from zero psi to full throttle usually around 12 to 15 psi. My thought is that your gage has paralysis by analysis in that it cant react fast enough to the multiple pulses per minute passing thru it..

in case my signature doesnt make it. 1997 ram 2500 cummins 5.9; stock; about 100k miles. all original . Fuel lift pump is original. The fuel psi gage departed this world after three months.
 

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I had a similar problem as you. One of my engines would fire up with a bump of the starter but idle a tad lower than normal for a second until fuel pressure rose to the normal psi. It turned out my fuel preheater was clogged with some thick gooey substance. I deleted it and never had a problem again. Possibly related to your problem?

Another possibility I suppose could be the OFV on the injection pump dumping your fuel pressure. Alot of p-pump guys have problems regarding the OverFlow Valve.

I've had trucks at work that had air in fuel issues and I installed clear hose on the return line to spot the bubbles. This might be something to try just to make sure it's not an air intrusion problem. Make sure the lift pump suction fitting/barb is sealed. Ive used pipe thread sealant before due to air being sucked in here.
Jake
 

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I had a similar problem as you. One of my engines would fire up with a bump of the starter but idle a tad lower than normal for a second until fuel pressure rose to the normal psi. It turned out my fuel preheater was clogged with some thick gooey substance. I deleted it and never had a problem again. Possibly related to your problem?

Another possibility I suppose could be the OFV on the injection pump dumping your fuel pressure. Alot of p-pump guys have problems regarding the OverFlow Valve.

I've had trucks at work that had air in fuel issues and I installed clear hose on the return line to spot the bubbles. This might be something to try just to make sure it's not an air intrusion problem. Make sure the lift pump suction fitting/barb is sealed. Ive used pipe thread sealant before due to air being sucked in here.
Jake
These trucks don’t have ofv issues like p pump trucks.... the ofv is just a fixed Orifice nothing really can go wrong unless it gets plugged and that won’t lead to low fuel psi.
 

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Slight Hijack.
billp, the snubber goes between the gauge and the TEE in lift pump / IP supply line.
It cannot reduce the flow to the pump unless it was plumbed in wrong.
The whole idea is to restrict flow to the gauge to reduce the pulsations from the lift pump, not the IP.

The lift pump is not positive displacement, if the outlet pressure is too high it holds the piston against the spring and there is no pumping action from the pushrod, pressure drops and the spring moves the piston back in contact with the pushrod.

Cheers Steve
 

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myother4x4isacj7 I totally forgot about that just being an orfice with a screen in it! Blonde moment I guess
 

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Discussion Starter #60
On the return line coming of of the injection pump, the banjo bolt that connects that line should have a small orifice in it. If that banjo isn't there that may let your pressure run low.
I'm looking at that return line banjo bolt still connected on the back of my injection pump, is there a spring or a valve in there that can possibly be bad and opening releasing fuel pressure?
 
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