Inconsistent Fuel Pressure

[Shibbyutman]

Have this posted in the 911 forum right now, but here goes.

Two weeks ago I installed my brand new FASS 150/150. No problems at all, and I only had to start it twice to get the air bled out, sweet. I left work late last night and my fuel pressure gage was fluctuating between 5-15 psi. It seemed to get lower when i tromped on it. My truck does have a larger siphon tube, I have verified 12V present, filters are new as of two weeks, and my tank is clean. No water in my fuel, and it wasn't cold enough to gel last night. How is the pressure regulated in the FASS is there something easy to check?

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2003 Dodge Ram 2500 4X4, Banks Big Hoss Bundle, K&N FIPK, 5" Turbo back Expand-It exhaust, Goerend Full Built Trans, Smarty REVO, DIY Fuel Control Actuator Mod, FASS 150/150 and custom big line kit.ABS Brake Specialist-You've got questions, I've got answers.

[Diesel-Dan]

Originally Posted by Shibbyutman

Have this posted in the 911 forum right now, but here goes.

Two weeks ago I installed my brand new FASS 150/150. No problems at all, and I only had to start it twice to get the air bled out, sweet. I left work late last night and my fuel pressure gage was fluctuating between 5-15 psi. It seemed to get lower when i tromped on it. My truck does have a larger siphon tube, I have verified 12V present, filters are new as of two weeks, and my tank is clean. No water in my fuel, and it wasn't cold enough to gel last night. How is the pressure regulated in the FASS is there something easy to check?

If you have the suction tube kit, how low was your tank? If you were about 1/4, the fuel can slosh away from the tube and suck air. I suggest that if you are going to do any daily stop-and-go driving, try to keep fuel levels about 2/5's or more. This will keep this from happening. Now on road trips on the hwy, you can run the tank down lower since you are not sloshing the fuel as much.

Let me know what you find.

[Shibbyutman]

I do have a suction tube, and my level was about 3/8s of a tank. but what concerned me is that after I topped the fuel tank off (literally fuel ran out) it was still doing it. Can the fuel get so airated that it would fluctuate like that?

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2003 Dodge Ram 2500 4X4, Banks Big Hoss Bundle, K&N FIPK, 5" Turbo back Expand-It exhaust, Goerend Full Built Trans, Smarty REVO, DIY Fuel Control Actuator Mod, FASS 150/150 and custom big line kit.ABS Brake Specialist-You've got questions, I've got answers.

[Diesel-Dan]

Originally Posted by Shibbyutman

I do have a suction tube, and my level was about 3/8s of a tank. but what concerned me is that after I topped the fuel tank off (literally fuel ran out) it was still doing it. Can the fuel get so airated that it would fluctuate like that?

Did it eventually stop after you filled up? With a full tank, you should have pretty solid pressure. It might have been working out some air from the low tank.

You might try the 5 gallon bucket test. Fill up a bucket with diesel. Put the return and suction line in the bucket. See if the pump sounds any different. If it sounds quieter, this might show a sign that you need to check out your draw tube in the tank. Check all fittings, height of tube off the bottom, etc.

Run with the full tank for a while and see if the issue reappears.

Did you have an in-tank pump? Is that why you went with the Suction Tube Kit?

[Shockwave]

Sounds like a leak somewhere on your fuel line. At least check for leaks before you start getting crazy. I found a slow leak like 1 drip per minute will cause this.

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2001 3500 DRW, Quadcab,NV 4500, Edge juice with Attitude,4in exhaust.