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Old 08-24-2008, 05:44 PM
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Exclamation Jumpy Fuel Pressure

I have a 95 PSD.

My Fuel Filter Light has been coming on and off for quite a few weeks now. I've been through 4 fuel filters in about as many weeks and the light will still come on after the changing the filter.

Today, I hooked a fuel pressure gauge up to the schrader valve and started the truck. The fuel pressure was bouncing between about 42 and 52 psi about 2-4 times per second at idle. I know the pressure is supposed to be around 40 psi. As I RPM up, the needle on the gauge starts bouncing faster and farther. Once the needle bounces below 30 psi, the fuel filter light comes on.

Any ideas what might be causing this bouncing fuel pressure?

I'm thinking it's the fuel pump, but I want some other opinions before I drop the cash and time to replace it.
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Old 08-25-2008, 12:00 PM
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Sounds like the fuel pump to me to, Have you tryed the fuel pressure reg shim? It can be done with a bb.
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Old 08-25-2008, 12:22 PM
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No, I haven't tried the bb in the regulator, but it wouldn't fix the problem anyway.

I'm gonna replace the fuel pump and see how that works out.
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Old 08-25-2008, 12:54 PM
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I would start with the filter, also, while you have the line loose, you may wanna try to see if there are any blockages in the line. I dunno if you could blow through it or not.
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Old 08-30-2008, 06:09 PM
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New Fuel Pump and she's running betther than ever! The fuel pressure is still jumpy, but the engine is much smoother.

A new problem has arisen though. While removing the old fuel pump, the tappet fell down into the engine. What an "Oh SH!T" moment. I turned the engine by hand quite a bit to make sure it wasn't blocking anything. I heard it fall past the crankshaft and I assume it is now in the oil pan. The truck runs fine except from a dead stop. When I accellerate, the engine will hesitate. If I let off of the gas, the engine will die but starts right back up when I turn the ignition. If I stay on the gas, the hesitation lasts .5-1.5 seconds and then continues on normally. If I'm on a slight incline, the hesitation is worse and lasts longer, like 3 seconds. The hesitation is like the engine is stuck at 2000 rpm even at WOT.

Any thoughts?

My plan is to pull the oil pan down as far as I can with the engine still in the truck during my next oil change and fish around with a magnet for the tappet. I'm hoping that will do the trick.
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Old 08-30-2008, 07:19 PM
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whats the tappet for?? havent done a fuel pump yet so i dont know.
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Old 08-30-2008, 09:02 PM
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the tappet is the part that rides on the eccentric cam lobe. Obviously, it comes out of the fuel pump when not installed.
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