I've noticed a tapping sound in my engine (1992 Formula L98). At first I thought it was a noisy lifter, but no. The sound is not coming from the valve cover, it's in the fuel rail. More specifically, it's in the FPR. The stethoscope really reveals it, but you can hear it clearly when the car idles, especially inside the cabin. There's the light tapping of the injectors, but this is a louder, heavier tap in the FPR. How normal is this, and what does it mean? I don't remember my other L98 I had years ago doing that. Fuel pressure is 35 with vacuum, 45 without.

 

im guessing it has to do with the fuel pump. theres a thing called a "pulsator" between the FP and hard lines in the tank. if it is replaced with hose, or gets hard from age, you will get this noise from the fuel rail.

 

Hmmmm, I'd hate to have to drop the fuel tank to work on something like that. I don't have a lift, and have never done it before. Seems like it would be a pain. So then if what you say is right, would I hear the sound along the fuel lines on the way up the chassis? If it's there too, or is even louder toward the back, then it might be coming from the FP area. The fp is a little noisy, you can hear it wind up and wind down when you start the car or turn it off. Crap, man I really don't want to have to mess with dropping the tank...... I'll let it go as long as I can if this is what it is.

 

But I don't know. The more I think about that sound the more I'm not sure it could resonate all the way from the back of the car. It's really loud right at the FPR, and I've never heard it at the back. When I put the stethoscope on the FPR it really did sound like the sorce. There is a slight smell of gas in the FPR vacuum connector when I pull it off the regulator nozzle too. You could be right, but I'll have to check around some more.

 

do a fuel pressure check, both with the FPR hose connected and not. as long as the pressure is within limits. you should be ok. HOWEVER if you smell fuel when you disconnect the FPR hose. you might be in for a diaphragm replacement. don't get all jittery just yet. im assuming your pump is ok

 

FP is 35 with vacuum, 45 without, so it's still in tolerances. But my thought exactly about the diaphragm, I'd bet it's OE. While we're talking about it, do you need a special tool to take the FPR cover off? I noticed its small hex bolts, but there's a small button in the middle of the bolt head. You know the one....seems like I read you need a special wrench?

 

that special tool can be had almost anywhere for $5. it is no big deal to find