WTF is going on??

[GLHNSLHT2]

So here's the problem. I've got what sounds like air going into my fuel filter. Sounds like bubbling or cavitating. I can only hear it while idling. If I blip the throttle it goes away as it hit's 0psi then comes back as soon as the vacuum increases. Also the fuel pressure reg you can hear thumping inside the car.

I've got a Walbro 255 pump and and custom fuel rail. The fuel rail is plumped the the feed line with Earls -6 line and fittings. I had just the feed in -6 line for a while and this noise wasn't there. The noise started after adding -6 line to the return from the FPR to the factory return. Also the wideband is jumping all over the place like air is getting into the system. I've tried a couple different FPR's now with different connectors to the -6 line.

What's got me baffled is that this only started happening when I added the line to the return. But the noise is in the feed line.

I've changed the fuel pump and the fuel filter and the FPR. That hasn't worked so far. I can't see that having -6 line for the return to be causing this. I'd like to go racing this weekend but the car doesn't like to idle and I hate it.

anyone have any ideas?

[puppet]

Are those compression fittings Jay?

[GLHNSLHT2]

On the feed from the hardline to the -6 line yes it's a compression fitting. But it was setup with that and I didn't have this issue when the fpr still had a regular hose to the return. I used tube nuts and sleeves on the return. Tonight I swapped to an 89+ FPR and used a metric to -6 adapter there but still have the tube nut and sleeve at the hardline connection. Still doing the same thing.

[jim34]

What kind of fuel pressure are you getting ?

[GLHNSLHT2]

Same fuel pressure as I've always had. Must of missed putting it in the post but the fuel pressure is rock solid. I would think it would be bouncing around all over the place. I started the car up today and the noise wasn't there but by the time I got a block down the road it was back and the a/fs were up and down again with about a 2:1 range swing. Course the car wants to die when they go lean. Really making me mad. It's a royal pain to drive around slowly now with it doing this. I'm going to try and go back to the stock rubber line tonight or tomorrow if I can get the tube nut and sleeve back far enough on the hard line to get the hose and a clamp over it.

[GLHNSLHT2]

Also was thinking of trying to test the pressure before the injectors instead of at the end of the rail. The FPR is thumping so loud it sounds like I have Venolia forged pistons in the car and they're cold.

[puppet]

Got a way to bleed the rail? Schrader valve? (off chance this is a on time thing)
You say you hear air in the filter. Pump has to be sucking air then. I know you said you changed it ... but have to check what it's putting out now to rule it out.

[GLHNSLHT2]

yes I have a shrader valve in the rail. It sounds like air. A cavitating sound at the filter that started when I put -6 line on the return from the FPR to the hardline. Does it with both pumps (original 255 walbro I put in a couple years ago, and the new Walbro 255 from FWD). Changed the fuel filter and the FPR. No change.

What do you want me to do puppet?

[jim34]

Could have burst the rubber hose inside the tank, ive had that happen, you will have a lot of fuel vapor smell

[jim34]

If its that loud you may be setting off the knock sensor too

[puppet]

Put some gas in the tank. See if you can bleed the air at the rail .... unless this is generating air continuously?

Connect the gauge and drive for 20 minutes or so. Not a quick check but to warm the pump to make sure it isn't fading. Watch the FP. Test the FP out of the pump first (crimp the return line). What the pressure doing after you shut it down? Is it holding?

If the pump is sucking air there has to be a problem in/at the tank.

[crazymadbastard]

Quote:

Originally Posted by puppet Put some gas in the tank. See if you can bleed the air at the rail .... unless this is generating air continuously? If the pump is sucking air there has to be a problem in/at the tank.

that probably is it- did you replace the in-tank lines too? could it a cracked housing- not sure about the pre-92 pumps though.

[GLHNSLHT2]

changed rubber hoses when I changed the pump and the clamps too. Pressure holds when I shut the car off. I've noticed that when I start the car the noise isn't immediately there at the filter. It takes 5-10 seconds before it starts up. The FPR get's louder the more noise it makes in the back too. I just don't think it's the pump or the rubber lines. Why? Because I just changed the return line to braided and that's when it started. Also swapped all that stuff in the tank too. It all looked good still (the original 255l/hr stuff.

There's no smell of fuel. Could air get in the return system through my new line and fittings and then fill the pump pickup with bubbles enough to have the pump suck it up?

[GLHNSLHT2]

put 5 gallons in, no change. Held the brakes and tried to drive the car around at 0psi in the parking lot. Soon as you give it gas and decrease the vacuum the sound goes away. If you're driving down the freeway and come to a stop the sound isn't there for about 10 seconds. Then you hear the sound, then the car stumbles, vacuum decreases, sound goes away and car idles back up, sound comes back and over and over till it's doing it continuously.

Here's what I had and it didn't make this noise. 100_1364

I did this and the noise and symptoms started. CIMG0678

Last night I took off the 87-88 style regulator and put an 89+ reg on with a metric adapter. No Change.

I'll try to go back to what I had and run around with the fuel pressure gauge on it and see what happens.

My ECU lets me prime the pump as many times as I turn on and off the ignition. The 1st 3 times or so there's no sound. but after that the sound comes back.

I really want to run the braided line. I like it, I like the looks of it. And as far as the feed line it was/is working. There's no gas in the FPR and no leaks I can see while the car is running. The current FPR has about 62psi static pressure (I dropped it and bent the vac nipple accidently but straightened it back out) My stock one had 60psi static. I guess I'll try the things above and let everyone know. I'm just sick to my stomach about this. When the car runs well it's an awesome Riot. When it does stuff like this I want to take it straight to the J-yard with all the race parts still on it.

[jim34]

Is it loud enough to set off the knock sensor ? pull the line off run it to a jar and emerse it in the fuel and see if its getting air somehow