Ducman82

jump the fuel pump relay. see what she does. and its the PRESSURE line making the noise right?

is it hitting anything under the car? check the frame spacer/cushion holder thing close to the end of the hard lines before it goes to rubber lines.

pokegama

Yep, it's the pressure line that has the thumping. All the lines under the car feel tight and solid. I can feel the pulsing in the pressure line under the car too.

I really need to try jumping the relay. Hopefully that will tell us something.
Could a relay going bad make the fuel pump cycle on and off?
Could the timing of the engine effect the way the fuel system works and cause this problem?
I'm starting to run out of ideas...

On your set up, did you use Carl's modified injectors with his rails?

It would be easier to figure out if the car didn't run. It seems like it might be running a bit rich. It takes longer to start it than it used to but I did remove the cold start equipment. It does start easily once it's been running a little. I blame that on the pressure dropping at the regulator.

Ducman82

I am running a different set of 4 hole injectors.
Building a little wire jumper with a male spade on both ends is easy, jump that sucker! If it makes he noise, sweet you can trace it till the battery dies. If it does not make the noise, is a pressure pulse of some kind. But pulsing happens , physical banging does not. My money is on something vibrating against the car somewhere.

pokegama

When jumping the fuel pump is it OK to just let it run even though the car is not running? That won't damage the pump?

Ducman82

not at all. fuel just goes back to the tank. and its a great way to check for leaks

Carl Fausett

+1

Jump the fuel relay and let the fuel pump run with engine off. No harm done. We shoulda thought of this sooner - with all other noises removed it should be much easier to isolate.

pokegama

OK, I jumped the fuel pump relay. Here's the video. The pressure jumped up and down a little bit. Not sure if that's normal. No thumping in the fuel lines.

Ducman82

That seems high......

pokegama

With the engine running at idle it sits steady at 48. When I rev it up it goes up and can peg the needle. After running the fuel pump for a while the gauge seemed to smooth out and not bounce up and down as much. I would still do it, just not as often.
I ran the car for a bit after that and thought, maybe it was the AC compressor making the thumping noise so I cut the belt off that. Wasted a good belt. The noise was still there.
The pulsing in the fuel line isn't terrible. It's the thumping in the passenger footwell that seems loudest. I thought it might be the board covering the fuse panel but it's not. I need to dig into the area under the console to see if something is moving in there. I'm starting to think it's exhaust related. Is there anything that needs to be done to the exhaust since I took off the air pump stuff? I capped the hard pipe that comes up behind the engine on the passenger side. It's the one that goes int the side of the catalytic converter.

Ducman82

There is the air injection ports on the back of the heads.

Carl Fausett

I would turn that fuel pressure down until the idle stumbles, then bring it back up a little bit. You have new injectors int here and the fuel pressure you have it set at may be too high. Confirm the tune with an O2 sensor - do you have one installed or available to install for diagnostic purposes?

pokegama

Carl, I have turned it both up and down but it doesn't seem to have much effect.
I do not have an O2 sensor. Is there one you can recommend? I don't mind buying new tools

In the video of the fuel pump running, is it normal for the pressure to move up and down like that?

What do you think the pressure should be at with just the pump running?

Carl Fausett

You NEED a wide-band O2 sensor.

I liked the Dynojet Wide Band Commander kit, but I don't know if you can get it any more. It was about $240 for gauge and sender as a paired set.

But there are many other good brands/models.

Ducman82

i like the Innovate MTX-L gauges.

Carl Fausett

I have several INNOVATE products and they are excellent. +1