Fuel pressure drop with increased throttle (Page 3/5)
fierosound JUN 27, 06:31 PM

quote
Originally posted by Patrick:

Actually, it's a fuel pump specific thing. The earlier years originally had pulsators installed as well. I forget the name of the style of pump from the factory, but a pulsator was required to reduce/eliminate pulses in the fuel pressure. The newer style fuel pumps don't produce these same pulses in fuel pressure, therefore pulsators have mostly become redundant. That's what I've read here over the years anyway.




They changed from a roller vane design to a gerotor design.
https://www.onallcylinders....t-fuel-pump-designs/




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[This message has been edited by fierosound (edited 06-27-2020).]

fierobear JUN 27, 07:06 PM
Great info guys, thanks.
fierobear JUN 28, 04:48 PM
Matt Meyer dropped by, and he noticed something that i missed. The vacuum line running from the evaporatorative canister to the throttle body wasn’t connected to the boot on the throttle body. He said that will keep the canister from opening to the gas tank, and will cause a vapor lock. I haven’t connected it yet and done a test run. Probably get on that tomorrow.

Sometimes, its the little stuff you miss...
Patrick JUN 28, 08:03 PM

quote
Originally posted by fierobear:

He said that will keep the canister from opening to the gas tank, and will cause a vapor lock.



I think Raydar's suggestion of temporarily loosening the gas cap while the engine was running would've eliminated that potential issue, but we'll see!
fierobear JUN 29, 01:51 AM

quote
Originally posted by Patrick:

I think Raydar's suggestion of temporarily loosening the gas cap while the engine was running would've eliminated that potential issue, but we'll see!



Good point! I did mention that to Matt. Ill run it past him.
fierobear JUN 29, 03:02 PM
Here is the problem...the vacuum line not working causes a vapor lock situation in the fuel lines, not the tank. That’s why loosening the gas cap didn’t make a difference. I have the Rodney Dickman stainless steel lines, and the bend was off just enough to keep the line from doing its job under vacuum.
Patrick JUN 29, 07:19 PM

quote
Originally posted by fierobear:

...the vacuum line not working causes a vapor lock situation in the fuel lines, not the tank.



Interesting. So it's okay now?
fierobear JUN 29, 08:01 PM

quote
Originally posted by Patrick:

Interesting. So it's okay now?



Well, no.i put it all back together. Now, instead of it dropping out and sputtering randomly, it has a regular surge and drop pattern under hard acceleration. I didn’t have the fuel pressure gauge on it. Ill rerun that test tomorrow.
fierobear JUL 13, 07:59 PM
I reran the tests, still had the fuel pressure drop problem

I replaced the fuel pressure regulator with a spare used part, inspected it carefully, looked good. No change to the fuel pressure drops. I figured this left only the hoses or the pump.

I removed the fuel filter, and noticed some rust-colored gas pouring out and some rust in the filter. I finally got a borescope, and took this picture inside the fuel filter:



I dropped the fuel tank, and noticed rust on the inside of the tank, and sediment in the bottom.





This images is larger than 153600 bytes. Click to view.



I am assuming that the pump is getting clogged with that rust/sediment.

A crusty old car guy buddy suggested I use something he called "sloshing compound" to coat the interior of the tank and seal the rust. Is there a modern name for this, maybe a product recommendation?

[This message has been edited by fierobear (edited 07-13-2020).]

Patrick JUL 13, 09:17 PM

quote
Originally posted by fierobear:

A crusty old car guy buddy suggested I use something he called "sloshing compound" to coat the interior of the tank and seal the rust. Is there a modern name for this, maybe a product recommendation?



I don't know if you've seen This recent post. Might do the trick!