Unemployed - Fuel Pressure Troubleshooting - 10/23/2012

The start up company I've worked for, for 6 years went belly up last week and I lost my job along with 90 other people last Friday. I lost about 160 hours of vacation [got it back 9 years later in 2021 after the whole bankruptcy processed through our court system] and only got a week's severance so that sucks pretty bad. It was pretty sudden so I didn't have a very good backup plan. Right now I'm looking around locally for another job, but that's a tall order in my area of the country, especially when the small market just got flooded with 20 other experienced engineers :( 
Luckily, my wife is a sugar mamma (doctor of physical therapy and makes decent money) so with careful budgeting I should still be able to keep the RX7. I would hate to start parting it out, but it is just a material possession, so if I have to I have to... Hopefully I can find a job before it comes to that though.

In the meantime I've got lots of time for projects that are time expensive but cheap otherwise. Enter my first project. Troubleshooting fuel pressure that was swinging between 55-59psi. Most of the parts for V2 of my fuel system rebuild were purchased while still employed.

Spoiler alert. Despite thinking I'd solved this problem below, there were more fuel system revisions after this and even more troubleshooting. Turns out I had a ball of epoxy from who knows where in my fuel tank that was too big to enter the fuel lines but big enough to wreak havoc on my fuel pump / fuel pressure.


09/24/2012
The colored blocks are simply divisions in my trip. The actual fuel pressure spikes in the colored blocks didn’t occur, I just put them in so I’d know where the divisions occurred. So.. Here’s how it’s ordered:

First section after the GREEN block is when I started my car this morning, adjusted my regulator, and drove to work (this is the only time I touched the FPR today). The drive to work is about 15 minutes. Half 60mph cruising and half 35mph stop and go.

The section after the BLUE block is my drive home at lunch time (4 hours after my trip to work).

The section after the RED block is my return to work after lunch (~30 minutes of letting the car cool down in-between trips).

The section after the YELLOW block is my drive to the gym after work (~ 4 hours after my return from lunch).

The section after the PURPLE block is my drive to the gas station from the gym (~ 1 hour of letting the car cool down in-between trips).

The section after the ORANGE block is my drive home from the gas station (~ 10 minutes filling the car and letting the car cool down between trips).

Pretty wild eh?



What I’ve tried so far:

1.  Cleaned out 100um pre-pump fuel filter and 10um post-pump fuel filter (they weren’t really dirty).
2.  Moved pump’s ground
3.  Moved post-pump fuel filter closer to pump. Moved from engine bay to under the car. This was more about a hood clearance issue, but I figured it was worth mentioning.
4.  Disassembled my FPR. I just took off the top to inspect the set screw and diaphragm. Everything looked fine
5.  Rerouted fuel return to the top of the tank to the stock fuel pump hanger lid (converted to 90 degree -6AN). More about this later.
6.  Rebuilt -6AN fuel return hose for #5.
7.  Installed mechanical gauge to verify digital sender’s output (it did verify).

My original fuel system layout was as follows

-8AN Pickup from aftermarket sump -> -8AN 100um Summit Racing Fuel Filter -> Bosch 044 In line filter -> -8AN 10um Summit Racing fuel filter -> Aeromotive 13101 FPR
Splits to -> -6AN to Stock LS1 Fuel rail
               -> -6AN return line to 2nd port on the aftermarket sump

On top of fuel pressure problems I’ve noticed my fuel pump getting loud sometimes. The led me to the #5 thing I tried. Here’s what my original layout looked like: