Troubleshooting Aero FPR and Walbro 400 set up
12-07-2019, 12:00 PM
#21
Staging Lane
Thread Starter
Thanks again for the input Mike.
12-18-2019, 05:51 PM
#22
Staging Lane
Thread Starter
Been about a week and a half since my last post and I've finally got some good results.
So I started out by pulling the fuel rails and crossover out to do some investigating and was surprised at how tiny the hole is for the factory pressure regulators return port in the rail. Even with the block off plug installed all the unused fuel still has to pass through it so it makes sense this would cause a lot of restriction. This was to be expected from other forums I've read and figured I'd just drill it out a bit to get some good fuel flow. BUT... I bored out just a hair too much and opened up a small hole in the backside of the regulator housing on the fuel rail. So I bought a Fasster fuel rail kit off ebay that comes with the nice AN crossover and put it on. Not what I was intending to do but, hey, they look nice lol
Next part I tackled was the return line. I barely had enough line to connect the FPR with the tank using 6an so it was just dangling under the truck to test things out. Ran a new one so I could actually drive it. No drama there really so I was moving on.
What I'm pretty sure was my actual problem was the fuel hat. I actually had a spare one from a long time ago and I got to looking at the return ports on it. At first glance the quick connect and "Leg" that the return fuel goes through seemed small but when I pulled the leg out there was a plastic ring cast in that was at best half the diameter of the the quick connect size. I was able to run a 15/64th bit through all this to really open it up. This idea really came from the Fuel Lab website that talks about fuel pressure issues. They have some pretty good pics of what I think is an F-body sending unit and the restrictions in it.
Put it all back together and reset the base psi to 58psi. Plugged the vacuum line in and got 52 psi at idle. Cruising around it's usually about 50 to 52. Decel is 49 to 50. WOT at high RPM is about 56 and converter forced to lock at WOT is 57 psi. Pressure fluctuates so much more with vacuum and just seems to drive better.
Something I've read probably twice is that the Aeromotive 13129 regulator doesn't quite flow enough for a Walbro 400 and that a 13109 is more up to the task. I emailed them and haven't heard anything back yet on this but I'm curious what regulators others have used with this pump.
I'm pretty happy to finally see this all working as it should today and am glad I can move on to getting the boost going.
So I started out by pulling the fuel rails and crossover out to do some investigating and was surprised at how tiny the hole is for the factory pressure regulators return port in the rail. Even with the block off plug installed all the unused fuel still has to pass through it so it makes sense this would cause a lot of restriction. This was to be expected from other forums I've read and figured I'd just drill it out a bit to get some good fuel flow. BUT... I bored out just a hair too much and opened up a small hole in the backside of the regulator housing on the fuel rail. So I bought a Fasster fuel rail kit off ebay that comes with the nice AN crossover and put it on. Not what I was intending to do but, hey, they look nice lol
Next part I tackled was the return line. I barely had enough line to connect the FPR with the tank using 6an so it was just dangling under the truck to test things out. Ran a new one so I could actually drive it. No drama there really so I was moving on.
What I'm pretty sure was my actual problem was the fuel hat. I actually had a spare one from a long time ago and I got to looking at the return ports on it. At first glance the quick connect and "Leg" that the return fuel goes through seemed small but when I pulled the leg out there was a plastic ring cast in that was at best half the diameter of the the quick connect size. I was able to run a 15/64th bit through all this to really open it up. This idea really came from the Fuel Lab website that talks about fuel pressure issues. They have some pretty good pics of what I think is an F-body sending unit and the restrictions in it.
Put it all back together and reset the base psi to 58psi. Plugged the vacuum line in and got 52 psi at idle. Cruising around it's usually about 50 to 52. Decel is 49 to 50. WOT at high RPM is about 56 and converter forced to lock at WOT is 57 psi. Pressure fluctuates so much more with vacuum and just seems to drive better.
Something I've read probably twice is that the Aeromotive 13129 regulator doesn't quite flow enough for a Walbro 400 and that a 13109 is more up to the task. I emailed them and haven't heard anything back yet on this but I'm curious what regulators others have used with this pump.
I'm pretty happy to finally see this all working as it should today and am glad I can move on to getting the boost going.
02-22-2020, 02:34 PM
#23
If you haven’t figured this out yet, I’d try a few things... first make sure that the system holds pressure with key on, engine off.
next, purge the air out of the system if you opened up any lines. You can do this by priming it a few times and using one of those FL test gauges on the shrader valve. You can purge the pressure on most of the FP test gauges.
also check your FPR.. I know u checked to see if the diaphragm was leaking fuel already... but with engine off, plug a mighty vac hand pump with gauge onto the reference port. Pump it up to a decent vacuum. I bet it’s leaking vacuum through the threads. If so, Take the bolt and jam nut all the way out and install either an o-ring seal under the Jam nut(a hard thin type) and/or some Teflon paste on the threads. Reinstall and check again for vacuum leaks.
if all else checks out and you’re still getting pressure drop, then you have a manifold vacuum leak or a restriction in you return line. I you may have to drill out the Venturi jet in the bottom of the stock fuel bucket, if you’re returning the fuel down the leg. Or run a bigger fuel line. Check your wiring to the fuel pump as well.
also keep in mind that -6an in not really the same as 3/8” fuel line. It’s actually slightly smaller. Make sure to limit the 90 deg bends and check for kinks in the lines
next, purge the air out of the system if you opened up any lines. You can do this by priming it a few times and using one of those FL test gauges on the shrader valve. You can purge the pressure on most of the FP test gauges.
also check your FPR.. I know u checked to see if the diaphragm was leaking fuel already... but with engine off, plug a mighty vac hand pump with gauge onto the reference port. Pump it up to a decent vacuum. I bet it’s leaking vacuum through the threads. If so, Take the bolt and jam nut all the way out and install either an o-ring seal under the Jam nut(a hard thin type) and/or some Teflon paste on the threads. Reinstall and check again for vacuum leaks.
if all else checks out and you’re still getting pressure drop, then you have a manifold vacuum leak or a restriction in you return line. I you may have to drill out the Venturi jet in the bottom of the stock fuel bucket, if you’re returning the fuel down the leg. Or run a bigger fuel line. Check your wiring to the fuel pump as well.
also keep in mind that -6an in not really the same as 3/8” fuel line. It’s actually slightly smaller. Make sure to limit the 90 deg bends and check for kinks in the lines
Last edited by chris99gmc; 02-22-2020 at 02:39 PM.
02-23-2020, 08:23 AM
#24
Staging Lane
Thread Starter
If you haven’t figured this out yet, I’d try a few things... first make sure that the system holds pressure with key on, engine off.
next, purge the air out of the system if you opened up any lines. You can do this by priming it a few times and using one of those FL test gauges on the shrader valve. You can purge the pressure on most of the FP test gauges.
also check your FPR.. I know u checked to see if the diaphragm was leaking fuel already... but with engine off, plug a mighty vac hand pump with gauge onto the reference port. Pump it up to a decent vacuum. I bet it’s leaking vacuum through the threads. If so, Take the bolt and jam nut all the way out and install either an o-ring seal under the Jam nut(a hard thin type) and/or some Teflon paste on the threads. Reinstall and check again for vacuum leaks.
if all else checks out and you’re still getting pressure drop, then you have a manifold vacuum leak or a restriction in you return line. I you may have to drill out the Venturi jet in the bottom of the stock fuel bucket, if you’re returning the fuel down the leg. Or run a bigger fuel line. Check your wiring to the fuel pump as well.
also keep in mind that -6an in not really the same as 3/8” fuel line. It’s actually slightly smaller. Make sure to limit the 90 deg bends and check for kinks in the lines
next, purge the air out of the system if you opened up any lines. You can do this by priming it a few times and using one of those FL test gauges on the shrader valve. You can purge the pressure on most of the FP test gauges.
also check your FPR.. I know u checked to see if the diaphragm was leaking fuel already... but with engine off, plug a mighty vac hand pump with gauge onto the reference port. Pump it up to a decent vacuum. I bet it’s leaking vacuum through the threads. If so, Take the bolt and jam nut all the way out and install either an o-ring seal under the Jam nut(a hard thin type) and/or some Teflon paste on the threads. Reinstall and check again for vacuum leaks.
if all else checks out and you’re still getting pressure drop, then you have a manifold vacuum leak or a restriction in you return line. I you may have to drill out the Venturi jet in the bottom of the stock fuel bucket, if you’re returning the fuel down the leg. Or run a bigger fuel line. Check your wiring to the fuel pump as well.
also keep in mind that -6an in not really the same as 3/8” fuel line. It’s actually slightly smaller. Make sure to limit the 90 deg bends and check for kinks in the lines
I had an old fuel pump assembly from my last NBS and went to modifying it. I removed the leg that the return runs through and instead ran a section of submersible 3/8ths fuel line and inside the hat I used progressively larger drill bits to open up where the fuel line connects and turns down to where the steel leg used to be.
When I tested my regulator, I applied a small amount of lithium grease to seal the threads to help seal it and, with a mighty vac, I worked as it should but I do like the idea of using one of those flat sealing o rings to help with vac loss for more accurate pressure control.
Doing so solved all my issues and now the truck is turbo’d and behaves as it should under boost as well. I know many people throw the pump in and tune around the high pressure but I like things to be a little more under my control lol
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