FPR is easy to check if you have a hand pump with a pressure gauge.
As a test you could also use it to pump up the regulator, go for a drive, and see if fuel pressure falls off under load and goes back up again, which would indicate a restriction or weak pump.
An aside on restriction. Used to do a lot of turbo Buicks(*) and when upgrading the pump, one of the Old Guys Who'd Seen It All was one of the parts suppliers, and he said you had to take a round file to the flares in the fuel sending unit and open them up. The lines were 3/8 but the swedge/flare/whatever would neck it down a sixteenth or so at the end, and he had seen that cause problems...
* - when PeteMom was a kid, she used to call the act of throwing up "doing Buicks", so "doing turbo Buicks" sounds like a really really bad time from that perspective
If it were me, based on my experience, do not ignore the noise the pump is making because it is telling you something. Pumps make noises, especialy squeals when they are sucking air, or the fuel is too hot.
Have you measured fuel flow? Does it meet your hp requirements?
Pete: Great suggestion on the hand pump, I have a mity vac that I think will do the trick. I did run a drill but down all of the flares in hard tubing to make sure they were a full 5/16" diameter, some definitely needed opened up after flaring. And years ago in college, I read some book that gave all the different euphemisms for puking and I remember "Buick" being one of them. I think for some reason Turbo Buick is awesome in that context 
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Bruce: I agree something is up and the pump sucking air is a big concern, just haven't seen evidence of that yet.. I sort of did a fuel flow test. When I was making sure the surge tank level idiot light was working I timed how long the old 255lph pressure pump took to drain the ~1.5 liter surge tank. It repeatably took 13 sec to drain about 1 liter. It was a 255lph pump, and rough math of 4.6L/min pump rate = about 276L per hour - but that's to into a fuel jug, so no backpressure. The stream was plenty strong and was not aerated. I need to do some testing with the new pump. I should measure the flow rate from the return line with the engine off and pumps running.
Yea good call on checking the flow from the return.
So, I checked the fpr rising rate function with 20psi from my air comp, and it worked as expected - 45 psi popped right up to 65psi with air applied.
Then I did some testing of the fuel flow rate:
With the car idling, and the pump seeing 12.9V, the return line flows right at 4.45 liters/minute or about 267 lph. At 62 psi (20psi ref signal to the fpr) it flowed about 4.55 lpm or 276 lph.
A good bit less than the 350lph pump rating, but still should be plenty to support the 275whp I am at, right? And it should perk up a bit with higher voltage off idle.
Summit's Fuel pump sizing chart:
Those flow numbers should be good for the hp. However it does seem odd the flow goes UP with added pressure and not down... may be worth describing your method in detail for reference.
Point of nitpick but it isn't a "rising rate" regulator because it keeps a 1:1 ratio with manifold pressure. Rising rate regulators were used on speed density cars to sort of make forced induction work with a stock computer by cranking the fuel pressure up 4psi or so for every pound of boost.
THAT SAID
275whp is about 350-400 crank horsepower depending on which dyno you use. Rotaries also are not very efficient, depending on who you talk to they need 10-20% more mass flow from a turbo to make a given amount of power, which requires a similar amount of fuel... the upshot is, you're close but should still be good.
I am curious what the voltage is at the pump at 60psi. Not the connector but the pump itself. This may be difficult info to get.
Paul_VR6 (Forum Supporter) said:Those flow numbers should be good for the hp. However it does seem odd the flow goes UP with added pressure and not down... may be worth describing your method in detail for reference.
Yeah, I saw that too. Honestly, the ~2% increase in measured volume at 62psi is within the margin of error for my "process".
The return line was diverted to an empty gas can, and I would just flip on the pump switch, start the car, and start the timer on my phone all in rapid succession, then turning off the pump when I got to either 1 or 2 minutes. Then measure the amount collected in the can by pouring it out into a 1L measuring cup as many times as needed to empty the can. So definitely not super repeatable on the exact time duration.
Pete. (l33t FS) said:I am curious what the voltage is at the pump at 60psi. Not the connector but the pump itself. This may be difficult info to get.
I may temporarily add extra wires to the pump posts and run them into the cabin connected to a volt meter, so an assistant can monitor during a drive.
Ok that's good to know. When I do it I measure from the return but just turn the pump on manually jumper or run it with the motor off and raise the pressure with a mity vac to the target. I usually weigh the fuel but your method should work fine the only wild card is the consumed fuel of the running car but it's likely negligible.
I moved the FPR vac reference line from the stock lower intake manifold port to being teed into the line that goes to the ECU from the UIM, so the FPR and ECU should see the same signal. That didn't change the behavior. Fuel pressure tracks fine when not under boost, then it doesn't keep up. I have an expected pressure max of ~55psi, but actual fuel pressure never quite gets to 50psi.
I added wiring to monitor voltage at the pump. I have about 1 volt drop below the voltage the ECU is reporting, so pump is seeing 12.9 volts under general driving conditions. Under full throttle and full boost it drops another .2-.3 volts. I never saw it go below 12.6V at the pump.
There is one other notable thing - in the last 5 miles of my test drive of roughly 30 miles, my pressure pump again started making a lot of noise, occasionally at first, progressing to near constant by the time I got back to my house. I thought it was possible the pump or a hard line moved was and contacting the unibody and amplifying the normal pump noise. However, idling in my driveway, I grabbed and moved all the various parts and could not get the noise to stop or start based on that. The noise is sort of cyclical, I can feel "pulses" on the rubber lines as it cycles. Fuel pressure is correct and steady, and the low level light for the surge pump never comes on. My pumps are currently wired to switches straight to the battery, and when I shut the car off - both pumps still running - the extra noise immediately stopped, the pressure pump went back to it's normal noise level.
Video of pump noise:
Ignoring the noise issue for the moment, I'm thinking there is a restriction somewhere that is limiting fuel volume.
You have pics of the physical layout of the surge tank and the lines? It almost sounds like the surge is getting air in it and the pressure pump is cavitating.
1.5L Surge tank is mounted in the stock tank, it has a level switch with a warning light that turns on when surge level gets to ~20%. The warning light has never come on at idle or any driving conditions. I also, ran the pressure pump straight into a gas can, and it had strong flow and did not appear to be aerated. So, I have been under the assumption that the pressure pump is receiving consistent fuel supply.
Greatly appreciate you taking the time to lend your expertise on this.
Here's a diagram of the system. I do have an additional fuel filter in between the surge tank and pressure pump, and then a stock Turbo II filter after the pressure pump.
Still sporadically working on this, some progress, but no breakthroughs.
To recap, there's 2 issues:
Issue 1: The fuel pressure does not rise 1:1 with manifold pressure. Where I'm at now with the larger pump and aftermarket FPR, and after I bypassed the filter between surge tank and pressure pump (I saw about 20% more flow with that filter bypassed), I am still seeing the fuel pressure rise with boost up to about 0 psi, and then it diverges, and gets to and holds about a 4.5 to 5 psi delta between expected and actual fuel pressure.
So - questions: The AFR from the wideband is staying within 0.1 of target Lambda (seeing WB at 11.3 at WOT with T-Lambda of 11.2). That seems well controlled. Do I need to be worried about the gap in expected vs actual fuel pressure if I am hitting my AFR targets? I read a thread on HP academy that mechanical FPR's may not control that tightly, but if AFR is good, no worries - seems too good to be true.
My next step on this issue is upsizing the supply line to the pressure pump from 5/16" to 1/2" line. The original, smaller pump had a ~5/16 input and output, and i didn't upsize the supply line with the new pump mainly because it required dropping the tank. I've since read that it is common to have the supply line larger than the output lines, so I'm tackling that next.
Issue 2: Pressure pump becomes weirdly noisy after a long drive. On this one, I emailed Deatschwerks, and they thought if the increased noise isn't from something resonating against the body of the car, then the only other thing would be debris. They offered to replace the pump, but suggested that first I reverse polarity and run it backwards to see if that flushes any debris out of the pump inlet and changes the behavior.
Is it worth asking the FPR manufacturer how much divergence they consider to be within spec?
Regardless of whether it's acceptable or not, if they regard it as acceptable then it's probably the best you can expect from that FPR? Conversely, if they think it should be more tightly controlled, they may have educated suggestions, living as they do at the intersection of "I just bought one of your FPRs" and "my fuel pressure still isn't right."
It should not diverge at all.
Ok, I am trying to be methodical about this - change one thing, test, then change something else. I am trying to learn and identify actual root cause.
If I just focus on the lack of fuel pressure rise, seems like one of 3 possible problems:
1. FPR is bad - I am discounting this one for now since it seemed to function as expected with 20 psi of shop air applied.
2. FPR reference signal not correct - The FPR reference signal is on the same circuit as the ECU MAP sensor and the factory BOV. When I tested the FPR, I put shop air just to the fpr. I plan to redo this test with shop air feeding the FPR, ECU, and BOV and see if it still rises as expected, and if the ECU rise matches the FPR rise.
3. Fuel pump isn't able to deliver needed pressure at higher flow rates. Possible causes:
-bad pump - Maybe, it is making funny noises sometimes.
- low voltage - I measured 13.1-13.2V at the pump under load - a little low, but seems ok.
- restriction in the fuel system - My next move is to install 1/2" line from the surge tank to the pressure pump and see if that changes anything.
Any other possible causes I'm missing?
Thank you for the diagram! Ok if the pressure pump is pulling UP from a bucket of fuel that is your issue. 044 is potentially the WORST pump out there for flowing well while trying to pull fuel. For this to work you'd have to have the pressure pump IN the surge tank or use a pump that can lift fuel (Weldon would be my go to)
We have run a normal lift pump to an 044 in external surge tank (no pressure between the two pumps) with the 044 submerged and it can make over 700whp.
In reply to Paul_VR6 (Forum Supporter) :
Wow, I missed that.
When the fuel gets hot, it will start boiling in the pickup line to the pump. That may be the noise.
I had a lesser Bosch that would do that, mounted in the stock pump location under the driver's seat, problem was fixed with the .7l capacity surge tank mounted to the kickup in front of the rear axle, so the pump would be fed by gravity and would never be able to suck air.
The LIFT pump could still suffer from vapor lock...
Sorry, the diagram is not accurate for my install. I have a Deatschwerks 340IL as the pressure pump - it is pulling up from a bucket. The Bosch 044 is the lift pump that fills the surge tank. I am pretty sure the lift pump is doing its job filling the surge tank since the low level light goes out 3-4 seconds after the pump turns on and then never illuminates.
Here's the surge tank assembly, the inlet for the Bosch pokes through the bottom of the assembly. The large diameter tube is the supply to the pressure pump:
Either way, high flowing fuel pumps do not like having to lift the fuel. Must be gravity feed. Lifting the fuel up and over the axle counts as lifting, even if the pump is technically below the fuel level.
I'd find a way to mount the pump IN the tank, or use an external surge tank with the pump inside or underneath it.
Yea I am having a hard time thinking of a good remedy. Likely the easy button is to put the 2nd pump in the surge with the inlet as close to the bottom as you can ~1 inlet dia away. That way the fuel head in the surge area is > the amount it has to lift. Also the 044 is a way better pump if you can make that the pressure pump and use the garbage one for lift it will be better (but overkill at your hp)
Hmmm... I hear you and value both of you providing your knowledge and experience. It's just that this surge setup was designed specifically for this application, and the designer ran it in his FB with a ported 13B, big turbo, etc putting down ~500whp. (I had not reached out to him on this yet because his surge tank system seems to be working as expected - but I'll send him a note and see what he thinks.)
Plus, it is pumping about 330 lph when I test it (w/o the pre pump fuel filter).
And Deatschwerks is a trash pump? I mean, sooo many good reviews on Amazon!! Seriously, I thought they had a good reputation.
IF it truly won't work as configured, I could probably route the output of the Bosch pump into the feed line for the pressure pump. That would eliminate the surge tank, with the Bosch pump drawing from the main tank and sending it to the pressure pump. Or I could swap the Bosch pump out for a true lift pump connected to the supply line. I see that Deatschwerks offers a nice looking one, lol!
Thanks for all the help, I'm pulling my hair out on this one.
Yea with it like that it shouldn't work well from my experience. At least at those power levels. The 044 is killer as long as you can keep it fed. One issue is most lift pumps can't keep up and thr 044 will try and pull through it and have issues.
if you are going to drop the surge the walbro 450 pump with a hydramat should work well. Good info here https://www.maperformance.com/blogs/tech/walbro-fuel-pumps-everything-you-need-to-know-for-500-whp
deatchworks is just the latest rebadged chinese junk, along with snakeater, grams and a few others
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