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Fuel pressure regulator failure?

mouserider

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Hi forum, trying to fix my fuel delivery for quite some time. Long story shot, I have 2x4 sniper efi, new aeromotive fuel tank with 360 in tank pump, Holley regulator, 6an feed and return lines. My fuel pressure is going crazy under acceleration, fluctuating 20psi very rapidly. What I did so far - new fuel gauge, changed inline Holley pump with twice more powerful aeromotive in tank pump, new lines, new 10 micron filter. Basically everything was replaced except fuel regulator. Does it sound like fuel regulator issue?
 
The return line can't be the same size as the supply line.
why is that? thats what aeromotive manual and sniper efi manual says
GEN-II-Diagras-Page-2 (1).jpg
 
I was always under the impression you wanted the supply line bigger than the return line. But I see I'm wrong
 
I have a similar setup on my Scamp. Have you checked the voltage at the pump to see if it spikes with RPM?
 
I have a similar setup on my Scamp. Have you checked the voltage at the pump to see if it spikes with RPM?
oh nope i didnt what would it tell me? not really familiar with that. Also please note same thing was with previous pump.
 
Hi forum, trying to fix my fuel delivery for quite some time. Long story shot, I have 2x4 sniper efi, new aeromotive fuel tank with 360 in tank pump, Holley regulator, 6an feed and return lines. My fuel pressure is going crazy under acceleration, fluctuating 20psi very rapidly. What I did so far - new fuel gauge, changed inline Holley pump with twice more powerful aeromotive in tank pump, new lines, new 10 micron filter. Basically everything was replaced except fuel regulator. Does it sound like fuel regulator issue?
I've seen a few of your threads on the Holley forum and you've had some hard luck getting that thing dialed in. I see you posted over there earlier and said you tested at the TB inlet and saw a gauge fluctuation.
Here you're saying it's happening under acceleration but if you're testing it under the hood at the inlet, it has nothing to do with the Sniper tune or hardware...your test is measuring at the end of the fuel line so that focuses the test on the fuel system alone.
Possiblities off the top of my head:
You've got crud in the lines/pickup/filters (new components should always be thoroughly flushed before using)
There's a voltage drop issue happening at the pump
The pump isn't big enough/can't quite keep up with 8 injectors and a tunnel ram
Could be a regulator problem I guess but it's really just a hole that provides restriction in the system (assuming it's sized properly)...I'd open the regulator up and check it all out before just replacing it.

For what it's worth....I've seen this happen when the regulator was mounted back near the tank, not that it's necessarily your issue, just throwing it out there.
Are you datalogging the problem and posting it over at the Holley site? This might tough unless you have added a pressure sensor for fuel but maybe they'll see something.
 
oh nope i didnt what would it tell me? not really familiar with that. Also please note same thing was with previous pump.
If the voltage is dropping too much the pump's output will as well.
Even just a few volts at the pump can drop the volume below what the engine needs.
They should have a flow chart for your pump somewhere in their tech documents, that shows the various flow levels at different psi and voltage/current.
 
I've seen a few of your threads on the Holley forum and you've had some hard luck getting that thing dialed in. I see you posted over there earlier and said you tested at the TB inlet and saw a gauge fluctuation.
Here you're saying it's happening under acceleration but if you're testing it under the hood at the inlet, it has nothing to do with the Sniper tune or hardware...your test is measuring at the end of the fuel line so that focuses the test on the fuel system alone.
Possiblities off the top of my head:
You've got crud in the lines/pickup/filters (new components should always be thoroughly flushed before using)
There's a voltage drop issue happening at the pump
The pump isn't big enough/can't quite keep up with 8 injectors and a tunnel ram
Could be a regulator problem I guess but it's really just a hole that provides restriction in the system (assuming it's sized properly)...I'd open the regulator up and check it all out before just replacing it.

For what it's worth....I've seen this happen when the regulator was mounted back near the tank, not that it's necessarily your issue, just throwing it out there.
Are you datalogging the problem and posting it over at the Holley site? This might tough unless you have added a pressure sensor for fuel but maybe they'll see something.
thats right, i came down to the fuel delivery problem as few people pointed it out. Therefore i bought whole new aeromotive tank with 340 intank pump as opposite to my inline 300 gph pump, new 10-micron filter, new fuel lines. Several people told me that both pumps should be more than enough for my setup, but still i went bigger and intank to eliminate possible gravity issues.
i will check voltage , than you!
Also will check the regulator. (regulator is placed just before the sniper EFI inside engine bay )
i have been dataloggin this for more than 6 months and eventually everything what i tried just didnt work out. My car still boggs on acceleration, while doing so i have AFR spikes and fuel gauge fluctuation.

i really dont think its voltage/pump/crud as i had exactly the same problem and fuel problem with old setup, i just cant believe 2 different systems (tank/sender/pump/filter/lines) can be faulty to the point where both lead to exact same fuel delivery readings.


i have googled that some fuel systems can pulsate just because and fuel pulse dumper can help.
 
if you're testing it under the hood at the inlet, it has nothing to do with the Sniper tune or hardware...your test is measuring at the end of the fuel line so that focuses the test on the fuel system alone.
This might have not come out the way I wanted; I interpreted this as watching the gauge and free-revving it in the garage...but if you're testing by driving and putting a real load on the engine, it very well could be in the tune.
I've heard that those 2x4 systems are tough to get dialed..I even remember reading on (that other Mopar site:rolleyes:) that Andy Finkbeiner struggled with one on a tunnel ram. What I'm getting at is, consider working with a professional remote tuner....I would with that setup.
 
This might have not come out the way I wanted; I interpreted this as watching the gauge and free-revving it in the garage...but if you're testing by driving and putting a real load on the engine, it very well could be in the tune.
I've heard that those 2x4 systems are tough to get dialed..I even remember reading on (that other Mopar site:rolleyes:) that Andy Finkbeiner struggled with one on a tunnel ram. What I'm getting at is, consider working with a professional remote tuner....I would with that setup.
yeah, exactly, while idling and revving everything is normal, but with actual load it does its thing. Yes i know, i have been trying to dial it in for a year, started from carbs, then efi. I do speak with one remote tuner, but as soon as he saw my data logs he said it looks like fuel delivery problem and i should sort it out first, he said that my inline pump my not be gravity fed properly, and i should reposition it, instead i took it to another level and replaced whole damn fuel delivery system and spent over 1k to see that it didnt fix it.
 
The pump isn't big enough/can't quite keep up with 8 injectors and a tunnel ram
^^^^ This, and IMHO the single -6AN supply line is a bit on the small side.

I would have run a -8AN line to supply with a Y junction after the last filter - splitting off to feed each Sniper. Basically you are trying to feed a Tunnel Ram with a standard 3/8" fuel line - where most guys would have used a 1/2" supply line.

A single return of -6AN is probably OK, but I think the problem is fuel starvation.

Also, has this problem changed since removing the Holley inline pump? I ask only because I had two of those flash billet body Holley inline pumps go bad on me. The cheap *** assembly inside is not properly connected IMHO, and is prone to disengaging - simply re-engaging is not an option in my book. I replaced it with a Bosch inline pump and cured that issue. I now have a Holley in-tank pump setup to convert in another month or so to really tidy things up.

Here is my video showing the problem of the Holley inline pump....


That video shows the second pump AFTER I had re-engaged that small brown castellated nut gear inside the pump housing. It probably would run OK now, but I'm not going to risk having to be towed home again or stuck on the side of the road. I was refunded for one pump, but the first one I bought was over the Summit 90 day return window.
 
^^^^ This, and IMHO the single -6AN supply line is a bit on the small side.

I would have run a -8AN line to supply with a Y junction after the last filter - splitting off to feed each Sniper. Basically you are trying to feed a Tunnel Ram with a standard 3/8" fuel line - where most guys would have used a 1/2" supply line.

A single return of -6AN is probably OK, but I think the problem is fuel starvation.

Also, has this problem changed since removing the Holley inline pump? I ask only because I had two of those flash billet body Holley inline pumps go bad on me. The cheap *** assembly inside is not properly connected IMHO, and is prone to disengaging - simply re-engaging is not an option in my book. I replaced it with a Bosch inline pump and cured that issue. I now have a Holley in-tank pump setup to convert in another month or so to really tidy things up.

Here is my video showing the problem of the Holley inline pump....


That video shows the second pump AFTER I had re-engaged that small brown castellated nut gear inside the pump housing. It probably would run OK now, but I'm not going to risk having to be towed home again or stuck on the side of the road. I was refunded for one pump, but the first one I bought was over the Summit 90 day return window.

Thank you, i understand, but as i said, there were dozen members on holley forum as well as remote tuners who told me that even 300 holley inline pump is good for my application, and still i went up with 340 aeromotive which should be enough to handle 700-900hp engines.
My engine is at best 350 hp.

Regarding feed and return lines i was just simply following sniper and aeromotive manuals

Screenshot 2023-09-03 031111.jpg


And no, changing fuel pump didnt change a thing.
 
OK....that's cool. I nearly went overboard and put in -8AN lines.....but realise now that would not help me at all with just a single Sniper.
I have plenty of flow.
 
Regarding feed and return lines i was just simple following sniper and aeromotive manuals
Do both return lines converge somewhere before running back to the tank?

And the entry point for the return line at the tank - is it high or low, and s it anywhere near the suction pipe to the pump for supply?

Cavitation can be an issue if the return is dumping next to the suction intake for the pump.


.....just trying to help you out here. Everyone can learn at the same time. :thumbsup:
 
Do both return lines converge somewhere before running back to the tank?

And the entry point for the return line at the tank - is it high or low, and s it anywhere near the suction pipe to the pump for supply?

Cavitation can be an issue if the return is dumping next to the suction intake for the pump.


.....just trying to help you out here. Everyone can learn at the same time. :thumbsup:
Why both?) i have only 1 return line from regulator straight to the tank, do i miss smth? (i hope i dont)

return line goes to the return port inlet on the pump itself , please take a look bellow
18162-3-600x400.jpg


I also have vent hose and venting cap , so this also shouldnt be a problem.

P.S much appreciate any help! I have been dealing with this car for a year now, starting to lose any hope, so any help/advice/point is at least smth else i can test or try.

i really hope its a regulator, i will get to it tomorrow, but i also understand its not very likely, its expensive 250$ holley regulator with less than 200 miles on it.
 
Why both?) i have only 1 return line from regulator straight to the tank, do i miss smth? (i hope i dont)
I was under the impression you had two throttle body units - as in 2 x 4BBL units - each one has a supply and each one has a return.

The supply lines will split off, as will the return lines.

As I have mentioned elsewhere, the return lines ideally will be equally sized to the supply lines.
 
1693701218778.png


I am curious to see how the pipework is inside the tank - do you have a picture of what that sender unit looks like ?
 
Thank you, i understand, but as i said, there were dozen members on holley forum as well as remote tuners who told me that even 300 holley inline pump is good for my application,
Please also bear in mind that experts can also quite easily overlook the basics.

They are more 'in-tune' with their technical expertise and diagnosing software issues or other high-end issues. Sometimes things such as basic plumbing get overlooked.
You could have a bunch of expert programmers poring over a computer all day, only to have the Janitor come in and plug the thing in again after finishing his floor cleaning.....as an analogy.
 
Do both return lines converge somewhere before running back to the tank?

And the entry point for the return line at the tank - is it high or low, and s it anywhere near the suction pipe to the pump for supply?

Cavitation can be an issue if the return is dumping next to the suction intake for the pump.


.....just trying to help you out here. Everyone can learn at the same time. :thumbsup:
This is the basic layout, the 2x4 doesn't have the internal regulator like the single unit does so the plumbing is a little different. I would mount the regulator as far to the front/nearest the TBs as possible.
Screenshot 2023-09-03 at 13-53-35 199r11770.pdf.png
 
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