SEFI Engine Fuel Pressure Drainback--Also BBK Opinions Please

[ZephyrEFI]

Alright, so today i did a fuel pressure drainback test on my car. It loses pressure very quickly after i turn the engine off. Since i have braided stainless fuel lines, i don't feel comfortable squeezing them with a clamp to determine which side is causing the drainback problem i have. Therefore, i got an AN -6 female plug to put on the springlock connector adapter I have on my fuel rail. I plugged the return side and pressurized the system. It held about 19 lb for quite a while. Longer than i cared to wait. Honestly I thought the problem was the pump, but apparently not so. I reinstalled the return line and tried again. It lost pressure like usual. So, what that means is, i have a bad regulator, correct? It's an Aeromotive adjustable one. I have it adjusted to 40 lb. Where it's adjusted shouldn't affect whether it lets the pressure drain back though, right? I don't know much about aftermarket ones and why people like them. I liked it because it has a gauge port and i got a good deal on it. I've got nowhere else to put a gauge because since i went to the different fuel lines, there's no shroeder valve.

So, anyway, i was looking on Summit to see what a new one costs. I noticed there's a BBK adjustable regulator with the vacuum port on top, instead of on the side where it interferes with the EGR valve like the Aeromotive one has. But then I read the reviews, and they were pretty much ALL bad on the BBK! I guess that answers that!

So, i have this 155 lph BBK fuel pump i was going to swap to (I have a parts store stock replacement now) when i thought the pump was the problem. It's new in box, but I think it's really old. I got a good deal on it too, because of that. But now having seen the reviews on the BBK fpr, I'm worried I'll be yanking my damn tank out to replace it right away if i install it. What are your thoughts? I HATE pulling the gas tank.

If I were to go to a different pump, which one do you like? My combo is pretty much '93 Cobra (Explorer intake, 65mm throttle body, 24lb injectors GT40P heads), and i plan to do a cam in the future (TFS1 or something similar), as well as a custom tune. What LPH do I need that will allow for those upgrades? What brand do you like? Walboro seems reasonably priced...

Thanks in advance for your input!

[87gtVIC]

I can only comment on not purchasing the BBK FPR. I did after my stock one started to leak externally. The BBK FPR had the same fuel pressure bleedback as your Aeromotive one did. I picked up another stock one and haven't been happier.

[Haystack]

The stock pumps had a one way valve installed. My 86 pump died at 318k miles with the stock Bosch pump. I did a pressure test on it before swapping the pump and it took forever to bleed down, 30+ mins. When I swapped the pump (for the 3rd time in 20 miles, dont get me started on airtek or other parts store pumps) every other pump I tried was missing the one way valve.

Walbro makes replacement pumps for Bosch now, and they are the pumps that everyone seems to like. There was an interesting youtube video I saw on here comparing a stock and 155lph pump to a 255+ aftermarket pump, and you wouldnt belive how much aireation(sp? Bubbles...) it dumped back in.

[erratic50]

I have a JEGS adjustable fuel pressure regulator - wish I also would have saved my stock regulator.

I believe the race oriented adjustables are designed to leak down rapidly when vacuum is gone as a safety feature but I'll be the first to mention that it makes it harder to start my car. I turned my pressure up immediately after I installed the new regulator along with my typhoon intake on stock E6 heads with a mild SD friendly cam and large throttle body, headers, etc, because my plugs showed my motor was leaning out and I could hear it in the exhaust note.

Im not so sure the adjustable was anythibg more than an answer to the problem it caused honestly. I suspect if it held pressure better I wouldn't see this happening. I'm running a 155 from a big box store that I've had for years. It was a Bosch if memory serves me correctly.

Just installed a Walbro 155 in my sons 1986 GT ragtop this weekend. It holds pressure just like the stock one did. Flip the key and it fires.

A 155 should be enough for his sleeper buildup he wants to do. If not he knows how to change it now.

Your combo it sounds like it's going to be on the edge of needing a 190. IMO don't go any larger than you need as you end up with a lot more heat in the fuel when it circulates repeatedly. That burns up pumps and causes vapor lock situations, etc. (don't ask me how I know...)

[ZephyrEFI]

Good info so far! I'm learning things i didn't know! Kind of sounds like a stock regulator is the way to go! I wonder if i can do a gauge port somewhere else. I'd really like to be able to monitor my fuel pressure given the issues I've had.

[ZephyrEFI]

Hey, look what I just found! Somewhere else to put my gauge!

http://www.jegs.com/i/Russell/799/670340/10002/-1

[ZephyrEFI]

I emailed Aeromotive to see what they have to say about it. Apparently their standard for tech emails is to get back to you "within FIVE business days". So now.... we wait. They made no reference to allowing drainback as a safety thing, but did say if you try to do a vacuum test using a vacuum pump, they won't necessarily hold vacuum, which seemed odd to me, but might verify what we're thinking here.

But an upgraded pump will work okay with a stock regulator right?

[homer302]

I think the overwhelming opinion on BBK parts is they are not very good. I know I made that bad decision ONCE but never again. I don't have any experience with the FPR though. I can't believe that they test fit any parts on any REAL cars. I think they have access to CAD drawings and design parts that SHOULD fit based on the drawings but in reality they are so far off it is ridiculous.

[ZephyrEFI]

Got my answer, and I'm impressed! Very thorough!

Brad,

This can be confusing, but basically performance regulators are not designed to leak down, they are simply optimized for performance when the engine is running, which in the end results in a regulator that may not hold fuel pressure when the engine is off. From an engineering standpoint a regulator can be created for a specific pump, a pump created for a specific engine, and performance can be acceptable while using a poppet that seals when the engine is off. However, when the engineering emphasis for the regulator is to handle a range of high flow pumps, allow a wide range of adjustable pressure and deliver accurate vacuum/boost reference, the poppet that delivers best performance across the board simply doesn’t seal reliably when the engine is off.

Ultimately, the solution is to simply extend the priming cycle from the factory setting of roughly 2 seconds to something in the range of 8-12 seconds. It’s rare that you have to run the pump that long, but it’s critical for easy starting to run in long enough to purge vapor from the fuel rail and then begin cranking the engine before the pump turns off.

If you can’t program the ECU for a longer priming cycle you can install a momentary button or switch that simply allows you to prime the fuel pump independent of the ECU. Just find the factory fuel pump relay and determine which side of the relay coil is switched by the ECU (the power or the ground side) and then splice into that to your button, then from the button to the appropriate power or ground supply and you’re good to go.

Hope that helps, let us know if you need further assistance and thanks for choosing Aeromotive!

Brett Clow
Tech Director

Aeromotive, Inc.
7805 Barton St.
Lenexa, KS 66214
913-647-7300 Ext. 109

His solution sounds reasonable (especially if you don't care about having everyday usability), but I think i'd rather have the convenience a stock regulator gives you. I think the plan at this point is to swap in a new stock regulator and a 190 lph Walbro. If you guys think that won't overwhelm the stock regulator or anything... I see no reason to need to adjust the pressure.

[cb84capri]

I think the overwhelming opinion on BBK parts is they are not very good. I know I made that bad decision ONCE but never again. I don't have any experience with the FPR though. I can't believe that they test fit any parts on any REAL cars. I think they have access to CAD drawings and design parts that SHOULD fit based on the drawings but in reality they are so far off it is ridiculous.

I could not agree with this guy more right now. Their stuff is made to a price point and that's it. I think the only part of theirs I would ever buy is their shorty unequal length headers after grinding the welds out of all the ports.

I would stick with the Aeromotive regulator and put a momentary switch in the car as they have recommended. I think it speaks highly of their company that they took the time to email you such a thorough response. You could put the switch in the glove box behind the door like Ford did with the fuel door release button and hatch if you have a spot and don't have both of those already there.

Cale

[ZephyrEFI]

I think it speaks highly of their company that they took the time to email you such a thorough response.

It absolutely does and I let them know that!

I ordered a stock Motorcraft regulator, so we'll see what happens. The button thing is a fine solution for a weekend car or whatever, but to me, at this point, it's a compromise I don't want to make. This is a car I want to jump in and drive to work anytime I feel like it. Use it like a daily driver. That's been a driving force behind every decision I've made so far on this car. However, if when the time comes to do my tune, it becomes apparent I need the Aeromotive regulator for things to work best together, I'll hold onto it.