Ever since I installed my Aeromotive AFPR I have noticed via the filter-mounted gauge, that the fuel pressure drops to >5psi when I shut off the car. With the stock FPR it would remain at nearly full pressure.

Is this normal?
Is this a problem?
Where is the fuel going?



Thanks


AFPR P/N 13301, Wally 255, RX7 550cc

thats the ONLY thing changed? And can you duplicate it at will? I mean, swap in the stocker and its holding, then swap in the Aeromotive and its falling, rinse and repeat with the same results?

I didn't really want to duplicate it, but can if I need to. I assume by your response and the lack thereof from others that this is not normal?

I will throw the stocker back on today and test.

Question: did you replace both the pump and regulator at the same time? I suppose my question is along the same line of reasoning as John's. The idea being that the problem might not be the regulator at all. In fact, it's usually not. It's usually the pump. Specifically, it's usually the o-ring that seals the output line to the pump. If that leaks, the pump is usually easily strong enough to deliver enough fuel to the rail to keep the pressure up, but as soon as the pump is off, all the pressure in the rail & lines leaks past the o-ring and back into the tank. Certainly, if there's no obvious external leak, this is the most common "internal" leak. There's probably a way to confirm if this is the problem, but I don't know what it is.

For the record, I've got the same setup as yourself: Walbro255 and an Aeromotive AFPR, and my system holds pressure. I think it eventually bleeds down, but it takes hours.

I have the aeromotive and mine does it too. There are a lot of people with that FPR that have the same issue.

Makes the car take a long time to start.

I just put an Aeromotive on my car a few days ago and noticed it takes longer for the car to start now too.

As Rob mentions, it seems alot of people with this regulator have the same problem. Maybe mine's a fluke? If so, it fits its owner perfectly. I did make the point of checking mine out when so many reported theirs didn't hold pressure. All I can say is, mine does. Mine seems to work beauty in every way. I've adjusted it a bunch of times. Pressure stays rock solid wherever I set it. I've got a bit of a love affair with mine. On occasion, I've been known to caress it briefly.

I just but on a Used Aeromotive and am having the exact same problem. Pressure drops to 0 immediately upon shutdown. The car takes a good 8 cranks to start in the morning now...

Well, at least I'm not alone.

Paul: the Wally has been in there for 2-years. The ONLY other thing I have done is put in a COP kit...but I doubt that could affect anything.

I didn't get to try switching it back yet...maybe tomorrow.

I did some searching, and seems like it's a common thing for these regulators, even outside of the DSM camp.

I also read that Aeromotive makes -6 and -10 check valves, and Earls makes a -8.
Pop one of those on the regulator outlet (or inlet, depending on the valve, or if you want to do some troubleshooting with it). Maybe they should go in the kit as is...

I think it can only be one of:

- bad check valves at the pump
- leaks to atmosphere (at line connections or injector o-rings)
- problem with the injector circuit (injectors continue to squirt after the motor stops)
- problem with the regulator (either allowing excess to the return, or there's a leak into the vac line)

Seems someone contacted Aeromotive & they were told because of the design of their regulators, they will eventually drop to 0psi once the cars shut off. Now with that being said, no its not normal for the fuel pressure to drop to 0 right away after the cars shut off. What mine does (& know of others that are the same) is drops to around 22psi when I first shut the car off & then over several hours it will eventually drop to 0psi. My car starts right away everytime.

Mine does the same thing as Darens
Has been since Day 1

Same here drops to zero after key is turned off.
I have done alot of testing including changing out pump, and o-ring in fuel pickup. Taking apart regulator, cleaning and re-assembling. It held pressure at about 20 for 15 minutes after cleaning and re-assembling. Now it is the same and drops to zero right away.

Hello,

Would this solve the problem, on the return, on the end of the afpr line to the tank?

http://store.summitracing.com/egnsearch.asp?N=400300+311574&autoview=sku

Chris. That would help if the problem was due to the pressure going back through the filter to the pump but I think the fuel is going through the regulator into the return pipe. If this is true, it is due to the AFPR not sealing properly and will be causing the pump to work harder all the time to keep pressure up during driving conditions.

I plan to take apart my AFPR and see if I can improve the sealing surfaces.