Fuel Pressure Issue

[b00stedAWD]

I know there have been many threads about fuel pressure issues but I'm having a different problem and would like to know if others are having or have had same issues. I have dual walbro intank pump setup with two -6 lines as feed into both sides of fuel rail and -8 for return . The problem is when I turn the ignition to "on" position to prime the pumps I'm able to see fuel pressure rise but it falls to zero as soon as pumps stop. When I prime with one pump fuel pressure rises to 43 and holds at 35 after pump stops priming. Fuel pressure holds while at idle and rises at 1:1 ratio when getting on boost. Anyone have any possible ideas?

 

[FORMONTOYA]

I don't and never have run a dual in-tank setup before; however, an issue that crops up on a replacement is that the o-ring in the fuel pump "hat" can get twisted or torn an have the same symptoms you are describing. Long starts, not holding pressure after shut-off, etc.

 

[b00stedAWD]

Sorry, I forgot to mention that I use a modified fuel pump housing. I use straight fuel hose with clamps.

 

[TSiAWD666]

This might be normal behavior of your fpr. Not sure which fpr you're using.

Aeromotive states their afprs bleed off fuel pressure due to the design and it is considered "normal". I am only familiar with this as I had the same question after recently installing one in my car. Searching found this answer, and Aeromotive confirmed this in an email to me as well.

 

[b00stedAWD]

Yeah, I read that thread also but what I don't understand is if I prime my fuel system with just one pump the fuel pressure holds after pump finishes priming. When I prime my fuel system with both pumps it falls to zero as soon as it finishes priming. If the pressure holds when I use one pump then it should also hold when I use two pumps. Don't you agree?

 

[FORMONTOYA]

How are the pumps hooked up? Is the pump that runs and does NOT hold pressure the "back" one if they're hooked in series? I would look at the connections for the pump that does not hold pressure.

 

[oldman]

Aeromotive states their afprs bleed off fuel pressure due to the design and it is considered "normal". I am only familiar with this as I had the same question after recently installing one in my car. Searching found this answer, and Aeromotive confirmed this in an email to me as well.

And they're full of shit. I can show you at least 5 cars with Aeromotive AFPR, mine included, that holds pressure for hours after shutdown. That said, don't ask me why yours doesn't but I suspect for pressure to fall off so quickly, the issue has to be either end of the system, pump o-ring or the AFPR.

 

[b00stedAWD]

Pumps are connected in parallel to each end of the fuel rail with return line coming out from center of the rail. No o-rings on the pump since I'm using fuel line hose with clamps. I'm using Aeromotive FPR currently.

 

[FORMONTOYA]

With what's been stated....I would not even look at the AFPR as it either works or doesn't, and it works fine for one side (I run the Aeromotive 13109 and it holds pressure for several hours before bleeding off to 0). Even if you were feeding too much pressure with both connected, it would bleed down to a certain level and hold, or you would blow seals and neither side would hold.

If there is no visible leaks, then I would look at the "feed" line that comes off the pump that does not hold pressure, mainly at the connection for the pump to make sure it's tight. If it is, then maybe you received a defective pump with "buggered" seals allowing the fuel to dump back through the suction side. You would almost have to pull the questionable pump and test it outside of the car in a bucket of fuel or something similar.

But with one side working fine and the other side not, something is up/leaking past seals on the non-working side...pump to rail.

 

[b00stedAWD]

Each pump have been rewired to have its own relay and fuse from battery. For example: When I take out one fuse for pump 1 and leave in fuse for pump 2 and prime my fuel system the pressure will rise to 43 and hold at 35 when the priming is finished. So I tested this time with fuse in for pump 1 and fuse out on pump 2 and primed my fuel system the pressure will rise to 43 and hold at 35 when the priming is finished. But, when I prime the fuel system with both pumps it rises to 43 and falls to zero as soon as priming stops. Are you guys having hard time understanding what I'm trying to say. If so then my bad.

 

[turbosax2]

Could you explain your "priming" procedure in detail?

 

[b00stedAWD]

I'm using aem ems. When I turn the key to "on" position aem activates fuel pump to prime the fuel system for however many seconds I set at. Default is 2sec. Is this what your asking?

 

[turbosax2]

I'm using aem ems. When I turn the key to "on" position aem activates fuel pump to prime the fuel system for however many seconds I set at. Default is 2sec. Is this what your asking?

Yes, that was what I was asking. I didn't realize that AEM EMS could do that. Pretty cool feature. Sorry I can't help you out with your problem though.

 

[TSiAWD666]

And they're full of shit. I can show you at least 5 cars with Aeromotive AFPR, mine included, that holds pressure for hours after shutdown. That said, don't ask me why yours doesn't but I suspect for pressure to fall off so quickly, the issue has to be either end of the system, pump o-ring or the AFPR.

I've read your posts on this matter and if I recall correctly you've never verified that the aftermarket fpr was responsible for these cases of maintaining line pressure. Their claim was that their fpr isn't maintaining the line pressure, not that maintaining line pressure isn't possible by some other mechanism in the fuel line.

What's interesting in these discussions is that the justification for worrying about this is that it varies from stock behavior. I've personally moved off to ignoring the issue as the only problem I believe I have fuel-wise is now it takes more cranks in order to start the car due no initial fuel-line pressure (though I'm open to others since I don't know much about the real details of the fuel system). There might be other problems but I don't know what they might be, if they even exist, and what effects they might have. So anyone know if any of us should stress that our fuel system doesn't hold fuel line pressure whiel the pumps are off?

 

[oldman]

I've read your posts on this matter and if I recall correctly you've never verified that the aftermarket fpr was responsible for these cases of maintaining line pressure. Their claim was that their fpr isn't maintaining the line pressure, not that maintaining line pressure isn't possible by some other mechanism in the fuel line.

Please do enlighten me on the other possible mechanism in the fuel line that can maintain pressure for hours if the FPR can't.

 

[TSiAWD666]

Please do enlighten me on the other possible mechanism in the fuel line that can maintain pressure for hours if the FPR can't.

I really can't. I was proposing this possibility but I don't know of what other mechanisms are there to do so, if any.

Please enlighten all of us as to why we should care if pressure isn't maintained while the pumps are off.

 

[oldman]

I really can't. I was proposing this possibility but I don't know of what other mechanisms are there to do so, if any.

FYI, though I can't speak for others since every situation is different but in my own case, I know for a fact (well 95%) that it was the Aeromotive unit that holds my pressure after shut off because I had an AEM universal unit that I bought used prior to Aeromotive that dropped off to 0 immediately after shutdown, nothing in the fuel system was changed.

Please enlighten all of us as to why we should care if pressure isn't maintained while the pumps are off.

I have never claimed that this condition will affect WOT operations, I've simply stated the facts and the facts are:

1. Some cars hold pressure while others don't and I want to know why.

2. Aeromotive's simple explanation does not hold water and the proof is in my own car.

I have personally spoken to Aeromotive once and emailed them twice asking for detailed explanation as to why some of their units do and some don't, the tech I spoke to couldn't answer it and my two emails remained unanswered to this day. There has to be a reason why some of you are not holding pressure regardless whether or not it will affect WOT, no one will ever know the effects under WOT until two cars of similar mods, one holding pressure and one not, are put to the test on a dyno until the point where each fuel pump is maxed out, we may be able to find some answers by comparing both logs. That said, since you're the one who is so sure that this is nothing to be concerned, I'm assuming you must have access to such comparable logs that show absolutely no difference. If not, I would suggest holding off your strong opinions on the subject.

 

[FORMONTOYA]

And back to our sponser....

Your symptoms do seem odd. I can't explain why it would hold pressure with pump 1 or pump 2, but not both pumps at the same time. It would definitely seem that all 3 scenarios would work, or none would work at all.

Which model of Aeromotive FPR do you have? Have you contacted them about any probable issue one might run into while using 2 pumps?

I personally couldn't think of any. If you were supplying too much pressure with both pumps running it seems it would just blow the seals and then the FPR wouldn't work at all.

Definitely let us know how it works out.

 

[b00stedAWD]

Currently I'm using Aeromotive A1000. I'm thinking about changing to Weldon unit to see if the problem get resolved. Thanks guys for all your support. As soon as I get the problem resolved I'll post with fix.

 

[danielbui]

The fuel pressure problem was fixed due to a leaky weld on the number 2 fuel pump connection. We welded a bung to the Fuel pump housing cover and used AN fittings to connect the fuel lines. It would hold pressure under one pump but having two pumps on it would leak pressure through the weld (pin sized hole.. scary). The pumps and FPR would hold pressure until car was turned off. Good thing He was over cautious.

 

[turboglenn]

When i bought a brand new wally 255 and posted on here about it not holding pressure when not running i was told that some wally pumps dont have the vlve in them that keep them holding pressure once the voltage is turned off to them. Neither of mine will hold pressure once the key is off. I have a stand alone EMS as well and use the samefunstion to prime the pumps. Now i'm wondering what the REAL deal is about these pumps and holding pressure????

 

[danielbui]

Yeah we were concerned about that aswell untill we fixed the problem and now no more fast bleed off.