Fuel Pressure issue

[DJ23GSX]

My first issue is when i shut the car down i lose all fp almost immediately. I mean within 5 seconds the fp gauge is at 0. Today i powered up the fuel pump and pinched off the return line and i was able to hold 70psi solid for a couple of minutes which tells me there aren't any leaks till after my afpr. I've searched under the car and can't find any obvious fuel leaks in the return line. What else should i look at? According to my fuel trims i am running lean no matter how much fuel i add with the safc. My gas milage is horrible. I've been averaging 13-14 miles per gallon lately and thats hardly getting on it too. Would a leak in the return line cause my fp to fall while under boost?

 

[DanThMan1983]

My first issue is when i shut the car down i lose all fp almost immediately. I mean within 5 seconds the fp gauge is at 0. Today i powered up the fuel pump and pinched off the return line and i was able to hold 70psi solid for a couple of minutes which tells me there aren't any leaks till after my afpr. I've searched under the car and can't find any obvious fuel leaks in the return line. What else should i look at? According to my fuel trims i am running lean no matter how much fuel i add with the safc. My gas milage is horrible. I've been averaging 13-14 miles per gallon lately and thats hardly getting on it too. Would a leak in the return line cause my fp to fall while under boost?

Im no expert but if you lose pressure immediately after you shut it off I would guess you need a fuel pump.

 

[DJ23GSX]

Why the fuel pump?

 

[DanThMan1983]

Well the pump has to be able to hold pressure, it doesnt hold it forever but if it bleeds off instantly the pump might be leaking in the tank or something of that nature.

 

[DJ23GSX]

Well the pump has to be able to hold pressure, it doesnt hold it forever but if it bleeds off instantly the pump might be leaking in the tank or something of that nature.

Then wouldn't it leak when im holding 70psi in the line?

 

[DoyoFCT]

it could be from a couple things. either some minor leak in the line somewhere that leaks the pressure. Or its leaking from the gasket for the sending unit, or how it secures to the sending unit in the tank that oring/plastic seal isnt all that great i generally cut that and secure the pump with fuel safe hose & hose clamps. Also rusty bolts/nuts that cant be properly torqued without breaking dont help either. My money is on the sending unit area of the car.

 

[DJ23GSX]

it could be from a couple things. either some minor leak in the line somewhere that leaks the pressure. Or its leaking from the gasket for the sending unit, or how it secures to the sending unit in the tank that oring/plastic seal isnt all that great i generally cut that and secure the pump with fuel safe hose & hose clamps. Also rusty bolts/nuts that cant be properly torqued without breaking dont help either. My money is on the sending unit area of the car.

When i pressurize the system and pinch off the return line isn't the sending unit also under pressure because its before the pinch? If it is under pressure and indeed there was a leak around there then the fp should of dropped even with the line pinched right?

 

[DirtyBirdRacing]

The fuel pressure does not drop with the car on becasue the fuel pump is pumping. But when you turn off the car the fuel pump/sending unit area might have a bad seal somewhere so that it can not hold the pressure anymore.

Bill

 

[GVR4592]

It's completely normal for fuel pressure to bleed off immediately with an adjustable fuel pressure regulator like an Aeromotive.

 

[andymoraitis]

It's completely normal for fuel pressure to bleed off immediately with an adjustable fuel pressure regulator like an Aeromotive.

Thanks for clearing that up Luke. I had the same symptoms and always wondered if it was normal since I've seen other 2G's with my same FPR hold pressure for a few minutes before hitting zero.

 

[vintagemuscle]

Mine does the same thing. It's just the aeromotive fpr. At first I found it strange and I pulled the sending unit to check the oring on the pump but that was just a waste of time.

 

[oldman]

I would have to disagree, my Aeromotive as well as others I've helped intalled locally holds for hours before bleeding down to zero. If the pressure goes to zero immediately, the problem is either a defective fpr or sealing problems at the pump like already mentioned, in most cases it's the later due to incorect size o-ring, torned o-ring, missing spacer....etc. which can also acount for lean conditions under heavy load. There are several threads in the past with this same exact issue that were resolved by a proper re-installation of the pump.

 

[andymoraitis]

Bruce,

At an 11.5:1 AFR and 27 psi on pump I have no lean condition. Also the AFPR fittings have all been wrapped in Teflon tape and the pump O-ring is in perfect shape. The pump is less than 6 months old as well.

Just chiming in.

 

[DJ23GSX]

There are several threads in the past with this same exact issue that were resolved by a proper re-installation of the pump.

When you say proper installation of the pump do you mean cutting off the bell and using high pressure fuel line with clamps? I bought a new pump and i think i am going to do this when i put it in. My walbro is 3 1/2 years old and wouldn't be suprised if its shot. It used to make weird screeching noise before. Not the typical walbro whine i mean like nails on a chalkboard screech.

All my fpr fittings are wrapped in teflan tape as well even the adjustment screw.

 

[oldman]

At an 11.5:1 AFR and 27 psi on pump I have no lean condition. Also the AFPR fittings have all been wrapped in Teflon tape and the pump O-ring is in perfect shape. The pump is less than 6 months old as well.

Andy, I'm not saying it WILL affect WOT but it can since the OP mentioned he was leaning out all the time. Dropping off to zero immediately means it has to be associated with the beginning or the end of the fuel system where massive amount of fuel is being bleed off back to the tank in a very short amount of time, any leaks in between, including vacuum/boost leaks at the FPR should not cause this condition. To say that it is normal for the system to drop to zero immediately is false and there are tones of examples/threads that suggest otherwise including members with this condition who were able to turn the situation around. Another example I would like to share is that I used to own an AEM unit (used) prior to Aeromotive that used to dropp off to zero as soon as the car is shut off. One of the AEM rep. I spoke to said that this was normal for an AEM unit, I didn't like or fully trust what he said becuase there was some hesitation in his voice. I ended up solving the problem by switching to an Aeromotive unit sold the AEM to a friend/member for cheap, the member also had the same issue and decided to take apart the AEM and resolved the issue by replacing the seal in the FPR.

When you say proper installation of the pump do you mean cutting off the bell and using high pressure fuel line with clamps? I bought a new pump and i think i am going to do this when i put it in. My walbro is 3 1/2 years old and wouldn't be suprised if its shot. It used to make weird screeching noise before. Not the typical walbro whine i mean like nails on a chalkboard screech.

I'm talking about the spacer and o-ring like descripted in this article.

 

[andymoraitis]

Thanks for the insight cousin Brucie. I'll pull the FPR apart and see what that seal looks like. While I'm at it I'll also switch to Teflon paste since it seems to do a much better job than the tape.

 

[oldman]

No problem Andy, his user name is eclipsh (Nick), pm him and get more details, I've never taken apart an AFPR so I didn't fully understand what he did either. However, I don't want every user who read this to go and immediately take apart the fpr becuase of all the ones I have helped resolved, the problem is at the pump in most cases.

 

[DJ23GSX]

Yes my fuel pump is installed properly with the spacer and o-ring. I had to change the spring in my afpr when i got it to increase the range of fp. Maybe i'll take it apart this week and check the seal. Say i did have a leak in the fpr regulator wouldn't the fp have gone down even when the return line was pinched? I was holding 70 psi in the fuel line from the pump all the way past the regulator so wouldn't it have been under pressure as well?

 

[oldman]

Yes my fuel pump is installed properly with the spacer and o-ring.

Many thinks that until they go back and double check, one common mistake is a torned or twisted o-ring due to lack of lubrication at the point of install as well as wrong size o-ring (too small).

 

[oldman]

Say i did have a leak in the fpr regulator wouldn't the fp have gone down even when the return line was pinched? I was holding 70 psi in the fuel line from the pump all the way past the regulator so wouldn't it have been under pressure as well?

No for several reasons.

1. The pump is still on so you're simply overcoming the "possible internal leaks" much like a turbo overcoming boost leaks.

2. Assuming you did this test via the fuel pump check connector so the injectors are not firing and there no chance of you maxing out your pump during a static fuel pump/system test.

3. You're basically cutting off the return capacity of the system by pinching off the return line completely so your testing method is basically pointless, a much better way is to apply compressed but well regulated air to the FPR to restrict flow instead of pinching the return line after the FPR.

 

[DJ23GSX]

No for several reasons.

1. The pump is still on so you're simply overcoming the "possible internal leaks" much like a turbo overcoming boost leaks.

How is the pump still on? i do this test with my pocketlogger and the car off and use the fp relay button in the logger to pressurized the system. If i don't pinch the return line and i push the logger fp relay button the fp jumps to 60psi then just leaks right down to 0 just like it does when i shut the car off after running.

i would never pinch off the return line while the car was running

 

[oldman]

I never said you pinched the return line while the car is on, and yes the pump is being turned on whether you use the fuel pump check connector on the firewall or the logger relay button, the only way you get pressure in the system is if the pump is on.

 

[DJ23GSX]

I never said you pinched the return line while the car is on, and yes the pump is being turned on whether you use the fuel pump check connector on the firewall or the logger relay button, the only way you get pressure in the system is if the pump is on.

ok so if i did this same test and once i built up pressure in the line and i unplugged the fuel pump what should happen? If there's no power going to the pump it can't be on right? I am just trying to understand as much as i can thanks for being patient with me.

 

[oldman]

When you hit the logger button, you're basically turning the pump on for a split second. Once the the pump is off, FP should slowly bleed off to zero in matter of hours, not seconds. The fact that you said the pressure drops off immediately even with the return line completely pinched off tells me the problem is at the biginning of the system, not the FPR.

 

[DJ23GSX]

When you hit the logger button, you're basically turning the pump on for a split second. Once the the pump is off, FP should slowly bleed off to zero in matter of hours, not seconds.

Right and by me pinching of the return line i can attain the hours of fp which leads me to believe that everything up to where i have it pinch off is holding the pressure just fine.