AFPR releases pressure after shut down?

[kamronman]

I recently installed my AEM fuel pressure regulator, and since i have every time i turn the car off my fuel pressure disappears! Thus making it about 5-6 seconds to start up every time..I've sealed any leaks up around the rail, fittings in the regulator, and the return line doesn't get pressurized...so you think the hose i put on my fuel pump might be leaking? Just installed the walbro 255 last week, but when i ran it without the regulator the car held fuel pressure fine after it shut off! Starting to piss me off because if it is lost so quickly it must be losing pressure while driving too!

 

[hhuricane]

I have an Aeromotive that does the same thing. Seems to be a pretty common thing.

 

[snowborder714]

Does it just drop to 0 or does it go down to 20psi or so immediately after shutting down? I believe mine (Aeromotive) drops to somewhere in the 20's right after I shut it down and then to 0 within a few hours. This seems to be normal.

I wired up part of my cruise control lever to power the fuel pump so I can get the fuel back in the system before starting, as I hated trying to start it multiple times.

 

[RT-AWD]

All aftermarket fpr will lose their pressure when the car is off. I have an aeromotive and mine does it my friends do it aswell. It should slowly dwindle, not disappear before you can pop the hood and read your guage.

Now why your car takes 5 seconds to sart beats me. mine starts right up first turn of the key, maybe 1-2 seconds of cranking depending on the temperature of the air and of the motor.

 

[Boosted98gsx]

You may have a pinhole leak at the seat of your intank pump that is causing these problems.

 

[Demon33]

This seems to be a pretty common occurrence when installing an AFPR. I had the same concern when I installed my Buschur AFPR. With the stock FPR, the fuel pressure in the line would hold for a long time (overnight or more) after the engine was shut down, but after the AFPR went on, it would immediately begin dropping to 0 when the engine was shut down. It also takes me a couple more seconds of cranking to get the engine to fire. It's a minor annoyance, but I've learned to live with it.

 

[Avionixx]

I have the same issue with my Aeromotive. I made double sure the O-ring in the pump was installed properly so I wouldn't have this issue and it worked for the first few days with the pressure slowly bleeding down. After about a week, pressure started to drop to zero immediately after shutting down and the car takes a number of cranks to start now when cold.

 

[Boosted98gsx]

This is also when DSMlink's fuel pump "on" feature comes into play. You can have the fuel pumps prime with the key at "on" and not just when it's cranking so you can make sure you have adequate pressure in the line when you crank the motor. I don't know what other tuning programs allow this, but I know DSMlink does, and it's very handy.

 

[Demon33]

This is also when DSMlink's fuel pump "on" feature comes into play. You can have the fuel pumps prime with the key at "on" and not just when it's cranking so you can make sure you have adequate pressure in the line when you crank the motor. I don't know what other tuning programs allow this, but I know DSMlink does, and it's very handy.

I thought about wiring in a momentary switch to accomplish the same thing Link would do in this case, but I figured that I would still have to sit and press the switch for 2-3 seconds vs. cranking the engine for the same 2-3 seconds. I didn't really see any advantage to priming and decided it would be a wash. I didn't have to run any additional wiring, fuses or the switch and I didn't have to cut up my dash to mount the switch.

 

[kamronman]

Demon33, There's a HUGE advantage to making a primer switch in the car to build pressure before cranking the car, i'm currently in a vocational automotive class where we work on customer's cars. Starter work their ASSES off pushing against the compression in the cylinder. 1g dsm's have a single armature starter as opposed to the 2g's with gear reduction starters, anything to make the starter's job easier, is going to help it to not deteriorate or wear the brushes on the armature. Please correct me if i'm wrong, but letting your starter work harder than it needs to is a BAD thing Today i'm running a 12 gauge wire to the relay i have on me re-wired walbro so i can prime the fuel pump when i hit the toggle! Thanks guys for contributing to the thread

 

[Demon33]

Please correct me if i'm wrong, but letting your starter work harder than it needs to is a BAD thing

I'm not going to say you're wrong, but I'm still using the original starter motor that is currently 20 years old. For over 2 years now I've had the AFPR and 190lph Walbro installed in my daily driver and to this day I have not had one problem with starting my car, save for the few extra seconds of cranking required, if you call that a problem.

While I don't disagree with you in general about keeping the load on the starter motor within reasonable limits, I have not found any evidence or proof that cranking for 2-3 extra seconds is outside this limit or that it hurts anything.

If you or anyone else can provide data that supports the idea of not cranking our (DSM) starters longer than say about 3-5 seconds, I'll certainly install a priming switch, but until then, I'm happy with what I've got.

 

[Colt4G63 also]

1g dsm's have a single armature starter as opposed to the 2g's with gear reduction starters

Actually that's wrong. 1g starters have a planetary gear reduction. But I agree with the posts concept in general.

My pressure gradually leaks back via my Walbro 255 HP. It pisses me off because of the extra moment it takes to start. I might just switch my pump on in link too. I hadn't really thought about doing it that way.

 

[johnmarines]

I might just switch my pump on in link too. I hadn't really thought about doing it that way.

looks like I will be doing the same... I just thought I had not properly sealed my afpr....

 

[kamronman]

I'm not going to say you're wrong, but I'm still using the original starter motor that is currently 20 years old. For over 2 years now I've had the AFPR and 190lph Walbro installed in my daily driver and to this day I have not had one problem with starting my car, save for the few extra seconds of cranking required, if you call that a problem.

While I don't disagree with you in general about keeping the load on the starter motor within reasonable limits, I have not found any evidence or proof that cranking for 2-3 extra seconds is outside this limit or that it hurts anything.

If you or anyone else can provide data that supports the idea of not cranking our (DSM) starters longer than say about 3-5 seconds, I'll certainly install a priming switch, but until then, I'm happy with what I've got.

The data is provided when you do a current draw test while cranking, Knowing about electricity I know that amperes are only used to the amount needed, when doing a proper draw test measuring the amps going from battery to starter the count is between 320 and 460 amperes, BUT, when fuel pressure is at 31psi and we cranked till start the amps didn't exceed 212 amps! This "data" shows that not only are you hurting the starter(by wearing the brushes on the armature) but you can also potentially hurt your battery. I'm pretty stoked that for two years the starter has held up on this guy's car!! That's amazing man. But i've done the homework, and not only is the 5-6 second crank time an inconvinience, it's damaging.

 

[Buurma]

I have a buschur afpr and my fuel pressure goes right to 0 after the car is off. i have pockelogger and with the fuel pressure test you flip it on and it reads the right pressure but as soon as its off it bleads down to 0 within seconds.

Am i looking at a fuel leak or normal operation of the buschur afpr?

 

[kamronman]

According to AEM and Aeromotive, the regulators are supposed to release pressure =/ I rewired the pump with a relay and 10gauge wire from the battery, then included a toggle switch mounted on my center console that goes straight to the original power wire activating the relay causing my fuel pump to turn on! Makes any startup take half as long as without fuel pressure built. I love it, if you guys wanna see pictures of my fuel system say the word!

 

[dsmfa9nutter]

That's what it's supposed to do. Thread over.

 

[Pirrofab]

There is 2 very common issues with fuel pressure bleed off. 1 being the anti drain back/ pressure hold inside the walbro pump which has happened many times before and also bleed down of a AFPR. There is a chance of an injector that also leaks but injector leak down comes with driveability issues. There is a simple test that I did to check for FPR leak down. It may not fix the issue of total leak down back to the tank but it will help check for fuel and vacuum leaks in the regulator so you don't lose the pressure increase during boosted driving conditions.

I did do a write up on it but I can't find it in the tech aticles anymore so I'll just sum it up real quick.

-Fill up a bucket with water
- Submerge the FPR undert the water keeping the inlet, outlet and vacuum lines ABOVE THE WATER SO NO WATER GETS INTO IT!!!!!
- Apply Shop Air Preferably REGULATED to the vacuum port and check for air bubbles around the housing, gauge threads, vacuum port, and adjustment screw.
- If leaks are found that is wer the pressure is being lost. Carefully take those items aprt and aply either thread sealant or very light coatings of rtv and retest.
- The slim deisgn Aermotive FPR has a plastic housing with the vacuum port and adjustment screw and seems to be VERY PRONE to leakage.


As far as strain on the starter from excessive cranking manufacturers recommend not cranking for any longer then 10 seconds at a time allowing for it to cool own in between as it does put an excusive load on the complete starting system. My car has had an extended crank for some time and my Factory Orignal Starter did fail just last week with 215,752 miles on it. I tok it apart to find a broken magnet, chip in the armature taken out, Brushes heavily worn and the bushings in the starter to be almost non existent. It was making noise for a while and cranking slow for some time but this was due to age and the abuse it had through the years. For the record the less the starter has to work and the easier it has to work then the less strain is on it and the longer it will last.

 

[kamronman]

To hopefully save you time in the future man, There's a MUCH quicker and efficient way to test the walbro's bleedback function. Simply start the car, pinch your fuel return line with needle nose pliers or vise grips (with a cloth so you don't damage the line). Then shut the car off, If you hold pressure you know it's the regulator letting pressure by into the return, if you don't you know that pressure is back-tracking in to the tank via the pickup!

 

[rampridersrider]

My car with the Aeromotive fpr holds pressure with no problems. I shut the car off and it stays around 40 or whatever. After the car sits for a few weeks there will still be around 20 psi in the system. I can crack a line and it will instantly drop to 0. I dunno whats different. I have a 255 intank, stock lines, etc etc.


My friend has a 1g and it will instantly drop to 0 after he shuts the car off.





Couldn't you just wire in a switch to turn the pump(s) on and run em like that? Flip a switch, on, let prime for a minute, then start the car? Like the RACECARS do? Hahaha. I wouldn't mind doing it to help with cold starting my car.

 

[Boosted98gsx]

To hopefully save you time in the future man, There's a MUCH quicker and efficient way to test the walbro's bleedback function. Simply start the car, pinch your fuel return line with needle nose pliers or vise grips (with a cloth so you don't damage the line). Then shut the car off, If you hold pressure you know it's the regulator letting pressure by into the return, if you don't you know that pressure is back-tracking in to the tank via the pickup!

Are you really recommending someone block off their fuel return when the car is on?

Wow, and you harassed me about the time it should take to bleed off pressure?

 

[kamronman]

hah no boosted98gsx, Read carefully my procedure, you start the car with vise grips or pliers on the return line, then quickly shut the car off if you want to. If you don't want to quickly shut the car off you don't have too. You can run all day without the return line . Have you ever seen under the hood of an srt4? Or a dodge dakota sport truck? Theres no return lines.

And I hope you would only prime with the switch for about 2.5 seconds, not anywhere near a minute. I now use a fuel primer switch. And link is in the mail anyway so i'll be able to prime just before crank instead of with the switch.

 

[Pirrofab]

hah no boosted98gsx, Read carefully my procedure, you start the car with vise grips or pliers on the return line, then quickly shut the car off if you want to. If you don't want to quickly shut the car off you don't have too. You can run all day without the return line . Have you ever seen under the hood of an srt4? Or a dodge dakota sport truck? Theres no return lines.

And I hope you would only prime with the switch for about 2.5 seconds, not anywhere near a minute. I now use a fuel primer switch. And link is in the mail anyway so i'll be able to prime just before crank instead of with the switch.

theres no return lines because they are designed to be a returnless system with the return in the tank. You should only be priming the system with the return line blocked not actually running the car. Just disconnect the crank angle sensor to kill the spark while doing this test.

 

[kamronman]

That works too man Thanks for clearing that up

 

[ZLODEY]

we have an idea to put fuel damper valve on fuel return line, as I have in my STi. what do you think?

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