AFPR

driller

driller

El Presidente
Staff member
I got around to installing my new AFPR this weekend.

http://mark8.org/users/driller/pics/AFPR1.JPG

Not that I was having any issues, just a hedge against problems in the future. The install wasn't too bad, but I did have to release the passenger side fuel rail to get the pressure regulator up and out enough to get to the three mounting bolts which for some reason come from the underside of the mounting plate.

http://mark8.org/users/driller/pics/AFPR2.JPG

Of course it wouldn't make sense to have an adjustable fuel pressure regulator without a fuel pressure gauge, so...

http://mark8.org/users/driller/pics/AFPR3.JPG

I felt like a dingbat for not installing the guage first and checking the setting of the stock regulator! :eek: I didn't have any issues with purging the system after the install. I cycled the key on and off per the manual for a half dozen times before starting it up. No surges or missing.

Anyways, the manual said 29.5 PSI was the normal fuel pressure, and I went online and found where vacumn off setting of 40 was normal. I disconnected the vacumn line from the regulator and adjusted it to 40 psi. Connecting the vacumn line back, I had right at 30 psi. Checked for leaks, went for a spin and checked again. No problems.

I do have one question. Notice the fuel guage sitting at zero pressure. I was under the assumption the system remained pressurized(to some extent anyways). According to the manual the supply manifold pressure should remain within 5 psi of shut-off pressure for 1 minute. Assuming a shut-off pressure of 30 PSI, it should take six minutes or more to bleed to near zero. As soon as I shut mine off it is zero psi. Anyone with a similar setup care to advise?
 
RE: AFPR

I set my fuel pressure up a bit. I was running 33 on idle and 42-44 on WOT. I upped the fuel pressure to insure that i was running a little fat when I hit the juice.

Here is the magic question for you. Do you have a electric or mechanical fuel gauge. I have an electrical Fuel gauge in the pearl car and it would show Zero soon after you shut it off. While the mechanical one that i have in the red car would show the rails holding pressure at 28psi aftger I shut it off, and would take about 30 minutes to bleed down. Sometimes after i got out of a movie it would still show 5-10 psi. Double check your fitting and make sure they are tight.
 
LMAO

LMAO

LOL. There were pictures with your post. HAHA! I went to go get something to drink in the lobby, came back up and took a look at the post and there are now pictures that loaded. I hate dialup. Nevermind all that about the electrical fuel gauge, ect..
 
Something's amiss

Something's amiss

As I thought, your example shows pressure remaining in the system after shut-off. I'll check again for leaks but I've got a gut feeling it's gonna cost money. Dang, I wished I'd checked the pressure with the stock regulator!
 
RE: Something's amiss

RE: Something's amiss

If your pump is old, higher mileage etc. it will "bleed" pressure.

My car has been sitting idle in the showroom for 3 monts now and it still reads 30 psi, it normally reads 50 but it did bleed down some over those months.

I have found some older cars bleed down in minutes to zero, new fuel pump time then.
 
RE: Something's amiss

RE: Something's amiss


I have found some older cars bleed down in minutes to zero, new fuel pump time then.
[/quote]

This isn't exactly 'bleeding', the best I can tell it's instantaneous. Running at idle with vacumn connected, 30 PSI, reach in door and turn off key, peek around hood, 0 PSI. :(

Next step will be following manual's troubleshooting for leak down. Disconnecting the return line(isolating the pump and regulator), etc... Does anyone know where the second schrader fitting on the fuel system is? The manual talks of one between the pump and filter. I've not seen it.

Funny thing is, I swear I saw the guage sitting between 20-30 PSI when purging the system WITH THE KEY OFF!

Dang it Geno, I knew I should've kept that fuel pump you 'sent' me! LMAO! :)
 
RE: Something's amiss

RE: Something's amiss

I have found some older cars bleed down in minutes to zero, new fuel pump time then.
Click to expand...

This isn't exactly 'bleeding', the best I can tell it's instantaneous. Running at idle with vacumn connected, 30 PSI, reach in door and turn off key, peek around hood, 0 PSI. :(

Next step will be following manual's troubleshooting for leak down. Disconnecting the return line(isolating the pump and regulator), etc... Does anyone know where the second schrader fitting on the fuel system is? The manual talks of one between the pump and filter. I've not seen it.

Funny thing is, I swear I saw the guage sitting between 20-30 PSI when purging the system WITH THE KEY OFF!

Dang it Geno, I knew I should've kept that fuel pump you 'sent' me! LMAO! :)
Click to expand...

Geno could be right, it is most likely time for a new pump. I ripped the entire fuel system out of these cars to replace with SS lines and never saw another scrader valve. There is not one there.
 
RE: Something's amiss

RE: Something's amiss

I have found some older cars bleed down in minutes to zero, new fuel pump time then.
Click to expand...

This isn't exactly 'bleeding', the best I can tell it's instantaneous. Running at idle with vacumn connected, 30 PSI, reach in door and turn off key, peek around hood, 0 PSI. :(

Next step will be following manual's troubleshooting for leak down. Disconnecting the return line(isolating the pump and regulator), etc... Does anyone know where the second schrader fitting on the fuel system is? The manual talks of one between the pump and filter. I've not seen it.

Funny thing is, I swear I saw the guage sitting between 20-30 PSI when purging the system WITH THE KEY OFF!

Dang it Geno, I knew I should've kept that fuel pump you 'sent' me! LMAO! :)
Click to expand...

Geno could be right, it is most likely time for a new pump. I ripped the entire fuel system out of these cars to replace with SS lines and never saw another scrader valve. There is not one there.
Click to expand...

Yeah that's wierd. I dont remember seeing one on a gen1 in that location.

JP, I can send another, lol.

Whats the mileage on your car anyway?
 
RE: Something's amiss

RE: Something's amiss

I don't remember seeing another one(schrader valve) either. It may just be the pump. There are no leaks I can find.

The car has 106K on the clock and starts and runs just fine. The fuel pressure running with vacumn on or off is fine. The zero pressure at shut-down haunts me. It is after all a brand new regulator, so it must be the pump.

Hmmmmmmmmm... I've got exhaust work coming up soon, maybe while it's on the lift I can have the man install a new fuel pump? Best time to have it done, right?

Is there any way it could be an injector? What would it run like if it was?
 
RE: Something's amiss

RE: Something's amiss

I Highly doubt it's an injector.

Usually when the pump bleeds down its down on volume under a load. You have to check the fuel pressure while the car is subjected to a severe load (WOT)

Hook a gauge up that is long enough to snake under the hood, tape the gauge to the windsheild high enough for your passenger to read, then take it out and romp it a few times, two or three full throttle stabs is enough, pay attention to the fuel pressure when your above 4k to shift point, this is the most critical. If your under 38 I would do it.

I usually do it rule of thumb if it's 100k or over. If you didn't already do a new filter yet then do it immediately.

Static fuel pressure means nothing. You could have a near dead pump idle normal pressure yet has nothing under a load.
 
RE: Something's amiss

RE: Something's amiss

John,
where did you purchase that pressure gauge from ? I know you always get cool deals ... LOL
 
RE: Something's amiss

RE: Something's amiss

How much does a gauage with an extention long enough to view while driving cost? I should check mine before the dyno tune.
 
RE: Something's amiss

RE: Something's amiss

I haven't been able to find one that i can view while driving. If someone finds one for a good price let me know.

I don't know why it would be leaking down. I left a gauge hooked to mine over a few days and it didn't lose more than 5-10 lbs. I suppose it could be leaking back through the pump, that's the most likely scenario. It would either have to be leaking through the pump, through the regulator, or through an injector. I'd pull the spark plugs and make sure none of them are wet with gas or look different from the others, that'll rule out an injector, but if it starts fine and runs fine, i doubt it's an injector anyway. An injector leaking that bad would cause big problems.
 
RE: Something's amiss

RE: Something's amiss

The only one you could view from the cabin would be the electronic one. The complete setup runs around $200 which is too much IMHO.
 
RE: Something's amiss

RE: Something's amiss

Noob question/comment here, would the fact that it's an adjustable fuel pressure regualtor make a difference? Like maybe a non-adjustable one holds pressure, but the adjustable ones reset to zero every time?????

???
 
RE: Something's amiss

RE: Something's amiss

Jeremi, the cheaper and easier way to view fuel pressure from the cabin is to get a regular gauge with a longer hose, and tuck it under the w/s wiper. A lot of people do this and leave them there... i personally would only use it for testing and diagnosis.

Dustin, that would depend on the design of the adjustable FPR. I suppose if it were designed based on a different principle than the stock unit, that could be true. But the way it is supposed to function is as a sort of on/off switch. There is a spring and a diaphragm in there, and when the fuel pressure pushes against the spring hard enough, the diaphragm is pushed back to allow fuel to flow back down the return line. You can adjust the pressure at which this happens by adjusting the spring. The vacuum is plumbed to the back side of the diaphragm, so if you have 10 lbs of vacuum on the back side, it should take 10 lbs less fuel pressure to open the diaphragm. Either way, once you shut off the car, the fuel pressure will drop until the diaphragm is closed, and any further drop is indicative of a leak somewhere.
 
RE: Something's amiss

RE: Something's amiss

Yeah for testing that would be enough, but if you wanted to monitor the FP when using n2o - well, still $200 is too much.

BTW, what size are the fuel lines ID and OD, in the engine compartment, against the firewall ???
 
RE: Something's amiss

RE: Something's amiss

no clue on the size of the lines. About this big (holding up fingers) :).

I have a friend who hooked up a fuel pressure gauge with a long hose and tied it down right next to the passenger side w/s wiper on his t/a. he just left it there (until it crapped out). So you can cheap out and still monitor your fuel pressure that way, but i don't know how good an idea that is. I'd definitely make sure it's a good quality gauge and line.
 
RE: Something's amiss

RE: Something's amiss

Ok then, what size hose did you use to extend the fuel lines to fit the cobra rails ? Is the 2-clamp connection holding up well ?
 
RE: Something's amiss

RE: Something's amiss

I pick the car up from the body shop this afternoon. I'll look to see what size hose i used then, if i remember. The clamped hose appears to work fine. I used two clamps on each end of each hose, for a total of 8. I tried pulling it off with my hand and i couldn't. I may or may not end up switching to compression fittings, we'll have to see how bored/motivated i am this summer.
 
You must log in or register to reply here.
Back
Top