AFPR problems help much needed

[chevy110]

Re: AFPR problems help much needed

Nope. 75 sounds like the internal relief pressure for the pump. So your FPR is good. Next step is to clamp the supply.

Unclamp the return, then (might take 2 people) while the pump is running and you have pressure, 40# or whatever, clamp the supply line and see if pressure holds. If it does your problem is in the pump. If it doesn't then the problem is one or more bad injs. or a leak you haven't found yet.

There is a check valve in the pump that prevents back flow so that is what you're testing. Also not unheard of is an internal leak in the tank.

Like Don said, get it all dry and clean and repressurize....leaks are easy to spot, especially if you're losing pressure at a fast rate (use test port to keep pressurizing system). On another note, if if still leaks down after the clamp test, you can clamp a section of the feed line and prime the pump to see if the pump is leaking down (or if there is a line leak pre-engine). Trouble is that you have to plumb a gauge in place of the fuel filter to see pressure.

Hey Don is this basically what your telling me to do. I think this would be eaisier for me. if i understand corectly. Remove fuel filter plumb in fp gauge, clamp after where filter was towards engine and prime pump. If it leaks down i need a new fp, if not i have some bad injs? Thanks for all the help

 

[sytyguy]

Re: AFPR problems help much needed

What Don is describing is the way to test injector leakdown and pressure test for leaks between the clamp point and the AFPR. If it holds pressure, you have no leaks and the injectors are sound. If it doesn't, you have a leak or bad injector(s). My method was a way to test the pump and connections between the clamp point and pump. But in reality, if you do Don's test and it holds pressure, you have a pump or leak issue near the tank/filter.

What Don is describing is far simpler and just as effective at determining the location of the issue.

 

[chevy110]

Re: AFPR problems help much needed

What Don is describing is the way to test injector leakdown and pressure test for leaks between the clamp point and the AFPR. If it holds pressure, you have no leaks and the injectors are sound. If it doesn't, you have a leak or bad injector(s). My method was a way to test the pump and connections between the clamp point and pump. But in reality, if you do Don's test and it holds pressure, you have a pump or leak issue near the tank/filter.

What Don is describing is far simpler and just as effective at determining the location of the issue.

Well i removed the fuel filter and did it that way. The person before me switched it to the push in style ff so it was easy. But i clamped about two feet towards the engine and fp gauge shot up 75 then within 10 secs dropped to 65 now about 5 mins shesw at 60. I dont see any fuel around the injectors. I pulled all the plugs none of them are wet at all. Safe to say fuel pump?

 

[sytyguy]

Re: AFPR problems help much needed

If you did it the way Don described, you should not have seen that jump in pressure. This is easier with two people as you can have one person put power to the test port to prime the pump, you can clamp the line, and have them remove power from the test port (to prevent pressurizing the pump until it hits the internal release). What Don is describing is to FIRST have the fuel system pressurized to 42 psi (or whatever AFPR is set to) by priming the pump, THEN clamp the line, THEN kill power to pump, and THEN observe fuel pressure behavior. This traps the 42 psi in between the clamp point and the AFPR. If you then have leakdown, it's a leak you haven't found yet or an injector(s). The method I described is a way to test the pump and line/connections between the pump and the clamp point. But, you can just use Don's method as you can be certain that if pressure does NOT fall, that you have a leaking connections, busted hose from to pump to sending unit, or bad pump. Easy peasy lemon squeezy.

 

[chevy110]

Re: AFPR problems help much needed

If you did it the way Don described, you should not have seen that jump in pressure. This is easier with two people as you can have one person put power to the test port to prime the pump, you can clamp the line, and have them remove power from the test port (to prevent pressurizing the pump until it hits the internal release). What Don is describing is to FIRST have the fuel system pressurized to 42 psi (or whatever AFPR is set to) by priming the pump, THEN clamp the line, THEN kill power to pump, and THEN observe fuel pressure behavior. This traps the 42 psi in between the clamp point and the AFPR. If you then have leakdown, it's a leak you haven't found yet or an injector(s). The method I described is a way to test the pump and line/connections between the pump and the clamp point. But, you can just use Don's method as you can be certain that if pressure does NOT fall, that you have a leaking connections, busted hose from to pump to sending unit, or bad pump. Easy peasy lemon squeezy.

I thought the pressure not holding the fule filter way ment fuel pump was wrong? Did i misunderstand something? Id rather just put new injectors. thanks again

 

[sytyguy]

Re: AFPR problems help much needed

I thought the pressure not holding the fule filter way ment fuel pump was wrong? Did i misunderstand something? Id rather just put new injectors. thanks again

This really is easy to understand.

If you clamp the feed line before the fuel rail, cut the pump on, cut the pump off, and pressure falls (only way to see pressure is to have a gauge between the pump and the clamp), you have a leak upstream or a bad pump.

If you cut the pump on, clamp the feed line before the rail, cut the pump off (thus trapping pressure between the clamp and the AFPR), and see pressure falling on the rail gauge, then you have a leak downstream or a bad injector(s).

Simple. As. That.

 

[chevy110]

Re: AFPR problems help much needed

This really is easy to understand.

If you clamp the feed line before the fuel rail, cut the pump on, cut the pump off, and pressure falls (only way to see pressure is to have a gauge between the pump and the clamp), you have a leak upstream or a bad pump.

If you cut the pump on, clamp the feed line before the rail, cut the pump off (thus trapping pressure between the clamp and the AFPR), and see pressure falling on the rail gauge, then you have a leak downstream or a bad injector(s).

Simple. As. That.

yeah i did the first one and the pressure dropped so that would mean i need a new fuel pump no?

 

[sytyguy]

Re: AFPR problems help much needed

Not necessarily. You could have a bad pump....but you could also have a leak between the pump and where you clamped (this includes the likely culprit, the hose between the pump and the sending unit...inside the tank).

 

[chevy110]

Re: AFPR problems help much needed

Not necessarily. You could have a bad pump....but you could also have a leak between the pump and where you clamped (this includes the likely culprit, the hose between the pump and the sending unit...inside the tank).

ahh shitty.:tdown: so im gonna have to drop the tank is what your saying? on the plus side i can fix the gauge. the previous owner chnged pump an gauge is 1/3 off. thanks again for all your help

 

[sytyguy]

Re: AFPR problems help much needed

ahh shitty.:tdown: so im gonna have to drop the tank is what your saying? on the plus side i can fix the gauge. the previous owner chnged pump an gauge is 1/3 off. thanks again for all your help

I'm not saying anything. But someone is gonna have to drop the tank.....unless they know of another way to access the sending unit/pump (besides cutting the floor). :lol:

 

[chevy110]

Re: AFPR problems help much needed

I'm not saying anything. But someone is gonna have to drop the tank.....unless they know of another way to access the sending unit/pump (besides cutting the floor). :lol:

Well its not my old firebird so i wont be cutting the the floor.
The boss doesnt like work being done on sundays but ill see if hell make an exception so i can get to work on dropping that, I wanna good run this season two years and no cruises for fun yet, I was so close until now. My season ends halloween :rant: Shit i think i have like half a tank a gas. I can burn it driving with datamaster watching for knock right?

 

[chevy110]

Re: AFPR problems help much needed

hello again and thanks for tunning in. Today i dropped the tank there was a rubber line that wasnt super tight so i took it off put a new clamp and voila it would hit 42 drop to 40 and hold steady. engine off key on then off vacuum plugged.with tank still hanging i start it and the the pressure quickly stabalizes bounching 1-2psi, i then plugged the vac liNE In and she drops like shes supose to. Awesome so stoked. Put the tank back together and test again, now the pressure spikes to like 70 then comes shooting back down to 40. Could i have kinked a ground or something to do this? I thought i had her. :rant:

 

[sytyguy]

Re: AFPR problems help much needed

Could have pinched a line or twisted one. Easy to do on a Ty tank. Double check it.

 

[chevy110]

Re: AFPR problems help much needed

Could have pinched a line or twisted one. Easy to do on a Ty tank. Double check it.

First thing tomorrow. Thank you sir. :tup: I just wanna go for a good rip

 

[chevy110]

Re: AFPR problems help much needed

Could have pinched a line or twisted one. Easy to do on a Ty tank. Double check it.

Thank you So i decided to take it slow and check after everything i do. So i dropped the cover, then checked fp. no go. Then I undid one bolt and checked fp etc. I just losened the nut until it was even withe the bolt. The pump looked like and i was told it was changed before so they where 3"x 3/8 bolts. I did that and on the third one the fp went back to normal. So i took a 3/4 thick inch nut and used them as spacers put the cover and now my fp is is good. Its not steady when its running its bouncing 1-2 psi, i think this is normal. So went and got 25 litres of 98 mixed witht he roughly 20 litres of 94 in there did so logging and just in park reving pretty good i get some up to 6-7* of knock. if its happening in park does this mean its false? Im bout to upload the run. its pretty long not many free ones left so its about 10 mins with 2 launches.

 

[sytyguy]

Re: AFPR problems help much needed

Might want to start a tuning thread so that those no tuning into this one might be able to help, but it's most likely that the KR you're seeing is false. Take some rubber hose (such as 3/8" fuel hose), cut two pieces about 6" long and slit them lengthwise so that you can open them up (like a hot dog bun). Take those pieces and wrap them around the fuel lines where they run past the bellhousing (up and toward the engines from the shifter linkage). This is a common rattle spot and it's proximity to the knock sensor makes it a likely culprit. A datalog will tell the whole story.

But, you shouldn't have to shim out the tank to get good pressure. It's obvious you have a pinch and it could now be opened up enough to provide adequate pressure, but it may still be pinched off enough to not provide necessary flow. Potentially dangerous to leave it like that. I know it sucks, but I'd drop the take down again and ensure the lines go back up unpinched.

 

[chevy110]

Re: AFPR problems help much needed

Might want to start a tuning thread so that those no tuning into this one might be able to help, but it's most likely that the KR you're seeing is false. Take some rubber hose (such as 3/8" fuel hose), cut two pieces about 6" long and slit them lengthwise so that you can open them up (like a hot dog bun). Take those pieces and wrap them around the fuel lines where they run past the bellhousing (up and toward the engines from the shifter linkage). This is a common rattle spot and it's proximity to the knock sensor makes it a likely culprit. A datalog will tell the whole story.

But, you shouldn't have to shim out the tank to get good pressure. It's obvious you have a pinch and it could now be opened up enough to provide adequate pressure, but it may still be pinched off enough to not provide necessary flow. Potentially dangerous to leave it like that. I know it sucks, but I'd drop the take down again and ensure the lines go back up unpinched.

Your the syty guy :rant: Tank comes down again. :roll: Pretty easy though if it wasnt for the plastic cover it would take no time. Air tools help. thought that was a pretty clever fix though :tup: Thanks again. Im uploading my log now ill start a new tune thread in a bit.

 

[sytyguy]

Re: AFPR problems help much needed

I would just hate to see you get to driving it and see a trend of lack of fuel at WOT.....then try and track down the source, only to find out months from now that it's the same pinched line you shimmed the tank out for. At least this way, you'll KNOW it's not the tank, lines, or pump if you have fueling issues.

 

[chevy110]

Re: AFPR problems help much needed

I would just hate to see you get to driving it and see a trend of lack of fuel at WOT.....then try and track down the source, only to find out months from now that it's the same pinched line you shimmed the tank out for. At least this way, you'll KNOW it's not the tank, lines, or pump if you have fueling issues.

yeah your right well im there and its fresh in my mind might aswell. thanks again

 

[KyS10]

Re: AFPR problems help much needed

Resurrecting an old thread here. I'm having a similar issue to the op. I recently installed an afpr, walbro 255 pump, sending unit, and hotwire kit on my Ty. I installed a fuel pressure gauge before any of the other parts and it was holding about 42psi with all stock components after shutting the truck off. After the install, pressure drops at a steady rate to 0 after about 2 minutes. I clamped the return line with vise grips, as suggested in this thread, and pressure dropped at a much slower rate. After about an hour, pressure had gone down to about 25psi. It's possible that the pressure loss this time was because I didn't have the hose clamped tight enough. If I understand what I've read here correctly, this is likely because of a faulty afpr. I've searched and can't find any external leaks. I'm assuming if it was leaking externally at this rate that I'd see/smell it. Does it sound like I need to return my afpr for a new one?