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1G installed fuel pump and AFPR now hard start! any ideas?

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DSM315

10+ Year Contributor
92
0
Mar 13, 2009
WATERTOWN, New_York
i installed a walbro 255 pump and aeromotive afpr over the weekend and now i have been having some issues ever since. the car just cranks for a like 10-20 seconds before it starts and it loses pressure as soon as its turned off.

i have no leaks anywhere. i was reading threw some old posts and one thing im not sure about is the fuel sending unit gasket being 100% sealed but i wouldnt think that would cause me to lose pressure so fast.

these parts are brand new just taken out of the box prior to install. also i did notice that sometimes when i start it the cars runs so lean my wideband dont even show any numbers. then i rev it up a bit and it goes to perfect the lean again on idle. this happens about 2/5 times i start it.

does anybody have any ideas bout this?
 
Last edited by a moderator:
i thought that so i replaced it already . im wondering if the pump and sending unit sealed together or not. does anyone ever get a bad walbro pump straight out of the box?
 
It's the regulator. They don't hold pressure after shut down so when you go to start it the system has to build up the pressure again. Common thing to happen and if you do a search you find it mentioned numerous times.
 
I've had a Walbro 255 lph and a Bushcur/SX AFRP for about 5 years without any starting problems. Turn the key and its running. My fuel pressure solenoid is also deleted. However just last week when I was swapping turbos I hit the alternator and caused an arc. Since then I've had trouble just like the OP stated, turning over for 10-15 seconds before starting. I've already replaced the ALT fuse but that did nothing. If I find the problem I'll let you know what it is. I think it is a relay or something.
 
i have no solenoids hooked to the regulator. i thought it was the regulator at first so i took it apart. looked fine nothing ripped,torn or broke. i keep searching this problem on different sites and i found that the valve inside the pump could be bad. has anyone heard of that before?
 
I've had a Walbro 255 lph and a Bushcur/SX AFRP for about 5 years without any starting problems. Turn the key and its running. My fuel pressure solenoid is also deleted. However just last week when I was swapping turbos I hit the alternator and caused an arc. Since then I've had trouble just like the OP stated, turning over for 10-15 seconds before starting. I've already replaced the ALT fuse but that did nothing. If I find the problem I'll let you know what it is. I think it is a relay or something.

100% completely my issue as well, even arcing during turbo swap. I have no fps, and ONLY on hot starts does it give me trouble. Any more input?
 
try turning the key on and let the pump prime, then turn it off and on again and let it prime once more, then try to start it and see how it goes.

I've seen many issues even without the AFPR where the wally's won't hold fuel pressure after shut down and need to completely prime the system, usually one prime cycle is enough but doing it twice will make a deffinate noticable difference to let you know what's going on
 
try turning the key on and let the pump prime, then turn it off and on again and let it prime once more, then try to start it and see how it goes.

I've seen many issues even without the AFPR where the wally's won't hold fuel pressure after shut down and need to completely prime the system, usually one prime cycle is enough but doing it twice will make a deffinate noticable difference to let you know what's going on

That sounds like it would work for my problem, at least as a temp fix. I've noticed that if I just turn the key and hold it, it will take 10-15 seconds to fire. However if I let it crank for a second, stop, and then crank again it will start up. I'll try just priming it twice.

The only thing is that I've never had this problem for the last 5 years with the same Walbro/AFPR until now so there must me something else.
 
the fuel pump only turns on when the engine is cranking, and stays on for a few seconds after you shut the engine off. is it really not normal for a car with an afpr to leak down pressure like that? mine leaks down to no pressure before i can even open the hood and watch it fall. when i had a stock fpr it would be random and sometimes hold for days, or bleed down within minutes. i have a 255hp pump too.

it wouldn't be a bad idea to make a monostable timer with a 555 to trigger the mpi relay for a few seconds when you turn the key to on.
 
man 90% of the cars i've worked on from hondas to DSM's have had a setup to where the fuel pump is triggered as soon as the key is put in the run position to prime the engine for starting, now it's been a long time since i messed with a stock 1g but i just assumed they primed like most other cars
 
man 90% of the cars i've worked on from hondas to DSM's have had a setup to where the fuel pump is triggered as soon as the key is put in the run position to prime the engine for starting, now it's been a long time since i messed with a stock 1g but i just assumed they primed like most other cars

That's what I was always told too, turn the key to ON and the fuel pump primes. It shouldn't have to be cranking.
 
well that's not how any dsm works at all. the ecu doesn't activate the mpi relay until it sees movement in the CAS. don't believe me? use a multimeter.
 
i used my dsmlink to turn on the pump when the key is on so i can really prime it without cranking. i also did a test to see what was bad my regualtor or my pump so i unhooked my return line to my regulator and ran it into a coffee can. had someone start it. then turn it off and as my pressure was going down nothing was coming out so i did it again and covered the return with my finger and it sucked my finger to the hose . so now i know that the pressure is going back into the tank. i have been searching this and i read that the walbro 255 or known for not holding pressure because there is a valve is the pump thats not working right . so the fix is replace and hope that the next works or use dsmlink and activate pump on when key on. Any other ideas lmk
 
well that's not how any dsm works at all. the ecu doesn't activate the mpi relay until it sees movement in the CAS. don't believe me? use a multimeter.

I turned the key "on" today and listened but I didn't hear the pump. I guess it's only when cranking. I always heard differently though.
 
What about one of these?
S.U.R.&R 5/16" In-Line Fuel Check Valve: eBay Motors (item 160449324114 end time Jul-26-10 08:20:00 PDT)
You could put it on the return side.
Any thoughts about this as i have the same problem, how ever its slowly getting better as time goes by.

According to DSM315, you'd want to place this check valve on the feeder-side of the fuel system and not the return side because it's the fuel pump that needs the one way valve - allowing fuel to be leaked back into the tank - not the return line as you've implied by place the check valve in the return line.

Of coarse this all depends on which way the fuel is truly leaking back to the tank and dropping pressure in your system. If you follow the link for your check valve, they too make it sound like their check valve is sold to fix a problem with fuel pumps leaking back into the tank (on the feeder side of coarse) and not to fix a leaking fpr (return side).

I'm beginning to think you miss typed by stating you'd place this in the return side as it could be problematic if you restrict flow back to the tank and if you meant to place it in such a way to restrict travel back to the engine (maybe to hold pressure with a vacuum) I'm not sure it would work due to the system possibly losing pressure through the injectors (not sure).

I may be looking into this because it doesn't seem as though priming with Link helps my problem. I still have some things to look into in my system though first.
 
i have the same problem with my 255 and my mini fuel lab regulator i have the "fuel pump on" checked in dsm link so i just leave the key on for 5 seconds before i start it.

i plan on putting a switch on the fuel pump relay so i can have it off because sometimes i need the key on and the fuel pump is running and i want a way to to kill the fuel pump.

it will also work as an anti theft device, so its not a bad idea anyway
 
What brand AFPR? Aeromotive says this is normal for their product. Right from the install instructions.

NOTE: Testing the enclosed regulator by applying air pressure or vacuum to the vacuum port with a
hand-held pump will yield poor results, due to the slight air leakage through the adjustment screw
threads. This minute leakage, which is typical of all adjustable fuel pressure regulators, does not, in any
way, affect the performance of the regulator.
The enclosed fuel pressure regulator may not hold significant fuel pressure after the fuel pump
stops running.
 
According to DSM315, you'd want to place this check valve on the feeder-side of the fuel system and not the return side because it's the fuel pump that needs the one way valve - allowing fuel to be leaked back into the tank - not the return line as you've implied by place the check valve in the return line.

Of coarse this all depends on which way the fuel is truly leaking back to the tank and dropping pressure in your system. If you follow the link for your check valve, they too make it sound like their check valve is sold to fix a problem with fuel pumps leaking back into the tank (on the feeder side of coarse) and not to fix a leaking fpr (return side).

I'm beginning to think you miss typed by stating you'd place this in the return side as it could be problematic if you restrict flow back to the tank and if you meant to place it in such a way to restrict travel back to the engine (maybe to hold pressure with a vacuum) I'm not sure it would work due to the system possibly losing pressure through the injectors (not sure).

I may be looking into this because it doesn't seem as though priming with Link helps my problem. I still have some things to look into in my system though first.

Yeah I must have had a knock on the head when I said that:ohdamn:
I think as I looked around I found better ones for the job but as long as people know these are available that’s what counts.
Saying that as I said when I first changed my fuel pump it was real bad at starting, but as time has gone by it’s almost unnoticeable :confused:
 
Yeah I must have had a knock on the head when I said that:ohdamn:
I think as I looked around I found better ones for the job but as long as people know these are available that’s what counts.
Saying that as I said when I first changed my fuel pump it was real bad at starting, but as time has gone by it’s almost unnoticeable :confused:

Can you post links to the better ones that you have found? I'd give it a try.
 
1g cars deffinately do not prime untill the key is turned to start. I had to empy out two gas tanks that way within the last few months. One way to fix this is to do the rewire which would give the pump a signal as soon as the key is in the on position, which should prime the fuel system.
 
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