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Fuel pump primes but doesn't build pressure pls help !

Old 05-10-2013, 10:34 AM
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Default Fuel pump primes but doesn't build pressure pls help !

Worked just fine 30 mins ago changed cap+rotor getting spark(confirmed) engine cranks I can hear the pump prime it's just not building/holding it's pressure pls help I need this car going as it's my DD

no cels 94 gsr

filter is under a year old and there is no leak in the gas line
Old 05-10-2013, 11:59 AM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

something not tightened properly making you suck air and not build pressure maybe.. fuel cap, fuel filter, fuel rail, fuel regulator?
Old 05-10-2013, 12:09 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Originally Posted by POPLERO
something not tightened properly making you suck air and not build pressure maybe.. fuel cap, fuel filter, fuel rail, fuel regulator?
The car was stationary for half an hour all I did was change the cap and rotor. I tightened all of those except the filter as i've never touched it since I replaced it in September. will check for signal to the injectors as soon as it stop raining.


This thread my very well have to be re-started as I get some psi(27-29) and if I hold the gas pedal down I can hear poping so I assume it's getting some gas.

so if i'm right a new pump takes maybe 30 mins to install and you don't need to drop the tank ? (looked at the FAQ section)

Last edited by B_Swapped93; 05-10-2013 at 12:34 PM.
Old 05-10-2013, 12:55 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Update #2 injectors are getting constant signal w/key in 2 position. however when pump primed it got 25psi then it dropped off pretty quick so I turned the key to #2 postion again primed it to 20psi . does this sound like the pump I find it VERY hard to beleave that all4 injectors went bad within 45 mins at the same time and are still receving signal. had a fuel cut out issue at idle with the injectors pulsing normally still sounding like the pump ? I hear it prime but I don't think it has the fource to pump enough fuel for the car to start


also where is this infamous "fuel pump relay" under the dash ? why would it cause the pump to prime but have little pressue ? that sounds like the pump it's self no ?

Last edited by B_Swapped93; 05-10-2013 at 01:15 PM.
Old 05-10-2013, 02:22 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Bump (sorry) but I'm getting the car tuned this Thursday at 5:00 i need the car to actually start to get down there.
Old 05-10-2013, 02:50 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Do you have gas? Or very low on gas?


The fuel pump relay would be the main relay I suppose, I don't think that's the cause.
Old 05-10-2013, 02:58 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Originally Posted by Builda'Teg_92
Do you have gas? Or very low on gas?


The fuel pump relay would be the main relay I suppose, I don't think that's the cause.
yes not more than or just under 1/4 mark of the tank. but I've started the car many another time on low/empty. pump primes,builds 25 psi try to start nothing just cranks over and over the plugs are dry(should be soaked) considering the amount of times it cranks(cycles). confirmed white/purple spark, all 4 injectors are getting signal(constant) so I don't think it's them. my fuel pressure when primed use to sit at 38/40 psi now it sits at 2oish. there are NO fuel leaks anywhere my thought is weak pump can't supply the pressure(enough fuel) to allow the car to get going. injectors all going bad at once and not firing even tho getting constant signal seems VERY unlikely that's why I was suggesting the pump as it's not building adiquite pressure plus I had another issue where at idle injectors would pulse spark was present but the fuel just sort of "cut out/stopped"


Cliffs: pump isn't building pressure like it used to and injectors are getting steady signal but not shooting enough fuel

Last edited by B_Swapped93; 05-10-2013 at 03:53 PM. Reason: Cliffs:
Old 05-10-2013, 04:21 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Fuel pressure regulator must be going bad. Do this as a test, get some vice grips, and PINCH your return line when the pump is trying to prime. It SHOULD shoot up. if it DOES shoot up, then your FPR must be going out. if it DOESN'T, then your pump is probably going out.
Old 05-10-2013, 04:30 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

ok so if the reg is bad it must be letting too much fuel return correct thus not letting the pump 1 prime 2 keep sufficaint pressure ?. will try that test
Old 05-10-2013, 04:34 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

You don't seem to be having much luck with your car lately. Hope you get it figured out soon.

Sounds like a fuel pump to me. Its a far fetched idea but the pickup in the tank may have cracked. I have a marine tank I use in my demolition derby cars that this happened to. Worked perfect until just under 3/4 of a tank then probs with fuel starvation and eventually no fuel delivery. Originally I thought the fuel pump cam on the engine (Pontiac 301) had worn out so I junked the car. When I put the tank in a fuel injected Volvo and it didn't run I was scratching my head for a while. Doubt it's your problem but its something to look for when you pull the pump.
Old 05-10-2013, 05:08 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Question will a 99dx pump work I have a dx sitting in my yard can I use the pump so I can at least try it and if need be drive to go get a 190plh or 255lph wally ?

the car had that REALLY bad running rich prob for a long time I replaced most of the components that would have been under stress from it just not the pump.
Old 05-10-2013, 05:31 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

The PGM-FI Main Relay is just above/behind the hood release lever.

I am confused, [injectors are getting constant signal w/key in 2 position] do you mean power, [12V+], if so, that would be correct, the "signal" would be a ground pulse from the ECU/ECM.

With the low fuel pressure, it is either the fuel pump, or the FPR, pinching off the return line will tell you which one it is.

Replacing the fuel pump on a 94 Integra is easy as cake/piece of pie, remove rear seat bottom, remove access panel, unbolt and remove fuel pump from fuel tank and thank the powers that be you have a G3 and not a G2. 94
Old 05-10-2013, 05:40 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Originally Posted by fcm
The PGM-FI Main Relay is just above/behind the hood release lever.

I am confused, [injectors are getting constant signal w/key in 2 position] do you mean power, [12V+], if so, that would be correct, the "signal" would be a ground pulse from the ECU/ECM.

With the low fuel pressure, it is either the fuel pump, or the FPR, pinching off the return line will tell you which one it is.

Replacing the fuel pump on a 94 Integra is easy as cake/piece of pie, remove rear seat bottom, remove access panel, unbolt and remove fuel pump from fuel tank and thank the powers that be you have a G3 and not a G2. 94
ok I think it's been replaced/re soldered as it looks newer than most things down there/isn't bolted in. by signal mean I just used a test light and have never yet had any issue with them(injectors) will do the test with the fpr. but will the 99dx pump fit/work ?
Old 05-11-2013, 05:07 AM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

ok pinched the return line fully psi rose buy 10-15. no fuel in the vac line. 2nd thing as soon as I touched the line between the rain and the filter the pressure driopped a fair bit(line still clamped). im thinking weak/dying pump. so can I get one from an ls and drop it in there ?

dat rust
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Old 05-11-2013, 11:54 AM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

well new wally 255 in there did help but till doing the same thing it's either the injectors not firing or no spark everything else checks out will confirm spark soon.
Old 05-11-2013, 12:33 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

Fule spark....mechanical timing is WAY the **** off that being said I happened whilst the car was sitting so im sure things will be fine
Old 05-11-2013, 02:08 PM
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Default Re: Fuel pump primes but doesn't build pressure pls help !

G/L. 4
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