FPR (fuel press. reg.) Question

[johnnymx5]

So im not quite sure how they work or exactly what they do but i have an unknown brand FPR gauge in my car that spikes at above 40 when i turn the ignition to the *on* position and i can hear the fuel pump priming but once the priming sound from the fuel pump stops, the gauge quickly drops to zero. i noticed this while trying to trouble shoot why my car wont start.

do some FPR gauges drop to zero after a few seconds or is something wrong with my fuel pressure? i know the Aeromotive FPR in my RX7 holds its place to only slowwwwlyyyyy taper down over a long period of time with the key still in the on position.

i figured this may be the reason my car isnt starting and was wondering if someone could lead me to a solution instead of getting raped by a towing company and then a mechanic lol thanks

[awesomeaustin99]

If it's an electric gauge in the car and not on the regulator (analog) it would make sense that the gauge drops instantly when the fuel pump cuts off because the pump is no longer building pressure or priming. Plus KA cars prime at like 43 psi. I don't think the fpr has anything to do with it not starting.

[johnnymx5]

thanx for your responce. im not near the car at the moment and wouldnt know how to check if the gauge is anolog or not but heres a short video i took of it yesterday. can you tell if it looks like its acting normal? if its electrical and cuts off after the few seconds of the ignition turning on, without pressure, would that cause the car to not start or am i having a different issue

https://www.youtube.com/watch?v=oPNPx-cdBns
https://www.youtube.com/watch?v=tw2LGtG5bZs
https://www.youtube.com/watch?v=q13vLmyeSMM

[Croustibat]

The pump is supposed to keep the pressure when it stops (at least not drop the pressure directly), if it does not it means something is wrong there. Could be a leak, an injector that is not closing, a faulty pump or a faulty FPR.

Still the car should start ... we can hear a "pop" on the second video, are you sure the timing is correct ?

[awesomeaustin99]

That's what's I was about to say. It being analog like that it should hold that pressure and the gauge should show that. Could be pump or injectors but there should still be fuel in the rail even it drops pressure. A friend and I both think you're not getting spark.

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[AsleepAltima]

Originally Posted by awesomeaustin99

If it's an electric gauge in the car and not on the regulator (analog) it would make sense that the gauge drops instantly when the fuel pump cuts off because the pump is no longer building pressure or priming.

really? in a more or less sealed system you think the pressure should drop to zero once the rail is primed?

[awesomeaustin99]

Originally Posted by AsleepAltima

really? in a more or less sealed system you think the pressure should drop to zero once the rail is primed?

Yea, I'm not even going to try to recuperate from that one...lol

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[AsleepAltima]

Originally Posted by awesomeaustin99

Yea, I'm not even going to try to recuperate from that one...lol

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lol, yeah it would be pointless.

[johnnymx5]

Originally Posted by Croustibat

The pump is supposed to keep the pressure when it stops (at least not drop the pressure directly), if it does not it means something is wrong there. Could be a leak, an injector that is not closing, a faulty pump or a faulty FPR.

Still the car should start ... we can hear a "pop" on the second video, are you sure the timing is correct ?

I beleive the timing is fine. it recieved a rebuild with new belts less than 5,000 miles ago in 2011. i THINK the pop in the second video is a backfire from the fuel building up and then ignited from trying to start it. the pop gets noticeably louder the more times i prime the fuel pump before trying to crank it over. like if i prime the fuel pump 3 times, it will be louder than when i only prime it once.

the car always needed a little "assistance" to start in cold weather ( < 65 degrees) because its such a radical swap (500+hp 2jz). on cold starts, i would usually have to keep my foot on the accelerator -keeping the revs up- to keep it from stalling. im assuming that means during cold starts, the car needs an extra supply of fuel by revving it up?

if your claiming it should still start even though its loses pressure, could it be a combination of a new problem (losing fuel pressure) and an existing problem (cold start issue)? cause if this car needs me to give it gas on cold starts but it doesnt have pressure, maybe thats it?... sorry if what im saying is confusing. im trying to articulate myself as well as possible but im not very mechanically inclined

[johnnymx5]

Originally Posted by awesomeaustin99

That's what's I was about to say. It being analog like that it should hold that pressure and the gauge should show that. Could be pump or injectors but there should still be fuel in the rail even it drops pressure. A friend and I both think you're not getting spark.

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ill try to test if im getting spark soon. so from the looks of it, its an analog gauge that should hold pressure even after the pump stops priming? thats not good than lol.. i can hear the fuel pump when i turn the ignition to the on position. can i rule out it being a bad fuel pump?

thanks everyone...

[awesomeaustin99]

Originally Posted by johnnymx5

ill try to test if im getting spark soon. so from the looks of it, its an analog gauge that should hold pressure even after the pump stops priming? thats not good than lol.. i can hear the fuel pump when i turn the ignition to the on position. can i rule out it being a bad fuel pump?

thanks everyone...

Correct, disregard my first post. I don't know what I was going on about. The gauge should hold the number as stated earlier it is, well should be, a sealed system. The reason the car would still start is because the fuel pump seems to be pushing fuel into the fuel rail which would mean that the car would ignite, even if only for a second or two because it has fuel. Before I ruled out fuel pump I would rule out spark. 2jzs are real iffy about cutting spark if something is wrong. They cut spark if they don't detect the crank position sensor or if there is something up with the TPS and a few other things. Could also be coil packs. I would start by making sure you have spark.

Also, what engine management are you running and do you know what fuel pump?

[VATOCLOWN]

i had an issue like this in a customers car turned out there was a hole in the rubber line that was in the gas tank (you know the line that goes from the fuel pump to the cap of the gas tank were the fuel pump goes) car had same issue would prime fuel just fine then pressure would drop when pump turned off. fuel would leak back into the tank

[Croustibat]

It still is getting 3bars when the pump is priming, so that is not what is preventing the car to start.

I really think you dont have ignition there (you DO have a problem in your fueling system, but it should not prevent your engine from starting).

I dont know the 2jz much though so cant say why you dont get spark, but this is a generic issue. Are you sure the timing belt is set correctly ? Is it possible to set it wrong like with the crank having a turn or a half turn more than it should ? (cant explain it in english, sorry, maybe someone can explain what i am trying to ) That would explain the pop / bangs too .

Keeping the foot down to start mostly means the car is overfueling, so that could be very leaky injectors ... are they the stock ones ? If not which ones are they (please dont say venom / TLF /TRE performance, if so you found the cultprits)