Fuel pressure regulator questions.

[panamarojo]

Ok, so I try to start the car, and it will semi idle but rough sometimes, sometimes not. It will idle good but if you give it gas it will die. I took the return line off on the fuel pressure regulator and I am not getting any gas to come out. While cranking and while its trying to idle. No gas comes out at all. Sounds to me like its plugged up? or does no gas come out when its cold?

 

[BIRDCLAWTSi]

did you disconnect the fuel line or the vacuum line, dumb question, but i have to ask.

 

[panamarojo]

No its all good hermano, but I disconnected the fuel return line. Not the vaccum line that connects to the seloniod.

 

[BIRDCLAWTSi]

No its all good hermano, but I disconnected the fuel return line. Not the vaccum line that connects to the seloniod.

i would check the fuel pressure. if there is the correct pressure ,then i would check if there is fuel in the vacuum line from the regulator, if not then run the vacuum line straight from the intake manifold to the regulator and see if that helps. if not then i would say the regulator is bad.

 

[panamarojo]

Cool ill try it out, gotta wait for day time tho. But for sure there should be gas flowing through this return line at all times?

 

[josh38127]

Cool ill try it out, gotta wait for day time tho. But for sure there should be gas flowing through this return line at all times?

Let me know what you find out. I suspect mind is faulty to.

 

[steve]

Cool ill try it out, gotta wait for day time tho. But for sure there should be gas flowing through this return line at all times?

If the fuel pump is running there should be. It's has to be able to pump enough fuel to support your injectors spraying 100% and still provide extra fuel to maintain the fuel pressure at WOT so at idle it should be dumping lots of fuel out the return port.

Remember that the pump only runs while cranking or while the engine it running.
Most DSM have a fuel pump test connector you can use to power the pump with the engine off (It's missing from some 91 cars harnesses). DSMLink allows you to turn the pump on and off, and a 1G datalogger will allow you to turn it on for a few seconds.

 

[panamarojo]

Hmm well I think the fuel pump is running because the car will idle and try to idle, but maybe its not strong anough for the whole system. I am going to get a fuel gauge here soon. But I had another question. How much vacuum should I be able to feel if I remove one of the vac lines from the intake manifold and put my finger over it? I dont feel very much at all. What could cause this? Or the vacuum line to the FPR, it doesnt feel like it has much vacuum at all either, and that vac line is connected to the selonoid and then its ran to the intake manifold but next the the coil pack. Is this right?

 

[steve]

What does your boost gauge say?
Without a calibrated finger all you can tell is if there is a vacuum or pressure in the hose.

 

[jed344]

so it sounds like your car is choking its self out. maybe simple as pluged fuel filter. iv seen it happen before? but im not for shure

 

[panamarojo]

What does your boost gauge say?
Without a calibrated finger all you can tell is if there is a vacuum or pressure in the hose.

Well I looked on a video from before, I noticed that the vacuum would drop on the stock gauge to -7 after reving it up and when it started to drop RPM's it would go to -7.

Well I though the problem was with my FPR because no gas was coming out of the fuel return line, so I got another one and still no fuel out of the return line. So I took the FPR off and tried cranking over the engine and no gas came out of the fuel rail, tried it again and some barely dribbled out.

I checked the pig tail for the fuel pump in the trunk, I am getting 12 volts on one pin, and 6 volts on another pin. The ground is good. I can hear the fuel pump turn on, like a winding noise.

Could the fuel pump be going bad and just getting weak? Because my issue did start happening slowly and got worse and worse slowly.

 

[Dharbeck]

I just bought a 90 galant gsx with a 4g63t swap, the guy told me that the regulator was bad because when he starts it and gives it gas it will cut out, or flooded if you will. The regulator reads 80-psi when the car first starts but will soon die when gets more gas. It has a air/fuel ratio gauge, and again reads green for a few then push the gas and floods out. After thinking about it, it sounds like its not the regulator just not tuned right. seeing how there is bigger injectors, headers and aftermarket manifold. I just started working on the 4g63t and a lot of friends say DSMtuners is the place to goto learn. So, anyone have any heplful infomation? thanks alot

Dave

 

[steve]

Sounds like your looking at the stock boost gauge. It doesn't really measure boost or vacuum. It's driven from the MAF signal and converted into an estimate of what the gauge should read.

When was your fuel filter last changed?

The regulator reads 80-psi when the car first starts but will soon die when gets more gas.

Dave

80 psi is more than what most fuel pumps will do. They have pressure relief valves that open around 70 psi. Your base pressure (with the reference vacuum line disconnected) should be around 36.3 psi on a manual car. The fuel pressure should track base pressure + reference pressure with the hose connected so that under normal vacuum you see about 26 psi fuel pressure and at 10 psi boost about 46 psi fuel pressure. 80's way out of whack unless you really looking at an oil pressure gauge.

 

[panamarojo]

Sounds like your looking at the stock boost gauge. It doesn't really measure boost or vacuum. It's driven from the MAF signal and converted into an estimate of what the gauge should read.

When was your fuel filter last changed?

K thanks for the info and yea I was looking at the stock boost gauge. Tomorrow ill see what my other one does when I try and start it. Like while it's cranking, but I am not sure if I can get it to idle. And its a new fuel filter by the way.

If I decide to test the fuel pump out before I just go and buy one. Would a fuel pressure gauge from like autozone work? Where should I test the fuel pressure at? At the fuel pump in the trunk or at the fuel filter?

The little filter on the fuel pump, I know this is really recommended to be replaced during replacing the fuel pump. Could this slow the pump down at all? Like if it was plugged up? Where would it be plugged up at, the outside of the screen on the filter or inside somewhere? Just wondering what I should look out for. Thanks for the help.