Need help: Fuel Pressure Regulator

[Daryl]

So most of you know I don’t know much about squat. But, I got it in my head to check fuel pressure on the existing Aeromotive vs a stock replacement (for smog test reasons). I have the replacement so I can compare and the FPR test kit, but have NO idea how to proceed from here! And I don’t mind admitting it because I want to learn. I’ve YouTube it and it looks pretty simple , but getting guidance from you guys helps the best.

Hope everyone had a good Thanksgiving. Cheers and Thanks!

 

[ttocs]

the easiest way is to add a pressure gauge to the schrader valve on the end of the fuel rail. You can put one inside the car if ya want but it will require more work.

 

[weendoggy]

Also, being in CA, the fuel regulator can NOT be any type of adjustable unit, even if you have it set correctly, but if it is CARB certified, all that goes out the door.

 

[Daryl]

Is there a particular sequence to testing it?

 

[duh09]

Put a gauge on it, read the gauge. That is all there is to it.

I feel like I've seen you talking about this for weeks. What's got you thinking there's something wrong with the fuel pressure?

 

[Daryl]

Duh09,
Yeah, sorry. I started this thread 11/30 (and a previous one 6/18!) but got side-tracked with a new granddaughter and of course Xmas stuff. Finally have a day to work on this, so here it goes!

I checked out a YouTube video by ChrisFix on this subject. Seems there’s a few iterations beyond just checking IF there’s pressure. What I’m after is checking to see a stock replacement FPR‘s pressure reading vs the AeroMotive adjustable FPR that’s on there now. I want to see how different, if at all, the readings are because here in CA an adjustable FPR is an immediate fail when it’s smog test time. So, I’ll take 2 separate tests: one with the AeroMotive (attach gauge, turn ignition to RUN, get fuel pressure reading, then get readings at idle, constant 2-3000rpms, quick/short acceleration pumps, then turn ignition off and do a 3-5 minute leak down check)… then do the same sequence with the stock replacement FPR and compare the two results.

If there’s a difference, no matter how significant, I will have to peruse getting the engine retuned to work as best it can with the stock FPR.

 

[Daryl]

Can I safely assume this should be done with a cold engine?? And I should detach the battery before removing the FPR??

 

[duh09]

You're overthinking this I think.

~38-39psi at idle, with the vacuum line unhooked is what a stock unit is going to put out.

Slap the gauge on your car with the Aeromotive, and see what it is at idle with the vacuum line out.

 

[cobrajeff96]

Ideally it's a liquid filled gauge on the front port (usually 1/8 NPT thread (with sealant)) so that the needle is more stable and reads better. Aeromotive units have a little plunger with a rubber plug so that they can reference to ambient a little better, increasing the accuracy. You just need gently lift the plunger for a second or two, and probably only one time. Anything else that's been said in this thread is probably correct as well. And I'm quite sure that Aeromotive has good instructions on testing/tuning whether included with the product or on their site.

 

[Daryl]

The AeroMotive unit started, idled, steady rpm’s and short accelerated at 50psi. Very little if any fluctuation. I did notice some baggy looking O-rings on it FWIW

 

[Daryl]

The AeroMotive unit started, idled, steady rpm’s and short accelerated at 50psi. Very little if any fluctuation. I did notice some baggy looking O-rings on it FWIW

 

[Daryl]

The stock FPR has a vacuum nipple on top. Not sure where it should go to ??

 

[Daryl]

Maybe in place of the FPR gauge front of the fuel rail?

 

[Daryl]

Stock FPR, w/o vac line attached, ignition in RUN position

 

[Daryl]

Very gradual leak down after ~ 5 minutes to 28-29psi

 

[Daryl]

Here’s the FPR gauge assembly. Would I remove all of it and just run a vac line from it to the FPR nipple? Or is there a fitting I would need?

 

[ttocs]

does a cobra FPR go a little higher than the GT since the injectors were 24 lb?

 

[Daryl]

Look what I uncovered!! This can’t be right! Looks like the wires coming off the fuel injector are frayed! WTF??

 

[Daryl]

In the meantime, took the fuel pressure gauge & assembly off, cleaned, wire brushed the thread and retapped in case I’m still going to use it.

 

[ttocs]

that one wire is not frayed it is just broken