Fuel pressure regulation

Thinking my regulator might be going out on my 2.7l Tacoma. Anyone have any info on how to test the regulator? Also is there a replacement part now thag Toyota discontinued the part? TIA

Fuel pressure 46 psi. Didn’t time what pressure was at the end of 5 minutes. Will try that later.

 

What makes you think the regulator is failing?
If you suspect a fuel pressure issue the first step is to actually check fuel pressure.
Fuel pressure on the 2.7L should be 41 psi +/- 1 psi and should hold under a load.
Also it should not drop below 21 psi for at least 5 min after the engine is turned off.

 

Dm93

Fixed my post, forgot to add that important step. Pulled off the regulator, applied vacuum to vacuum line and tried blowing air through line. No release if pressure with or without vacuum on regulator.

my thinking is as vacuum increases, regulator opens more (could be wrong) don’t want to throw parts at it before getting help on testing

 

What is the symptom you're experiencing? Lack of power? Check engine light?

 

That's not exactly how it works, it's meant to maintain constant fuel pressure.
Pressure at the inlet has to be higher than the set pressure before it opens and allows pressure to bleed off, increasing vaccum at the reference port lowers set pressure while applying pressure to the reference port raises set pressure.

 

I’m getting misfire on cylinder #4 at first, then it moves to all cylinders except #3. Changed plugs(it needed new ones). I had a coil go out before all this happened and replaced it. So I know I have one working coil for sure. Moved the known good coil to #4 but still had the misfire. Tested all other coils and all are still good.

 

If I was to apply vacuum to regulator while vehicle is running, thag should lower fuel pressure?

 

Yes but the main thing is that fuel pressure is in spec with everything connected properly, stays in spec under load, and doesn't bleed off with the engine off.

 

There's no point in worrying about the regulator until you confirm fuel pressure from the pump is good

 

Random misfires are typically not caused by a fuel pressure issue, typically low fuel pressure would result in lean codes and a lack of power and excessively high fuel pressure would set rich codes and the engine would run poorly.

When do the misfires occur?

 

I’ll come back with my results once I get home and test the fuel pressure with the engine off. out of curiosity, why would it be a problem the pressure bleeds off with the engine off?

Misfires are happening at idle. I can clear the CEL and it’ll be a single cylinder misfiring. After a minute or so of running, I get the misfires on other cylinders.

 

Because this would allow the fuel to boil out of the rails and go back to the tank leaving vapor in the rails and resulting in a long crank as it takes time for the fuel pump to refill everything.

I would want to look at live misfire counters to see which cylinder(s) mifire under what conditions.
Is it a hard miss or light miss?

 

Finally got a chance to work on it some. Here’s pressure running and after 5 minutes of being shut off. Also included is freeze Frame of CEL.

 

Will try and figure out if I have a live misfire counter with this scanner.

 

Just looking at the freeze frame data it looks like it may be a biased AFR or MAF sensor, I would want to look at live data with the engine running and see what the upstream and downstream sensors and MAF sensor are doing.

Throttle body may be dirty too, your at 15% throttle angle at 650RPM.

 

I’m gonna have to buy you a beer or lunch for the help! Thought I knew a little about being a mechanic but I don’t

I’ll have to take the TB off and clean it. I know it was done at least a year ago but how good the shop did. Here’s the live data I pulled from the scanner. Running out of daylight so I’ll have to start again tomorrow.

 

Well we definitely have an issue, your at -25% fuel trim.
I'm thinking first clean the throttle body and MAF sensor and see where that get's us.
Need to let it run longer so the downstream O2 sensor comes online so we can make sure the upstream sensor isn't lying.

 

Cleaned MAF and TB last night. Let everything sit overnight to make sure all was dry before putting back together. Here’s the results from running it. What line is the downstream sensor located?

 

Downstream O2 will be O2B1S2.
It looks like your MAF sensor is over-reporting, we typically look for Grams/Second to be about equal to engine displacement in Liters at a hot idle.
You have a 2.7L engine so you should be around 2.7 g/s (0.357 lb/min) but your at 0.623 lb/min (4.7 g/s) which is almost double.
Are you running the stock intake system?

 

I did have a p0172 CEL now with the misfire codes. Seems the next logical step would be to run the truck to get that downstream 02 to come on, Then compare numbers.
Truck is completely stock