Fuel pressure regulator

OK! Read some posts on checking the fuel pressure regulator. removed the hose and there seems to be an excessive amount of fuel coming out of the regulator when it starts. How much is too much??

 

Cold Start problem

Took to dealer. Pulled some codes. Ran fuel pressure test. Holding 45psi. Said the reason would not start was due to throttle body needing to be cleaned. (Did not work) drove to visit family where the temp is down to 30. As soon as it cooled down it no longer starts. Just noticed the immobilizer light on. Any ideas how to bypass this system?

 

Is there anyone capable of helping with this issue? Update: This issue is still going on, Not the immobilizer, Dies intermittently under light acceleration, no lights, no indicators, not losing power to electrical, Now it does it intermittently all the time, not just cold weather as was the case a year ago.
Normal day, cranks first one or two times and does not start, then starts and may not have an issue for a day or two. once or twice during the week dies with no explanation while driving. NO codes EVER! Has to be a mechanical issue. Did it before it had a new fuel pump, does after new fuel pump, cleaned throttle body multiple times with no help to issue.

 

Was leaky fpr changed?

 

performed check last year as per service manual and does not appear to be an issue. Took to dealer as in my earlier post and pressure was 45psi.

 

just noticed another interesting symptom. When the engine will NOT start, the screw on the damper is all the way down. When the engine will start the screw on the damper jumps up. NO pressure in rail, pressure in rail. I cant find the thread I saw a while back that described how to check the pressure regulator return test. Can you point me back in that direction? Either the new fuel pump I installed is intermittently not building pressure, OR the regulator is intermittently dumping pressure. Like I said before, there are NEVER any DTC's so I have ruled out anything electrical, i.e fuel pump relay, etc... I installed a new fuel pump last year when this problem began and it has never changed. I vacuum tested the regulator today and the diaphragm is OK but I am not ruling out a sticky valve. Especially since the unit dies on acceleration. From what I can tell there is vacuum dumping pressure at idle, and an absence of vacuum on acceleration allowing for more pressure. Thanks for any thoughts!

 

"OK! Read some posts on checking the fuel pressure regulator. removed the hose and there seems to be an excessive amount of fuel coming out of the regulator when it starts. How much is too much??"

If the above refers to the vacuum line connected to the FPR then there should not be any fuel coming out of the FPR at this point.

 

Unfortunately no. No fuel out vacuum line. I was measuring the amount that was being bypassed out the return line.
I thought I had read a thread discussing timing the leakage and what was acceptable. Thanks!

 

I guess the only way to prove to yourself if fuel pressure is a problem is monitor with a pressure gauge attached.

Other then that i would monitor engine parameters with scan tool. Look for what would affect the fuel/air ratio at start up since that seems to be the main concern.

 

Went ahead and replaced fpr. No change. Pretty consistently has no pressure (judging by screw on dampner) after setting awhile.
What else would cause fuel pressure to be lost? Leaky injector? Possible new fuel pump could be defective? Seals on lines leaking?
Any help is appreciated!!

 

"What else would cause fuel pressure to be lost? Leaky injector? Possible new fuel pump could be defective? Seals on lines leaking?"

Regarding leaky injectors do you notice exhaust at start up showing signs of too much fuel also do you have negative fuel trim?

Fuel pump has a check valve that keeps pressure on the fuel rail. If this is failing pressure would drop when pump not running.

 

It does not appear to have any signs of a rich condition at start up.
I do not understand the fuel trim question. Please explain.

I was looking at evap system last night thinking maybe a vacuum lock was occurring in the tank?? I would think if anything were not functioning there, some kind of DTC would show.

May have stumbled onto something that would shut down the pump and not set codes. Fuel Pump Resistor??
Saw it in my factory manual. Mounted on top of right fender apron. Could possibly explain dying on the road. This car was in a front right collision just before this problem started.
It tested at 1.0 ohm. It has .55 on the part. Book says .7 to .78.
My guess is that maybe something is loose? Wiggles and loses connection periodically? Pump runs slow at times and loses juice? Disconnected it and semi duplicated the starting issue. No codes set.

What kills me is I just drove this thing on a 4000 mile trip. Never died on hwy. Would not start on 7 occasions. Died once town driving. Good luck I guess.

 

Also. I am going to hook a factory pressure gauge tomorrow and see WTH that is actually doing.

 

Yes, fuel pressure test needed verify operation. Idle, leak down, snap throttle( higher RPM)
While you have it attached take time to do complete checks. Lots of available info on these tests.

The fuel trim can be seen using a scan tool. It's a feedback from the AF sensor telling PCM add or subtract fuel. The engine parameters can be monitored using a scan tool to quickly give you a reading on the engines health. Worth looking into, especially useful in narrowing
down potential problems.

Rereading your post besides the long cranking at start up does the engine also cutout when driving? You mentioned a front collision. There is a fuel pump cutoff switch that activates during a collision. Don't know if this is the resistor you are looking at.

 

Yes. Random as it can be. It has died while driving. No codes. Does not lose electrical power.
I'll check into the cutoff you mentioned.
The resistor the way I understand it is simply to operate the fuel pump after startup, to lessen the draw on the electrical system.

 

Here are the scan tool results the only time it ever set a code. i believe it only set the code because it died twice in a short amount of time. Can you help me understand what this info is?

PS. I tested the crank sensor and it did not ohm within specs so I replaced it....to no avail....problem reoccured the very next day.




Parameter Description Results
DTC for which Freeze Frame was StoredP0335
Fuel System 1 StatusOpen Loop
Fuel System 2 StatusOpen Loop
Calculated LOAD Value61.96 %
Engine Coolant Temp194.00 °F
Short Term Fuel Trim - Bank 10.00 %
Long Term Fuel Trim - Bank 11.56 %
Short Term Fuel Trim - Bank 20.00 %
Long Term Fuel Trim - Bank 21.56 %
Engine RPM192.75 rpm
Parameter Description Results
Vehicle Speed Sensor44.12 mph
Ignition Timing Advance #1 Cylinder0.00 °
Intake Air Temperature96.80 °F
Air Flow Rate Mass Air Flow Sensor0.74 lb/min
Absolute Throttle Position16.47 %
Commanded Secondary Air StatusAtmosphere / Off
Oxygen Sensor Output Voltage (B1-S2)0.06 V
Short Term Fuel Trim (B1-S2)99.22 %
Oxygen Sensor Output Voltage (B2-S2)0.04 V
Short Term Fuel Trim (B2-S2)99.22 %
Time Since Engine Start167 sec

 

I have seen the injector o rings leak. I don't live in a very cold area but have had a couple of these and tundras leaking causing similar problems. I would pop the hood and see if you can smell fuel under the hood before you think the condition will happen. Also check to see any signs of seepage around the injectors or unusual amounts of dirt/dust around them. Fuel pumps are extremely uncommon but wouldn't rule anything out


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Definitely don't see any signs of an external leak anywhere. No dirt buildup, no smells. Still trying to locate a pressure gauge. Will update when that is done. Thanks!

 

The P0355 needs to be further looked at. With this code PCM shuts off spark or fuel or both. If the crank signal is borderline it could be causing the intermit no start and stalling while driving.

You have changed the sensor and problem reoccurred, so that leaves intermit caused by either connector/wiring, crank reluctor ring.

To check intermit connector /wiring you could wiggle wire/connector to see if you can reproduce error code. If you have wiring diagram, check resistance,continuity,ground..

To see if signal is at spec or borderline suggest you have a shop scope the signal for you. Also ac voltmeter could be used but don't know how accurate this would be.
Regarding the shop, i would ask around first who has experience with this particular problem. There is a code to go on so maybe its worth it to buy an hour of shop time.

The freeze frame data indicates that the engine was in OL at the time so the fuel trim and O2 sensor data isn't live. There is a lot of info out there on OBD2 diagnostics to explain this operation.
You could run a scan while in closed loop to get live data. Look for LT fuel trims to be no more than +- 10.

I quick check of a good crank sensor signal in some PCM is that the RPM indicator is turned on.
Don't know if it applies in your case but worth checking on.

 

I had a similar problem with my GMC Yukon XL. Vehicle was only 18 months old and had the shut off problem. Hard to start problem. Took it to shop several times and used the "on star" and nobody could solve problem. Finally found someone who experienced same thing...turned out the fuel pump was too small for the load put on the vehicle. This caused the fuel pump to overheat with a lot of driving. Once the pump cooled off, it would run again for a short time. If left overnight and left to completely cool...then would run fine again for a couple of days. If the pump was changed to a "racing" pump (his words not mine) then the vehicle ran fine.

My sequoia is doing the same thing as yours. What did you find out?

Thanks,
JS in Canton, GA

 

Nothing yet. Bought a scanner. hooked it up. No codes. Has died twice while driving the last few weeks. Has had the no start issue multiple times.
I actually pulled a PO230 code for a fuel pump relay issue the other day and havent had time to research. THink it may be an intermittent wiring issue since I have already replaced the pump, relay, etc... OR an ECM issue..

 

Odd that my sequoia (I bought it new in april 04 and now has 241,000) is acting so strange. Starts fine. Will run ok but not like it should. When gets hot will start to run worse and I avoid giving fuel to accelerate because it might start skipping and barely run at all. Will not go past 1700 rpm when hot. If I drive short distances and keep my foot out of it...it runs but not good.

Have been told to check the cats (just replaced mine in May with universal ones not OEM). Replaced the plugs and coil packs. Cleaned throttle body. Changed air filter. Has no check engine lights or any codes. Had it hooked to the scanner yesterday while running rough and found that cylinders 2 and 4 would skip and pulled the MAF sensor and cleaned it. Ran good for 4 minutes then back to running rough. It acts like giving it fuel will flood the engine.

I don't think its something major but I cannot find anyone who can figure this out. I planned on driving this car for many years but the way its running now makes me want to trade to another vehicle.

 

Maybe the ECT? In this case that was my issue.