Codes with new fuel rail

White Lincoln

1st Gear Poster
Joined
Oct 2, 2023
Messages
64
Location
southwest
Vehicle Details
1994 Mercury Cougar XR7 all stock
Country flag
Hello!
I recently replaced my fuel rail with one from an identical car from the yard. Many, many years ago I was trying to trace down a problem and stuck a fuel rail from an 89 Continental (3.8l) in to 1994 Mercury Cougar, 3.8l. For the new rail, I bought a new fuel pressure regulator because the original one, to my knowledge, had over 200k on that engine. After I finished and took the car for a test drive, I was smelling fresh fuel. When I put the car in the garage the odor got worse. My wife was screaming at me to do something! Today I removed the upper intake and checked the fuel rail, fuel lines to the rail, lines in the rail (I had to replace the fuel rail line due to rot). Today I took off the upper intake and while checking around, pulled the new pressure regulator. To my amazement, the O-rings had a pinch in one and the other was torn. I wrote to Walker Products about this issue. I used my o-rings from the old pressure regulator with some engine assembly lube.

Anyway, after driving around for 30 minutes, hitting 90 on a straight away, I ran codes and am still getting 173 and 137 (same as I was getting when the car ran like it was flooded) no other codes though. The car is not acting like it is flooding anymore or running rich. The transmission shifts properly now, and the car has much better pick up.

Do I need to drive it for a while (like for a full tank) to clear out the crap in the O2 sensors before the codes go away or do I have some other issues still? Do I need to replace the O2 sensors? I replaced them less than 10k miles ago. I had read in my research to test the fuel rail pressure to make sure it is not over, what... 35psi? Guess I need to order a meter from Amazon.

Thanks for reading and I hope you have some input into my dilemma.
 
The codes will remain in memory until the driveline cycle completes, if you pull the PCM fuse it will reset and relearn any adaptive routines during said driveline cycle.

The fuel pressure in the rail varies - it is relative to manifold vacuum. Injector flow is modeled and stored in the PCM at (IIRC) 43.5 PSI, and it uses this data to calculate exactly how long to open the injectors to deliver the precise amount of fuel needed onto the intake valve. Vacuum in the intake increases the pressure differential between the fuel in the rail and intake valve, and "sucks" fuel out of the injectors at a higher rate. To avoid this, pressure in the fuel rail is reduced by the same amount of the vacuum in the intake via the vacuum pressure regulator to keep the fuel delivery pressure into the intake constant.

Generally speaking, for every 2" of manifold vacuum the fuel rail pressure should drop 1 PSI; a typical manifold vacuum at idle is 17-21" Hg. So with 20" of manifold vacuum you will see 32-33 PSI in the fuel rail. The pump will prime the system for a few seconds before start, so if you turn the key a few times it should build up to about 39 PSI.
 
The original orings on the injectors are known to leak; I've seen a few cars that have been on fire from leaks at the fuel rails. The new type orings are different, Blue and green. They are made of different material that resists ethanol better. Blue on the pressure side, green on the vacuum side. I bought them, and new filter screens when I cleaned a bunch and refurbed them a few years ago. Chemtool b-12,a pwm driver, and some 20ml syringes, and I was able to clean and test them.
 
Here's where I got my parts:
 
Do I need to drive it for a while
Typically it takes three consecutive drive cycles without the PCM sensing the data out of range to turn off the malfunction indicator lamp. But pulling a fuse or clearing the code with a scan tool helps to speed up the diagnostic process.

The O2 sensor upstream of the catalytic converter primarily drives the length of the fuel injector pulse (width), but they're all connected, the one downstream from the catalytic converter (your P0137 code) can affect the fuel injectors too. I wouldn't jump to changing O2 sensors, it would be interesting to see the voltage output of Bank 1 Sensor 2 first. Maybe its just a bad electrical connection.

With any of the 170 codes, I'll first spray a liberal amount of MAF sensor cleaner on the MAF sensor and see if that helps. Then check for any air leaks between the MAF sensor and throttle body. Leaks in the air intake or exhaust can confuse the PCM into not knowing how much fuel to inject for the amount of air it thinks is going through the engine.
 
The codes will remain in memory until the driveline cycle completes, if you pull the PCM fuse it will reset and relearn any adaptive routines during said driveline cycle.

The fuel pressure in the rail varies - ....
Awesome bank of knowledge! This is excellent information to know. Thank you.
 
Last edited:
The original orings on the injectors are known to leak; I've seen a few cars that have been on fire from leaks at the fuel rails. The new type orings are different, Blue and green. They are made of different material that resists ethanol better. Blue on the pressure side, green on the vacuum side. I bought them, and new filter screens when I cleaned a bunch and refurbed them a few years ago. Chemtool b-12,a pwm driver, and some 20ml syringes, and I was able to clean and test them.
What kind of pissed me off was Walker had NO information about using the regulator. It has a black square spacer type thing and I did not know if that was for shipping or if it was supposed to be used. It is possible that "spacer" could have kept the manf o-rings from failing, but that is the first time I have seen such a device come with a part that was not used for shipping purposes. Live and learn. The original o-rings will get replaced after I order some more or find that bag of o-rings I got with the AC system that may have the same size. Or just buy a few more to replace the ones I used.
 
Here's where I got my parts:
When I was trying to track down my problem with codes 173 / 137 running rich (and it acted like it was flooding) was to wonder if the injectors I bought were the correct ones. I could not find the original information on them. I bought a whole new set that were specific for my car, so now I know they are the right ones. I bought a can of injector cleaner, made a pressure switch to mount the injectors with a electrical switch to open the injector and check the spray. What a PITA. I wish I had some $300 to buy an injector spray device / cleaner, but well.. I still drive a 25 year old car. I asked the shop if they could check the spray, they said all they can do is clean them. Heck I can do that. Anyway, another fun lesson learned about injectors.

Anyone looking for a set of injectors that are still good?
 
Typically it takes three consecutive drive cycles without the PCM sensing the data out of range to turn off the malfunction indicator lamp. But pulling a fuse or clearing the code with a scan tool helps to speed up the diagnostic process.

The O2 sensor upstream of .....
Thank you for sharing this information. I did use my Snap-On Scanner to clear the codes and run the test again and the only codes I was getting were the 173 and 137. I will try pulling the fuse to reset the PCM. Actually, I replaced my PCM several years ago only to find out my OEM one was fine. I plan to put that one back in soon.
 
Last edited:
If the Bank 1 Sensor 2 code persists, there's always the ole swap the downstream O2 sensors and see if that causes a Bank 2 Sensor 2 code.
 
If the Bank 1 Sensor 2 code persists, there's always the ole swap the downstream O2 sensors and see if that causes a Bank 2 Sensor 2 code.
As I mentioned in the other thread, I think it may just take some time to clean the buildup out of all the sensors including the O2's. Even the upper intake has build up from the returning gas from the EGR, PVC, etc. I wondered too if the cold air intake I put in when it was running rich may be causing some issue. Once I got the car running right, I was going to put the OEM filter box back in since we mainly use the car for errands (stop and go driving).
 
I will try to run some codes this weekend and see what I get, if I get the same 173 / 137 rich O2 again or if they are finally gone after driving it for a month.

Follow up to come!
 

Similar threads

Back
Top