Express trouble codes 0137 and 0452

[tbpavi]

My 2000 Express 5.7 is giving codes 0137 and 0452. It is getting really poor gas mileage and the tailpipe is really black. I replaced the fuel pump last fall and the tank pressure sensor (0452) along with it. The 0137 is the downstream O2 sensor and should not affect mileage from what I understand. It was very sluggish including when cold so I sprayed B 12 Chemtool into the MAF while running. After that it had so much power it lit up the tires. It is better now but still gets poor mileage and after clearing the codes, the idiot light came back on in short order. The last time that I replaced the fuel pump, I had to siphon out the fuel and in the process, I bent the silver flap in the fuel filler neck. Could that give the code 0452? I never had a code for the MAF and I have never run an aftermarket air filter so I am really scratching my head as well as paying through the nose with gas prices and the bad mileage I am getting.

[MT-2500]

Check codes and then Clear codes and recheck for what comes back.
Post code no"S.
For codes 137 and 452 you need to get a good repair flow chart for the code and go threw it.
There is a lkot of wiring problems that can give you the codes.
Also scan for missfires and camshaft retard setting and test fuel pressure.
NT

[tbpavi]

I was just curious about the bent flap in the fuel filler neck. Does that do anything to maintain pressure in the fuel tank? I know that aloose fuel cap can cause codes and I wondered if that could be similar.

[MT-2500]

No if it is inside filler neck.
Actually the tank EVAP system pulls vacuum on tank not pressure.
I would run a fuel pressure test also.
MT

[tbpavi]

Could a faulty fuel pressure regulator cause a problem like this. Several people have commented that the fuel pump seems to be running pretty hard and nwith the fuel mileage problem, I wonder if these problems could be the regulator. I bought a couple of O2 sensors but have not put them in because I was not convinced that they were the problem. I think that I am going to return them and get a fuel pressure test gauge.

[MT-2500]

No ion pressure regulator.
Have you cleared codes and see if they return?
If so what code comes back?
The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

[tbpavi]

Cold start gives me about 50-52 psi. Does not appear to be any leak down after shut off. Could it be fuel filter? I replaced it last year but the one I replaced was installed backwards by someone who apparently couldn't read three letter words like "out". I replaced it correctly and also the fuel pump.

[MT-2500]

One way to find out is to pull and check it.
But You need to.
Run the full pressure test.
Post back results.

[tbpavi]

I ran the tests and came back with theses results.
key on with engine off gives 60.
Cold start gives me a fluctuation between 50-52.
Under acceleration it will hit 60 and then slowly back off to 55.
Pressure never gets above 60.
After shutting engine off, pressure remains at 60. I checked after about 45 minutes and pressure was still around 40. There was no quick leak down.

[MT-2500]

Sounds like you have the aftermarket airtex fuel pump blues.
Cold start is to way to low.
Engine running is low.
Did you drive it 30 minutes or more with gauge on it.?
Chck direct full pressure at fuel filter or with return line blocked off.
If full pressure does not go over 85-95 replace the fuel pump.

And use a good AC-Delco/Delphi fuel pump.
Good luck
Crunch

[tbpavi]

I replaced the fuel pump and the van runs better but still not right. It still is sluggish and the fuel pressure still reads low. I also replaced the fuel filter. It is also still sucking gas like crazy and the tailpipe is still getting really black even on the outside. I still suspect the fuel pressure regulator. I don't see what else it could be. The check engine light has not come back onso I don't have any codes to go on.

[MT-2500]

Did you repace it with a ac pump?
Rerun the fuel pressure test as outlined in upper post.

Have you checked the camshaft retard setting with a scanner?
What is the fuel trim readings?
MT