Code 55 Diagnosis Help

[Athens91ZR1]

Hello all,

I have a code 55 presently (lean AFR).

Here is what I have done so far:

- Jumpered the fuel pump underhood connector to the battery via a VOM and got 9.1A (fuel pumps pass electrical test)

- Connected fuel pressure gauge to service port on fuel rail and found the following when key was turned to the ON position:

FP1 pulled - 50 psi (tapering to 45)
FP2 pulled - 36-38 psi

**Fuel filter replaced in late 2013 but no record of fuel pump replacement in the past**

Do I just assume that the primary fuel pump is bad or has a loose connection somewhere? Or could it still be the fuel filter?

If you think I should just plan to replace both fuel pumps, please advise what you think would be the best new pump.

Thank you!
Jordan

[indy91zr1]

I had same problem when I bought my car. I started with plugs. Previous owner put wrongs one in. Didn't solve it. Next tested all the injectors and they were all withing spec. Tested fuel pumps and had good voltage also. I too wasn't sure when pumps where last replaced. So I went ahead and ordered new pumps,o2 sensors, fuel filter. As of right now it hasn't come back. Then again I haven't been able to recreate the conditions which set it. Another thing to think about is if your pumps are original or haven't been touched in awhile could have the plastic clamps on the lines which could be bad or a split y fitting in the tank. I used the performance electric pumps from rockauto. p240kc. They are recommended by marc haibeck so good enough for me. Hopefully somewhat helpful. Without having a tec-1 code reader or its kinda a crap shoot.

[Athens91ZR1]

I had same problem when I bought my car. I started with plugs. Previous owner put wrongs one in. Didn't solve it. Next tested all the injectors and they were all withing spec. Tested fuel pumps and had good voltage also. I too wasn't sure when pumps where last replaced. So I went ahead and ordered new pumps,o2 sensors, fuel filter. As of right now it hasn't come back. Then again I haven't been able to recreate the conditions which set it. Another thing to think about is if your pumps are original or haven't been touched in awhile could have the plastic clamps on the lines which could be bad or a split y fitting in the tank. I used the performance electric pumps from rockauto. p240kc. They are recommended by marc haibeck so good enough for me. Hopefully somewhat helpful. Without having a tec-1 code reader or its kinda a crap shoot.

Thank you for the feedback and I think I am headed in the same direction you went. I am very confident that the pumps are the original ones from 91. I will likely get the p240kc pumps as well.

I was reading about the y-split fitting earlier...What is the best replacement solution?

Also, do you know what the P/N is for a new gasket to go between the neck and tank?

[TX '90 ZR1]

Check out this thread I posted when I was having fuel pressure leakage issues.
Need to replace the "Y" with the one Carter is making.
http://www.zr1.net/forum/showthread.php?t=29393&highlight=Fuel+pump+unit
:cheers:

[indy91zr1]

Thank you for the feedback and I think I am headed in the same direction you went. I am very confident that the pumps are the original ones from 91. I will likely get the p240kc pumps as well.

I was reading about the y-split fitting earlier...What is the best replacement solution?

Also, do you know what the P/N is for a new gasket to go between the neck and tank?

Like tx90zr1 said check his thread. I believe his name is carter200 on here and he machines a y adapter out of aluminium. I bought the spectra gasket from rockauto LO148 is the part number for it. Ac delco has one also but it is twice the price.