Bad fuel pump? Code 1 & 2?

[GreyHoundSteve]

91 mt 130k aftermarket headers,tp and exhaust.

I was finally able to capture the check engine code that i sometimes get while driving my car. It is a 1 & 2 code which im told is the 02 sensor. I had the 02 sensor checked and its fine. I had the fuel pressure checked and its 6 lbs under the pressure it should be. So what do you guys think, fuel pump?

If it is the fuel pump then which pump do you guys recommend replacing it with? I was thinking about possibly going FI or stroker on down the road but if i decide not to then i would want a fuel pump that doesn't cause any problems.

Recommendations?

 

[Larry Bastanza]

There is a "return" fuel line coming out of the fuel pressure regulator. Pinch it so it is closed off, then check the fuel pressure. If it shoots up, your fuel pressure regulator is most likely bad. If it still stays too low, it may be the fuel pump or something electrical with the fuel system, like a bad Main Relay.

If your Main Relay is 130K miles old, I would change it as a matter fo course.

Regards,
LarryB

 

[GreyHoundSteve]

There is a "return" fuel line coming out of the fuel pressure regulator. Pinch it so it is closed off, then check the fuel pressure. If it shoots up, your fuel pressure regulator is most likely bad. If it still stays too low, it may be the fuel pump or something electrical with the fuel system, like a bad Main Relay.

If your Main Relay is 130K miles old, I would change it as a matter fo course.

Regards,
LarryB

Thanks for the quick reply Larry. It shouldn't be the main relay because i replaced it within the last 6 months 1,000 miles because of a starting issue.

I will test the FPR using the method you suggested and get back to this thread with an answer for you on what happens to the fuel pressure when i pinch it.

If it stays low when pinched then what would be your next guess?

 

[Larry Bastanza]

If it stays low when pinched then what would be your next guess?

From Above:

If it still stays too low, it may be the fuel pump or something electrical with the fuel system, like a bad Main Relay. ....

You want to also make sure you are getting the proper voltage at the pump , before you call it "bad".

HTH,
LarryB

 

[pingu81]

Interesting situation. I've got a 91 5MT, 103K miles, aftermarket headers, test pipes, and exhaust. It's throwing a code 1. I got new 02 sensors 4 months ago. It affects my car in a way that whenever I mash on the gas, there's a bit of hesitation. I installed mechanical O2 simulators and they seemed to stop the hesitiation for a bit, but CEL still went on and threw code 1. Now, after about 1000 miles later, the hesitation is starting again.

 

[GreyHoundSteve]

Interesting situation. I've got a 91 5MT, 103K miles, aftermarket headers, test pipes, and exhaust. It's throwing a code 1. I got new 02 sensors 4 months ago. It affects my car in a way that whenever I mash on the gas, there's a bit of hesitation. I installed mechanical O2 simulators and they seemed to stop the hesitiation for a bit, but CEL still went on and threw code 1. Now, after about 1000 miles later, the hesitation is starting again.

I should have mentioned that my car also seemed weaker than before but i havent pushed it hard since i started getting the CEL.

 

[Larry Bastanza]

BTW,

How were the 02 sensors tested?

Regards,
LarryB

 

[GreyHoundSteve]

BTW,

How were the 02 sensors tested?

Regards,
LarryB

I will ask today when i go back up there to test the pressure regulator. Also, whats the best way to test the voltage to the fuel pump?

 

[GreyHoundSteve]

Okay, i tested the FPR and there was no increase in fuel pressure. It is still about 6lbs lower than it should be.

I asked how the o2 sensors were tested and he told me that only the voltage to the o2's were tested and that the voltage to them was correct. What would be the proper method of testing them to see if that is indeed the problem?

Also, where is the best place to test the fuel pump? Should i be testing the amperage or voltage to the pump?

 

[C-speed]

There is a "return" fuel line coming out of the fuel pressure regulator. Pinch it so it is closed off, then check the fuel pressure. If it shoots up, your fuel pressure regulator is most likely bad. If it still stays too low, it may be the fuel pump or something electrical with the fuel system, like a bad Main Relay.

If your Main Relay is 130K miles old, I would change it as a matter fo course.

Regards,
LarryB

Larry,
I believe you have this test procedure backwards. If you pinch off the fuel return line on the stock fuel pressure regulator, the pressure reading MUST go *up*. If it does NOT go up, then you have a bad fuel pump.

Reason being, is if you pinch off the return line, the fuel has no where to go to relieve the pressure in the lines. Thus the FPR CAN'T relieve the pressure either, so the pressure in the system MUST increase if the pump is working properly.

To test the FPR itself, pinch or remove the vacuum line from the FPR. If the pressure go UP, then the FPR is good. If it does not go up, then the FPR is bad.

:biggrin:

 

[Larry Bastanza]

Larry,
I believe you have this test procedure backwards. If you pinch off the fuel return line on the stock fuel pressure regulator, the pressure reading MUST go *up*. If it does NOT go up, then you have a bad fuel pump.

Reason being, is if you pinch off the return line, the fuel has no where to go to relieve the pressure in the lines. Thus the FPR CAN'T relieve the pressure either, so the pressure in the system MUST increase if the pump is working properly.

To test the FPR itself, pinch or remove the vacuum line from the FPR. If the pressure go UP, then the FPR is good. If it does not go up, then the FPR is bad.

:biggrin:

I stand corrected:redface:

Thanks,
LarryB

 

[GreyHoundSteve]

I stand corrected:redface:

Thanks,
LarryB

So when the return line is pinched the fuel pressure is supposed to jump up? If so then the FPR might be the problem since they said they did this test and there was no increase in fuel pressure.

 

[C-speed]

So when the return line is pinched the fuel pressure is supposed to jump up? If so then the FPR might be the problem since they said they did this test and there was no increase in fuel pressure.

If the fuel pressure did NOT go up when you pinched off the fuel return line, then you most likely have a bad fuel pump.

 

[NSXclear]

I had a similar problem. If you are getting a O2 code 1 and 2, then you can sometimes rule out the O2 sensors because it is rare that both go bad a the same time.

If you need to replace your fuel pump, replace it with a Walbro 255lph fuel pump.

 

[C-speed]

I had a similar problem. If you are getting a O2 code 1 and 2, then you can sometimes rule out the O2 sensors because it is rare that both go bad a the same time.

If you need to replace your fuel pump, replace it with a Walpro 255lp fuel pump.

Make sure its the High volume/LOW PRESSURE Walbro...

 

[GreyHoundSteve]

Make sure its the High volume/LOW PRESSURE Walbro...

does anyone have a source for these?
are they as quiet as stock?

 

[NSXclear]

It seems pretty quiet to me. Not much difference in noise. If you can, it is best to solder the wires instead of using the included crimp connectors.

This is where I got it from:

They offer 3 kits for the NSX. The WAL GSS-341 is probably the best kit out of the three for our cars.


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