Questions about the Walbro 255LPH Fuel Pump.

[drweeser2]

A friend of mine is driving a 2g gs-t with a 14b on it. He has the Walbro 255LPH Fuel Pump but lacks the after market FPR. He constantly complains that the car smells like gas, and now the car feels like it cuts out under any boost ofver 10 psi. Is it possible that the 255 is over loading his stock injectors? Could their be too much fuel going to the cylender and the spark plug cannot get a good fire? He just bought a SAFC hes hoping to be able to fix the problem, i'd like to see him get a FPR, what do you guys think? If you could help me get some clerification that would be much appreciated.

 

[AllBoostNoJuice]

Defanitely sounds like an overloaded FPR. The 255 almost always does it. If you don't want to get a new FPR u should stick to the 190.

 

[boostedinaz]

Yes the 255 is overunning the stock FPR. He needs to get a good one, not the B&M, and try that. It should help his problem.

Michael

 

[trapspeed]

I've been getting this problem, also. Although, I have a 190. Recently whenever I run the car sort of hard I can smell gas. Pretty strong, too. And I thought us 190 guys didn't need an FPR?

 

[drweeser2]

Ok, so i've finally had a chance to look at his car a little more. First off he's running super lean, which makes me wonder what really happens when you overload a stock FPR. Does it stop giving fuel? Can you ruin a set of stock injectors? I'm asking alot of questions because not only do i want to help fix the problem but i also want to understand what is happening. We installed his S-AFCII this weekend to try to see if we could even move the Air/Fuel meter away from lean, but with no sucess. Let me know what you think, and thanks for all the input so far, we're shopping for a nice FPR right now, waiting on the paycheck

 

[psychlow]

No - the opposite occurs, actually. When you overrun a stock FPR, the fuel rail (and the injectors) get too much pressure, and there for too much fuel. It'll run rich in the low RPM ranges.

I'm thinking he might have a problem elsewhere as far as the fuel system or fuel tuning. Also, if he has an exhaust leak or an old O2 sensor, that might make the A/F gauge show lean no matter how much you try.

You're using a logger, correct? Unless you have a logger or a WIDEBAND A/F gauge, I would absolutely not be messing with the fuel system. You're asking for a trashed engine otherwise. A/F gauges that use the stock O2 sensor are a step short of utterly worthless for tuning.

 

[drweeser2]

psychlow, thanks for the reply. So an exhaust leak can cause an o2 sensor to read lean 24/7. Just to let you know, were really not tring to tune the car as much as just finding the problem. We figured if he was running way too rich we could have a little bit of adjustment with thw afc. I'm aware that stock o2 sensors have 2 positions, i'd just really like to see his in the rich side not the lean . So from here it looks like i need to get a pocket logger, and start dumping information from his setup. If an o2 sensor is indeed going bad, would the engine pull timing in order to correct any readings that might be incorrect from that sensor? And on another note, what frequency is an o2 sensor supposed to be running at in hz? Were keeping his car at 10 psi right now with no issuses, havent turned it up. Thanks everyone for all of your help so far, were narrowing the problem down each time you guys reply.

 

[psychlow]

No problems.

Yes, an exhaust leak can cause it to read lean all the time. The reason being, you get ambient air mixed in with the exhaust, which would make it look like there is more unburnt oxygen in the exhaust than there actually is.

Oxygen sensors don't run in cycles (Hz), they actually just report back a voltage by means of resistors in the sensor. The range is 0-1 volts, and good WOT voltage is usually around .92v-.94v is good for a system with a good oxygen sensor and no exhaust leaks.

The A/F gauge with a properly functioning sensor is always going to show a "needle" (lights) sweeping from rich to lean repeated during normal, low to mid throttle driving, (closed loop operation). When you go WOT, though, it should go to about that .92-.94 range.

The bad part about using oxygen sensor voltage to compare cars' A/F ratios, though, is that it varies like crazy from car to car. One car might have slightly longer O2 harness wiring, leading to more voltage drop on the line. Also by merely monitoring the voltage (using an A/F gauge), you're taking some of the voltage off of the line, resulting in a slightly lower reading.

 

[midnght]

So what are you using to determine that he is Lean? Plugs or just the A/F light.


Getting a logger is your best choice. An overload with an 255 is going to cause a RICH condition. The smell of gas is the give away. If you are seeing that he is running LEAN but you are still smelling gas you should check the whole fuel system run. From tank to fuel rail. There might be some corroding or pinching that has caused a leak. Even a slight leak is going to cause problems.

I am using a 255 Low Pressure. I have NO fpr but at idle and in between shifts I can see smell the rich condition. I have NEVER been lean because my FP is pumping too much fuel.

 

[drweeser2]

psychlow: I'll make sure to fix any kind of exhaust leaks he has. Hope fully that will get the a/f to move a bit better. Thanks for the voltage for the 02, i'll put a meter on it on monday night.

midnght: We had a look at the plugs, we thought they looked rich but i'm no expert at reading plugs. I'm just trying to cover my bases by looking at the a/f.

I'm going to split the cost of a pocket logger with him, as soon as i recover from the cost of my shep tranny .

Thanks again everyone for your help.

 

[psychlow]

Well, if you can buy me a shep tranny, I'd be your best friend....

Good luck with the car.

 

[drweeser2]

For those interested we did find out what the problem was. We snagged the plugs from my gsx and put then in his gs-t. The car ran great, turned up the boost, ran great, turned it up again and shot a flame out the back Thanks for the input fellas. He has denso irridiums i think i just had some ngk's.