Bad Walbro 255 or something else?

[Dustin Frazee]

Has anyone ever had problems with the Walbro 255lph fuel pump. I have a pretty stock R32 GTR and was running fine and pulled well through boost with low knock. I decided to put a Walbro GSS342 255lph on cause my stock pump seemed to be given up from setting around. With the Walbro my knock goes through the roof if I try to make a pull. I ran a 12v to the back on a relay cause I thought it might not be getting enough juice. The car ran great last I drove it about 6 months ago. I have had the car in a storage container waiting on a new radiator. The pump was bought from amazon so was thinking I might have got a knock off.  Do fuel pressure regulators go bad? Should I just buy a Tomei pump or look for other issues.

[BK]

Fuel pums can stuff up permanently from sitting around. I've had multiple pumps from Nismo, Walbro and Bosch all do it, so just get another pump.

[Dustin Frazee]

That is what happened to my stock pump. The walbro was new and not used, but I have had it about a year waiting til my stock one kicked the bucket. Surely it would not go bad from not being used if it had never been used. 

[BK]

On 19/03/2022 at 11:34 AM, Dustin Frazee said:

That is what happened to my stock pump. The walbro was new and not used, but I have had it about a year waiting til my stock one kicked the bucket. Surely it would not go bad from not being used if it had never been used. 

Definitely unlikely for an unused fuel pump to be bad, but anything is possible. Go change your fuel filter first.

[blind_elk]

The fuel is at least 6 months old. May well have gone "off". Try some new fresh fuel first.

[Dustin Frazee]

Yeah I put some new fuel in and still the same. Should I be running the little regulator thing with the new pump? I am not sure if it is a check valve or what.

[GoHashiriya]

I had some weird hesitation issues after installing my Walbro 255, I have been meaning to try it with a 12v supply but just haven't gotten around to it. I've since returned it to the stock pump as the pump wasn't the cause of my issues in the first place anyway. 

I'm interested to know how your situation goes.

[BK]

On 19/03/2022 at 1:59 PM, Dustin Frazee said:

Yeah I put some new fuel in and still the same. Should I be running the little regulator thing with the new pump? I am not sure if it is a check valve or what.

Fuel pressure relief valve, get rid of it as it can cause more dramas than retaining it, as the opening pressure is fairly low from memory. If it fails or activates, it just pumps the fuel out into the tank and you get no fuel to your engine.

This may be your problem if it has stuck open or partially open.

So if your car is actually running, what is your actual fuel pressure at idle and on load ? Really gotta go back to basics here and make sure you have an unblocked fuel filter then confirm your actual fuel pressures before guessing about anything.

[Dose Pipe Sutututu]

On 19/03/2022 at 3:29 PM, Dustin Frazee said:

Yeah I put some new fuel in and still the same. Should I be running the little regulator thing with the new pump? I am not sure if it is a check valve or what.

Remove it asap!

Every S15 I tuned with lean out issues turned out to be running the OEM pressure relief valve in the tank, as soon as you hit about 1 bar or so of boost you see AFRs lean to the moon.

Deleted it and had to redo the entire fuel map.

[joshuaho96]

Don't fuel pumps already have pressure relief valves?

[BK]

On 23/03/2022 at 10:24 AM, joshuaho96 said:

Don't fuel pumps already have pressure relief valves?

External pumps no. Intank pumps like the Walbro or AEM pumps yes, but generally the ones that are internal to the pump on these are usually rated to something around 120psi. This is definitely an area that is compromised on knock off pumps too.

That Nissan heap of shit is something as low as 75psi. Now imagine 40+psi base pressure, 15psi boost plus fuel line losses of 15psi upwards with shitty 5/16" lines and you are already getting scary close to it opening - IF it is working correctly.