Fuel pump R&R

[Racerxjling]

I am attempting to do the Walbro 255HP fuel pump in a 92 NSX.

I dropped the fuel tank straps and unplugged the 2 sensor harnesses. I am having difficulty w/ accessing the fuel lines. Should I attempt this from the bottom of the car ?? Any tips?

TIA

Jeff

 

[DanO]

Hi Jeff

1st I’d search this site and see if there are some DIY fuel tank writeups, I seem to remember at least one person needing help with this.

I think the big fuel hose and other smaller lines are “easier” to get to underneath the car, but you might try removing the intake box and see if you can get to the hoses from the top side. One of the hoses can be removed from the top of the fuel filter.

HTH,
DanO

 

[Briank]

Removed my tank a few months ago. I disconnected all the hoses from the top in the engine bay.

Fuel line from the pump I disconnected at the Banjo fitting at the filter.

The return line right below the filter

The vapor line at the charcoal canister

And the fill and vent at the fire wall above the tank, removing the air box and/or the coolant tank helps with access for this.

Disconnected the fuel tank wiring harness behind the drivers seat and pulled it through the round access panel

The worst part of the whole project was draining the tank, always a mess and a whole lot dangerous one spark and ...

 

[sjs]

Removed my tank a few months ago. I disconnected all the hoses from the top in the engine bay. ...

Brian, glad you came along for this. It's been a couple years for me and all I remember clearly is that it was a PITA.

The guys at Factor-X seem to think, from experience, that the Walbro 255hp is not up to the task for anything over about 400hp at the wheels. That's quite a bit lower than manufacturer specs, but then again, manufacturers have been know to be optimistic. In nay case I'm disappointed by that news but also wonder to what degree it's limited by the stock fuel line diameters.

Has anyone used the 255hp on other high HP cars? In theory it has been used on various American iron and some Supras but those guys are not above exaggerating either. I'm wondering just how much it really can flow.

 

[Briank]

sjs

I only had my tank out to repair a leak so I no experence on updating the pump for FI.

In a fuel injection application the volume of fuel that any pump can supply is reduced compared the feeding a Carb. There is a big difference with pumping into a 50 psi head pressure compared to just filling a float bowl. I would think that Walbro could provide pressure / flow curves and with that and the injector spec. you could calculate expected performance.

 

[Racerxjling]

Thanks guys

Did the job...what a PITA. THANKS guys!! The biggest tip (OEM manual doesn't help) is to gain access to the wiring harness from behind the driver's side seat. The Walbro instructions state to use their supplied butt connectors between the oem harness and the new harness. Is there any danger to having this butt connector sitting in the middle of the fuel tank?? kaboom!!

Jeff

 

[Briank]

Connections inside the fuel tank? It is unlikely that even with a spark you would have an explosion not enough air. I would think solder and shrink wrap would be better but that’s my opinion. Butt splices are only good when crimped with the correct tool.

 

[Racerxjling]

I thought solder and shrink wrap would work better but didn't have any available and just wanted to finish the job. I figured they never would have suggested it if it were dangerous. Good point being not enough air for a spark tho.

Thanks again Brian

Jeff

 

[drew]

I just installed a Walbro, here are some of my observations:

- OEM pump is *extremely* well made, in fact it appears to be much better than the Walbro. I cut apart the old pump with a sawzall. This way I could use the embedded threaded connectors --no cutting of the OEM harness-- and used large heat shrink to cover the connectors. (add an hour to the process and I don't recommend it except for folks that do not want to cut OEM wires and have a decent amount of tools.)

-My OEM had been obviously worn out at 105K miles. My occasional false starts have now vanished and I have a significant more HP. (No, really....I can take certain hills in higher gear than was possible before and throttle response is noticebly better.)

- Use vice-grips to "stage" the hose clamps on the filler neck. They are very difficult to spread from their relaxed state. Almost no room for human hands either...so use the vice-grips to grab the clamps and keep them stable until you reinstall them.
- The tank is VERY light. Easy job with jackstands on garage floor.
- Only had to remove the front side of the tank straps and loosened the rear nuts and swung the "L" straps out of the way. Minor PITA to keep them out of the way when reinstalling the tank.
- Have some undercoating spray to fill in the areas that you will knock away during the installation.

-The hardest part of the job IS draining out the fuel.

Drew