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Fellow Mustang Squirrels, Help!? - Fuel Pressure Related


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I recently installed a Walbro 255HP (High Pressure) in the fox to cure my lean condition under boost.

 

The car is back together and running, but ever since the pump swap my fuel pressure doesn't hold when the pump is off. Not at all. I can turn the car off and by the time I walk to the front of the car it's back to zero. The car holds pressure while the pump is running just fine.

 

Has anyone ever had a Walbro without a check valve of sorts in it? The old pump I removed was a Denso 190LPH and it would hold pressure just fine.

 

I suppose it could be an injector leaking down, but it seems odd that it would suddenly happen right after swapping fuel pumps. I even swapped in a new fuel pressure regulator thinking that might be leaking, but that made no change.

 

Ideas? I'm lost. Maybe it doesn't matter since the car seems to run okay, I have just never seen this happen before.

:fa:

Edited by twistedfocus
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I found alot of other people with this pump crying about it too, so it appears it doesn't have a check valve. It just has me a little scared that there's potentially something else wrong I'm overlooking. I should be hitting the dyno soon to finish the tune, so I'll know soon enough.

 

I guess that's not a big surprise, given their universal nature, I have always used Walbro pumps and they had check valves... but I never ran the High Pressure 255 model before.

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I found alot of other people with this pump crying about it too, so it appears it doesn't have a check valve. It just has me a little scared that there's potentially something else wrong I'm overlooking. I should be hitting the dyno soon to finish the tune, so I'll know soon enough.

 

I guess that's not a big surprise, given their universal nature, I have always used Walbro pumps and they had check valves... but I never ran the High Pressure 255 model before.

 

As long as it works when it's on, then you should be good. Have someone watch your gauge, if it's under the hood, when you turn the key "on" to see if it comes up quickly too.

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