Weird fuel pressure issue
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From: Thibodaux LA
Weird fuel pressure issue About a week ago, my fuel pump(racetronix 255) tripped the 20amp fuse on the harness. i thought it was the pump. so i ordered a new one. noticed the fuse was tripped, put a new on in and fired right up.
when it tripped the fuse, it wasnt a sudden thing. when i drove the car before it tripped i noticed it was idling funny and shaking(almost like it was cammed) pressure was at 30 psi. drove it home, turned it off, then on and barely ran(10 psi) turned it off then on again and nothing. no fuel pressure.
put the new pump in for piece of mind. pressure was at 35-38 psi at idle and when warmed up 33-35 and about the same driving. 40-42 at wot. pulled the vacuum line off regulator and pressure was at 42psi. pressure warmed up seems low. put new filter and regulator in. pressure at idle is now 331-32 psi. driving is at 33 psi. wot is at 40 psi. remove vacuum line its at 42 psi
why would my pressure be low after new pump, filter, and regulator. im stumped. im using an electric fuel pressure gauge at the end of a 1 foot line before my fuel solenoid. any suggestions??? pls help. im at a loss.
when it tripped the fuse, it wasnt a sudden thing. when i drove the car before it tripped i noticed it was idling funny and shaking(almost like it was cammed) pressure was at 30 psi. drove it home, turned it off, then on and barely ran(10 psi) turned it off then on again and nothing. no fuel pressure.
put the new pump in for piece of mind. pressure was at 35-38 psi at idle and when warmed up 33-35 and about the same driving. 40-42 at wot. pulled the vacuum line off regulator and pressure was at 42psi. pressure warmed up seems low. put new filter and regulator in. pressure at idle is now 331-32 psi. driving is at 33 psi. wot is at 40 psi. remove vacuum line its at 42 psi
why would my pressure be low after new pump, filter, and regulator. im stumped. im using an electric fuel pressure gauge at the end of a 1 foot line before my fuel solenoid. any suggestions??? pls help. im at a loss.
I think the tolerance for pressure is between 42 and 45psi with 43.5 being perfect? As asked, how does it run now with the new pump? Have you checked pressure in the past with the old pump and had a differing measurement?
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From: Thibodaux LA
Thread Starter
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From: Thibodaux LA
the old pump(also a walbro) would be 42 at cold startup. Then slowly drop down to 30 over an hour. It would be at 32-33 cruising. 39-40 WOT.
Teching In
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From: Marianna, Fl
If you are not noticing a difference without a data log before and after we can not confirm but it may be with a more stable flow rate the idle pulse is better giving a more efficient burn allowing less idle correction. This in turn increases the vacuum is higher in turn lowering the pressure. If with the vac line off you still see 42psi and it runs fine I would not worry tbh.
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Thread Starter
TECH Enthusiast
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From: Thibodaux LA
If you are not noticing a difference without a data log before and after we can not confirm but it may be with a more stable flow rate the idle pulse is better giving a more efficient burn allowing less idle correction. This in turn increases the vacuum is higher in turn lowering the pressure. If with the vac line off you still see 42psi and it runs fine I would not worry tbh.
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From: Marianna, Fl
incomplete burn is the rich smell. This is caused by too much fuel for the air you are getting in or not enough time to burn the full load ie not enough spark advance.
Stock tuning is a bit rich for the engine at stock pressure. what aused you to run a .35 gap?
Stock tuning is a bit rich for the engine at stock pressure. what aused you to run a .35 gap?
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From: Thibodaux LA
Thread Starter
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From: Thibodaux LA
Staging Lane
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This may not be related but I had a set of circumstances whereby the car became progressively richer. By the end of the summer it smelled like a Holley with a torn power valve.
The check engine light was not illuminated but a scan showed that the rear O2 sensors were "not heating". I ignored this since the rears don't impact fuelling.
I was convinced that a new tune was in order so I purchased a Jet DST, wideband O2 and new O2 sensors and a MagnaFlow catted Y pipe (surprisingly not a bad purchase but a whole other story).
Put it all together and watched as the engine/exhaust warmed up and the air/fuel ratio fell right in line.
In the end the only thing I had ever really needed were two new front O2 sensors. I could have saved a bunch of money had I started there.
No idea if this is really your issue but this came up coincidentally on the heels of a couple of unrelated mods and maintenance. If you haven't done so already it might be worth having the car scanned.
Jon
The check engine light was not illuminated but a scan showed that the rear O2 sensors were "not heating". I ignored this since the rears don't impact fuelling.
I was convinced that a new tune was in order so I purchased a Jet DST, wideband O2 and new O2 sensors and a MagnaFlow catted Y pipe (surprisingly not a bad purchase but a whole other story).
Put it all together and watched as the engine/exhaust warmed up and the air/fuel ratio fell right in line.
In the end the only thing I had ever really needed were two new front O2 sensors. I could have saved a bunch of money had I started there.
No idea if this is really your issue but this came up coincidentally on the heels of a couple of unrelated mods and maintenance. If you haven't done so already it might be worth having the car scanned.
Jon