Whine at WOT - fuel pump or ...???

Necromancer · 08-14-2006, 06:17 PM

OK here we go again... I've been trying to diagnose this problem for literally years now and the chance has finally come to pull whatever parts I might need.

Symptoms:
- High-pitched whine under high load / WOT (kind of like "shhhh")
- Car stumbles and hesitates after being driven hard for a while (running lean --> overheating?)
- High NOx reading at emissions check (seems lean to me)
- Otherwise seems to run normal (never throws a CEL)

I pulled the fuel pump and the strainer sock looked perfectly clean. Is it worth replacing the thing???

Any other suspects?

Master2192 · 08-14-2006, 06:32 PM

What year car? I am not sure how you could test it. Maybe put in a fuel pressure gauge and somehow test the maximum pressure the pump will hold? You may just want to replace it based on its age and see if it fixes your problem.

Tim Sanderson · 08-14-2006, 08:14 PM

How many miles on the vehicle? When was the last time you changed your fuel filter?

I would test the fuel pressure with and without the vacuum line on the fuel pressure regulator.

msm98lw · 08-15-2006, 01:09 PM

My '97 LGT (95K) has a whistle at wOT that I thought was a vacuum leak, but the dealer told me it was a failing muffler baffle.

Necromancer · 08-16-2006, 06:25 AM

Thanks for the responses so far. The car is an '01 2.5RS with about 70K miles. Fuel filter, spark plugs, and lots more are new.

I guess the fuel pressure test would be the obvious thing to do -- not exactly easy but I'll give it a try.

An exhaust leak wouldn't normally cause this kind of lean situation, right?

Anyway, thanks for the thoughts -- I'll keep the board updated with where this is going.

Nemesis Digital · 08-16-2006, 08:35 AM

Quote:

Originally Posted by Necromancer

Thanks for the responses so far. The car is an '01 2.5RS with about 70K miles. Fuel filter, spark plugs, and lots more are new.

I guess the fuel pressure test would be the obvious thing to do -- not exactly easy but I'll give it a try.

An exhaust leak wouldn't normally cause this kind of lean situation, right?

Anyway, thanks for the thoughts -- I'll keep the board updated with where this is going.

An exhaust leak large enough could allow more Oxygen to cause a false reading. My wideband read higher AFRs when I had a leak.

08-14-2006, 06:17 PM	#1
Necromancer Scooby Specialist Member#: 477 Join Date: Oct 1999 Location: Vancouver Vehicle: GC4 -> GGA -> GM6 Yeah, that's about right.	Whine at WOT - fuel pump or ...??? OK here we go again... I've been trying to diagnose this problem for literally years now and the chance has finally come to pull whatever parts I might need. Symptoms: - High-pitched whine under high load / WOT (kind of like "shhhh") - Car stumbles and hesitates after being driven hard for a while (running lean --> overheating?) - High NOx reading at emissions check (seems lean to me) - Otherwise seems to run normal (never throws a CEL) I pulled the fuel pump and the strainer sock looked perfectly clean. Is it worth replacing the thing??? Any other suspects?

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08-14-2006, 06:32 PM	#2
Master2192 RIP 10/12/83 to 02/10/08 Scooby Specialist Member#: 83254 Join Date: Mar 2005 Chapter/Region: NWIC Location: Roy, Washington Vehicle: 98 2.5 RS 04 WRX	What year car? I am not sure how you could test it. Maybe put in a fuel pressure gauge and somehow test the maximum pressure the pump will hold? You may just want to replace it based on its age and see if it fixes your problem.

08-14-2006, 08:14 PM	#3
Tim Sanderson Scooby Guru Member#: 6486 Join Date: May 2001 Chapter/Region: MWSOC Location: S.E. wisconsin Vehicle: 00 Impreza 2.5 RS Blue Ridge Pearl	How many miles on the vehicle? When was the last time you changed your fuel filter? I would test the fuel pressure with and without the vacuum line on the fuel pressure regulator.

08-15-2006, 01:09 PM	#4
msm98lw Scooby Newbie Member#: 55849 Join Date: Feb 2004 Location: Danbury, CT Vehicle: 2000 Impreza 2.5RS '97 legacy GT wagon	My '97 LGT (95K) has a whistle at wOT that I thought was a vacuum leak, but the dealer told me it was a failing muffler baffle.

08-16-2006, 06:25 AM	#5
Necromancer Scooby Specialist Member#: 477 Join Date: Oct 1999 Location: Vancouver Vehicle: GC4 -> GGA -> GM6 Yeah, that's about right.	Thanks for the responses so far. The car is an '01 2.5RS with about 70K miles. Fuel filter, spark plugs, and lots more are new. I guess the fuel pressure test would be the obvious thing to do -- not exactly easy but I'll give it a try. An exhaust leak wouldn't normally cause this kind of lean situation, right? Anyway, thanks for the thoughts -- I'll keep the board updated with where this is going.