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1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 08-01-2005, 04:18 PM   #1
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Default Fuel pumps

I've had a suspicion that my pump is slowly dieing on me. So, this past weekend I finally hooked up a fuel pressure guage. I'm getting 48 lbs. with the key on, engine not running. With the engine running I'm getting 40 lbs. The odd thing is (maybe it'* normal) when you rap the throttle the pressure spikes to ~55 lbs. and then snaps back to ~35 lbs. If I hold the throttle at about 2,000 RPMs I'm able to maintain 40 lbs. of pressure.

Is that normal?

My fuel pressure regulator was replaced this past winter thanks to the GM recall.

The reason I thought my pump is getting weak because I have a high RPM stumble that I can't seem to cure. It'* gradually getting worse. I've done all the tune up things to it and just can't cure it. Plus, my sender is bad (guage doesn't work....and yes, I'm positive it'* the sender).
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Old 08-01-2005, 04:38 PM   #2
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Default Re: Fuel pumps

Quote:
Originally Posted by vital49
I've had a suspicion that my pump is slowly dieing on me. So, this past weekend I finally hooked up a fuel pressure guage. I'm getting 48 lbs. with the key on, engine not running. With the engine running I'm getting 40 lbs. The odd thing is (maybe it'* normal) when you rap the throttle the pressure spikes to ~55 lbs. and then snaps back to ~35 lbs. If I hold the throttle at about 2,000 RPMs I'm able to maintain 40 lbs. of pressure.

Is that normal?

My fuel pressure regulator was replaced this past winter thanks to the GM recall.

The reason I thought my pump is getting weak because I have a high RPM stumble that I can't seem to cure. It'* gradually getting worse. I've done all the tune up things to it and just can't cure it. Plus, my sender is bad (guage doesn't work....and yes, I'm positive it'* the sender).
With the key on I get 52 psi, engine running is more in the neighborhood of 40-50psi depending on manifold vacume to the FPR...

Its strange tho, The best I could do on the old pump was 47ish, and that was with the key on if memory serves... I never did any better than that when I hit the throttle... It would usually drop off... Lowest I saw at one point was 32psi... Usually idle was 40psi, hold 2000 rpms or so and the pressure would go down to 36-37psi... Seemed like the Fuel pump was not keeping up with demand... I thought it may have something to do with the strainer sock, but the tank was clean...

After replacing the FP and the strainer sock I have 52psi with the ignition on, 40-42 at dead idle, and when I hit the throttle it goes up to 50-52 really quick... Exactly what its supposed to... Runs a ton better...

Also my FPR was replaced about a year ago due to fuel pressure issues... It helped some, but the pump was making more than enough noise to be heard... The new pump freaked me out.... After the install I hit the key, and I heard nothing... I thought * Oh **&^ * Thought I forgot to plug the connector in...LMAO... The pump was just super quiet... lol..

Not too sure what to tell you about your pump... My pressure was off for the last 20,000 miles... I just didn't trust the amount of noise that pump was making, plus the low pressure... So I decided to replace it...

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Old 08-01-2005, 04:44 PM   #3
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My pump doens't make much noise, but I can hear it everytime I turn the key. I'm at 121,000 on the factory pump so I'm getting a little concerned about it.

I talked to the guy at AutoZone to get a price on an AC Delco pump and they don't even sell them. However, he HIGHLY recommended a Bosch pump. He said they have a lifetime warranty and are a million times better than their plugs would ever dream of being. (Remember...Flint is a pure 3800 town..he knows his stuff!!)

Anyone have any experiences with Bosch pumps? It'* $289. The AC Delco is $177 (includes the strainer) and includes a 1 year warranty.
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Old 08-01-2005, 04:46 PM   #4
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140,000 miles and my AC Delco pump was still going... Hadn't quit yet.... I'd say it did pretty good for 10 years...

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Old 08-01-2005, 05:16 PM   #5
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Since at the moment you are not in a "rush" for it. I'd suggest sticking with good old Delco as it was originally.
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Old 08-01-2005, 05:20 PM   #6
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Ya, that'* what I'm thinking too...

The word "Bosch" just makes me cringe! LOL

Hopefully this will restore some power and affect the high RPM stumbling I'm getting.

The other thing happening is that when I first start the car, the engine lobes. It'* not present on the tach, but if you stand outside the car and start it the engine doesn't start smoothly...it wavers up and down (within 100 or so RPMs) for the first 5 seconds. Think that'* pump related too?
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Old 08-01-2005, 07:25 PM   #7
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What brand and model of fuel pressure tester’* are you all using?
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Old 08-01-2005, 09:44 PM   #8
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Quote:
Originally Posted by ron350
What brand and model of fuel pressure tester’* are you all using?
Actron( Sunpro ?? ).... I think it is...

For a while there my 91 had better pressure than my 95...

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Old 08-01-2005, 10:27 PM   #9
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It'* an Actron.

The engine lobing isn't present on the tach...just heard in the exhaust tones.
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Old 08-01-2005, 10:37 PM   #10
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Thanks and thanks Jr’s3800 for posting your real world fuel pressures.
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