95.5-2004 Tacomas & 96-2002 4Runners 4th gen pickups and 3rd gen 4Runners

3.4 fuel pump issues???

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Old Sep 22, 2013 | 08:39 AM
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3.4 fuel pump issues???

Can some one tell me what fuel pressures I should be seeing running and not running
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Old Sep 22, 2013 | 11:55 AM
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From: I live in New Tripoli Pa out in the woods
Red face

It would depend if your trying to pump Vapor or Liquid

Because was it not you that said it is better to use vapor
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Old Sep 22, 2013 | 12:19 PM
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Its 38-44psi running and more than 21psi after stopping after 5 minutes
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Old Sep 22, 2013 | 02:39 PM
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Yes Wyoming it is but its back factory cause I have a weak fuel pump
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Old Sep 22, 2013 | 02:41 PM
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It has about 32 pounds before its even started !!!!!
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Old Sep 24, 2013 | 09:48 AM
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What about compression I bought a comp tester n kinda need an idea of what numbers I should see
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Old Sep 24, 2013 | 12:13 PM
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1.21 gigawatts.
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Old Sep 24, 2013 | 12:36 PM
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Seriously
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Old Sep 24, 2013 | 06:06 PM
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I thought maybe I could get a helpful answer but .........
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Old Sep 24, 2013 | 06:15 PM
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Good compression numbers will be be around 150-160 psi. There should be no more than 15% difference between all cylinders (within 20 psi).
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Old Sep 24, 2013 | 06:21 PM
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Thank you very much I got 180 or so on the 4 corners and 168 or so on the middle two ? Is it normal for the middle one to be less or is that a coincident?
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Old Sep 24, 2013 | 06:38 PM
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3.4(5VZ-E) Cylinder Compression:

-Standard
(218 PSI)

-Minimum
(145 PSI)

(Reading the above compression seems "normal" and with-in specification.)

3.4(5VZ-E) Fuel Pressure:

Ignition On, engine not running - (38 to 46 PSI)

Engine Idling *Vacuum hose attached* - (31 to 37 PSI)

Engine Idling *Vacuum hose detached* - (38- 44 PSI)

Fuel system hold pressure - (21 PSI)

Last edited by Kiroshu; Sep 24, 2013 at 06:41 PM.
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Old Sep 24, 2013 | 06:41 PM
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Originally Posted by wyoming9
It would depend if your trying to pump Vapor or Liquid

Because was it not you that said it is better to use vapor
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Old Sep 24, 2013 | 06:55 PM
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Thanks for specs . Can it show normal pressure while key on and idle but still drop out while running down the road or at wot ??? Is that poss and wouldn't that be a volume problem
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Old Sep 24, 2013 | 07:03 PM
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Originally Posted by raretaco02
Thanks for specs . Can it show normal pressure while key on and idle but still drop out while running down the road or at wot ??? Is that poss and wouldn't that be a volume problem
If it was starting to fail, yes, you could see issues when running. The only way to be sure would be to monitor fuel pressure under those conditions, such as wot like you say. At work we tap into the fuel system with a t and then watch how it fluctuates on a test drive.
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Old Sep 24, 2013 | 07:09 PM
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OK thanks I believe it is dropping under load its got 206000 on the pump it prob tired thanks for reply
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Old Sep 24, 2013 | 07:25 PM
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Wouldn't surprise me...my little brother lost one on his 2000. I think he was somewhere around 150k...
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Old Sep 24, 2013 | 07:34 PM
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Dang I reckon lol I'd say its done its duty huh I really don't know how to check it without the proper tools . Is there any other signs that this could be what's happening or should I just get a new one ? no hard feelings , by the way and thanks for the input I love learning
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Old Sep 24, 2013 | 07:35 PM
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Better now then to be stranded in a strange place far from home...

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Old Sep 24, 2013 | 07:39 PM
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Very true I think we can agree on that lol I go to Ohio to deer hunt every year and its a long way fro. Here so its prob a good idea
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