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Fuel Pump Pressure?????


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9 replies to this topic

#1 river2surf

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Posted 19 October 2004 - 11:45 PM

Anyone know the specs for:

1988 XT 1.8 MPFI Fuel pump pressure?

I found some specs stating 61 - 71 psi......is this right?

Is the SPFI fuel pump different?

My pump is about 32 psi about 30 psi low when I check it with an inline fuel pressure guage at the fuel filter.

Is there another filter after the fuel pump but before the main fuel filter under the hood?

#2 calebz

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Posted 20 October 2004 - 12:52 AM

Theres no other filter. 61-72 is the right pressure for an MPFI turbo car.. I am not sure if MPFI N/A is the same.. wouldn't surprise me though.

When testing the pressure, be sure to pich off the return line going back to the tank . Without the return line piched, mine sits at about 32-35 psi.. with it pinched, I get 60-65

1: Pinch return line
2: connect green diagnostic connectors
3: Turn key to 'on' position

The pump should cycle every 1.5 seconds or so.. after a couple of cycles, it will reach max pressure.

#3 Subi81

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Posted 20 October 2004 - 01:19 AM

Dude where did you get your inline pressure gauge, I am looking for one right now.

#4 calebz

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Posted 20 October 2004 - 01:48 AM

The Snap-On man is your friend :grin:

I think AutoZone carries them as well.. I like my Snap On though.. its old and still works great

#5 river2surf

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Posted 20 October 2004 - 03:27 AM

Cool, thanks for the info. Need to rerun my check. Did not clamp off return line. I will check it tomorrow.

#6 rallyruss

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Posted 20 October 2004 - 05:27 AM

just a note. its usually not advisable to check fuel pressure with the return pinched. the actual pressure you need to be concerned about is the running pressure(low 30s)

pinching returns can be dangerous. and it really does not tell you a lot except that your pump can put out a lot of pressure when dead headed(bad for pumps)

ok mr safety out

#7 calebz

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Posted 20 October 2004 - 07:49 AM

Hmm. Never heard someone recommend against deadheading in short bursts. Thats what they taught us in school and thats whats been recommended by some of the best mechanics I have known (one or two of them here) as the best way to determine fuel pump pressure on the car.
I have never seen, nor heard of damage or safety issues resulting from 3-4.5 seconds (2-3 diagnostic cycles on a subaru) of deadheading..

But then again, thats the beauty of this board. There are a lot of people that know a lot of things and a lot of different ways of doing them.:D

#8 river2surf

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Posted 20 October 2004 - 02:26 PM

Correct me if I am wrong, but the procedure I have does not mention the return line in checking just fuel pump. If I were checking the pressure after the pressure regulator, I would then be involved with the return line. I believe then my pressure should be 26 - 30 psi not the 61 - 71 needed prior to the pressure regulator (between the fuel pump and the fuel filter)?

#9 rallyruss

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Posted 20 October 2004 - 03:43 PM

Correct me if I am wrong, but the procedure I have does not mention the return line in checking just fuel pump. If I were checking the pressure after the pressure regulator, I would then be involved with the return line. I believe then my pressure should be 26 - 30 psi not the 61 - 71 needed prior to the pressure regulator (between the fuel pump and the fuel filter)?


not really.
all the regulator controls is pressure from the pump to the regulator(30ish). behind that you should have no pressure.

the pump is capible of creating pressure 60psi or greater if you block the return flow.

the system never sees this kind of pressure under normal conditions. now say you have an injector seal or hose connection that is a bit old and brittle. this is the time when it will fail under the excessive pressure. now say your car is runing fuel squirts near the exhaust or ignition wires. now you have a bit of a problem.

my instructor recomended against this for the reasons of safety and it really does not tell you any thing usefull as far as trouble shooting goes. and if you have worked with pumps much you find out that the do not like to be deadheaded it causes lots of stress on it.

now if you really want to try it. do it quickly. just enough to see your gauge jump and then release it.

the best way to check fuel pressure is to actually put the gauge on the windshield and drive the car. this is as real a test as you can get.
you need to understand how the pressure regulator works before you try it.

when there is vacume applied to the regulator it drops the pressure a bit(idle or deceleration) when vacume is absent (acceleration) pressure rises.

#10 river2surf

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Posted 20 October 2004 - 09:52 PM

Thanks for all the great info guys!

Well, the fuel pump is OK!

So at least I do not have to buy a new one!




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