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Need to Test Fuel Pump


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14 replies to this topic

#1 LanceGillette

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Posted 13 April 2006 - 11:32 PM

I've got a 98 Forestor with 129,000 miles on it. The car runs smoothly for 10-15 seconds and dies. I've replaced fuel filter and their is no CEL illuminated. Seems the next step should be to test fuel pump. How does one go about testing the fuel pump. Looks like one can access it directly behind rear right seat under the floor.

Initially the car was only running rough. I changed plugs and wires and that helped some. So I thought maybe the injectors needed cleaning so I put in a can of Sea Foam injector cleaner. The car ran for about ten miles and died just about 1/2 mile from home. I was able to start the car and get it to run for 30 second before dying and did this a number of times until the car was running reasonably well again. I was able to drive to the top of the mountain and back home but as soon as I got home it started acting up again.

#2 NoahDL88

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Posted 14 April 2006 - 01:12 AM

It dosn't seem like a fuel pump issue, if it runs you should have a good pump.

Unless, the computer sends a signal to the pump to cycle when you turn the key, so that when the engine starts it has operating pressure. and after the engine gives the computer confirmation that the engine is spinning, it tells the pump to start pumping, so my theory is that it may not be doing this.

thats a long shot, but who knows. you could also have water in the gas, a clogged fuel filter, depending on how recent that replacement was.

#3 LanceGillette

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Posted 14 April 2006 - 09:56 AM

It dosn't seem like a fuel pump issue, if it runs you should have a good pump.

Unless, the computer sends a signal to the pump to cycle when you turn the key, so that when the engine starts it has operating pressure. and after the engine gives the computer confirmation that the engine is spinning, it tells the pump to start pumping, so my theory is that it may not be doing this.

thats a long shot, but who knows. you could also have water in the gas, a clogged fuel filter, depending on how recent that replacement was.


Fuel filter was changed yesterday. I started the car up this morning and after a few tries I got the car to run fairly smoothly for about a minute.

#4 grossgary

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Posted 14 April 2006 - 10:11 AM

i also doubt it's the fuel pump.

i would look at the ignition pack (the black box the spark plug wires plug into). don't know if there's a good way to test those, but i'd swap in a used one to test it. this is somethign that would be intermittent like you're experiencing.

did you use Subaru OEM ignition wires? if you didn't use Subaru wires i'd replace them. unfortunately these engines are not very forgiving with other wires. although - i doubt this is your current issue because if it was you should get a "cylinder misfire" code and a CEL light.

#5 LanceGillette

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Posted 14 April 2006 - 01:08 PM

i also doubt it's the fuel pump.

i would look at the ignition pack (the black box the spark plug wires plug into). don't know if there's a good way to test those, but i'd swap in a used one to test it. this is somethign that would be intermittent like you're experiencing.

did you use Subaru OEM ignition wires? if you didn't use Subaru wires i'd replace them. unfortunately these engines are not very forgiving with other wires. although - i doubt this is your current issue because if it was you should get a "cylinder misfire" code and a CEL light.


When I start the car up it now runs very smoothly until it begins to die. It acts more like it runs out of fuel. I think it is a good idea to test the fuel pump to elimate it as the problem. The fact that I put in a can of Sea Foam Injector cleaner right before this problem developed seems to indicate it is a fuel problem and that it would be best to rule it out first.

#6 grossgary

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Posted 14 April 2006 - 03:42 PM

this isn't the "clean" way to do it, but i just pull the most convenient fuel hose i can. pull the one right at the fuel filter. place it in a bottle/bucket if you like. i usually like to let it just pour out the hose because i'm weird, don't care and like to see continuous flow with no spurting/bubbling. anyway, disconnect a hose and turn the key. when you first turn the key ON (engine not starting yet though), the fuel pump should (or may) cycle for 1.5 seconds, that's normal. after that turn the key and crank the engine (or have someone crank it for you while you watch the hose, but i can see mine from inside the cabin), you should see fuel come out of the hose. there are cleaner and more official methods, but this is the easy way to do it.

#7 friendly_jacek

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Posted 14 April 2006 - 05:53 PM

To test the pump/pressure regulator combo, you need fuel pressure gauge, $30-50.

#8 tcspeer

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Posted 14 April 2006 - 07:26 PM

I agree with grossgary I think you are having problems with the coil pact. I also check my fuel pump the way he said, if it is coming out it should idle fine, but if it wont run going up a hill then you may need to check the pressure as jacek says.

this isn't the "clean" way to do it, but i just pull the most convenient fuel hose i can. pull the one right at the fuel filter. place it in a bottle/bucket if you like. i usually like to let it just pour out the hose because i'm weird, don't care and like to see continuous flow with no spurting/bubbling. anyway, disconnect a hose and turn the key. when you first turn the key ON (engine not starting yet though), the fuel pump should (or may) cycle for 1.5 seconds, that's normal. after that turn the key and crank the engine (or have someone crank it for you while you watch the hose, but i can see mine from inside the cabin), you should see fuel come out of the hose. there are cleaner and more official methods, but this is the easy way to do it.



#9 nipper

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Posted 14 April 2006 - 07:28 PM

The ignitor when it goes bad can either totally cut out, not start at all, or act like the car is running out of gas. Check for spark the next time the car dies.
It may be the ignitor, i doubt its the fuel pump. A fuel pump the car either would not start, or hesitate badly under full throttle or at high speeds. The fuel systems on these cars are fairly robust. They are electric motors with no parts to wear, and motors usually work or they dont. Check the fuel pump relay to make sure it is working right.

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#10 LanceGillette

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Posted 14 April 2006 - 09:39 PM

The ignitor when it goes bad can either totally cut out, not start at all, or act like the car is running out of gas. Check for spark the next time the car dies.
It may be the ignitor, i doubt its the fuel pump. A fuel pump the car either would not start, or hesitate badly under full throttle or at high speeds. The fuel systems on these cars are fairly robust. They are electric motors with no parts to wear, and motors usually work or they dont. Check the fuel pump relay to make sure it is working right.

nipper

I checked for spark by disconnecting all four plug wires from the ignitor and had spark continuously. So there is no indication there is a spark problem. We did it three times. After I got everything connected again I started the car and noticed that the fuel pump seemed to make some noises just as the engine would die. I can't find any port to connect a fuel pressure guage to either. I checked a 1999 Forestor manual (my Forestor is a 1998) and it says to disconnect fuel supply lines from the fuel filter and hook up the guage and test fuel pressure when disconnecting pressure regulator vacuum hose from collector chamber and again after reconnecting it. My friend has a pressure guage that can only be attached to a threaded port. So I may need to go purchase one.

#11 LanceGillette

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Posted 14 April 2006 - 09:42 PM

The ignitor when it goes bad can either totally cut out, not start at all, or act like the car is running out of gas. Check for spark the next time the car dies.
It may be the ignitor, i doubt its the fuel pump. A fuel pump the car either would not start, or hesitate badly under full throttle or at high speeds. The fuel systems on these cars are fairly robust. They are electric motors with no parts to wear, and motors usually work or they dont. Check the fuel pump relay to make sure it is working right.

nipper

I tested for spark (see reply to the other guy) and there didn't seem to be a problem there. Fuel pump seems to make some noises when the engine dies. I'm in Fairbanks Alaska and we have cold winters which may be harder on fuel pumps.

#12 nipper

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Posted 14 April 2006 - 09:54 PM

I checked for spark by disconnecting all four plug wires from the ignitor and had spark continuously. So there is no indication there is a spark problem. We did it three times. After I got everything connected again I started the car and noticed that the fuel pump seemed to make some noises just as the engine would die. I can't find any port to connect a fuel pressure guage to either. I checked a 1999 Forestor manual (my Forestor is a 1998) and it says to disconnect fuel supply lines from the fuel filter and hook up the guage and test fuel pressure when disconnecting pressure regulator vacuum hose from collector chamber and again after reconnecting it. My friend has a pressure guage that can only be attached to a threaded port. So I may need to go purchase one.


Spark continously? or spark at the apropriate time? Can you hear the fuel injectors operating when the car dies?

nipper

#13 LanceGillette

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Posted 14 April 2006 - 10:00 PM

Spark continously? or spark at the apropriate time? Can you hear the fuel injectors operating when the car dies?

nipper


Sparking at regular intervals at appropriate time. I just had my wife start the car and let it run until it died. I couldn't differentiate any noise from injectors. Car runs smoothly until it sounds like it gets starved for fuel. Fuel pump seems to make some unusual sounds when the engine begins to die.

#14 LanceGillette

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Posted 17 April 2006 - 09:47 AM

I got a fuel pressure testor and the normal range of fuel pressure is 30-34 psi and I got a reading of 28-30. Guage of course may not be super accurate. One is supposed to test with the Pressure regulator vacuum hose disconnected which should result in a pressure 40-43 psi. I could never figure out which hose this was. I disconnnected several but must not have found the right one. Anyway when the engine begins to die and vacuum decreases the fuel pump pressure climbs to 40 psi. So it seems the fuel pump is fine. I did do spark plug test on Friday and the spark seemed ok. But perhaps the test wasn't long enough.

#15 LanceGillette

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Posted 17 April 2006 - 09:51 AM

The ignitor when it goes bad can either totally cut out, not start at all, or act like the car is running out of gas. Check for spark the next time the car dies.
It may be the ignitor, i doubt its the fuel pump. A fuel pump the car either would not start, or hesitate badly under full throttle or at high speeds. The fuel systems on these cars are fairly robust. They are electric motors with no parts to wear, and motors usually work or they dont. Check the fuel pump relay to make sure it is working right.

nipper


I seem to have elimated the fuel pump as a problem. I did do a spark test but perhaps for not long enough. I'll check on replacing the ignition pack.




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