Fuel Pump Bad? Anything else to test?
03-24-2009, 02:17 PM
#16
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Blown994 is correct. I was thinking back to when I was having a relay start issue and had put a jumper in for the relay. Then when you turn it on you will hear the pump cycle on.
03-24-2009, 03:54 PM
#17
Got Nothin'
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Another reason for a no-start, like you are having is the speed/reference sensors. My car sat idle, for almost a week as I trouble shot everything from a bad DME relay, to a bad DME on down, until finally I got to the reference sensors, and one of them was bad, due to a bad wire. Was intermittant at first, but eventually became fatal.
03-24-2009, 06:05 PM
#18
Burning Brakes
@peanut - thank you for all your suggestions. To be clear, the original problem was not the battery. I tested the old pump double jumping off of an industrial strength battery on a tow truck with a brand new DME relay installed and it didn't work. After the fuel pump change, jumping off an old mitsubishi mirage starts it up right away.
Changing out the fuel pump seems to have been a success. The only issue was I ran down the battery during my earlier testing (after trying to jump it), so when I went to test the new pump it didn't work, but a jump fixed it.
This is my first serious repair attempt and it has been a very postive experience for me - I correctly diagnosed the orginal problem and successfully performed the repair (swaping out the fuel pump). When this didn't work at first, I managed to figure out that something had changed, tested the battery and noticed it was now low. Now everything works.
I'm not sure why you'd want to discourage me just because I didn't have all the right electircal equipement (no, I have no spare wire laying around, but said I would pick some up immediately and follow your suggestion) or realized I could use a coat hanger. I appreciate all your help, but understand I am still learning and all I can do is be as open to suggestions and advice as possible. The subject of this thread was, afte all, "anything else to test?" so your suggestion was exactly what I was looking for.
Changing out the fuel pump seems to have been a success. The only issue was I ran down the battery during my earlier testing (after trying to jump it), so when I went to test the new pump it didn't work, but a jump fixed it.
This is my first serious repair attempt and it has been a very postive experience for me - I correctly diagnosed the orginal problem and successfully performed the repair (swaping out the fuel pump). When this didn't work at first, I managed to figure out that something had changed, tested the battery and noticed it was now low. Now everything works.
I'm not sure why you'd want to discourage me just because I didn't have all the right electircal equipement (no, I have no spare wire laying around, but said I would pick some up immediately and follow your suggestion) or realized I could use a coat hanger. I appreciate all your help, but understand I am still learning and all I can do is be as open to suggestions and advice as possible. The subject of this thread was, afte all, "anything else to test?" so your suggestion was exactly what I was looking for.
Glad you sorted the problem and got the car going again. Afterall thats why we are all here ,enthusiasts all, trying to help out when we can. Sid's advice is very sound and his response more calm and measured than my own and puts me to shame
Thank you for your detailed reply
03-25-2009, 01:06 AM
#19
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@PeteL - yeah, good thought. Maybe this is just because I am new to this, but there seem to be so many details and things that can go wrong, so its good to know of other items to keep my eye on.
@N_Halbert - thanks for the additional details.
@peanut No problem! It is really wonderful that everyone is so willing to help out here and you and blown 944 are definitely right I went about diagnosing the problem incorrectly, but it was a good learning experience. I had never touched a multimeter before this, but I feel I know so much more about my car after attempting the repair. All the best!
@N_Halbert - thanks for the additional details.
@peanut No problem! It is really wonderful that everyone is so willing to help out here and you and blown 944 are definitely right I went about diagnosing the problem incorrectly, but it was a good learning experience. I had never touched a multimeter before this, but I feel I know so much more about my car after attempting the repair. All the best!
03-25-2009, 10:01 PM
#20
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09-03-2011, 04:11 PM
#21
Three Wheelin'
Another reason for a no-start, like you are having is the speed/reference sensors. My car sat idle, for almost a week as I trouble shot everything from a bad DME relay, to a bad DME on down, until finally I got to the reference sensors, and one of them was bad, due to a bad wire. Was intermittant at first, but eventually became fatal.
Last edited by 944_S_TYPE; 09-03-2011 at 04:12 PM. Reason: because I can't spell
09-03-2011, 06:47 PM
#22
Burning Brakes
Will bad speed/Ref sensors kill power to the fuel pump, or do they shutdown ignition?
Both.
If the ECU doesn't see at least 200-225rpm from the speed reference sensor then it won't ground the DME relay which means no fuel pump or injector pulsing or ignition . Its a safety feature in the event of an accident to prevent fuel being pumped and causing a fire.
The ECU grounds everything internally and controlsthe fuel pump injector pulsing and ignition pulsing (via the ignition amplifier.)
Both.
If the ECU doesn't see at least 200-225rpm from the speed reference sensor then it won't ground the DME relay which means no fuel pump or injector pulsing or ignition . Its a safety feature in the event of an accident to prevent fuel being pumped and causing a fire.
The ECU grounds everything internally and controlsthe fuel pump injector pulsing and ignition pulsing (via the ignition amplifier.)
Last edited by peanut; 09-03-2011 at 07:13 PM.
