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Electrical failure

Tiny
KELLY MAAG
  • MEMBER
  • 1993 BUICK CENTURY
  • 3.3L
  • V6
  • 2WD
  • AUTOMATIC
  • 107,000 MILES
With the car running when cooling fan kicks on, but not every time, but on occasion the car will idle rough. Checked fuel pressure about 40 lbs. While checking the fuel pressure I took the fuel pump fuse out then put back in and the cooling fan kicks over when inserting fuse. So my question is why would the orange wire that comes off fuel pump fuse that goes to oil pressure sender and to ecm? Would it affect the green wire that comes from ecm to the cooling fan relay? That is hot until the ecm is told to shut off power to the fan relay to turn on fan. Correct me if I am wrong. Thanks.
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Sunday, May 8th, 2016 AT 6:54 PM

9 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
First thing the fuel pressure should be 41-47 no lower or will give problems. The wire you are talking about has nothing to do with system it may be a partially broken fusible link and was a coincidence. Check the items in picture then the coolant temperature sensor wire connection and switch, some of those had problems.
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Monday, May 9th, 2016 AT 7:01 AM
Tiny
KELLY MAAG
  • MEMBER
  • 4 POSTS
When the car is warmed up it will kick the fan over just enough to get it to spin over a couple of turns by unplugging the fuel pump fuse I can unplug it and plug it back in it will spin the fan over I have unplugged the fuse and plugged it back in as many as 6 times all within a few seconds and it spins the fan everytime. It is the craziest thing I have ever seen. When just checking voltage with multimeter on the green wire of fan relay it stays stable till I plug the fuel pump fuse in then the voltage drops. I installed a new coolant sensor and the plug looks good.
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Monday, May 9th, 2016 AT 7:14 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,961 POSTS
The wiring going from the oil pressure sensor is to cut the fuel pump when there is no oil pressure to save the engine from internal damage. It is normal for the cooling fan to move slightly when the engine starts/fuse installed etc, the ecm controls it so a small command for the computer when activated is normal.
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Wednesday, May 11th, 2016 AT 6:05 PM
Tiny
KELLY MAAG
  • MEMBER
  • 4 POSTS
Thanks 2carpros Ken I am still confused as to why the engine will idle rough at times when the coolant fan kicks in but it is not all the time. I have had it run for 1/2 a day and run good. Then all of a sudden it will run real fast or idle real slow and about die.
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Wednesday, May 11th, 2016 AT 7:08 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,961 POSTS
It sounds like you have some kind of ignition like a coil problem, or the idle air control motor needs to be serviced.

Ignition coils on these engine went out all of the time, also the crankshaft angle sensors. Btw
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Saturday, May 14th, 2016 AT 12:26 AM
Tiny
KELLY MAAG
  • MEMBER
  • 4 POSTS
I have replaced harmonic balancer, crankshaft sensor, O2sensor, throttle position sensor, cleaned mass air flow, new spark plugs, tried a used ignition control module with coil packs. I am wondering if the fuel pump is drawing to many amps causing electrical problems through the car.
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Saturday, May 14th, 2016 AT 5:58 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Ya know you said you had 40 psi on pump that is not enough your need at least 41psi which on GM cars normally is higher than that anyhow. I am probably sure you need another pump. Replace the fuel filter as well.
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Saturday, May 14th, 2016 AT 4:24 PM
Tiny
KELLY MAAG
  • MEMBER
  • 4 POSTS
Changed out engine control module with a reman and the car does not skip a beat. Thanks for the help.
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Sunday, May 22nd, 2016 AT 6:46 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,961 POSTS
Good to hear, thanks for getting back to us, one of the injector drivers must have been bad causing the misfire. Nice work, please visit us again when having a car repair problem.
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Sunday, May 22nd, 2016 AT 7:27 PM

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