1999 Malibu, no fuel pressure

Tiny
RANDYJ
  • MEMBER
  • 1999 CHEVROLET MALIBU
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 211,000 MILES
1999 malibu 3.1L, new rebuild, started then idled fine. Died on acceleration. Now it won't start, new fuel pump, no fuel pressure. All relays and fuses okay. Need to know what to check. Systematic checklist/trouble shooting sequence would be nice.
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Sunday, July 31st, 2011 AT 2:29 AM

15 Replies

Tiny
WRENCHTECH
  • EXPERT
You need to systematically follow a wiring diagram.
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Sunday, July 31st, 2011 AT 2:46 AM
Tiny
RANDYJ
  • MEMBER
Thanks! I'll see if I can decipher that one and hope it solves my problem.
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Sunday, July 31st, 2011 AT 2:58 AM
Tiny
WRENCHTECH
  • EXPERT
Remember, the fuel pump only powers for 2 seconds when the key is first turned on until the computer sees a crank signal.
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Sunday, July 31st, 2011 AT 3:01 AM
Tiny
RANDYJ
  • MEMBER
I assume this to be true but I have read that it is not activated until the switch is turned to crank the engine. Right or wrong, I can't say. I have a fuel pressure gauge hooked up and have watched it when switching the key. The only time I've seen a change in pressure was while cranking engine. I've got various kinds of volt meters so will be checking electrical in the morning. Hope I can decipher that wiring diagram with no problem.
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Sunday, July 31st, 2011 AT 3:15 AM
Tiny
RANDYJ
  • MEMBER
From the looks of the relay, can't tell if there is a right or wrong direction for it to be plugged in?
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Sunday, July 31st, 2011 AT 3:17 AM
Tiny
RANDYJ
  • MEMBER
I'm going to post some thinking (logic) here. Please correct me if I'm wrong. When the switch is turned on there is always power to the fuse and relay under the hood. The relay is switched on by the relay in the PCM. Right? The ground for the signal from the PCM comes from the AC compressor control (this doesn't make sense?) So, pretty much it is the PCM that has ultimate control of the fuel pump. So, where does the PCM get the signal to turn on the fuel pump? Does the oil pressure switch have anything to do with it as other posts on the internet suggest. And if so, which sensor on the side of the motor is the correct switch? There are 3 of them. One on the back side of the engine (I think it is the crank position sensor) and there are 2 sensors on the front. One appears to be the traditional looking oil pressure switch and one is very small which I kind of assume is a temperature sensor since I don't recall seeing one anywhere else on the engine?
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Sunday, July 31st, 2011 AT 12:08 PM
Tiny
WRENCHTECH
  • EXPERT
I know the relay position is confusing and I think it wooll work either way but you should be able to match the position to the rest of the relays.
As I stated earlier. It gets a 2 second prime when the key is turned on. You can apply power to the gray wire at the relay to test the pump itself.
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Sunday, July 31st, 2011 AT 12:13 PM
Tiny
WRENCHTECH
  • EXPERT
Your most recent post wasn't there yet when I posted the last answer.

Yes, the PCM controls the relay by supplying trigger power on the GRN/WHT wire. What you need to test is how the relay is responding to that. The relay should have supply power with key on or in start position coming from the fuse box itself on pin #87.
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Sunday, July 31st, 2011 AT 12:30 PM
Tiny
RANDYJ
  • MEMBER
Thanks. I did that and am getting about a 2 second supply to the relay. When I checked with the ohm meter for continuity I'm not getting a ground to the relay through what appears to be 88. The ground side coming from the a/c compressor controls. I ran a hot wire from the battery then was able to crank and run the engine with no problem. The check engine light is staying on.
Question. Would it hurt anything if I ran a hot wire to beat the relay? Like a wire from a source that is on when the switch is on? Mainly, I just need this car going asap.
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Sunday, July 31st, 2011 AT 1:22 PM
Tiny
RANDYJ
  • MEMBER
Okay. Here's the latest. I've got it working but don't know if this is an acceptable bypass or not. The schematic is so blurry that I can't tell if the relay terminal is 86 or 88 (and I don't have the relay in front of me. I ran a small ground wire from a bolt on the fender well to this terminal of the relay. This is the terminal which connects to the AC compressor control and continues to the ground splice pack G103. Where is G103 located? I suspect a broken or disconnected ground unless this is some kind of switch that switches grounding circuits?
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Sunday, July 31st, 2011 AT 2:04 PM
Tiny
RANDYJ
  • MEMBER
BTW. With this ground wire jumper from the fender bolt to the relay the fuel pump appears to be working correctly. If it is supposed to be on continuously as long as the switch is on and car is running. It does come on for 2 seconds when the switch is turned on. Then shuts off and comes on and stays on while the car is running. I'm assuming this is the correct operation for the fuel pump. Please confirm or correct me.
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Sunday, July 31st, 2011 AT 2:07 PM
Tiny
WRENCHTECH
  • EXPERT
Yes, that is correct operation. The computer needs to see a tach signal or it shuts it down.

It appears that you have found your problem.
Here is the location of G103
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Sunday, July 31st, 2011 AT 2:25 PM
Tiny
RANDYJ
  • MEMBER
I'll definitely have to go look again. There is a very similar plug with 10 or 12 wires on the front side of the engine near the starter rather than the firewall side. I do recognize the bolt to which the ground pack is attached(which the bolt was originally missing when I pulled the motor). I hope Autozone will take the fuel pump back after it has been installed. Yeah, right.
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Sunday, July 31st, 2011 AT 3:20 PM
Tiny
RANDYJ
  • MEMBER
YES! THAT WAS IT! I found the gang of ground wires were hidden and failed to be connected. Put them on and VOILA! Problem solved. Now, for the next problem (fans not coming on). I think this will constitute a new thread. THANKS!
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Sunday, July 31st, 2011 AT 3:48 PM
Tiny
WRENCHTECH
  • EXPERT
Yes it does require a new thread but before you post it, make sure you understand how the fans work and when they should be on.
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Sunday, July 31st, 2011 AT 5:42 PM

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