1998 Blazer 4.3 W Engine with low voltage at fuel pmp connec

Tiny
JAY COWEN
  • MEMBER
  • 1998 CHEVROLET BLAZER
I have a 98 Blazer, 4.3 W engine. I’m having what seems like fuel issues. When you turn the key on the fuel pump will start for a few seconds then stops which is normal. Pulled the connector off of the tank & I am only getting 4 volts in the acc pos & crank pos. I should have 11 or 12 right? I put twelve volts to the pump & it will run non stop which is good. Switched relays no diff. Any ideas?
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Thursday, October 11th, 2007 AT 10:46 PM

13 Replies

Tiny
SERVICE WRITER
  • EXPERT
The connectors on those had a lot of issues, get an updated connector from the dealer. Anytime we do a pump, we replace them.
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Friday, October 12th, 2007 AT 6:11 AM
Tiny
JAY COWEN
  • MEMBER
Paul here's alittle better info,
It quit on the highway, after waiting for a trailer, it re-started & drove on the trailer. After getting it home it re-started & made it back off of the trailer. Before I dropped the tank, I don't remember for sure if I heard the fuel pump run in ACC. Pulled the connector off of the tank & I am getting 12 volts in the crank pos. I put twelve volts directly to the pump & it will run non stop which is good. Switched relays no diff. I re-connected the pump while out of the tank & it ran for it's 3 to 5 seconds & stopped which it should. Seems like the pump is okay. Any ideas?
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Friday, October 12th, 2007 AT 8:47 AM
Tiny
SERVICE WRITER
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Maybe it isn't a fuel issue, but I would still be leary of the connector. You initially were not getting enough voltage, now you are.I'd still replace the connector unless you can pinpoint the voltage loss that was happening.
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Friday, October 12th, 2007 AT 3:18 PM
Tiny
JAY COWEN
  • MEMBER
Sorry Paul, I wasn't very clear in my first post. I have 4 volts in ACC & Crank on one pin & 12 volts on the second pin in the crank postion only. I believe these are the normal voltages. When I get a chance in a day or two I'm going to put the pump back in the tank, put under the Blazer & hook up the feed & return lines and check the pressure at the fuel rail. What is the min. Pressure I want to see here? The connector seemed okay. Did an ohm's check & all 4 wires are good.
Thanks for the response, waiting on your next one.
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Saturday, October 13th, 2007 AT 1:34 AM
Tiny
SERVICE WRITER
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According to Mitchell, it should be 60-66 psi-(CSI),
Vin W should be (CSI), like you have.

56-62 psi (SFI) should be Vin X.
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Saturday, October 13th, 2007 AT 3:47 AM
Tiny
JAY COWEN
  • MEMBER
I now have the pump re-installed & I am getting 50-55psi at the Schrader valve. It runs for 4to5 minutes with the pressure changing a pound or two but nver drops below 40psi. When you floor it (in park) it will stall or after 4 or 5 minutes, it'll stall. No codes either. Wait for five minutes & it'll re-start again. Plugged filteror a weak pump?
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Sunday, October 14th, 2007 AT 7:48 PM
Tiny
SERVICE WRITER
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Based on what your getting, I think you have a bad pump. I would use a delco or delphi pump on the and changed the filter at the same time.

Before you do that, unplug the MAF sensor and run it for the heck of it and see if the stalling symptoms change. I have seen pumps that were technically out of spec, but the MAF was the source of the problem. Yours is pretty low if it's getting into the 40psi area and don't expect the MAF to change things, but it's easy and quick anyways.

Another Member mentioned a few things and I will ask him to post his thoughts.
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Monday, October 15th, 2007 AT 5:18 AM
Tiny
CHEVYII
  • MEMBER
Keep an eye on your oil pressure when the vehicle is running to see if it drops too low or is erratic
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Monday, October 15th, 2007 AT 6:39 AM
Tiny
JAY COWEN
  • MEMBER
Thanks Paul, I'm still questioning the pump too. Just didn't want to shell out 600 bucks for a non-returnable item. I'll try the MAF but I doubt it too.
Thanks again, Jay

Tonight I did the following cold start.
With the key on ACC I had 53 PSI
Engine running 50 PSI
It ran for two minutes & quit at 44 PSI
Turned the key off & after 10 minutes it dropped to 20 PSI
WOULD NOT re-start until 5-10 mins. Later.
I know there is no leaks. If you think it might be the regualor, where is it located? Pic? Post, ( no links or downloads having computer issues as well.)
I forgot the MAF. S@#T!

P.S.
I want to hook up a 4 pin trailer connector for him as well, (white, green, yellow, brown) I know the folowing.
White= Ground
Yellow= Left Turn
Green= Right Turn
Light Blue= Stop
Light Green= Back up(don't need)
Can I tie in the stops or does he need a after market connector? (Doesn't matter, just figued I'd save him 20-30 bucks. Again post if you can no links
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Monday, October 15th, 2007 AT 4:07 PM
Tiny
CHEVYII
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If the pressure is dropping l;ike that your regulator may be failing, it is located under the upper intake plenum on the rear of the spider, one clip gets it off
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Wednesday, October 17th, 2007 AT 6:22 PM
Tiny
SERVICE WRITER
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Jim & Jay,
Thanks for jumpin in ol'buddy :D
I know you have top notch skills and glad you looked at this. Hopefully Jay's customer will throw us a donation for the help. :Wink:

I'm thinking to check the pressure of the pump before the filter to differentiate the regulator from the pump. If it reads good, its the regulator, if it reads low its the pump. Assunming the filter is not a problem.
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Wednesday, October 17th, 2007 AT 8:21 PM
Tiny
CHEVYII
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My thought was the same until I read the post where it stated pump pressure was ok for 10 minutes, then he checked the pressure and it dropped below 40 psi, so if it was in spec at the schrader for some time? But I always check pressure ther and always replace the filter no matter how old it is, the other alternative could result in damaged parts but you could pinch off the return line while checking pressure to confirm,

thanks paul
and good luck jay
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Wednesday, October 17th, 2007 AT 9:19 PM
Tiny
JAY COWEN
  • MEMBER
Replaced the fuel pump, all is good, thanks guys
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Wednesday, October 17th, 2007 AT 10:06 PM

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