There is a Rapid ticking sound coming possibly coming from the fuel pump, fuel pump relay or wiring?

Tiny
SMITHEE
  • MEMBER
  • 1999 CHEVROLET BLAZER
  • V6
  • 4WD
  • AUTOMATIC
  • 237,787 MILES
I’ve been having a rapid ticking sound coming from the fuel pump relay, it lasts for about 5-10 minutes, then car starts right up and runs great. I bought a new fuel pump, and 2 new relays still makes the ticking sound. I have a feeling it’s something with the wires or wiring. I just have no clue where to start if anyone can help, I would really appreciate it.
Sunday, March 2nd, 2025 AT 9:48 PM

6 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,271 POSTS
The fuel pump relay is controlled by the PCM which might be going bad. Do you have any trouble codes?

This guide can help:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Also, when trying to start the engine do you have a security light flashing? Here is the wiring diagram for the fuel pump relay and PCM so you can see how the system works. I would also check the ground for the relay which is on the rear of the engine block which I have marked on the diagram as well. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.

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Monday, March 3rd, 2025 AT 12:25 PM
Tiny
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I’ll try that and when it does the clicking the engine light comes on but once it’s done doing the ticking it turns off. I tried to hook up my scanner tool while it’s doing but can only get codes while it’s running.
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Monday, March 3rd, 2025 AT 1:00 PM
Tiny
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This is what it does.
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Monday, March 3rd, 2025 AT 2:53 PM
Tiny
KEN L
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Thanks for the video. Is the ticking duration the same each time? If so, it looks like the PCM needs to be replaced. Here is how, you can get a preprogrammed unit by searching Google or Ebay. I would also check the grounds from the battery to the engine and chassis/body.
Check out the images (below). Please let us know what happens.
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Tuesday, March 4th, 2025 AT 10:31 AM
Tiny
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Yeah, it’s about same amount of time each time it does which it only does it after not driving it after a few hours and the ground to the chassis is good because I did have to replace that since I touched it and broke off.
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Tuesday, March 4th, 2025 AT 12:49 PM
Tiny
KEN L
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Yep, the PCM is the only thing I can think of that would do that. Let me know after you have replaced it.
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Wednesday, March 5th, 2025 AT 8:45 AM

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