Conversions & Swaps LSX Engines in Non-LSX Vehicles
Sponsored by:
Sponsored by:

Fuel pump relay issue

Thread Tools
 
Search this Thread
 
Old Mar 16, 2008 | 02:27 PM
  #1  
76LQ9TA's Avatar
Thread Starter
Launching!
iTrader: (1)
 
Joined: Jul 2006
Posts: 244
Likes: 2
From: Montgomery, IL
Default Fuel pump relay issue

What controls the length of time that the fuel pump runs when the ignition switch is first turned to the run position? My car is cycling the relay on and off very quickly and doesn't stop until the key is off. I have checked the wiring on the four pins of the relay and swapped out the relay. I am thinking that I have a bad pcm. Everything was working two weeks ago. Is there anything that I can check before I send out the pcm?
Reply
Old Mar 16, 2008 | 04:16 PM
  #2  
jay_lt4's Avatar
10 Second Club
iTrader: (4)
 
Joined: Oct 2006
Posts: 855
Likes: 0
From: wisconsin
Default

check your supply voltage at the relay, low voltage can cause relays to pulse on and off
Reply
Old Mar 17, 2008 | 08:21 AM
  #3  
76LQ9TA's Avatar
Thread Starter
Launching!
iTrader: (1)
 
Joined: Jul 2006
Posts: 244
Likes: 2
From: Montgomery, IL
Default

The voltage is good. I thought about that. The car was also hooked up to the battery charger.
Reply
Old Mar 17, 2008 | 10:27 AM
  #4  
Carshopinc.com's Avatar
LS1TECH Sponsor
iTrader: (5)
 
Joined: Sep 2007
Posts: 645
Likes: 0
From: Moline, ILLINOIS
Default

Is the battery good? The pcm may be acting funny if the voltage is low...
Reply
Old Mar 18, 2008 | 07:01 AM
  #5  
76LQ9TA's Avatar
Thread Starter
Launching!
iTrader: (1)
 
Joined: Jul 2006
Posts: 244
Likes: 2
From: Montgomery, IL
Default

I found the problem last night. One of the ground wires was loose. The bolt bottomed out and left the terminal a little loose.
Reply
Old Jul 13, 2010 | 06:38 AM
  #6  
pushrod36's Avatar
On The Tree
 
Joined: Jul 2009
Posts: 122
Likes: 1
From: Richmond, VA
Default

I want to resurrect this thread because I am having a similar problem. My fuel pump relay is cycling very quickly, but I do not believe that it is because of a bad ground (grounded to the same location as the negative battery terminal). I also know that I have 12 volts coming from the ECU.

Just like 76LQ9TA said, the relay chatters and does not stop until the key is off. I have the added complication, though, of the engine won't start with the relay connected. If I build fuel pressure, and then disconnect, it fires right up. This makes me think there is short through it (short would still provide the 12v that I see).

Any thoughts?
Reply
Old Jul 13, 2010 | 12:05 PM
  #7  
Pop N Wood's Avatar
TECH Junkie
iTrader: (1)
 
Joined: May 2006
Posts: 3,402
Likes: 8
Default

Could be a bad relay. Could also be wired wrong. Has the harness been modified?
Reply
Old Jul 13, 2010 | 07:49 PM
  #8  
pushrod36's Avatar
On The Tree
 
Joined: Jul 2009
Posts: 122
Likes: 1
From: Richmond, VA
Default

More information...

If I unhook either the lead from the battery, or the wire to the fuel pump the relay behaves exactly as it should. I am thinking that this means a bad ground at the fuel pump. I'll let you know how that pans out for me.
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?

 Pouria Savadkouei
story-1

Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine

 Verdad Gallardo
story-2

7 Most Reliable High-Performance Engines GM Has Ever Built

 Verdad Gallardo
story-3

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-4

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-5

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-6

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-7

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-8

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-9

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo




All times are GMT -5. The time now is 04:39 PM.

story-0
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?

Slideshow: We take a close look at the ONE and Artidiag 800BT2 diagnostic tools from Topdon and the reasons to buy one over the other.

By Pouria Savadkouei | 2026-05-28 11:05:11


VIEW MORE
story-1
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine

Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.

By Verdad Gallardo | 2026-05-26 18:23:54


VIEW MORE
story-2
7 Most Reliable High-Performance Engines GM Has Ever Built

Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.

By Verdad Gallardo | 2026-05-21 16:45:27


VIEW MORE
story-3
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-4
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-5
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-6
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-7
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-8
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-9
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE