Bad fuel pump OR bad pressure regulator??


Old 05-23-09, 12:06 PM
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Join Date: Feb 2002
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Talking Bad fuel pump OR bad pressure regulator??

OK--this is an easy one. Chevy tries to start--runs for two seconds and shuts down. Prime throttle body--engine runs 'til fuel is exhausted. Removed fuel filter--turned on key--small amount of fuel present. Installed in line fitting before fuel filter and attached fuel pressure gauge. Turned on key--ZERO reading. Cycled key several times--Zero--cranked engine--Zero. Question: If the fuel "pressure regulator" is shot would that prevent the fuel pump from operating? In other words is the fuel pressure regulator electrically connected thru the ECU to the pump or is the pressure regulator's only function to maintain pressure at the injectors and has no bearing on the fuel pump?

This is a one ton dully and I want to be sure before I drop the gas tank.


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Old 05-23-09, 03:21 PM
Join Date: May 2006
Location: Iowa!!!!!
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I haven't seen them all, but normally the pressure regulator has three lines hooked to it. The inlet fuel, the outlet fuel and the vacuum line. If this is what you have you have determined pretty well you have a bad fuel pump.

At this point the considerations are:

* Did your pump run (usually hear it through the tank filler) /
* Do you have an obstruction between the pressure gauge and the pump (probably not)?
* Is there fuel in the tank (probably yes)?
* Finally, is there anything in the tank disconnected that keeps the pump from picking up fuel from the tank (probably not, but you have to pull the tank anyway = check it then)?
Old 05-23-09, 06:37 PM
Join Date: Apr 2009
Location: Hammond, Louisiana
Posts: 94
sounds like a bad fuel pump to me. if u disconnected the fuel line right after the pump and no pressure was reading that should tell u there that the fuel pump is bad. the regulator is farther down the line with an inlet line, and three outlet lines.
Old 05-24-09, 04:58 AM
Thread Starter
Join Date: Feb 2002
Location: USA
Posts: 86
I Agree

You guys confirmed my diagnosis. I was "almost" sure the fuel pump was the culprit, but removing the gas tank from a one ton dully truck is not my way of spending Sunday afternoon.

I am going blame this malfunction on our Congress, 'cause they mandated Ethanol which is eating up our vehicle's rubber and plastic parts.


Old 05-24-09, 05:52 AM
Join Date: Jan 2007
Location: North Central Indiana
Posts: 912
Fuel pump

Did you hear the pump running ? if not make sure you have power to the pump. There are some electrical problems that can keep the pump from running. RW
Old 05-26-09, 02:38 PM
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Join Date: Feb 2002
Location: USA
Posts: 86
Smile We were all wrong.

To "retired wrench": I checked the "relay" and the "fuse" before I tested the pump. Both were OK.

My original question was "is the fuel pressure regulator connected thru the ECM that would stop the fuel pump from operation".

I prepared to drain the fuel so as to remove the gas tank. I decided to try one one test. I disconnected the negative battery terminal to clear any codes in the ECM. Next, I disconnected the "IN" fuel supply to the throttle body. I put a fire extinguisher nearby, reconnected the negative battery terminal, placed a container under the disconnected fuel line, and turned on the key. THE FUEL PUMP WORKED NORMALLY.
I ordered a fuel regulator kit for installation tomorrow.

This post may help others with a similar problem. Lesson learned that the fuel regulator must regulate the operation of the fuel pump on a General Motors vehicle.

My method may not be scientific, but I don't have to remove the gas tank--------yet. After all it is a 1991---maybe later after another 100,000 miles.

Thanx to all who responded.
Old 05-26-09, 05:04 PM
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Not sure if this is true or not. I have heard that it is easier to take out the bolts holding the bed to the chassis and have some friends help lift the bed off of the chassis to gain access to the gas tank. Forgot to mention taking off the fuel filler neck before lifting the bed. Is this actually easier than dropping the tank? I have dropped a tank before and it is not my idea of a good time.
Old 05-26-09, 06:15 PM
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If you think ethanol is bad for your cars, you should see what it's doing to your lawn equipment. Completely rusts and pits out your carbs and injectors.

I've changed a few Chevy pumps. Never dropped the tank. Unbolted filler neck, disconnect tail light harness, and propped the bed up with a 2x4. The bed on a short bed truck is HEAVY, can't imagine a dually.

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