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Username Post: '97 Tahoe - possible fuel pump issue.        (Topic#186157)
dcbc991 
Senior Member
Posts: 132

Loc: Rockford, IL
Reg: 05-03-02
04-01-08 12:15 PM - Post#1401578    

Hi friends!

Yesterday while driving my '97 Tahoe was stumbling under load. After about 10 mins of driving, I was able to get to a gas station where I turned off the ignition. Now it won't start, just turns over. It also occured to me that I no longer hear the 'whirring' noise when I turn the key so I'm thinking my fuel pump is bad. At 129k miles, I'm due I think but I want to be methodical at troubleshooting and not just blindly throw parts at the problem. So, I'll test the fuel pressure tonight, but I'm wondering under what other conditions will the fuel pump not function? I thought I read somewhere here that a possible ignition problem could be the culprit? Can somebody elaborate a little more on this? My Haynes manual doesn't say anthing about this. Thanks for any and all feedback.
Dean Christensen
Northern Illinois
1997 Tahoe 2WD


 
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someotherguy 
Moderator
Posts: 25633
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
04-01-08 12:33 PM - Post#1401599    
    In response to dcbc991

Before assuming the pump is bad, check the fuel pump relay in the convenience center under your hood. Pop it out, see if any of the pins on it look tarnished or burnt, clean/replace as needed and see that it fits snugly in the socket.

Richard
94 C2500LD / 94 C1500 / 06 300C SRT8
Check out my truck shop projects


 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
04-01-08 12:34 PM - Post#1401603    
    In response to dcbc991

Check the fuel pump relay first, take it out and check the pins. If they are discolored at all, I would replace it. You can clean up those pins and try it, and make sure the female spring clips are tight too.

There is a hotwire straight to the pump but it's usually a real PITA to find. It's in the big harness leaving the underhood fuses, running under the brake booster.

 
dcbc991 
Senior Member
Posts: 132

Loc: Rockford, IL
Reg: 05-03-02
04-01-08 12:50 PM - Post#1401619    
    In response to CDAUSA

Thanks guys.

I did in fact pull the relay, but didn't pay too much attn to the contacts. I'll do that again tonight. So instead of replacing it, is there a procedure to just test it with a multimeter? If so, do you know the specs?
Dean Christensen
Northern Illinois
1997 Tahoe 2WD


 
Bad Bowtie 
Valued Contributor
Posts: 4544
Bad Bowtie
Age: 42
Loc: TX
Reg: 07-04-03
04-01-08 01:23 PM - Post#1401647    
    In response to dcbc991

When did u replace the fuel filter last?
GMC. We are Professional Grade.

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dcbc991 
Senior Member
Posts: 132

Loc: Rockford, IL
Reg: 05-03-02
04-01-08 02:21 PM - Post#1401684    
    In response to Bad Bowtie

Well, I've only owned this vehicle for not quite 2 years...and admittedly I've never changed it. I'm curious what effect that would have on the pump not 'whirring' anymore? It seems more than a fuel filter issue to me...but that's why I'm here. Thanks.
Dean Christensen
Northern Illinois
1997 Tahoe 2WD


 
59 EWW 
Very Senior Member
Posts: 1871
59 EWW
Loc: Kansas City Kansas
Reg: 08-31-03
04-01-08 02:47 PM - Post#1401700    
    In response to dcbc991

Hey Dean

All good advice so far, the prime wire is normally red or black with a connector on the end of it, it breaks out of the main harness about six inches from the fuse relay center.

The relay needs to be in the fuse/relay center to use the prime wire, the prime circuit runs thru a normally closed set of contacts in the fuel pump relay.
Just apply 12 volt + to the prime wire, the pump should run.

The relay is pretty simple, 2 terminals is the coil, the other 3 terminals is a common, a normally open contact, and a normally closed contact, easily checked with a volt/ohm meter.

Before you get too excited, take a 2X4 and wack the bottom of the fuel tank a couple times, to see if the pump will start running again, I know sounds stupid, but it Works sometimes, this procedure has saved many a tow jobs to a shop.

It doesnt fix the problem, it just gets you going sometimes.
Ernie

59 Biscayne 2dr
65 Elcamino
97 Z71,K1500,5.7
06 GMC Canyon


 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
04-01-08 02:57 PM - Post#1401712    
    In response to 59 EWW

  • 59 EWW Said:

Before you get too excited, take a 2X4 and wack the bottom of the fuel tank a couple times, to see if the pump will start running again, I know sounds stupid, but it Works sometimes, this procedure has saved many a tow jobs to a shop.

It doesnt fix the problem, it just gets you going sometimes.



Ernie is correct, it also helps if you can have someone in coordination with you, to whack the tank at the precise moment you hit the key---or vice-versa.

Unless the pump has gotten something inside of it, or a piece of the plastic impeller came off and has it wedged, the motor is just a stator/brush arrangement. The winding on the stator is black from the brushes running on it, all it needs is to move 1/16" to find another spot to run on and it will most likely run til you shut it off.

Some guys here have run them another 20K miles after, but it isn't advised and they also carried a "whacker" around with them.


 
dcbc991 
Senior Member
Posts: 132

Loc: Rockford, IL
Reg: 05-03-02
04-01-08 06:35 PM - Post#1401894    
    In response to 59 EWW

Hi Ernie,

Thanks for your help so far. I'm having trouble locating the "fuel pump test terminal" near the relay center.

Apparently this is what you are referring to as the 'prime' wire? Per some diagnostic data I subscribed to, if I apply 12 volts to this test terminal, I should hear the pump run. But I can't find this test terminal. Do I need to pull back some of the wire looming?

Dean Christensen
Northern Illinois
1997 Tahoe 2WD


 
59 EWW 
Very Senior Member
Posts: 1871
59 EWW
Loc: Kansas City Kansas
Reg: 08-31-03
04-01-08 06:42 PM - Post#1401902    
    In response to dcbc991

It should be sticking out of the main harness, midway between the fuse/relay center and the firewall.

Its only 1-2 inch long, it may be taped down to the harness, but I have never seen one on the inside of the harness.

I guess banging on the tank didnt get the pump to start running?
Ernie

59 Biscayne 2dr
65 Elcamino
97 Z71,K1500,5.7
06 GMC Canyon


 
Boog 
Super Senior Member
Posts: 3536
Boog
Loc: Central Arkansas
Reg: 04-28-02
04-01-08 06:53 PM - Post#1401922    
    In response to 59 EWW

These fuel injected critters can be ornry sometimes. My 97 came with a Carter pump and it was fairly loud compared to a Delco. One day the truck just quit running like I turned the key off. Of course it was in rush hour traffic and pouring down rain. When I got it home and checked it I found the pump still ran but was really quiet. I also found it pumped up to 16# but it was not nearly enough to start the engine. My filter had been changed previously too. It was just time for a new Delco pump!
Have you pressure checked yours?
Boog
69 Chevy step
06 GMC ccsb Z71
00 GMC excab Z71
All GM...'nuff said!
JR Nation


 
dcbc991 
Senior Member
Posts: 132

Loc: Rockford, IL
Reg: 05-03-02
04-01-08 07:05 PM - Post#1401937    
    In response to 59 EWW

Ernie...thank you! I found it. I was just looking too hard apparently.

I jumpered over to the postive feed for the relay center and get nothing.

At least I located that test terminal.

And nope...I banged on that poly tank all around and it made no difference.
Dean Christensen
Northern Illinois
1997 Tahoe 2WD


Edited by dcbc991 on 04-01-08 07:07 PM. Reason for edit: No reason given.

 
dcbc991 
Senior Member
Posts: 132

Loc: Rockford, IL
Reg: 05-03-02
04-01-08 07:10 PM - Post#1401941    
    In response to Boog

Hi Boog. No I haven't yet tested the pressure. I'll do that next. I definitely no longer get that 'whirring' noise that I sorely miss now...
Dean Christensen
Northern Illinois
1997 Tahoe 2WD


 
Big_Paul 
Old as Dirt Member
Posts: 7306
Big_Paul
Age: 29
Loc: Turlock, California
Reg: 09-24-01
04-04-08 02:30 PM - Post#1404124    
    In response to dcbc991

When my pump went out I kept a spray bottle of gas in the truck. Then I left the intake tube boot loose, every time I needed to start it, I would pop the hood and spray gas into the throttle body then run back to turn the key. All it needed was to be primed to start and it would still run okay. The pump was ultra quiet and the truck didn't get up and go like normal, wierdest thing, but it kept me going for about a month.
'96 C-1500 305
'00 Monte Carlo SS
'02 Silverado 2500 HD
------------------------


 
marquezrm 
Forum Newbie
Posts: 1

Reg: 04-08-11
04-08-11 08:07 AM - Post#2073622    
    In response to 59 EWW

I have the exact same problem with my tahoe. I found the test connector red wire it is a ground is that normal.

 
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