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 Page 1 of 2 12
Username Post: fuel pump 92 Suburban        (Topic#229159)
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-06-09 03:22 PM - Post#1800850    

ok. have the pump out and need to know how to test it with the pump out. I wont bore you with details but it wasnt that hard to pull it out this time, thankfully.

There was not any fuel that drained out of the fuel line so I am guessing right up front like you suggested, the pump is bad..

 
Low priced Genuine GM Auto Parts
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-06-09 06:11 PM - Post#1800952    
    In response to 81FLT

I am unsure why or how I ended up with a new topic and subect line, I was attempting to respond to my original questions about why my 1992 Suburban stopped running:

http://www.chevytalk.org/fusionbb/showtopic.php?ti...

 
someotherguy 
Moderator
Posts: 25879
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
11-07-09 10:30 AM - Post#1801228    
    In response to 81FLT

The sending unit has a 4 pin connection, 2 are for pump power and the other 2 are for the fuel gauge; you could use test leads to power the pump and see if it runs. Obviously you'll want to be really careful because the pickup (bottom of pump) needs to be submerged in fuel, so you don't want to make any sparks anywhere near that area!

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-07-09 12:06 PM - Post#1801267    
    In response to someotherguy

update.

replaced the fuel pump after trying to test the old one, got the impression that it was not working. Put the new one in, wired things up and still no fuel coming out of the fuel line to the carb. And I dont hear the fuel pump running when i turn it on. Its going to be something simple but it isnt going to make me happy, when i find it.

 
ltlvt 
Senior Member
Posts: 1638

Age: 62
Loc: Wichita Falls Texas USA
Reg: 09-17-00
11-07-09 05:01 PM - Post#1801416    
    In response to 81FLT

Are you checking for fuel while cranking the engine or just with the key on? The system needs to kow 2 things to energize the pump. #1 is rotation of the distributor and #2 is oil pressure. If you don't have these you will not have fuel. If you are cranking the engine and still have no fuel I would start with the fuel pump fuse and if it is okay check to make sure the fuel pump relay is being energized. They are both located on the firewall close to heater/a/c unit.
Runs like a Scalded Dog!!


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-07-09 05:30 PM - Post#1801436    
    In response to ltlvt

I disconnect the fuel line to the base of the carb and crank the engine. Not a drop.

I have looked for the fuel relay and cant seem to locate it.

 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-07-09 06:03 PM - Post#1801452    
    In response to 81FLT


I just spent a good 30 minutes looking under the dash, on the firewall, both sides, passenger and drivers, wheel wells, and no sign of anything that even resembles a fuel pump relay.

I did find a goofy alteration to the wiring under the dash that has a plug in connector with a resister stuck in it, looping to both sides. It was taped up and i unwrapped it to find that.

Yes, I bought the truck used. THere were no complications until it died.

Also, where would I look for the fuel filter for this rig, I see nothing inline from the tank to the carb.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3071

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
11-07-09 06:37 PM - Post#1801469    
    In response to 81FLT

  • 81FLT Said:

I just spent a good 30 minutes looking under the dash, on the firewall, both sides, passenger and drivers, wheel wells, and no sign of anything that even resembles a fuel pump relay.




The fuel pump relay is under the hood on the passenger side of the firewall. It is to the center of the truck next to the junction block.

It should be on the fire wall very close to where the transmission dipstick is located.

If the plastic cover is still there that covers the junction block area you will have to remove the cover to see the fuel pump relay.


Your truck should be like the illustration in the link below, accept your truck will only have one relay in this location.
http://autorepair.about.com/library/illustrations /...


  • 81FLT Said:

Also, where would I look for the fuel filter for this rig, I see nothing inline from the tank to the carb.



It is on the inside of the driver’s side frame rail in the area under the driver’s seat.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-07-09 07:00 PM - Post#1801484    
    In response to Chevytech

thank you all. and thank you, ChevyTech for the details.

 
ltlvt 
Senior Member
Posts: 1638

Age: 62
Loc: Wichita Falls Texas USA
Reg: 09-17-00
11-07-09 11:18 PM - Post#1801571    
    In response to 81FLT

I'm not sure what model you are talking about . Mine is an 88 . If you want you can email me and i will send pics of the fuel pump fuse and fuel pump relay. ltlvt@yahoo.com Terry

By the way welcome to the forum.
Runs like a Scalded Dog!!


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3071

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
11-08-09 06:01 AM - Post#1801628    
    In response to 81FLT

You’re welcome!

There is an inline fuel pump fuse in the junction block area also. The fuel pump fuse is at the extreme passenger side end of the junction block and is in a black plastic oval cover. If you slide it out of the cover you can test for voltage to the fuel pump without getting under the truck or taking anything apart.
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
someotherguy 
Moderator
Posts: 25879
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
11-08-09 08:21 AM - Post#1801690    
    In response to 81FLT

  • 81FLT Said:

I just spent a good 30 minutes looking under the dash, on the firewall, both sides, passenger and drivers, wheel wells, and no sign of anything that even resembles a fuel pump relay.


I'm sorry, I thought I posted this as a reply to you but it was another thread where someone is having fuel system problems.

88-94 pickup, 92-94 SUV fuel pump & relay location:



Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-08-09 01:55 PM - Post#1801846    
    In response to someotherguy

someotherguy: ty vm for the photo. you did post it for me, I missed it in the earlier discussion. My apologies.

Ok. I pulled the fuel pump relay off the firewall, gently separated it, and tested all of the wires with the key ON. I tested the gray wire mostly knowing that there is the gray going back to the fuel pump. I grounded the neg pin on the multitester and touched positive to the gray. nothing. I tested it on the battery to make sure the multi was working. no problem.

I tested all of the wires coming into the relay, and none showed any voltage or increase in voltage on the meter. I used 10 volts DC and multiple others with absolutely NO jumps.

I should mention I am not the best with a multimeter but I did ground the negative cable on it to the engine, then tried using the alternator bolt, then the frame, keeping the positive on the gray wire. nothing.

 
squidley63 
Member
Posts: 513

Loc: NY
Reg: 09-23-04
11-08-09 04:17 PM - Post#1801920    
    In response to 81FLT

the gray wire that goes back will only have power to it when the relay is on and tripped. You should have one of the plugs with 12 volts. In order to positively test your pump you would need to jump a 12 volt power source to that gray wire and a ground to the black wire that goes back for good measure.

1963 Chevrolet C-10 Fleetside SWB
400 sbc 3 speed manual

95 Chevy Suburban 5.7TBI 4X4


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-08-09 04:39 PM - Post#1801936    
    In response to squidley63

got it. will do that tomorrow. thanks!

I should mention that there is no sound of the fuel pump running when i turn the key on and am beginning to suspect the relay may well be bad.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3071

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
11-08-09 04:43 PM - Post#1801940    
    In response to 81FLT

Squidley63 is correct that the relay should not be applied and not power should be on the Gray wire when you did the testing.

The Orange wire should have had voltage when you did the testing.

The ECM controls the fuel pump relay.

The truck has a fuel pump relay that supplies power to the fuel pump when:
- Anytime the ECM receives a distributor reference pulse. (Engine running / engine cranking)
- The key is turned on engine not cranking – relay applied for 2 to 20 seconds (most trucks 2 seconds), depending on emissions equipment. Trucks over 8500 GVW and some other vehicles have and electronic Fuel timer module that allows the pump to run up to 20 seconds.
The key must be turned off for a certain amount of time before it will prime the system again when turned back on.

There will only be power to the fuel pump for a few seconds when you first turn the key to the on position. If you are turning the key on then walking around the vehicle testing for voltage to the fuel pump circuit there will be no voltage and should not be power to the pump.

The ECM should store a code 54 if this relay fails.


Fuel pump relay wire colors:
Red – ALDL connector terminal “G”
Dark Green with white tracer – to PCM (computer) this controls the relay
Gray – to fuel pump
Black with white tracer - Ground
Orange – power from fusible link at firewall junction block

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-09-09 09:25 AM - Post#1802315    
    In response to Chevytech

Chevytech:

Ok. I have no way to test the ECM. Vehicle is dead in the yard with no way to get it to someone who can.

Voltage to orange wire is strong, both with key on and off. With key on, there is no voltage showing on gray wire. I had someone turn the key on while I was standing at the relay, no sign of current at all.

With fused jumper running to gray, no sound of pump running, both with key on or off.

 
355Cheyenne 
Senior Member
Posts: 3765
355Cheyenne
Loc: Northern MN
Reg: 10-27-04
11-09-09 09:28 AM - Post#1802316    
    In response to 81FLT

just thought this diagram may be handy. Any thoughts about a bad oil pressure switch?

98 Silverado k1500 4x4 350


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-09-09 12:21 PM - Post#1802392    
    In response to 355Cheyenne

Thanks for that diagram, 355!

Heres what I did today. (its sucking money out of my fists faster than my ex did! lol)

1) put the new fuel pump in yest.
2) today I put in new fuel pump relay
3) new fuel filter

Turned the key, heard the relay work for 2 sec, hit the ignition and ... nothing...cranked and waited and not a thing. NO fuel comes out.

Next choice is to bypass the inline wire connection where the fuel pump connects back at the tank, and eliminate that plastic connector to see if THATS it. Then with that wired directly I will try starting it again.

If not that, I will go to the oil pressure switch. Is there an easy way to test that??

 
355Cheyenne 
Senior Member
Posts: 3765
355Cheyenne
Loc: Northern MN
Reg: 10-27-04
11-09-09 12:47 PM - Post#1802406    
    In response to 81FLT

sounds like it primes, but when it gets to the run state it isn't running. So that could be the oil pressure switch. Well There are two possible situations. either you have the dummy oil light or you have the gauge. I am expecting, thinking with the dummy oil light the same sensor is used and it is a two wire connection. so it is as simple as running a continuity tester on it to see if it enables. I would also think there would be a correlation to the light on the dash. I will look at my truck when I get home.

if you have the gauge, I think this is a multi wire connection and at that point I wouldn't be much help... in-fact I could be completely wrong with everything I just told you because I have limited knowledge on the subject.

if it is sucking more money out of you then your ex, I would say just like your ex, it may be time to get rid of it.

I joke.
98 Silverado k1500 4x4 350


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-09-09 01:33 PM - Post#1802429    
    In response to 355Cheyenne

I am not going to lie, i am stumped. I did spend a little bit of time under the truck looking for the oil pressure switch, am going to jack it up so I have a little more room to look around.

 
355Cheyenne 
Senior Member
Posts: 3765
355Cheyenne
Loc: Northern MN
Reg: 10-27-04
11-09-09 01:57 PM - Post#1802438    
    In response to 81FLT

I was just doing some research because that wiring diagram makes no sense.

http://www.thirdgen.org/techboard/tbi/518382- tbi-d...

they say that the oil pressure switch doesn't kill the motor under whatever psi. it seems to be two paths... not sure why, but I guess it works like this, the ecm controls the relay. Once the motor starts it doesn't matter what the relay is doing because if you pull the relay, as long as there is oil pressure the power should run through the switch.

I am going to try this when I get home, should be fun.

BTW it is a 3 wire connector...

I am not sure why they did it that way, but I guess when you shut your truck off, the ecm kills the relay, but the pump still runs until the motor stops rotating and building oil pressure...

it does sound like you could pull this connection and jumper it to force the pump to run, but you could short it out at the relay as well.
you could also "

Terminal "G" on the aldl

When this terminal is present, it is possible to check for a non-operating fuel pump. By applying 12V to this terminal, you can check the fuel pump. If the pump runs, the non operating condition is upstream from it
"

I am thinking if you short it at the relay and the pump doesn't run, either the fuse link is burnt or bad ground.


Tom
98 Silverado k1500 4x4 350


Edited by 355Cheyenne on 11-09-09 02:05 PM. Reason for edit: No reason given.

 
someotherguy 
Moderator
Posts: 25879
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
11-09-09 02:06 PM - Post#1802444    
    In response to 355Cheyenne

On the '92 the oil pressure switch is combined with the gauge sending unit, it's at the top rear of the block behind the distributor. It's tough to get to and the double whammy is that it's screwed sideways into a brass 90 degree elbow; crank on it too hard and the elbow will happily snap off in the block.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-09-09 03:01 PM - Post#1802481    
    In response to someotherguy

whew, thanks for THAT info. That would really ice the cake about now, having to tap and remove a brass fitting from the rear of the engine that is already almost impossible to get to.

You may have earned yerself a beer!

Heres one for ALL of you, thx a million for the support and help so far!



 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-09-09 03:04 PM - Post#1802482    
    In response to Chevytech

Chevtech: question for you.

Can you elaborate on the red wire off the relay, I dont know what an ALDL is? Where should that wire be attached to? At this point it has a connector on it and is hanging loose.

 
355Cheyenne 
Senior Member
Posts: 3765
355Cheyenne
Loc: Northern MN
Reg: 10-27-04
11-09-09 05:18 PM - Post#1802573    
    In response to 81FLT

the aldl is the diagnostics port. located under the dash, driver side to the left. use a flashlight and you will see each pin has a letter.

Tom
98 Silverado k1500 4x4 350


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-09-09 05:36 PM - Post#1802594    
    In response to 355Cheyenne

So if its not connected to anything it wont affect it starting, is that correct? The red wire that comes off the fuel pump relay is not hooked to anything, just hangs there.

 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3071

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
11-09-09 06:19 PM - Post#1802647    
    In response to 81FLT

  • Quote:
Chevtech: question for you.

Can you elaborate on the red wire off the relay, I dont know what an ALDL is? Where should that wire be attached to? At this point it has a connector on it and is hanging loose.

355Cheyenne bet me to it. The ALDL is the connector under the dash for doing diagnostics, plugging in scan tools, reading codes from the ECM...

The red lead can be used to power the fuel pump. This will ONLY be connected to the fuel pump when the fuel pump relay is NOT applied. As soon as the relay is applied the fuel pump relay disconnects the red wire from the circuit.

  • Quote:
So if its not connected to anything it wont affect it starting, is that correct? The red wire that comes off the fuel pump relay is not hooked to anything, just hangs there.

This circuit in not used in normal operation of the vehicle. The lead useful for testing. I have often put a jumper from 12 volts to the red lead to use the fuel pump to empty a gas tanks that needed to be removed. I don’t expect you to understand that part of the circuit unless you looked at the schematic.

355Cheyenne comments stating that it should run with the oil sending unit unplugged are correct. If the fuel pump relay is working well the oil sending unit circuit is not needed to keep it running.

Here are some more comments on this:
When the engine has oil pressure a redundant circuit supplies power to the fuel pump. This circuit goes through an oil pressure sensor/sender. This circuit is independent of the fuel pump relay.

If you remove the fuel pump relay, the engine will have to crank until it gets oil pressure, and then the fuel pump will get power.

Once the engine has oil pressure the fuel pump should get power even if the relay has failed.


If you pull the fuel pump relay while the engine is running it should keep running. If it dies the oil sender or its wiring is bad or the engine lacks oil pressure.

If you unplug the oil sender while it is running it should keep running also. If it dies the fuel pump relay or it circuit is bad.

If the fuel pump relay is bad the computer should have stored a trouble code 54.

A code 54 happens when the computer does not see power on the circuit from the fuel relay to the fuel pump, when the computer is sending power to the relay to apply the relay.


For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3071

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
11-09-09 06:26 PM - Post#1802653    
    In response to 81FLT

You are getting no fuel to a disconnected fuel line correct?

Do you realize you can read ECM trouble codes without a scan tool on your 1992 vehicle?

Have you made sure the fuel filter is not plugged?
For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If the it has been altered from stock let us know about that too.


 
81FLT 
Forum Newbie
Posts: 23

Reg: 11-02-09
11-09-09 06:29 PM - Post#1802656    
    In response to Chevytech

I want you to know I appreciate the time you guys are taking to help me on this.

I replaced the fuel filter today with a new one. Still no fuel flowing after that.


Chev: I was NOT aware of that, no. Please enlighten me.


I will check out the oil pressure switch tomorrow and let you know what I find out.

Edited by 81FLT on 11-09-09 06:31 PM. Reason for edit: No reason given.

 
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