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banjoman09

Well-known Member
I posted a few days ago about fuel pump issues on my Chevy 2000 truck; any chevy technitions here? Not me! If so please email me to help me figure out mu problem- I dont want to post here again. Thanks!
 
It would probably help if you would get more involved. I found the post 4 pages back and Hobo NC posted a schematic of the wiring. Have you done any testing to see if you are getting power to the relay and to the pump? You know today it's not uncommon to purchase new parts that are junk. The new relay may have gone out. Myself I've started buying only AC Delco parts for electrical components in my GM vehicles.
 
More involved? Really? Did you go back and read that post? It might help! I did reply to HOBO two days ago so Im reaching out again because I need to get this fixed. No one answered my last post.
 
There are other forums for chevy trucks. They are the ones to go to for advise.
 
Are you checking for power at the pump by going across the power and ground terminals with a light? I've seen open ground issues where the ground wire mounts to the frame near the filler hose (assuming this is the old body style). If I remember correctly from your other post you did have power coming out of the pump relay. If so it's pretty straightforward from there to the pump. Again, if my memory is correct, grey wire at pump is + and the large gauge black wire is ground. Make sure its actually the power side you're chasing. If its 4x4 I've seen the wiring harness under the cab come loose and rub on the front driveshaft. Hope this helps
 
Thank you :) Ok Ill try to start from the beginning; Our 2000 3500 Chevy Pickup just died this summer in the field. So- Fuel pump
does not run- so I replaced the Relay- nothing still. I pulled the relay out and checking the 5 relay pins in the box; pin 86 is
ground and I checked it -it is good. Pin 87 is HOT all time and it is hot. Pin 85 comes on for 2 seconds with the key...and it
does! So I put relay back in and nothing...pump not running. So I took a paper clip and jumped pin 87 to pin 30(the fuel pump
wire) and walla! Tha pump is running! BUT, when I put new relay back in the fuse box- pump does not run? SO now what do I do?
Thanks again.
 
(quoted from post at 09:18:00 11/09/20) Thank you :) Ok Ill try to start from the beginning; Our 2000 3500 Chevy Pickup just died this summer in the field. So- Fuel pump
does not run- so I replaced the Relay- nothing still. I pulled the relay out and checking the 5 relay pins in the box; pin 86 is
ground and I checked it -it is good. Pin 87 is HOT all time and it is hot. Pin 85 comes on for 2 seconds with the key...and it
does! So I put relay back in and nothing...pump not running. So I took a paper clip and jumped pin 87 to pin 30(the fuel pump
wire) and walla! Tha pump is running! BUT, when I put new relay back in the fuse box- pump does not run? SO now what do I do?
Thanks again.
Click to expand...

1. Will the truck start and run with your paper clip "jumper" in place and the fuel pump running?

2. With the relay back in place, have a helper cycle the ignition switch, can you hear and/or feel the fuel pump relay click closed, then open after a couple of seconds?
 
I will check after lunch- thanks. Im guessing "no" the the "relay clicking" because with the key on I can plug the relay in the
box and feel or hear nothing. Somehow its not getting excited.?
 
Using a pin jumper the pump runs, but what pressure does it develop ?
There are multiple body grounds that can fail and give your problem. BTDT.
You say pump doesn't run with relay but it could be making insufficient
pressure.I wore out my patience and the brain trust of two mechanics with
decades of GM experience. Verify fuel pressure and ground connections.
 
I have gotten many brand new parts that were bad out of the box. I also bought a brand new Delco Remy starter that had a "Made in China" sticker on it. You just never know what is made where anymore.
 
I hardly ever get bad parts! But I know it can happen; I jumped pin 87 to 30 and truck starts and runs.... I put Relay back in and
starts and runs...so now Im really confused.
 
I spoke too soon- truck does run when I jump pin 87 to 30; when I put relay back in it will not run- Relay is new...something
must not be activating the relay to connect 87 and 30 . Thanks
 
(quoted from post at 09:18:00 11/09/20) Thank you :) Ok Ill try to start from the beginning; Our 2000 3500 Chevy Pickup just died this summer in the field. So- Fuel pump
does not run- so I replaced the Relay- nothing still. I pulled the relay out and checking the 5 relay pins in the box; pin 86 is
ground and I checked it -it is good. Pin 87 is HOT all time and it is hot. Pin 85 comes on for 2 seconds with the key...and it
does! So I put relay back in and nothing...pump not running. So I took a paper clip and jumped pin 87 to pin 30(the fuel pump
wire) and walla! Tha pump is running! BUT, when I put new relay back in the fuse box- pump does not run? SO now what do I do?
Thanks again.
Click to expand...
So if 86 is grounded and 8t is hot with key on and cranking and it runs with a paper clip between 87 and 30 a failed relay is the only possible problem. Double check to make sure all of your inputs are correct. If they are see if you can get an OE number off your original relay and have your parts supplier cross it, as not all relays that look the same are the same. Let us know when you solve it or if you need more help
 

Try loading circuit 85/86 use a parking lamp bulb a 1156/1157 will do, wire the bulb up jump pin 85 to 86.

Jump pin 87 to 30 with your pin start the engine does the bulb burn bright...

There are several replays in the junction box that are the same swap one to the fuel pump...

(30) A/C relay
(33) Brake lamp relay

Your box ?
(29) Fuel pump relay


mvphoto64665.png
 
yes- my box....I think the SHO62G is the right relay as this is what we have been using. Thanks I will check in morning.
 
Well its fixed- I think- but yes your right; I tried one of the other relays in the box and it started up and runs; put the new
relay back in and it did nothing; so my new relay from O'reilys is no good! I hope they take it back! This is hard to
believe...and thanks a bunch too all of you who helped me on this project! Sometimes I get lost in the trees. Thanks!
 
We have had alot of relay issues with this truck...any ideas? How can I check amperage draw on this pump? Can I do this through
relay box with truck not running? Thanks
 

3 ways use a jumper across the fuse and a amp clamp are the amp function on a good voltmeter. The same across pin 30 and 87 with the relay removed are a low amp probe and DSO...

The other, does the relay feel hot if so its pulling to many amps are the connections are bad where the relay plugs in...

With a DSO and amp probe That I doubt you have you can check the fuel pump amps, RPM, and the commentator bars on the armature in the pump.

If it has 100K are more on it a pump is in your future... : (

Google, Fuel Pump Current Ramp Test- Diagnostic Quick Tips | Snap ...
 
(quoted from post at 11:55:11 11/10/20) We have had alot of relay issues with this truck...any ideas? How can I check amperage draw on this pump? Can I do this through
relay box with truck not running? Thanks
Click to expand...

Good to hear you have it running, for now at lest.

I have seen these trucks in the past where as the pump starts to fail it will draw high amperage leading to melted connectors and relays on up to blowing the fuse that supplies terminal 87.

As far as checking amp draw one could use a clamp on DC amp meter on the power supply line to the pump to see what the draw is, problem with that is when the pumps start to go they do 1 of 2 things.

1-They die and stay dead.

Or

2-They work intermittently;
- cycle key 5 times and on the 5th try sometimes it goes.
-cool off overnight sometimes it goes.
-full tank vs 1/8 tank sometimes it goes.
-beat on tank with rubber hammer or boot and sometimes it goes.

In most all of the #2 reasons they will tend to momentarily draw high amps which can be hard to detect with a meter.

Water/ice can cause high amp draw as can a badly plugged filter or other fuel flow restriction.

ECMB should take a 20 amp fuse, a good fuel pump typically will draw less than 10 amp.

If you were to for test purposes install a 15 amp then a 10 amp fuse and test drive the truck to see if the fuse blows it will give you a reasonable idea the pump is pulling more than it should.

Last thought if you are having numerous intermittent issues I have had to lift a few of those fuse boxes after mice decided to have a feast on the wire insulation, purple seems to be their favorite flavor.
Lift off the box and find a half a dozen wires bare for a couple of inches, does real neat things when you go over a bump.
 

a good fuel pump typically will draw less than 10 amp.

7/8 is the norm with 8 on the high side, I have seen quite a few new pumps draw 8 amps...
 
Good afternoon, Banjoman09: Just some sympathy here, I have a 2005 Silverado that I drove to gas station a mile from home, filled up, then it would not start, i.e. NO START, NO CRANK. It was diagnosed as most likely battery, installed new, same symptom. Then diagnosed as starter, installed new, same symptom. A shop found and replaced a bad fuse, truck started ok. I asked why fuse blew, they said they could not find the reason. Truck is still starting and running when I need it after six months, but I am glad it is not the only vehicle in family. These things will make you crazy!! Good luck with yours.

Dennis M. in W. Tenn.
 
ok...right or wrong i pulled the relay, checked pin 87 to 30...with Amp meter and reads 1.9 amps.... is this ok way to do this ?
Thanks
 
(quoted from post at 09:55:11 11/10/20) We have had alot of relay issues with this truck...any ideas? How can I check amperage draw on this pump? Can I do this through
relay box with truck not running? Thanks
Click to expand...
Are you talking about the fuel pump repeatedly failing? Theres no way a failing pump would draw too much too burn up a relay. It will blow the fuse first
 
I believe the pump has been changed one time(my cousins farm truck) but there are 6 Relays laying on his dash from a period of 2
or 3 years that have gone bad- he claims that when the truck dies that the Relay gets hot and quits working. So ???
 
(quoted from post at 20:25:41 11/10/20)
(quoted from post at 09:55:11 11/10/20) We have had alot of relay issues with this truck...any ideas? How can I check amperage draw on this pump? Can I do this through
relay box with truck not running? Thanks
Click to expand...
Are you talking about the fuel pump repeatedly failing? Theres no way a failing pump would draw too much too burn up a relay. It will blow the fuse first
Click to expand...

In a perfect world your statement could be correct.

Proper or not one of the first things that happen when the 20 amp fuse for the circuit blows is someone replaces it with the handy 30 amp spare fuse GM includes in the box and for a while they think their problem is solved.

But now the fuse is no longer the weak link.

Question for Banjoman - In the under hood fuse box in the ECMB fuse location does it have a green one installed.
 

I don't believe that reading not at all..

You need to cut the pins out of one of those relays and check pin fit in the relay sockets... I am betting one are more are spread open it will have less retention when you do a slid test...

I have ran into this and had to install new (used out of another relay center) connectors in the relay center. Someone mention the replay pins will will look black that's your sign.. This issue was self inflected by ME that's why I cut the pins out of a old relay for my test now...
 
I did a "slip test" on the plug in the box with a spade from another relay- pin 85 and 86 have no resistance...the others have
some; can I reach in there and tighten those two up somehow? Thanks
 
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