fuel pump wont work

[sandypants]

1989 k5 with tbi manual...

ok got a list of problems, im am on leave from Germany where im stationed so i will list the top two to get it started.

one.. old gas very old, so my injectors wont squirt... how do i take them apart and clean them up so i can get past that?


two.. my fuel pump isnt working, replaced fuel pump, computer, and chected relay on fire wall passanger side. checked both wires, the tan with white strip both are good from the computer, and the dark green one. if you pull the computer and looking at cabels closed to you... green on left is good the one on the right doesnt show a light, and if i turn the power on with my test bulb (wired to battery) my pump turns on, from the out side power.

so far the fues hasnt blown but normaly fues ECMB blows with no key in ignition or anything on jut pop. checked wires nothing... i only have two weeks please help... i hope i wrote enough details.. i love my k5 i just want ol girl back!!!!!!!

 

[shaun89]

i would try and follow the 12v wire to the pump. every 2ft or so,poke the wire and ground the meter and see if u have 12v still. keep going til u dont get 12v. it could just be a corroded wire. thats happen to me before with my rear tail light. it let enough through for it to ring out on a continuity test but wouldnt send enough voltage through to light it. after a couple hours i figured out part of the wire was green powder inside

 

[89GMCK5]

Sounds like you definitely have a short to ground there somewhere in that ECMB circuit, ie blown fuses. You will have to trace it out and find where your issue is. It's got to be pinched, insulation compromised, or other wise damaged to allow direct contact to ground.

Might be easier to run an external set of wires to the back, tank/fuel pump, just for trouble shooting purposes. That way you don't have to fight with everything under the truck and the old split loom falling apart in your hand. This way you will also know with confidence that you have good solid connections from point "a" to point "b" with a straight run.

 

[sandypants]

ok, well i will try to run a new wire, now should i still run it to the fuse box, just splice in before the computer, or just put a fues inline and run a seporate switch to it, im stationed in germany, once i get back i will just do an engine swap to a 6.0. so any ideas on the fuel problem?

one quick think to mention, after the computer we connected power and the pump turned on... even though the comp is new.. AHHHH I HATE WIRES

 

[89GMCK5]

It's hard for me to understand what you have going on with the computer, but I think you are saying that you introduced 12 vdc to the wire after the ECM and the pump cycled. How did you check the fuel pump relay?
If you run a second "trouble shooting" set of wires, yes make sure they are fused and try to mimic exactly what GM had stock, just not running through fire walls, under the floor, behind the dash, etc. so you can see it all. Try to keep and trouble shoot the components of that circuit one by one.
Are any of your other ignition hot (run) circuits getting hot with the key in the run position? May not be getting 12vdc to turn the pump on if the ign switch is bad. If there is a problem with the ign switch, it could explain your fuse issue with no key in the ignition. Something shorting to ground on the ign cold side. Maybe start with a verification of the ignition switch.
Sorry, just thinking out loud. Idea is to eliminate as may things as possible. You know if the pump gets 12vdc it runs. So we need to figure out why it is not getting 12vdc supply. It starts at the ign switch. Start there and move down the line to say the fuel pump relay, verify you are getting input to it as you should with the key switch from off to run. If that proves out, move along to check from the relay to the pump. You should be able to narrow your components or harness issues.

 

[sandypants]

You are exactly on point, i just might not be the best person to type it all out. yes if it gets power it runs... right now it is the ONLY thing that is being affected, so nothing else is hot. i checked the relay with my buddies truck, just swapped relays since its the same it at was just fine, also took it out of case and checked it for burns, dirt etc...

any ideas where i can get an easy to read or just any diagram on all this?

as for the other problems how the heck to i take apart the injectors clean them?

 

[miniwally]

It sounds like you are blowing a fuse to the computer so what ever is causing that is most likely your issue. BUT

I would try jump starting the vehicle, I can't remember exactly but I think the TBI wants to see near 12 volts at start up. If it doesn't see 12 volts it holds the fuel and only sparks? OR maybe the other way around. Any time I come across a TBI vehicle that won't start I always try jump starting it first, sometimes that is all it takes.

 

[sandypants]

ok well now my problem consists of injector trouble, i can get fuel if i add power through testing, so i know they have the ability to squirt and they squirt well, replaced computer, ignition module in distributer, and a relay checks out. but i have a ground problem. the injectors are not grounding properly so they don't work. everything checks out as mentioned above. problem is from computer to injectors...

i add power to the injectors they squirt... where do those wires ground to?

ugh... i hate all this i just wanna get past it all.

 

[miniwally]

ok well now my problem consists of injector trouble, i can get fuel if i add power through testing, so i know they have the ability to squirt and they squirt well, replaced computer, ignition module in distributer, and a relay checks out. but i have a ground problem. the injectors are not grounding properly so they don't work. everything checks out as mentioned above. problem is from computer to injectors...

i add power to the injectors they squirt... where do those wires ground to?

ugh... i hate all this i just wanna get past it all.

The computer controls the fuel, spark, when to squirt fuel, timing etc. So how do you know that the computer is telling the injectors to fire? That's my point.

Everything grounds through the fuel injection wiring and wiring harness. There isn't a "injector" ground wire going to a specific ground lug per say. It's just part of the wiring harness, the ground could go to the computer then ground or tie with other grounds then into one major ground.

Does the service engine soon light come on? I'll try to scan my howell TBI section on this and post it.

 

[miniwally]

This is for my howell stand alone harness system. They use all Gm connectors and components so it should be a good guide to trouble shooting.

 

[sandypants]

wow awesome diagrams! well tested everything on there pointed back to the computer... but after TWO BRAND NEW COMPUTERS THAT DIDN'T WORK FROM AUTOZONE, i finally got one from o'ryllies that did!!!! problem solved for now. thanx for yalls help!!!!!!!!!!!!!!!!!!!