OK Team,

I have read alot of posts on this topic, but none that copy my condition. The truck was stalling anytime it felt like it. Everyone told me it was the ignition mod, so I spent the $15 and replaced it. Same problem. I then began looking at the fuel pump (hp, located in the frame rail). I found the connections sloppy and actually broke off one of them accidentally. I put a meter on the leads and had 12volts. I plugged the good one on and touched the wire to the other terminal and we had fuel delivery. So, I replaced the connection and re-installed the pump. Truck fired up and ran about 3-4 minutes and stalled. I checked the power at the pump again and I have no power at the pump. I removed the fuse and it was good. I checked the inertia switch and it was not tripped. I unplugged the wires and I have no power at the wires that go to the inertia switch. Where do I go from here??? Fuel regulator?? Where is it located and how do I check it???

Thanks for your help,

John

 

The power to the inertia switch comes from the fuel pump relay, it's located under the hood, passengers side.

 

OK,

I have located and replaced the pump relay and still no power to the inertia switch. Getting frustrated now......

TK

 

I know it's tedious, but have you picked up a wiring diagram and traced the circuit? It's not a difficult circuit. You say you don't have power at the inertia switch. Do you have power at the fuel pump relay? Do you have power at the EEC relay? Do you have power to the fuse/fusible link? It should be as simple and tedious as tracing the circuit and figuring out where you have power and where you don't have power. And, remember that circuits have to be complete -- don't neglect the ground side.

 

Like mrshorty sez, if you dont have a wiring diagram & VOM you're just wasting your time trying to fix this.

You should be able to find an online wiring diagram at Autozone.com

 

I can email you a wiring diagram if you need one, just drop me an email, remind me about your truck, problem and needs.

 

Thanks for your help so far team,

Here is where I am now. I got the wiring diagram and started tracing power. At the pump relay harness, I have 12 v coming in (yellow) all the time. I have 12 v coming in (red) with the key turned on. Also, with the key on, I have 12 v going out (tan/lt green). The problem is I only have .1 v going out (org/lt blu) to the inertia switch. I get the same reading coming into the inertia switch.

Anymore ideas????

TK

 

Your new relay might be bad. If the EEC & pump relays are interchangebale try swapping them & see if you still have voltage coming in on the red at the pump relay.

If you do it sounds like org/ltblu is open at the relay

 

Got to think this through carefully. Assuming all voltage measurements were referenced to the same point (preferably negative battery post or other good ground spot), then those would be normal readings KOEO. For the first few seconds after turning the key on, the compuer commands the fuel pump to run (via the tan/ltgrn wire), then turns the pump off until you start the engine. In this state (KOEO waiting for engine to start) what you describe is what I would expect to see. You have 12V to the red wire and tan/ltgrn, but there is no current flow as the circuit is "open" at the switch inside the computer.

As a help, they put a fuel pump test lead in the self-test connector (same tan/ltgrn wire I believe) in the short end of the connector. Ground this wire to test the circuit in it's "pump on" state.

If your voltage measurements were made in a known "pump on" state, then they do look like the relay is not closing.

 

Hers a slick trick for keeping the relay energized while testing voltage. www.superhighoutput.com/tech_view.php?id=5

 

I would suggest jumpering across the fuel pump relay (yellow to org) and see what you have at the inertia switch. I would also suggest jumpering across the inertia switch wires to see if the pump runs then. Often times the lead at the inertia switch is bad as the switch heats up because of poor contact internally and that messes up the connector as well. Don't operate the vehicle on the road with the inertia switch disabled. I got an inertia switch for my 87 from the dealer a couple of years ago but I know they are getting hard to get. If you get an inertia switch you will likely need to replace the connector as well. My bet is the inertia switch and connector are bad.

 

OK,

So before I throw the towel in, I am going towards the inertia switch. Can I cut the connecter off and connect the wires to bypass the switch? If this is ok to do and it works, I can purchase a new switch and connecter.

John

 

You could cut the connector off and wire it together. Personally, I would rather disconnect the connector and jumper the wires, but to each his own.

Based on the voltage measurements described above, there isn't any power getting to the inertia switch, so the break in the circuit is upstream of the inertia switch. I would be surprised if bypassing the inertia switch fixes the problem.

 

Thanks for your patience team. I can perform alot of mechanical stuff, but I am weak in auto-electric. But, learning all the time.

Ok Shorty, when you say to jumper the wires, do you mean at the inertia switch harness? Or, up at the pump relay where I have no power coming out? Can I jumper the yellow wire to the org/blu going to the inertia switch? I want to make sure, I don't need to cause "other" problems.

Thanks again,

 

If you jump yellow to orange/light blue the pump should turn on with ignition on or off

If the pump does run the O/lb is apparently open where it connects to the relay mount.