Friday I went for a test ride in my RCSB to get some 50% throttle data for tuning. As soon as I began to lay into it the engine completely died and I almost pooped my pants. Tried to start again and I noticed right away the fuel pump wasn't priming but the engine turned over and seems healthy. Called my neighborhood golf cart brigade and got a tow home. Checked all fuses and connections and everything is fine I even put power directly to the pump and it pumps good as new.

Basically what I'm down to is Relay 5* (aka IGN 1) is only getting 1.5v to terminal 30 which is battery (+) and should have 12v. In turn this is causing the relay to constantly try to latch and fail making it click wildly and not tell the fuel pump to kick on.

I have checked every single fuse by removing it and OHM testing it with a certified Fluke multimeter.
I have tested every relay by swapping them to other positions and verifying that circuit works as it should.

I'm pretty lost Google hasn't been much of a help and I don't know what specific wire should supply IGN 1 with battery positive.

Anyone have a good wire diagram of this specific circuit?
Maybe one of the GM master techs on here has seen this before?

 

Power destined for that relay coil goes from the ign sw to the interior fusebox at the left side of the dash first; a pink wire to terminal A of the fusebox. One thing that runs off of that is the turn signals. If those are working right, then you have juice getting that far at least.

Next a pink wire goes from pin A2 of that fusebox, to the one under the hood, pin A9 of its C1. (probably real obvious; like a 5mm pink wire) If there's a bad connection leading to that point, some other things powered from it won't work right. Among those, rear defogger and backup lights are easy to check on.

The contact (pin 30) of the relay gets its power from battery; a metal strip that runs around under the terminals of the underhood fuesbox for relays & fuses to all get their power from. Not likely there's anything wrong with that. It feeds headlights, door locks, radio, etc. Can't imagine how you could only have 1.5V there. If those things work there's battery where and how it's supposed to be.

Regardless, nothing about the voltage there, can make the relay buzz. It's the batt feed to the contact, not the ign feed to the coil. If the relay is buzzing, that's more likely to be something wrong in the coil circuit.

The IGN1 relay doesn't power the fuel pump, at least not directly. It supplies the fuel composition sensor if you have Flex Fuel, the PCM, TAC module, coils, and injectors.

Might want to try making a jumper wire (12 gauge) with male slide terminals on it, and plug it in where terminals 30 & 87 of the relay plug in; and see if that makes it work. Probably won't be able to turn the motor off with the key with it like that though, but it should start up and run normally.

 

RB04v thank you for the great insight!

I'll go step by step of what you've said to check.

Turn signals work

The pink wire appears to be perfectly intact but I lose it in the dash so I skipped ahead. Also I don't have tail lights hooked up since the bed is off and across my yard and don't have rear defoggers either.

Contact 30 is getting 3v ground with ignition off and 8v ground with ignition on. The 2 posts on the side and right corner of the fuse box directly connected to the metal strip you referred to are getting the full 12v from the battery.

I did not know IGN1 didn't control the fuel pump. When I jumped from 30 to 87 on the Fuel Pump relay the pump engages like normal but then won't shut off. Which led me to believe it wasn't getting the signal from the ignition somehow.

Give me a minute and I'll post pictures.

 

Alright you might think I'm crazy but just walked outside checked 30 with the ignition off and saw 0v so I switched the other lead to a positive source and saw 12v meaning 30 has a good ground suddenly. Clicked key to run and with the positive lead on a power source and the ground lead on 30 it jumped to showing 8v then 3v then 8v and repetes the cycle.

 

Removing the bed did you happen to remove the screw that grounds the braided ground wire coming from the filler neck? That screw is necessary to ground the fuel pump.

 

It is still connected on both ends and I actually don't remember ever removing it when I've pulled the bed. Maybe I rerouted it the first time years ago.

I do have a racetronix hotwire kit but its been installed for years with no issues.

 

You don't appear to be using your DMM correctly. The black lead should be on ground. You should be probing things with the red lead, looking for 12(ish)V.

Terminals 30 & 87 shouldn't ever get ground, except to the extent that when the relay is Off (or unplugged), one of the 2 should have 12V on it at all times and the other should appear to be at ground because it's grounded by all those loads that it powers.

A relay is nothing but an electrically operated switch. It's as simple as a ball of mud. It has a coil that is energized by some small amount of power, which magnetizes it; there's a piece of iron somewhere nearby; when the coil magnetizes, it attracts the iron, which moves; there are one or more contacts attached to the iron that change state from open to closed (i.e. not touching to touching), or vice-versa; this allows a very small amount of power to control power to a MUCH larger load.

The way the specific circuit in question works is, the ign sw only has to carry enough current to operate the relay coil, therefore the ign sw and wires don't have to be so big and otherwise suffer the problems caused by high current, like burning up. Then the relay sends power to that list of things I posted.

Note that the ECM is in that list; therefore, it not receiving good constant power from the relay may be what's causing the fuel pump (driven by the ECM) to appear to fail. However, the Problem is neither the ECM not the pump; the Symptom just appears there. In this case, Symptom != Problem. You can't fix the Problem by dinking with the Symptom.

Keep in mind that if the relay is "buzzing", there will only be a contact made for some fraction of the time, and the meter may read any random weird thing between 0 and 12V. For example if during the "buzz" it spends exactly half the time with the contact made and the other half with the contacts broken, the meter will read somewhere close to half of the batt voltage. Pay less attention to the exact values of weird numbers, and more to the yes/no function of the relay. What you need to be working on is the buzzing, not whatever is going on at terminals 30 & 87. Fix the buzzing, the other will clear up.

Note also that the relay is a single-pole, form A (normally open) contact. Pins 30 & 87 are the 2 sides of the contact. Either one might be "power" and the other "load". The FSM doesn't show which number pin is which, it just shows the contact. You may well find that pin 87 has nice hard battery like it's supposed to, but pin 30 has some weird low intermediate voltage while it's "buzzing", because the relay is sending it power only part of the time. Or vice-versa. I can't tell you which is which.

A "buzzing" relay is a problem in the coil circuit, not the contact circuit. Probe the coil terminals with your meter while the ign is turned on. One should be ground at all times, the other should get solid 12V when the key is On. If the 12V one is getting some oddball lower voltage, then the Problem is in that part of the circuit (pins 85 & 86). In any case, the Problem is not the batt part (pins 30 & 87).

 

I do realize that I had the leads reversed on the DMM I did that so I could read in positive voltages not negative since the contact was reading at ground not positive current. (I hope that makes sense)

Ok focusing on 85 and 86. With the key to run (IGN on) both terminals 85 and 86 are reading 12v+. If you are saying that one should be 12v and the other should be grounded at all times then whichever one is supposed to be grounded is obviously wrong.

 

When IGN is off only terminal 86 is reading 12v, 85 is reading grounded.

 

According to the FSM, one of those coil terminals is supposed to be grounded at all times (no matter whether key On or Off). The other gets switched 12V from the ign sw.

Looks like you're getting close to The Problem. Find the one of those 2 pins that gets the switched power, then track down why the other one isn't staying grounded. Should resolve it.