Brake lights robs power from fuel pump

[Lasive]

I’ve had issues in the last year where my 2011 ford ranger 2.3l 2 wheel driver xl model has randomly stalled while coming to a stop. I troubleshooted and found out it was related to pushing the brakes or turning on the running lights. The rpms would drop and the truck would shudder and stop. I got a mechanic to look at it and they found out it had too much dielectric grease in the wiring connection under the truck under the driver seat area. The truck seemed to be fixed but the same issue happened 5 months later. Again, I got a mechanic to look at it and we found a bad ground coming out of the wires that go down from the cab and underneath the truck. It’s right next to the fuel filter on the left side. We found out it caused a voltage drop for the fuel pump causing low fuel pressure. We fixed it and by cutting the bad ground and splicing in a new wire and it ran for another month or two until it happened again. This time some dielectric grease in the connector fixed the issue and it ran good for another 2 months until today. I was able to drive it home as long as the ac fan stays on 2, but it does not blow anywhere close to what it should. Activating the hazards gives it power enough to run the fuel pump, but at a slight drop in power. The rear brake lights are dim and the 3rd brake light is normal. When the flashers are on, the license plate lights flash dimly along with them. Headlights are fine. Fuses are fine. Battery shows 12.3 volts and boost to 14.6-14.7 when running. I think there is corrosion somewhere in the wires leading back to the taillights.

 

[sgtsandman]

Ar 12.3 volts, it's tume to be thinking about a new battery but that is an aside.

I agree on your assessment that there is an issue with the wiring harness. If you can get your hands on an electrical schematic and you have a multimeter, you can start narrowing down where the problem is by checking continuity, power, and ground at the connectors. That will eliminate what sections of the wiring harness that doesn't need looked at.

Chances are it chaffed through the protective tape and loom somewhere and you'll just have to find it. Wiring issues are a PITA to troubleshoot and you may need to pull the bed to check the wiring to the fuel pump since it all sits on top of the fuel tank.

 

[SenorNoob]

Sounds like you have more than one bad ground...

If it were in the incoming power it'd only affect a circuit (or two). The power for the fuel pump going up when other circuits are activated makes me think that it is grounding through them instead of where it should be. That's be my 1st check. Fuel pump ground. Does your gauge work? Does it change when the pump acts up?

 

[19Walt93]

Before you spend a bunch of time and money chasing the problem, try cleaning the IAC and throttle body. It may be just a low base idle or sticking IAC and not low fuel pump voltage.

 

[Lasive]

Ar 12.3 volts, it's tume to be thinking about a new battery but that is an aside.

I agree on your assessment that there is an issue with the wiring harness. If you can get your hands on an electrical schematic and you have a multimeter, you can start narrowing down where the problem is by checking continuity, power, and ground at the connectors. That will eliminate what sections of the wiring harness that doesn't need looked at.

Chances are it chaffed through the protective tape and loom somewhere and you'll just have to find it. Wiring issues are a PITA to troubleshoot and you may need to pull the bed to check the wiring to the fuel pump since it all sits on top of the fuel tank.

I went ahead and cleaned the connector with electrical contact cleaner and left the battery unhooked for a while to make sure it was completely dry. This got rid of the dielectric grease that I had put on, finding out after a few searches that I put too much on, and on the pins themselves. Dumb move. After reconnecting, it had a bit of a rough idle for a moment but returned to normal. The connector has a broken clip so I added a zip tie for the old zip tie trick.

I checked the battery after being disconnected for a few hours and it’s reading 12.43 volts which makes it somewhere between 25-50% of life left.

 

[lil_Blue_Ford]

I’d probably go ahead and replace the main body and frame grounds… if you already found smaller bad grounds, there’s a good chance these are less than great

 

[Lasive]

I’d probably go ahead and replace the main body and frame grounds… if you already found smaller bad grounds, there’s a good chance these are less than great

The picture shows where we replaced the ground wire. It’s black due to the heat shrink. Do you think it still could be a bad body or frame ground?

 

[lil_Blue_Ford]

The picture shows where we replaced the ground wire. It’s black due to the heat shrink. Do you think it still could be a bad body or frame ground?

That... is not what I'm talking about. Other than the fact that if that ground was bad, the main grounds are probably bad.

The main grounds come off the negative battery post. There should be two or three. A big one (4 gauge) to the frame and to the block/starter plus a smaller one (usually about 10 gauge) to the body (usually the the core support right by the battery). Personally I use 4 gauge welding cable and make my own cables plus upgrade that smaller ground to 4 gauge welding cable. I make sure to clean where they attach well and use No-Alox (find it in the electrical section of a decent home improvement store) on the connections. No-Alox is electrically conductive and is used primarily to prevent corrosion where aluminum wires are terminated in electrical panels and outlets. Dielectric grease is not electrically conductive, but is good for insulating, preventing water intrusion and preventing corrosion.

Those main grounds are where all of the electric in the vehicle is returned to the battery, so they are very important and can cause all sorts of headaches when they're faulty. I've seen them corrode to junk inside the insulation to the point where outwardly the wire looks fine but it's really not passing much juice along.

 

[Lasive]

Another possible clue here: I had the issue one day taking a long right turn on an onramp, and it took me a minute to get the truck back to be able to drive. There’s moisture in the left tail light harness and when the issue has happened last week, the left blinker would go fast, more often than the right side.

Does this bulb socket look old and used or close to burning out?

I bought a new socket in my first “throw parts at it and hope”. The wires go to the rear lights and license plate light connector that’s at the back of the bed. I’ll run a resistance these from the connector under the driver seat (shown before) and check those wires.

 

[Uncle Gump]

Those bulbs produce heat. Some discoloration in the sockets is normal.

 

[pjtoledo]

check ground G103 near the front of the underhood fuse/relay box.
half of the stuff you mentioned grounds there.
there is also a G102 in the same location.

relays for engine cooling fan, A/C clutch, fuel pump are on the battery junction box.
all use G103

 

[Lasive]

Fixed (most probably)!

I got a new battery because the guys at NAPA were having a sale and they were surprised that my 7 year old battery was still working.
Today I was just checking the grounds to see if they were tight, and I had the issue reoccur! I went ahead and cleaned off the ground point in front of the battery at the front of the vehicle and it seems to have fixed the issue! Since it was such a difference after 1 ground point, I stopped there.

 

[sgtsandman]

7 years out of a battery is indeed a very rare thing anymore. I've only experienced that once. It was a Panasonic battery of all things too.