i think the ballast resistor(ceramic thing on driver side with two wires on it) is bad in my jeep, can i connect the two wires directly together and eliminate it from the system with out messing up anything

 

never heard of that, but it may mess with the fuel system because im pretty sure that controls the fuel pump. just replace it its only like ten bucks

 

if its bad or disconnected the engine wont run, it will run for few seconds then cut off, the idea for the resistor is to give the motor maximum volts when starting, once the motor starts it lowers the volts back down to 5v, you can jumper the wires together while they are still hooked up to the resistor, this was an easy fix to a lot of common problems on the renix system

 

With electrical in general here, if you have a ballast, resistor, fuse, relay, fusible link, ect... basically anything in an electrical circuit, its there for a reason, if its bad, replace it.

Bypassing such things can ruin other components, and/or be a fire hazard....if its bad just find a replacement, dont bypass

 

You will be fine, from what Ive heard the ballast resistor is just there to keep the fuel pump quiet...

 

My Cherokee occasionally spits and misses like a low fuel pressure problem. I have changed about everything I can afford to change and it still does it.

One leg of the fuel pressure ballast resistor is somewhat loose on the resistor itself. However, it runs with it in the circuit and will die shortly after pulling it out of the circuit. I bought a new one today an RU17 part at the auto parts store. The engine runs worse with the new ballast resistor in it.

Here the voltage measurements....the old resistor has 13.8 volts into it and 9.5 volts out. The new one has 13.8 volts into and about 5.5 volts out. The fuel pump doesnt' apparently produce enough pressure running at a lower speed on 5.5 volts.

I'm going to the local Jeep graveyard tomorrow ( lucky to have one nearby) and get a replacement that doesnt' have a broken lead.

Anyone agree with my guessing? If I still have the intermitting missing and stalling, the fuel pump is coming out next.
Dave

 

I went to the local jeep cemetery today and got a fuel pump ballast resistor. Brought it home and ohmed it out at 1.3 ohms. I put it in tonight and measured the voltages. It was 11.5 volts output to the fuel pump side with 14.3 volts into it.

The Jeep ran smooth as silk with the new resistor inline. The old one has 9.5 volts output, and the new one I bought from Oreilly autoparts had 5.5 volts. The engine would not run with the 5.5 volts output, and didn't run well with the 9.5 volts output.

So thats where the story ends for now. One good thing, its sure easy to change vs changing the crank position sensor on the back of the engine.

Dave....hope everyone has a Very Merry Christmas, and a good 2010.

 

Yes. My 1987 didn't have it, my 1988 has the "recall performed" tag noting it was added.

The ballast was added mid-1988 to handle NVH (Noise, Vibration, Harshness) issues - primarily to quiet down the pump some. It's a current-limiting device, by slowing the fuel pump motor down, you reduce the "rumble/howl" noise of the pump.

My 88 had it added as a recall, it went bad, I removed it and connected the two wires together. That was six years ago.

 

OK where can I get one of this fuel ballast resistor from an auto parts store?? (Graveyards run low on jeep in my area and if they do they have grand cherokees not cherokees) Because I'm having lots of problems stay running or not wanting to start so far rebuilt steering column changed fuel pump relay jeep ran for a bit changed that silver box next to the batter attached to the relay fuse box thing on my 88 on the passenger side wheel wall changed positive lead wire to starter, changed starter, fuel pump, that black box under the steering column that attaches to all the wires opened PCM looked for burn marks on the motherboard. bought CPS (crank position sensor) waiting to install tomorrow. changed fuel filter twice! getting fuel to fuel rail when running. HELLLLPPPPP!!!!

 

If you can't find one. You can eliminate it all together. The only thing that you may notice will be the pump will be a bit loader. It won't cause any problems running it with out one. I had a few older Chrysler in my day and removed them and never had a problem. All they do is lower the voltage to the pump and make them run a bit quieter.

 

BWD RU12 will make your jeep run. The ballast resistor life is greatly reduced as it is not the correct ohms.(approximately 3-6months) Best used as a spare and replace with OEM part from dealer.

 

that's why they installed it but fuel pump shuts down without it.

 

Fuel pump does not shut down without the resistor provided that the resistor is bypassed; that is, provided the two wire ends leading to the resister are hooked together.

 

X2, Bypass it. Then when you see that's not the issue, check that CPS!