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Old 11-22-2009, 03:39 PM   #1
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Question Fuel Ballast Resistor

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
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Old 11-22-2009, 03:56 PM   #2
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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
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Old 11-22-2009, 03:57 PM   #3
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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
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Old 11-22-2009, 03:59 PM   #4
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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
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Old 11-22-2009, 04:00 PM   #5
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You will be fine, from what Ive heard the ballast resistor is just there to keep the fuel pump quiet...
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Old 12-23-2009, 08:36 PM   #6
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Default ballast resistor

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
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Old 12-24-2009, 06:44 PM   #7
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Default Fuel pump ballast resistor

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.
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Old 12-24-2009, 10:26 PM   #8
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Quote:
Originally Posted by XJ_SPORT View Post
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
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.
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