HOrnbrod Posted January 2, 2013 Posted January 2, 2013 My engine has been cutting out randomly lately and I think I found the cause. The crappy spade connectors used on the fuel pump ballast resistor. These type of connectors suck for automotive or any other use that has inherent vibrations, as they tend to loosen up over time. Especially on circuits that can leave you dead in the water. I found an ignition ballast resistor with the same value as my old one (1.2 ohms) but it has the more secure ring connectors. I've been driving it for two weeks since I did this and it hasn't cut out yet. Just a tip for those who still have the ballast resistor in the pump circuit (as it should be). :yes:Standard Ignition Resistor RU29T
HOrnbrod Posted January 2, 2013 Author Posted January 2, 2013 Out of curiosity, why'd you relocate it? I used to have hydraulic struts on the hood (pre-cowl hood) and it was in the way of the strut bracket.
Keyav8r Posted January 2, 2013 Posted January 2, 2013 Where did you get it? NAPA? Might as well replace mine while I'm bolting almost everything else!
HOrnbrod Posted January 2, 2013 Author Posted January 2, 2013 Ebay. RockAuto has them among others too.
cruiser54 Posted January 3, 2013 Posted January 3, 2013 I had identical symptoms on my wife's XJ. I released the terminals from the plastic holders, cleaned and crimped them , and reinstalled. worked great. Yours seems like a more permanent solution.
jpdriver1 Posted January 3, 2013 Posted January 3, 2013 nice find -- good to know we can get replacements :banana:
ParadiseMJ Posted January 3, 2013 Posted January 3, 2013 I have an intake and a coolant bottle squeezing my resistor...I've relocated everything else...good call. Is there any dirt in Alabama?? If so, apparently none of it has made it to your engine bay. Squeaky!!
MJRemi Posted January 3, 2013 Posted January 3, 2013 The ballast resistor has been MIA on the 87 since I bought it and I haven't noticed any problems, but then again, I don't drive it very much. If I really need one, I will upgrade with Don's idea. Does anyone know what, exactly, the resistor function is and why my truck runs just fine without it?
Geonovast Posted January 3, 2013 Posted January 3, 2013 It's just to quiet the fuel pump a bit, and supposedly lengthens the life of the pump. The resistor was introduced during the 87 model year, it's quite possible your truck left the factory without one.
HOrnbrod Posted January 3, 2013 Author Posted January 3, 2013 Noise doesn't bother me, but I like anything that might lengthen the fuel pump lifespan by limiting the current through it and postponing that nasty job. I'd much rather replace the resistor than the fuel pump anyday. :thumbsup:
JeepcoMJ Posted January 3, 2013 Posted January 3, 2013 I can understand your point on that, Don. We still run a ballast resistor on my bro's '88....but keep a factory bypass jumper in the glovebox, because we trust the resistor about as far as we can throw it. What did they do to counteract the lack of balast resistor in late 91+?
Geonovast Posted January 3, 2013 Posted January 3, 2013 because we trust the resistor about as far as we can throw it. That's actually quite a bit of trust, I imagine you could chuck the thing pretty far.
JeepcoMJ Posted January 3, 2013 Posted January 3, 2013 I learned to throw when I was 23. I'm 25. My hand eye coordination is about that of a person plagued by parkinson's.
HOrnbrod Posted January 3, 2013 Author Posted January 3, 2013 I can understand your point on that, Don. We still run a ballast resistor on my bro's '88....but keep a factory bypass jumper in the glovebox, because we trust the resistor about as far as we can throw it. What did they do to counteract the lack of balast resistor in late 91+? The parts manual shows the ballast resistor was used through 1993. I think the XJ fuel pump changed in 1994 though and it didn't need current limiting. But not sure.......... And yes, I keep a jumper wire on board too.
NotMatt Posted January 3, 2013 Posted January 3, 2013 I always thought the ballast resistor was a Renix-only thing, but either way... I remove it when I see it... just a part waiting to fail and leave you stranded. I don't think there was ever any reason for it other than people complained about the fuel pump noise on the 87's so they band-aid'ed it on to quiet the pump down... In my opinion it doesn't have any effect on fuel pump life. :dunno:
HOrnbrod Posted January 3, 2013 Author Posted January 3, 2013 I always thought the ballast resistor was a Renix-only thing, but either way... I remove it when I see it... just a part waiting to fail and leave you stranded. I don't think there was ever any reason for it other than people complained about the fuel pump noise on the 87's so they band-aid'ed it on to quiet the pump down... In my opinion it doesn't have any effect on fuel pump life. :dunno: Yep, ballast resistors have no effect on electrical system loads. That's why automotive manufacturers hang ballast resistors in series with ignition coils, blower/fan motors, LEDs, CDI systems, and other applications. Ever hear of heat dissipation?
NotMatt Posted January 3, 2013 Posted January 3, 2013 I understand what the function of a resistor is. In this case, it lowers the voltage to the pump to reduce noise at idle and part throttle, not significantly lengthen the life of the pump, IMO. The load on the pump is not a factor, since the fuel pressure regulator will bypass any excess pressure above the preset and not allow the pump to struggle. It only SOUNDS like it's struggling because it's spinning faster and making more noise. Does it NEED to when the rig is just idling or at part throttle? No, but it's not hurting it... as long as the fuel pressure regulator is successfully doing it's job and bypassing excess pressure created by the fuel pump back to the tank. Without the resistor, it simply has to bypass a bit more pressure. The ballast resistor is not a necessary part of the fuel pump electrical circuit, unless you are annoyed by the extra noise the pump makes without it. You can take it out like I do to avoid potential issues with the ceramic cracking and breaking or connectors becoming loose or corroded, you can leave it in and carry a spare jumper wire for when it fails, OR you can do what hornbrod did and replace it with one that's less prone to failure. It's up to you. You should hear the externally mounted Airtex pump running at full 14.1 volts pulling from the fuel cell on my YJ if you wanna talk about loud. :D
abeb123 Posted July 23, 2025 Posted July 23, 2025 Hi i know this is an old thread but does anyone have an updated part number? Standard Ignition Resistor RU29T Seems to be discontinued
89 MJ Posted July 24, 2025 Posted July 24, 2025 On 7/22/2025 at 8:38 PM, abeb123 said: Hi i know this is an old thread but does anyone have an updated part number? Standard Ignition Resistor RU29T Seems to be discontinued You can also bypass the ballast resistor with no negative effects. Just hook the two wires attached to the ballast resistor together.
abeb123 Posted July 24, 2025 Posted July 24, 2025 2 minutes ago, 89 MJ said: You can also bypass the ballast resistor with no negative effects. Just hook the two wires attached to the ballast resistor together. I totally understand that i can. I want to have one for noise reasons
ghetdjc320 Posted July 24, 2025 Posted July 24, 2025 You can still get a stock style replacement https://www.summitracing.com/parts/cwa-33000682 It doesn’t have the ring terminals as the one posted here but will function the same
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