Ωhm Posted March 3, 2018 Share Posted March 3, 2018 I need a project so I'm looking for some information. I'm interested to see if I (we) can determine fuel pump health by using the fuel pump ballast resistor. What I need is two (2) voltage measurements, one (1) resistance measurement and type of fuel pump, if known. Requirements: Any 4.0L and those still using the fuel pump ballast resistor. Conditions: Engine running @ idle. Measurements taken: 1. Battery voltage. 2. Voltage across the ballast. (polarity doesn't matter). 3. Ballast resistance measured in ohms. Also include type of fuel pump. IDK is good for 'I Don't Know'. Example: 1. 12.70 vdc 2. 3.00 vdc 3. 1.1 ohms 4. Type of fuel pump if known, otherwise use IDK. 5. Vehicle: MJ88, XJ89, TJ90, MJ89-RED, MJ89-YELLOW (examples) I'm not sure where this will lead or what results I can conclude, but I think its worth a shot. I'll post results later if enough data is supplied. Thanks, in advance to any and all that participate. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 3, 2018 Share Posted March 3, 2018 Why are you excluding the HOs? Same pump, ballast resistor, and voltage feed. Link to comment Share on other sites More sharing options...
Ωhm Posted March 3, 2018 Author Share Posted March 3, 2018 Big mistake on my part. I'll edit request and drop renix only. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 3, 2018 Share Posted March 3, 2018 1. 14.40 v 2. 4.36 v (using Standard Ignition Resistor RU29T, 1.6 Ω) 3. Bosch 69302 Note: FP pressure = 39psi w. vacuum, 49psi w/o vacuum Link to comment Share on other sites More sharing options...
cruiser54 Posted March 3, 2018 Share Posted March 3, 2018 I'm feeling kinda left out......LOL How come not Renix? Link to comment Share on other sites More sharing options...
Ωhm Posted March 3, 2018 Author Share Posted March 3, 2018 Thanks for helping me tune-up my request for information. Re-read request (post #1). Link to comment Share on other sites More sharing options...
cruiser54 Posted March 3, 2018 Share Posted March 3, 2018 57 minutes ago, Ωhm said: Thanks for helping me tune-up my request for information. Re-read request (post #1). I've got 3 of them I can gather info from. It will be a bit later. Link to comment Share on other sites More sharing options...
Ωhm Posted March 3, 2018 Author Share Posted March 3, 2018 I've adjusted request/data form for multiple vehicles. Good point. Re-read request (post #1). Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 4, 2018 Share Posted March 4, 2018 C'mon guys, break out your voltmeters. Ωhm needs some data... Link to comment Share on other sites More sharing options...
DirtyComanche Posted March 4, 2018 Share Posted March 4, 2018 Bump this in two weeks and I'll do it. Link to comment Share on other sites More sharing options...
gogmorgo Posted March 4, 2018 Share Posted March 4, 2018 What exactly are we looking to do? Like, where are we taking these voltages? My ballast resistors have been bypassed, but I didn't remove them so I could easily plug them back in. As I understand it, you're looking for the voltage going into and then out of the ballast resistor, with everything hooked up, running, with the engine (and presumably the resistor as well at that point) up to operating temperature? Or are you looking for battery voltage across the battery terminals and then voltage at the fuel pump connector? Cause I could get the former later today (probably) but if you're looking for me to crawl under my MJ you'll have to wait two-six weeks for the snow to melt out from under it. Link to comment Share on other sites More sharing options...
Ωhm Posted March 4, 2018 Author Share Posted March 4, 2018 2 measurements. Battery voltage and voltage across the ballast (when hooked-up). No one needs to crawl under their vehicle. Link to comment Share on other sites More sharing options...
gogmorgo Posted March 4, 2018 Share Posted March 4, 2018 Yeah that's exactly what you said before so I'll ask more clearly because I'm trying to clarify what you're asking for. Where should we put the voltmeter probes for each of these readings? Do you want us to probe both of the terminals on the ballast resistor for voltage going into it and voltage going out of it with one voltmeter probe grounded, or do you want it somewhere else? I won't profess to be an expert in electrical systems, so I'm making sure I'm interpreting your instructions correctly. The reason I'm asking is that when you're doing something semi-scientific like this you need to be specific or your results will be all over the place and pretty much meaningless. When you say "battery voltage" that tells me to either read it off the dash gauge (probably not useful) or take it directly off the battery (which wouldn't account for any voltage drop before it gets to the resistor) but it makes more sense to me to take it going into the resistor. I'm also curious how the data from the ballast resistor will be helpful for measuring fuel pump health, which is why I was asking about crawling underneath (I would expect voltage drop across the pump itself to be more useful). In my mind all that the output of the ballast resistor would show is voltage drop across the resistor which I don't think would be affected much by what's going on downstream from that point. Unless you're expecting the higher draw from an "unhealthy" pump would cause the resistor to heat up more than it would with a "healthy" pump, affecting the voltage drop across it, which leads to my question about how long you want the engine running for (and presumably how close to operating temperature the resistor gets) to try to quantify that particular variable. My MJ hasn't been started for over a month and it's been below freezing that whole time (not to mention it hasn't seen power for a few years) so that ballast resistor and the fuel pump will be stone cold until it's run for a bit. I can take an IR temp off the resistor too if you'd want that I guess. I'm not trying to pick holes in your project, just trying to make sure as many variables as possible get eliminated in the data I'm giving you to ensure your project's accuracy. I'll take the measurements however you want them, I just want to be sure I'm taking them exactly the same way as everyone else. Link to comment Share on other sites More sharing options...
Ωhm Posted March 4, 2018 Author Share Posted March 4, 2018 Yes, I've been vague about the voltage measurements. Keep in mind I understand what I'm saying, that don't mean others do. Let's clear up the voltage measurements. One voltmeter needed. Battery voltage to be taken at the battery, using both battery posts (terminals may be dirty). If no post is available, connect VM to terminals. As for the ballast resistor voltage, connect one lead to one terminal of the ballast and the other lead to the other terminal of the ballast. Across the ballast. Polarity doesn't matter, what I need is the number. Voltage drop at the ballast and knowing ballast resistance, one can determine current flow thru the ballast. Since the ballast is in series with the fuel pump and current flow is the same in a series circuits, we now know fuel pump current. Using fuel pump current and battery voltage minus ballast voltage drop, one can conclude fuel pump running resistance. This resistance value is what I'm trying to tie into fuel pump health. Everyone punch holes into this. I know I'm leaving a bunch of open ended variables like different voltmeters, ambient temp, fuel density, fuel rail pressure (HOrnbrod), altitude, is it raining, etc, etc. As for engine at normal operating temperature, some will be and other won't. But I have one constant, engine running at idle. So any and all value will reflect this, engine running and at idle. Numbers that fall out of this yet undetermined window, could show as a problem. Link to comment Share on other sites More sharing options...
gogmorgo Posted March 4, 2018 Share Posted March 4, 2018 Gotcha. One more hole, then I'm done. Does the health of the ballast resistor matter? I would expect they would degrade somewhat over their lives which means a change in resistance. Would an ohm value be at all helpful there? It's laundry day and somehow I've managed to put in ALL of my pants. As soon as I have something to wear I'll go out and fire some machines up. Link to comment Share on other sites More sharing options...
Ωhm Posted March 5, 2018 Author Share Posted March 5, 2018 I'm making a a$$umption here, I'm using 1.1ohms for the ballast resistor, unless I know of an exception (HOrnbrod again). Too keep this simple, voltage reading are fairly consistence between meters, ohmmeters are not. Ohmmeters rely on the condition of the internal battery. Maybe the results could ask a question: "What are the ohms at the ballast"? But yes, you're right about this. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 5, 2018 Share Posted March 5, 2018 19 minutes ago, gogmorgo said: One more hole, then I'm done. Does the health of the ballast resistor matter? I would expect they would degrade somewhat over their lives which means a change in resistance. Would an ohm value be at all helpful there? Best to pull a wire off one end and measure across the the resistor. Mine was close to it's rated value (1.3Ω) at 1.6Ω. Link to comment Share on other sites More sharing options...
Ωhm Posted March 5, 2018 Author Share Posted March 5, 2018 Time to add more request to the request. Ballast resistor resistance. Like mentioned above remove one wire and measure resistances. Re-read request (post #1). HOrnbrod you want 1.6Ωs? Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 5, 2018 Share Posted March 5, 2018 Yep, 1.6 is the actual. Link to comment Share on other sites More sharing options...
Ωhm Posted March 5, 2018 Author Share Posted March 5, 2018 Done Link to comment Share on other sites More sharing options...
gogmorgo Posted March 13, 2018 Share Posted March 13, 2018 Two vehicles. vehicle 1 1992 XJ, 2dr Sport , 4.0/5-speed/231 1. 14.62 2. 3.64 3. 1.5 4. IDK suspect original @336,000km... Almost everything else is original. Frankly amazed the resistor still works. The reason I had bypassed it was because the terminals felt loose (and I didn't like how quiet the pump was, lol), but ceramic actually split in half when I plugged it back in. Had to scrub a ton of corrosion off the contacts before I could get a consistent reading. Incidentally in doing so I discovered one says 1.1 ohm on it. If anyone is curious what they look like inside: After running the resistor winding was warmer than ambient (~40°F) but not really warm to the touch, maybe just under body temperature. Vehicle 2, 1991 MJ, 4.0/aw4/242, 535,000km. 1. 14.76V 2. 0.221V 3. 1.5 4. Brand spanking new Bosch 69302, unsure of exact mileage on it but it was installed in November and it's mostly been parked... Maybe 100km, if that. I'll add a caviat to this that I've misplaced the keys for the MJ in a recent move (mostly I'm too lazy to look for them, my guess is they're in a jacket pocket somewhere), and I started it with a jumper wire from the constant 12V at the starter relay to the ignition fuse to turn it "on" and then another jumper across the terminals of the starter relay socket to crank it over. When I find the keys I'll start it "normally" to see if there's much change. My concern is the ecu circuit that bypasses the resistor won't have been disengaged by my, er, unorthodox starting method, especially given how my voltage drop across the resistor is an order of magnitude less than others. I had to scrub some corrosion but it stabilized at that, so I couldn't really do much more than that. Link to comment Share on other sites More sharing options...
Ωhm Posted March 13, 2018 Author Share Posted March 13, 2018 Yeah, Veh 2, Item 2 looks a little low. lol. Thanks for your time and hope you find your keys. Link to comment Share on other sites More sharing options...
gogmorgo Posted March 14, 2018 Share Posted March 14, 2018 So in a classic herpityderp moment I got home after an exhaustingly repetitive day at work today, grabbed a beer, picked up my bottle opener off the counter beside it, and went "huh". It's the opener I keep on my Jeep keyring. I've literally had my keys in my hand three to six times a week for the last month and a bit, and been wondering the whole time what I did with them. Lol. So, vehicle 2 from above revisited. 1. 14.67 2. 3.82 3. 1.5 4. Pretty much as close to a brand new Bosch 69302 as you'll find. I also confirmed that my hotwiring technique does in fact hold the ballast resistor out of the circuit, as I could start and run it that way with the resistor wires disconnected, or pull them off while running without killing it. In contrast when started with the key it would die after a couple seconds if started disconnected, or instantly if I pulled a wire off while it was running with the keys. So now I'm wondering why it does that... Based on previous readings of the wiring diagrams I assumed all I was doing was alternatively turning the key, (and everything works when I start it like that! Except the steering and shifter interlocks) but I guess not. Obviously whatever tells the ecu to switch circuits isn't getting triggered. Huh. Link to comment Share on other sites More sharing options...
Ωhm Posted March 15, 2018 Author Share Posted March 15, 2018 Chart is sorted by Ballast Resistor Current (Amps). Chart shows two (2) of the three (3) measurements taken by vehicle owners: Ballast Resistance (ohms) and Voltage Drop Across Ballast (volts). The other two are calculated. Ballast Resistor Current is Voltage Drop Across Ballast divided by Ballast Resistance. E/R=I Fuel Pump Running Resistance is (Battery Voltage minus Voltage Drop Across Ballast) divided by Ballast Resistor Current. E/I=R As stated earlier, I'm looking for a trend by using Fuel Pump Running Resistance to check fuel pump performance. Link to comment Share on other sites More sharing options...
gogmorgo Posted March 15, 2018 Share Posted March 15, 2018 I'll point out that for my '92 XJ the resistance was 1.5Ω, not 1.1 as in your chart. 1.1Ω is stamped on one of the terminals but I measured 1.5Ω. Link to comment Share on other sites More sharing options...
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