TheSiLvAPython Posted July 6, 2022 Share Posted July 6, 2022 I'm having issues with my truck it is an 89 I6 5 speed manual. I had an electrical short happen a few days ago. And it started and ran 4 times. But now It just cranks and acts like it wants to run but immediately dies. I am lost. I know very little about these trucks and vehicles in general. I think it may be the fuel pump because i don't hear it with the key on. Are there any ways I can test this myself? I have multimeter Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 6, 2022 Share Posted July 6, 2022 So what’s happening is when the key is switched to the on but not start position, the fuel pump ballast is bypassed to prime the fuel rail. If this is correct, your engine should be cranking, fire a couple pistons and stop because now the fuel pump ballast is no longer being bypassed during crank. If the ballast hasn’t been bypassed or replaced, your truck won’t run longer than a second. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted July 6, 2022 Author Share Posted July 6, 2022 5 minutes ago, eaglescout526 said: So what’s happening is when the key is switched to the on but not start position, the fuel pump ballast is bypassed to prime the fuel rail. If this is correct, your engine should be cranking, fire a couple pistons and stop because now the fuel pump ballast is no longer being bypassed during crank. If the ballast hasn’t been bypassed or replaced, your truck won’t run longer than a second. Yeah cuz it starts up but then after a second literally it shuts down. So could I just run a temporary jumper wire between the two wires in the ballast to bypass it just to get it home? Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 6, 2022 Share Posted July 6, 2022 Absolutely. Or delete the ballast all together honestly. It’s a “fix” that Chrysler did to “quiet” down the fuel pump. It was more applicable to the XJ than the MJ but they are prone to breaking and overheating which leads to failure. Bypass it and drive it around all day. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted July 6, 2022 Author Share Posted July 6, 2022 15 minutes ago, eaglescout526 said: Absolutely. Or delete the ballast all together honestly. It’s a “fix” that Chrysler did to “quiet” down the fuel pump. It was more applicable to the XJ than the MJ but they are prone to breaking and overheating which leads to failure. Bypass it and drive it around all day. Well I bypassed it and it started and stayed running for a little bit but then I noticed some smoke coming from the fuel filter area and my truck shut off again so do you think it could be a bad fuel pump now at this point? Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 6, 2022 Share Posted July 6, 2022 Yeah it could be. Know any history on the truck? Like has the fuel system ever been serviced? Link to comment Share on other sites More sharing options...
Eagle Posted July 6, 2022 Share Posted July 6, 2022 49 minutes ago, eaglescout526 said: So what’s happening is when the key is switched to the on but not start position, the fuel pump ballast is bypassed to prime the fuel rail. If this is correct, your engine should be cranking, fire a couple pistons and stop because now the fuel pump ballast is no longer being bypassed during crank. If the ballast hasn’t been bypassed or replaced, your truck won’t run longer than a second. You have it backwards. The "On" position is the 'Run" position -- power to the fuel pump goes through the ballast resistor. The resistor is bypassed when the key is turned to the "Start" position. Link to comment Share on other sites More sharing options...
Eagle Posted July 6, 2022 Share Posted July 6, 2022 13 minutes ago, TheSiLvAPython said: Well I bypassed it and it started and stayed running for a little bit but then I noticed some smoke coming from the fuel filter area and my truck shut off again so do you think it could be a bad fuel pump now at this point? On an '89 MJ the fuel filter is mounted to the frame rail, beneath the vehicle on the driver's side. If that's not where you saw smoke, what you saw wasn't the fuel filter. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted July 6, 2022 Author Share Posted July 6, 2022 Unfortunately no I don't know any history of the vehicle. The guy I got it from just said when he got the truck it was on a flatbed trailer and he got it running again and used it daily until he had his third kid and he decided to sell it thats when I got it. But yeah now it's doing the same thing it starts up and then immediately dies. I don't know where the smoke was coming from exactly because I look under the truck where it was coming from but none of the wires look melted so I'm really lost right now. This is another one of those times where I just wish my truck was carbureted instead of fuel injected Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted July 6, 2022 Author Share Posted July 6, 2022 11 minutes ago, Eagle said: On an '89 MJ the fuel filter is mounted to the frame rail, beneath the vehicle on the driver's side. If that's not where you saw smoke, what you saw wasn't the fuel filter. Yes that is where my fuel filter is on the driver side Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted July 6, 2022 Author Share Posted July 6, 2022 That is also where I saw the smoke coming from Link to comment Share on other sites More sharing options...
Eagle Posted July 6, 2022 Share Posted July 6, 2022 3 minutes ago, TheSiLvAPython said: That is also where I saw the smoke coming from Check the wires the run along the frame in that area. Look for abraded insulation or broken wires. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted July 6, 2022 Author Share Posted July 6, 2022 49 minutes ago, eaglescout526 said: I'm doing that right now. Also two of my fusible links wires have melted as well could that have anything to do with what I'm dealing with could I just use a like a butt connector to just connect those two wires in the fusible link back together and continue on? Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 6, 2022 Share Posted July 6, 2022 1 hour ago, Eagle said: You have it backwards. The "On" position is the 'Run" position -- power to the fuel pump goes through the ballast resistor. The resistor is bypassed when the key is turned to the "Start" position. It is?! Well shoot. I am a fortunate soul to have an 88 produced without it. Either way I feel we have helped the PO get closer to his issue. Link to comment Share on other sites More sharing options...
Eagle Posted July 6, 2022 Share Posted July 6, 2022 2 hours ago, TheSiLvAPython said: I'm doing that right now. Also two of my fusible links wires have melted as well could that have anything to do with what I'm dealing with could I just use a like a butt connector to just connect those two wires in the fusible link back together and continue on? Fusible links are fuses. I would not try to repair them. Downoad the electrical manual, find out what their rating is, and replace them with new wire and actual fuses. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted July 7, 2022 Author Share Posted July 7, 2022 5 hours ago, Eagle said: Fusible links are fuses. I would not try to repair them. Downoad the electrical manual, find out what their rating is, and replace them with new wire and actual fuses. Do you know what page it is on? I can't seem to find it in my electrical service manual. I have a physical copy but I do not know how to read wiring diagrams at all. Also I found out it was one of my fusible links though. To get home I just twisted the wire on the newest broken fusible link. Been spending all day replacing melted wires that all stem from..... The light switch in the dashboard.. This will be fun.. Link to comment Share on other sites More sharing options...
Eagle Posted August 3, 2022 Share Posted August 3, 2022 On 7/7/2022 at 12:36 AM, TheSiLvAPython said: Do you know what page it is on? I can't seem to find it in my electrical service manual. Sorry, I don't know. I'm pretty certain I stumbled across it once, many years ago, but I certainly don't remember page numbers. Link to comment Share on other sites More sharing options...
TheSiLvAPython Posted August 3, 2022 Author Share Posted August 3, 2022 22 minutes ago, Eagle said: Sorry, I don't know. I'm pretty certain I stumbled across it once, many years ago, but I certainly don't remember page numbers. It's okay. 8W-3. I got the truck running again. my fuel gauge stopped working for a little bit after because the variable resistor melted! I replaced it with a sending unit i got one with a gas tank that i purchased from someone. had to pull the sending unit off of that assembly and put it into mine because that assembly was really rusty. but I broke off the little tab so I just rigged a 16g primary wire through the hole that the tab was connected to on the plastic tab that the variable resister is. my gas gauge works (sort of) it reads anything over a 1/4 tank haha i will have to fix it better but for now its okay. whew that was long story my bad. off topic a little. I appreciate your help with this though Link to comment Share on other sites More sharing options...
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