jtdesigns Posted April 1, 2009 Share Posted April 1, 2009 Trucks not starting... Well it will,,,, just got to kinda let it crank, then stop, then let the pump prime a few times.. I don't think the fuel pump is working right.. It'll start sometimes idle up to around 1000 rpm, like a normal start then while its idling down just keep going down till it stops running. Then you can start it right up after that. No problems... It takes it forever tuning over to start, but I swear I hear the pump turn on (sorta a roar) and she'll fire right up... Here's what I know.. (not much but.......) Ign switch powers up one side of fuel pump relay coil. ECU supplies the ground of coil, which switches the fuel pump on. How does the ballast resistor come into the system? Link to comment Share on other sites More sharing options...
Geonovast Posted April 1, 2009 Share Posted April 1, 2009 All I know is it switches to run through the resistor after startup so it runs quieter. If it's grumbling, then I bet a bearing in the pump is dying and you need to replace it ASAP. Link to comment Share on other sites More sharing options...
jtdesigns Posted April 1, 2009 Author Share Posted April 1, 2009 All I know is it switches to run through the resistor after startup so it runs quieter. If it's grumbling, then I bet a bearing in the pump is dying and you need to replace it ASAP. I just replaced the pump 2 weeks ago.. Runs good after it's started. Link to comment Share on other sites More sharing options...
BLHTAZ Posted April 1, 2009 Share Posted April 1, 2009 The ballast resistor is by-passed at start-up, so starting has nothing to do with that...however, since you say it starts and then slowly dies, you may want to try eliminating the resistor with a jumper and see if anything changes. Link to comment Share on other sites More sharing options...
jtdesigns Posted April 2, 2009 Author Share Posted April 2, 2009 I was thinking about doing that too Brent, just havent had any time to wrench.. Hopefully this weekend.. If rain doesnt stop me from it. I can hear the pump prime, but not when turning over. Link to comment Share on other sites More sharing options...
Wildman Posted April 2, 2009 Share Posted April 2, 2009 Knowing all what you tossed into this the past month........the only thing I can think of is the pressure regulator :hmm: Sounds like low pressure in the rail before the start, then getting a rush of pressure when it starts, and it dwindles down and stalls out. Hows the EGR valve??? still hooked up???.......take the vacuum line off it, and plug it, and see if that makes any difference on how it starts and dies......ah er.....runs. Link to comment Share on other sites More sharing options...
jtdesigns Posted April 2, 2009 Author Share Posted April 2, 2009 Knowing all what you tossed into this the past month........the only thing I can think of is the pressure regulator :hmm: Sounds like low pressure in the rail before the start, then getting a rush of pressure when it starts, and it dwindles down and stalls out. Hows the EGR valve??? still hooked up???.......take the vacuum line off it, and plug it, and see if that makes any difference on how it starts and dies......ah er.....runs. :thumbsup: Link to comment Share on other sites More sharing options...
jtdesigns Posted April 2, 2009 Author Share Posted April 2, 2009 I just don't get it... Hooked the fuel pressure tester up to it and did some digging.. felt the ballast resistor getting pretty warm pretty quick.. I jumped the resistor and she fires right up every time.. unhook it, it won't crank, or have any pressure at all. Hook it up and its like a hit or miss if it cranks or not... I thought the fuel pump bypasses that resistor on starting.. What gives????? Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 2, 2009 Share Posted April 2, 2009 I just don't get it... Hooked the fuel pressure tester up to it and did some digging.. felt the ballast resistor getting pretty warm pretty quick.. I jumped the resistor and she fires right up every time.. unhook it, it won't crank, or have any pressure at all. Hook it up and its like a hit or miss if it cranks or not... I thought the fuel pump bypasses that resistor on starting.. What gives????? The ballast resistor is bypassed at startup unless some PO altered the original circuit. Once running, the ECU immediately sends a signal to the ballast resistor relay and it's latched into the fuel pump voltage supply circuit. The resistance value on the ballast is critical; some of the "universal" ones are not the correct value and drop the voltage too much or not enough to the pump. I'd pick up a new one from the dealer (p/n 33000682, about $7.00), reterminate the spade connectors on the wires, and install a new resistor. Link to comment Share on other sites More sharing options...
jtdesigns Posted April 3, 2009 Author Share Posted April 3, 2009 I just don't get it... Hooked the fuel pressure tester up to it and did some digging.. felt the ballast resistor getting pretty warm pretty quick.. I jumped the resistor and she fires right up every time.. unhook it, it won't crank, or have any pressure at all. Hook it up and its like a hit or miss if it cranks or not... I thought the fuel pump bypasses that resistor on starting.. What gives????? The ballast resistor is bypassed at startup unless some PO altered the original circuit. Once running, the ECU immediately sends a signal to the ballast resistor relay and it's latched into the fuel pump voltage supply circuit. The resistance value on the ballast is critical; some of the "universal" ones are not the correct value and drop the voltage too much or not enough to the pump. I'd pick up a new one from the dealer (p/n 33000682, about $7.00), reterminate the spade connectors on the wires, and install a new resistor. Yeah I know thats the thing,, it won't start with the resistor unhooked.. But it will hooked up.. I omhed it out at just a tad under 1 ohm. I'm guessing Ill get another one, but still isnt working like y'all say it should, by bypassing at start-up. WAIT,,, ballast resistor relay...... where is that??? Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 3, 2009 Share Posted April 3, 2009 One ohm is a bit low JT. Mine measures about 1.3 ohms (just checked it). The resistors were the same from 84-94. The HOs have both a fuel pump relay and a ballast resistor relay; probably the Renix has only the fuel pump relay to do the ballast switching. Link to comment Share on other sites More sharing options...
jtdesigns Posted April 3, 2009 Author Share Posted April 3, 2009 One ohm is a bit low JT. Mine measures about 2.3 ohms. The resistors were the same from 84-94. The HOs have both a fuel pump relay and a ballast resistor relay; probably the Renix has only the fuel pump relay to do the ballast switching. OK that makes alot of sense.. I'm still searching through the wiring diagrams trying to find the ballast and switching circuit... Found this... Still looking for the wiring diagram Link to comment Share on other sites More sharing options...
jtdesigns Posted April 3, 2009 Author Share Posted April 3, 2009 Still don't see any way the resistor is switched in the system.. Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 3, 2009 Share Posted April 3, 2009 I think you need the next sheet as the "RESISTOR PACK" I believe is the ballast resistor. Link to comment Share on other sites More sharing options...
jtdesigns Posted April 3, 2009 Author Share Posted April 3, 2009 I was going to ask about that resistor pack.. I found it (the ballast resistor) in a 93 FSM but still not in the 88... :wall: Link to comment Share on other sites More sharing options...
Wildman Posted April 3, 2009 Share Posted April 3, 2009 The ballast resistor didn't come in the '87, it was "added" in the '88+, so the '88 FSM might not show it, the '89 FSM shows it. Link to comment Share on other sites More sharing options...
jtdesigns Posted April 3, 2009 Author Share Posted April 3, 2009 The ballast resistor didn't come in the '87, it was "added" in the '88+, so the '88 FSM might not show it, the '89 FSM shows it. Hey Wildman could you scan me a copy of the wiring diagram?? Link to comment Share on other sites More sharing options...
Wildman Posted April 3, 2009 Share Posted April 3, 2009 Yea, tomorrow.......getting too late tonight :( Link to comment Share on other sites More sharing options...
jtdesigns Posted April 3, 2009 Author Share Posted April 3, 2009 Yea, tomorrow.......getting too late tonight :( Roger that.. :thumbsup: Link to comment Share on other sites More sharing options...
Wildman Posted April 3, 2009 Share Posted April 3, 2009 Yea, tomorrow.......getting too late tonight :( Roger that.. :thumbsup: Who's Roger???? :hmm: Link to comment Share on other sites More sharing options...
Wildman Posted April 4, 2009 Share Posted April 4, 2009 Check your PM's JT :D Link to comment Share on other sites More sharing options...
jtdesigns Posted April 4, 2009 Author Share Posted April 4, 2009 Check your PM's JT :D No.. Check your PM's...... :doh: In my best CA gov's voice...... I'll be back.... Link to comment Share on other sites More sharing options...
jtdesigns Posted April 11, 2009 Author Share Posted April 11, 2009 Another topic about the same for future reference http://www.comancheclub.com/forums/viewtopic.php?f=2&t=16008&start=0 Link to comment Share on other sites More sharing options...
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