co-MAN-che Posted August 8, 2015 Share Posted August 8, 2015 I have checked my fuel pressure. I have checked my pump and sending unit. I have checked the circuit to the pump and sending unit. I have replaced every relay and fuse associated with the fuel and ignition system. I have replaced every sensor and switch associated with the fuel and ignition system.Is there something I'm missing that could lead the truck to start, idle quite high for 3-4 seconds, then begin to slow down so much in idle speed that it starts shuddering until it utterly dies? I'm starting to think this truck cannot be fixed. Link to comment Share on other sites More sharing options...
sinkrun Posted August 8, 2015 Share Posted August 8, 2015 We will need more info, year,engine,standard or auto. Link to comment Share on other sites More sharing options...
Eagle Posted August 9, 2015 Share Posted August 9, 2015 Sounds to me like the fuel pump ballast resistor isn't conducting. It gets bypassed on startup, so when cranking the fuel pump will run and allow the engine to start. Once you release the key to the RUN position, the fuel pump cuts out and the engine burbles along for a few seconds until it uses up the fuel and pressure in the rail, then it dies. After the truck has been sitting overnight, when you turn the key to RUN (not to START), do you hear the fuel pump run? Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 9, 2015 Author Share Posted August 9, 2015 I hear fuel pump working, but I have no current going to the ballast resistor when key is in run position Link to comment Share on other sites More sharing options...
Crash Posted August 9, 2015 Share Posted August 9, 2015 Bypass/jumper the ballast resistor, see if it runs. Also, if you go to start it and hold the key between the run/start position does it continue to run? I have had these issues, the first time, my ign switch failed, so I bypassed it with a switch and push button. The second time my ballast resistor failed. I permanently bypassed that. Everything is just fine meow. Link to comment Share on other sites More sharing options...
reubj Posted August 10, 2015 Share Posted August 10, 2015 Perhaps a faulty Fuel Pressure Regulator. Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 10, 2015 Author Share Posted August 10, 2015 New ignition switch, fuel pump regulator,. If ballast resistor is bypassed there is no improvement in performance Link to comment Share on other sites More sharing options...
1stDeuce Posted August 10, 2015 Share Posted August 10, 2015 If I read correctly, you already said that there was no power to the ballast resistor in "run". That's your problem, not the resistor itself. I gather you've tried bypassing the resistor, but have you tried giving it 12v directly? If the resistor is good, applying 12v to either side should get your pump powered up full time, and my guess is that your engine will run fine then. If so, then you'll need to figure out why the resistor isn't getting power in "run". There is a fuse, but I don't recall where it's at... Chris Link to comment Share on other sites More sharing options...
1stDeuce Posted August 10, 2015 Share Posted August 10, 2015 I should clarify, you can't leave the resistor powered full time, just do that to run the truck and verify that it solves the problem. :) I remember tracing that wiring on my '92 Cherokee, but I don't recall where it went. And I recommend you bypass the resistor anyway, so it can't ever leave you stranded. The fuel pump will appreciate it as well. :) Chris Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 10, 2015 Author Share Posted August 10, 2015 I'll try to bypass and power it for a moment to see if there is any improvement, then trace it because i need to find where the circuit is compromised anyway Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 11, 2015 Author Share Posted August 11, 2015 Force fed power to the fuel pump, retested my fuel pressure and it measures at 40 psi. Now it starts but still immediately dies. I can't get my hand out of the drivers window and 2 feet to the throttle body in time to try to hit the IAC with throttle body cleaner to see if it helps any Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 13, 2015 Author Share Posted August 13, 2015 went ahead and got a brand new throttle body, IAC motor, valve, sensor, and hose so I didn't have to worry if I got it clean enough. No improvement in performance. still dies immediately after starting Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 13, 2015 Author Share Posted August 13, 2015 Thinking about the auto shutdown relay and its associated fuses. Will get back after I check these and post results Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 15, 2015 Author Share Posted August 15, 2015 I have checked everything that I thought could be related to stalling immediately after starting, and have followed all suggestions I have received this far, and have not resolved the issue. I have checked every mounting bolt after I put a fresh gasket on my air intake, along with replacing every vacuum hose on it, have checked map sensor, new throttle body with new IAC system and new TPS, restored power current to the ballast resistor, then bypassed it. Verified I have correct fuel pressure and voltage to fuel pump. Checked auto shutdown circuit. Verified wiring harness at distributor, coil, and alternator is in good shape. Is there ANYTHING I'm missing, please tell me I am. Link to comment Share on other sites More sharing options...
reubj Posted August 16, 2015 Share Posted August 16, 2015 There is a camshaft position sensor (sync signal generator) in the distributor that may be bad. Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 16, 2015 Share Posted August 16, 2015 You still haven't stated what year and engine you are driving. Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 19, 2015 Author Share Posted August 19, 2015 it's in my information. If it can't be seen for some reason (Or I very well could be mistaking this site for the layout of JeepForum), I have a 1991 jeep comanche 4x4 with the HO 4.0l with AW4 automatic transmission Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 19, 2015 Author Share Posted August 19, 2015 My current plans are to rent a Noid light set and see what kind of current I'm getting at my injectors, and to jump my Auto Shutdown relay and see if that corrects my issue. will post results Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 19, 2015 Share Posted August 19, 2015 it's in my information. If it can't be seen for some reason (Or I very well could be mistaking this site for the layout of JeepForum), I have a 1991 jeep comanche 4x4 with the HO 4.0l with AW4 automatic transmission Since you have a 91, have you checked for fault codes? http://comancheclub.com/topic/28111-reading-obdi-91-and-92-mj-fault-codes/?hl=fault+codes Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 20, 2015 Author Share Posted August 20, 2015 Throws no trouble codes to my dismay Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 20, 2015 Share Posted August 20, 2015 Did the light flash at all? Even with no fault codes you will get a 5-5 code. A non-flashing code light is a symptom of a bad ECU. Link to comment Share on other sites More sharing options...
Comanche County Posted August 21, 2015 Share Posted August 21, 2015 Does it start and die with the shifter in Neutral also? Also, what does the rotor and cap look like on the inside? Link to comment Share on other sites More sharing options...
co-MAN-che Posted August 24, 2015 Author Share Posted August 24, 2015 Hornbrod, I got trouble code 12, and trouble code 55, which are normal because I plugged a new pcm in within the past 50 keystrokes, but registered no other trouble codes flashed when the problem persisted Comanche County, Brand new distributor, rotor button, cap, wires and plugs because I overdo tune-ups every 1000 miles Jumped 30 to 87 in my ASD relay connector in the fuse box, ran like a charm. found that wires in the bottom side of said fuse box leading to the 87, 87a, and 85 pins were rubbed free of their insulation and sharing continuity. made the necessary fix and solved my issue Link to comment Share on other sites More sharing options...
shelbyluvv Posted August 24, 2015 Share Posted August 24, 2015 Way to stay at it! I'm glad you figured it out. Bravo sir! Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 24, 2015 Share Posted August 24, 2015 Concur! I've seen the ASD relay cause a no-run condition because the relay was bad, but never from skinned wires under the PDC where the relay sockets are wired. Do you know how the wire insulation got rubbed off? Was some previous owner fooling around under the PDC? This could help all of us with the HO models. Link to comment Share on other sites More sharing options...
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