Mekanik Posted July 15, 2009 Share Posted July 15, 2009 We have a 2006 F450 or F550 coming in the shop(again). The vehicle will stall and not re-start and always has a P0231 in memory. We have never got the problem to happen, but have replaced the fuel pump and the CJB which has the fuel pump relay inside. Any ideas? BTW, I'm not the one working on it. I'm just trying to help. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted July 16, 2009 Share Posted July 16, 2009 I can't say for certain in your case, but I have replaced quite a few inertia switches. It seems odd that they would go bad seeing how they last forever on a gas vehicle. It would be nice to get the truck to act up, but they are cheap and easy to replace if you want to chuck one at it. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted July 16, 2009 Author Share Posted July 16, 2009 For real? I don't think I have replaced a single inertia switch in 16 years. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted July 16, 2009 Share Posted July 16, 2009 Yea, just on the sickos. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted July 17, 2009 Author Share Posted July 17, 2009 Brad, you hit the nail on the head. The tech found that if he flicked the inertia switch with his finger the engine would shut-off. On this engine the inertia switch not only shuts off the fuel pump, but the PCM too. I have a 7.3L that has the same problem. I wonder if that thing has a bad inertia switch too. Thanks for the tip Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted July 17, 2009 Share Posted July 17, 2009 Excellent to hear! Put another one in the books. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted July 17, 2009 Share Posted July 17, 2009 Brad, you hit the nail on the head. The tech found that if he flicked the inertia switch with his finger the engine would shut-off. On this engine the inertia switch not only shuts off the fuel pump, but the PCM too. I have a 7.3L that has the same problem. I wonder if that thing has a bad inertia switch too. Thanks for the tip I have also never seen a bad inertia switch. You state it shuts off the PCM, but I can't find any reason for this in the schematics. Can you enlighten me on how you came to this conclusion? In the schematic, it appears the inertia switch is in series with the FP and should not affect the PCM at all. Also, on many 6.0/7.3 engines, they will run with the FP or inertia switch disabled. Maybe not run well, but most will still run. I have proved this out in class by smacking the inertia switch hard while running, and all that happens is a DTC sets while the engine continues to run. I've also had a couple of trucks with bad wiring where the owner would continue to drive it with the pump disabled, and another shop who inserted a anti-theft kill switch (unsuccessfully) in line with the inertia switch. Thanks for the tip! Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted July 17, 2009 Share Posted July 17, 2009 I have seen two bad inertia switches on 6.0L vehicles. They both ran and one of them not all that badly either. The inertia fuel cut-off switch simply interrupts the secondary fuel pump circuit when tripped. It does not shut down the PCM. The PCM does monitor the IFS output circuit to the fuel pump for control and diagnostic purposes. Quote Link to comment Share on other sites More sharing options...
Aaron Posted July 18, 2009 Share Posted July 18, 2009 It'll run long enough without a fuel pump to pound all the fucking injectors out of an 6.0 econoline. Quote Link to comment Share on other sites More sharing options...
joshbuys Posted July 18, 2009 Share Posted July 18, 2009 Originally Posted By: Mekanik Brad, you hit the nail on the head. The tech found that if he flicked the inertia switch with his finger the engine would shut-off. On this engine the inertia switch not only shuts off the fuel pump, but the PCM too. I have a 7.3L that has the same problem. I wonder if that thing has a bad inertia switch too. Thanks for the tip I have also never seen a bad inertia switch. You state it shuts off the PCM, but I can't find any reason for this in the schematics. Can you enlighten me on how you came to this conclusion? I've seen several bad inertia switches(mostly on oil field service trucks that see alot....i mean mostly offroad driving!) same thing usually....intermittent stall/no start. The inertia switch is in series with the fuel pump, but the fuel pump monitor circuit is in the same circuit in parallel with the pump and in series with the inertia switch. If the fuel pump monitor circuit(pcm circuit) sees 0 volts, it will not allow the truck to start. The inertia switch does not disable the pcm, but the pcm disables the truck when the inertia switch goes open. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted July 18, 2009 Share Posted July 18, 2009 The inertia switch does not disable the pcm, but the pcm disables the truck when the inertia switch goes open. I'm not sure I agree with this all of the time. I have a friend who installed a kill switch on a later 6.0 to open the FP circuit at the inertia switch and the truck would still start with the kill switch opened. This is something that could depend on calibration, though. It may act one way or the other depending on what flash level it has. Thanks! Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted July 18, 2009 Share Posted July 18, 2009 We are talking about a 6.0L right? As of yet I haven't seen anything like this and I have never heard of it happening. Like Bruce stated, this would be achievable through the processor. Now if we move up to a 6.4L engine the answer is YES. I have had a tow in that had a failed fuel pump - the fuel pump monitor recognized that there was not load on the pump circuit and disabled the starter. No crank. Unfortunately this is not stated in the manual anywhere, or at least at the time I encountered this is was not. When I discussed this with the Hot-Line they confirmed my findings. Since a 6.4L will not run without fuel supply pressure it seems needless in a way. But, since 6.0L injectors can draw fuel and the engine can run with a bad fuel pump or tripped IFS this starter disable strategy would be better suited to a 6.0L in my opinion. I would save some injectors from destruction for sure. I think this was discussed here somewhere... Quote Link to comment Share on other sites More sharing options...
GregKneupper Posted July 18, 2009 Share Posted July 18, 2009 All of the bad inertia switches that I have seen fail have only tripped p0232 codes. Not a p0231. Quote Link to comment Share on other sites More sharing options...
joshbuys Posted July 19, 2009 Share Posted July 19, 2009 Originally Posted By: joshbuys The inertia switch does not disable the pcm, but the pcm disables the truck when the inertia switch goes open. I'm not sure I agree with this all of the time. I have a friend who installed a kill switch on a later 6.0 to open the FP circuit at the inertia switch and the truck would still start with the kill switch opened. This is something that could depend on calibration, though. It may act one way or the other depending on what flash level it has. Thanks! I can't dispute that since I'm not completely sure and can't find any documentation supporting one way or the other. I can say that we do Wynn's Diesel Injection flushes on occasion and have to unplug the fuel pump at the pump or pump harness because we found that when the inertia switch is tripped or fuel pump fuse removed the truck will just crank over and not start. but once we left the inertia switch and fuse alone and unplugged the pump it starts and runs fine on the injection flush machine. An open fuel pump won't cause this issue since it parallels the FPM circuit but opening the circuit previous to this seems to have that affect in my experiences. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted July 19, 2009 Author Share Posted July 19, 2009 For some reason I can't log into FMC dealer right now. I think that joshbuys is right. there is a circut after the inertia switch going to the PCM. I think the PCM won't let the truck start if it does not have 12V at that circut. Now I'm not saying that every 6.0L will do this. I once had a 2003 excursion that came in with a lack of power complaint and the vehicle was recently repaired at a body shop because of an accident. nobody ever re-set the inertia switch on the vehicle. Believe it or not, it also required an injector after I re-set the inertia switch. This is why I had such a hard time believing it could be a pump or anything in that circut. I didn't work on this truck, but I can tell you that it would shut down when the tech would flick the switch with his finger. I will say this, the tech that is currently married to this vehicle was on vacation one time it was in the shop and my boss wanted someone to put a fuel pump in it because of the DTC it had in memory. I told him I didn't think it was the problem and I even demonstrated un-plugging the pump with it running and it didn't stall. But there was still power on the wire after the inertia switch to the PCM. Quote Link to comment Share on other sites More sharing options...
BrunoWilimek Posted September 11, 2014 Share Posted September 11, 2014 I have an 06 in my bay that had an intermittent no start and set code P0231. After reading this thread, I discovered a kill switch had been spliced in at the inertia switch. The kill switch was extremely hot, showed signs of melting the electrical tape around it. When I cleared the code, disconnected the inertia switch, truck would start, then stall. Also, it set code P0231 with the switch disconnected. Quote Link to comment Share on other sites More sharing options...
BrunoWilimek Posted September 26, 2014 Share Posted September 26, 2014 Just got a hug from the customer today. No more starting issues. Removing the corroded kill switch and re-joining the wire fixed it. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted September 27, 2014 Share Posted September 27, 2014 Looking at the wiring schematic will tell you how the fuel pump circuit is supplied voltage and how the inertia switch is employed - IF there is one on the truck. F-Series and E-Series 6.0L AND F-Series 6.4L PSD engines - the IFS completes/interrupts the fuel pump power circuit between the switched site of the relay and the pump itself and the relay is controlled by the PCM which grounds the relay coil. The PCM monitors the voltage on this circuit to determine fuel pump status. * In all of the service literature there is no documentation indicating that the IFS plays a role in in commanding the fuel pump on or off. F-Series 6.7L PSD engine - the IFS completes/interrupts the fuel pump power circuit between the switched site of the relay and the pump itself and the relay is controlled by the PCM which grounds the relay coil. The PCM monitors the voltage on this circuit and also monitors the "open" side of the IFS to determine the fuel pump status. * In all of the service literature there is no documentation indicating that the IFS plays a role in in commanding the fuel pump on or off. Transit 3.2L PSD engine - The RCM (Restraints Control Module) Communicates with the BCM (Body Control Module) which will interrupt power to the fuel pump control module by turning off the fuel pump relay. There is no IFS Rather the RCM determines if there has been a condition (collision) requiring the fuel pump to be disabled and sends the appropriate data VIA a dedicated communication circuit or ENS (Event Notification Signal) to the Body Control Module. The event notification feature provides other vehicle subsystems with information pertaining to SRS deployment or fuel cutoff status. When an impact occurs which exceeds a pre-determined threshold, the RCM sends a signal on a dedicated circuit to the BCM. When the crash signal input is transmitted, fuel cutoff is initiated, disabling the fuel system. The event notification signal is a signal provided by the RCM to the Fuel Pump Control Module. Signal communication between the RCM and the Fuel Pump Control Module allows the PCM to shut-off the Fuel Pump. * I have researched all of the WSM documentation and so far cannot find any PCM strategy for fuel shut off operation - still looking. Sometimes you have to go into other systems on the vehicle to find related information that is not included where you might expect to find it. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted September 27, 2014 Share Posted September 27, 2014 Sidebar- Interrupting the FP circuit on a HEUI engine does not always cause a no start. I know of several times where they still run, including an unhappy shop owner who installed a kill switch in a 6.0 to find it did not kill........ Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted September 27, 2014 Share Posted September 27, 2014 Sidebar- Interrupting the FP circuit on a HEUI engine does not always cause a no start. I know of several times where they still run, including an unhappy shop owner who installed a kill switch in a 6.0 to find it did not kill........And ironically the engine can sometimes run surprisingly well with the fuel pump not running. I think it was a 7.3L I discovered this on. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted September 27, 2014 Share Posted September 27, 2014 I was toying with a 6.7 the other day upon Glen's (8WA Sman) run-in with a inertia switch issue. I know some 6.0L and 6.4L engines will run all day with the inertia switch unplugged and the fuel pump itself unplugged for that matter. Can't tell you how many times a customer has come in for fuel filters only to find the engine wouldn't run afterwards because the pump had shit out no telling when and the fuel prime had been lost once the system was opened to remove the filters. Anywho a 6.7L will shut down immediately after the switch is tripped. I am not sure what the PCM is disabling after it sees the loss of voltage on the pump output line (FPM pin 32) and switched voltage on the (FDSOM pin 49) line. Quote Link to comment Share on other sites More sharing options...
8WA Sman Posted September 28, 2014 Share Posted September 28, 2014 * I have researched all of the WSM documentation and so far cannot find any PCM strategy for fuel shut off operation - still looking. Sometimes you have to go into other systems on the vehicle to find related information that is not included where you might expect to find it. I looked all over the place in SI/PCED for more concrete info on that third circuit operation or software strategy. I even looked at some EU or models that were out of the states, I just didn't come up with lot of real concrete info. I also searched some SAE stuff. I also came up with the fact that is almost certainly a crash event strategy. I also found out that Ford used the same IFS on the 6.4L but did not have a wire in that third circuit. There is also a Pid for the IFS on the 6.7. See Brad's comment...We/He(Brad) tried like crazy to duplicate my weird no crank/no start that I had on that 6.7L. We never posted anything because I didn't do enough testing when I had the truck in my shop....That and the fact I am still trying to convince myself that I was not crazy Quote Link to comment Share on other sites More sharing options...
BrunoWilimek Posted September 29, 2014 Share Posted September 29, 2014 Sidebar- Interrupting the FP circuit on a HEUI engine does not always cause a no start. I know of several times where they still run, including an unhappy shop owner who installed a kill switch in a 6.0 to find it did not kill........And ironically the engine can sometimes run surprisingly well with the fuel pump not running. I think it was a 7.3L I discovered this on. I agree. I did fuel filters on a 6.0 once and it quit on me after a very short road test. The fuel pump was bad and opening the system caused a break in the suction that was drawing fuel from the tank with an inoperative pump. This was confirmed to me from an instructor at one of the Ford diesel courses and we were told not to rely on the inertia switch to kill the engine in the event of a rollover. Regardless, the customer's truck would run all day, it just would not restart after shutting down hot until it had cooled off for 20 minutes to half an hour. This topic made it simple to find the cause and make for a happy customer. Thanks DTS. Quote Link to comment Share on other sites More sharing options...
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