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Truck stalls..loses spark

 
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Old 04-10-2016, 07:45 AM
mwilliams0326
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Truck stalls..loses spark

I have a 1988 F350 7.5l 460 that fires up great when cold. It will stall typically within a couple of minutes and if I try to restart immediately I have no spark. If I turn the key off, it will restart with no problem but will stall again at some point. I'll refrain from listing everything I've replaced as I know new parts can be bad. Interested in hearing what you all think!
 
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Old 04-10-2016, 07:54 AM
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Why make everyone guess?

Give us the laundry list...
 
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Old 04-10-2016, 12:42 PM
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Ok so far I have verified I have 12v and ground to the TFI module after it stalls. However I have no switching signal...unless I turn the key off and reset..then I get a switching signal from the TFI. I have no signal at all from the PIP (using an LED tool for both of these tests). When I pierce the top wire of the TFI connector, which I show is the PIP signal, I get nothing at all when trying to crank the engine on the LED. I also don't see anything when I reset but It is probably too fast to detect? So that would make me think the PIP sensor is bad.

I have replaced the entire ignition system, TFI module, PIP sensor, dist cap, button, wires, ignition switch and key lock, coil, battery, fuel pump and eec relays and pigtails and the EEC itself and checked all the grounds, vacuum lines and wiring. I have also replaced almost all EFI sensors, O2, ECT, TPS,IAC valve etc. We are restoring the entire truck. All fuel pumps are new as is filter and fuel pressure regulator. Fuel pressure is correct during all phases and doesn't drop. The cat is gone as is the air pump and EGR is blocked off.

My have gotten most everything from Motorcraft,,,except the PIP sensor. So its new but its from AZ. The truck runs great when cold but after a couple of minutes starts to stall and will always re fire if the key is turned off. Hope I remembered everything. I appreciate anyone with advice for me!
 
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Old 04-10-2016, 02:53 PM
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The coil switching signal should be the same frequency as the PIP signal. The PIP wheel has 8 teeth that correspond to the 8 cylinders of the engine. Each tooth tells the TFI when to fire the coil.

The classic failure mode for a bad PIP module or TFI module is erratic behavior when it gets hot, then working briefly again when it cools back down.
 
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Old 04-10-2016, 03:43 PM
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When you have no spark pull the SPOUT shorting bar jumper out and see if spark returns.
 
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Old 04-10-2016, 07:52 PM
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I ran test again after it stalled before resetting and pulled the SPOUT and still no spark unless I turn it off and back on. I did notice since it was dark outside this time I do have a VERY tiny amount of a spark after it stalled this time but once I turned the key off and back on it had a very strong spark on the tester. I didn't see any spark before but there is a clear difference after it stalls how much spark I get (barely there) and it returns to normal and fires right up after I turn the key off to recrank. Even when its hot it will restart but stalls pretty quickly. I have already put one new stator in this distributor but we had to beat the hell out of it to get it out as it was seized in the block. Should I just look for a new distributor or get a Motorcraft stator instead of one from AZ? Thanks to everyone! I think I am close to getting her back on the road!
 
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Old 04-13-2016, 04:52 PM
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She lives!!!! I had to think that since I had a brand new stator in the distributor and a brand new Motorcraft TFI that the distributor itself must be having issues so I ordered a brand spanking new distributor and new TFI and no more stalling! I almost panicked because she ran really rough for a bit but I guess thats the PCM relearning everything. I know I probably need some new plugs to smooth everything out but boy am I stoked! I had read another thread that SubFord had suggested a new distributor because it might be losing ground to another poster having similar issues so I went that route and Voila! You guys are all AWESOME!!! Thank you so much for your help!!!!
 
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Old 04-13-2016, 05:00 PM
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New does not necessarily mean a good part. Glad you found it.
 
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Old 04-13-2016, 06:08 PM
Kyle Campbell
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Yeah my truck is doing the same exact thing. . So it is the pip sensor.in the distributor huh?
Maybe I'll just replace the whole thing too
 
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Old 04-13-2016, 06:14 PM
Kyle Campbell
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Was your truck coming up with a code 14 or code 18
 
 
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