Intermittent stalling
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Intermittent stalling
'97 F350, 4x4, cc, 351, E4OD. I need help with this one guys. Truck stalled 4 days ago coming out of an intersection. Engine was at normal operating temp. Engine cranks but doesn't start. I do a couple of things-switch tanks,etc., nothing helps. After about 5 mins. truck starts up, and everything seems normal. Get home, pull codes-all clear.
2 days ago, truck stalls as I'm leaving work for home. Engine cranks, so now I start checking-got spark, switched tanks, I can hear fuel pump running. This time it won't start again, this is good, tow it home. Check fuel pressure-40#, got spark at coil and at plug. After numerous bouts of cranking engine (while checking spark, fuel press., etc.) I floor the accelerator and crank motor and it starts. Now it seems that engine runs a little rough, and during start up seems to "hic-cup" before turning over.
So now it's running again, but I can tell it's not running normal with the rough idle and funny starting. Can anyone point me in the right direction? Thank you much in advance.
2 days ago, truck stalls as I'm leaving work for home. Engine cranks, so now I start checking-got spark, switched tanks, I can hear fuel pump running. This time it won't start again, this is good, tow it home. Check fuel pressure-40#, got spark at coil and at plug. After numerous bouts of cranking engine (while checking spark, fuel press., etc.) I floor the accelerator and crank motor and it starts. Now it seems that engine runs a little rough, and during start up seems to "hic-cup" before turning over.
So now it's running again, but I can tell it's not running normal with the rough idle and funny starting. Can anyone point me in the right direction? Thank you much in advance.
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From: Saint John, New Brunswick
Since you mentioned the fact that the truck started when you had the pedal to the floor I would suggest looking into the throttle position sensor, there may be a "bad" spot on the potentiometer inside the sensor where the signal cannot be established in which case it just isnt going to fire.
However you did say that you have spark when you rolled it over while the pedal was not pressed. This makes me think that the coil may be shorting occasionally. Check the primary side( across the connector pins) and secondary side resistance. The important thing to remember with this test is that if the values you find are high but within the manuals acceptable range the coil still has a tendency to break down when it gets warm.
With the ignition aside the fuel filter may be starting to get plugged. Despite the 40 psi with the pump running there may not be sufficient flow. Check the filter out and also run a good fuel injector cleaner through the system. Hope this helps,
However you did say that you have spark when you rolled it over while the pedal was not pressed. This makes me think that the coil may be shorting occasionally. Check the primary side( across the connector pins) and secondary side resistance. The important thing to remember with this test is that if the values you find are high but within the manuals acceptable range the coil still has a tendency to break down when it gets warm.
With the ignition aside the fuel filter may be starting to get plugged. Despite the 40 psi with the pump running there may not be sufficient flow. Check the filter out and also run a good fuel injector cleaner through the system. Hope this helps,
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Thanks for the information Motoshrump. I replaced filter 6K miles ago, ran cleaner through about 3K ago. Both times that the truck stalled, one was running temp., the other was cold, but will check coil to be sure.
If TPS was a problem, wouldn't it pull a code? I will pull sensor and run check when I get home from work today, thanks again Motoshrump, aloha.
If TPS was a problem, wouldn't it pull a code? I will pull sensor and run check when I get home from work today, thanks again Motoshrump, aloha.
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If the fuel pump runs while the engine is stopped, the computer is suspect. If the computer is not running, you will have spark but no fuel at the injectors. Flooring the accellerator may be enabling "limp home" mode to work well enough to start the engine.
Alternatively, a leaking fuel pressure regulator or dripping injector may be flooding the engine. Flooring the accellerator admits enough air and/or puts the computer into "clear flood mode". This allows the engine to start. The engine runs OK (albeit roughly) at idle when the idle vacuum reduces fuel pressure and the computer may be compensating for the leak through feedback from the oxygen sensor. Check how fast the pressure bleeds down when you cycle the key from off to on to off.
Is this a 1997 or a 1987 truck?
Alternatively, a leaking fuel pressure regulator or dripping injector may be flooding the engine. Flooring the accellerator admits enough air and/or puts the computer into "clear flood mode". This allows the engine to start. The engine runs OK (albeit roughly) at idle when the idle vacuum reduces fuel pressure and the computer may be compensating for the leak through feedback from the oxygen sensor. Check how fast the pressure bleeds down when you cycle the key from off to on to off.
Is this a 1997 or a 1987 truck?
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Hey fefarms thanks for the reply. Sorry, let me correct some of above information. Fuel pump runs when KOEO, pump shuts off after approx. 5-7 secs. I will check fuel pressure bleed down and get back to you. Truck is a 1997 w/59K miles, thanks much, aloha.
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OK got an update. Got a diagnostic tool and found truck to be running in open loop, then closed, back to open again. Checked ECT on tool and found temp. fluctuating between 35-90 degrees c. Changed engine coolant sensor and problem seems to be gone. I just changed that sensor about 1 month ago (NAPA). Goes back to the old saying "what was the last thing you touched?" I hope that takes care of it, thanks for all your help.
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