1991 F250 351 - Won't Start
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1991 F250 351 - Won't Start
1991 F250 351, manual, 165k
The truck has been running well but wouldn't start a couple of mornings back. It had sat for 1-2 days max. I have battery and it is turning over. The starter had been a little weak at times in the last few months and have one on hand that I haven't installed yet. I can hear the fuel pump whirring when I turn the key. I checked the fuel pump inertia switch and it is fine. I did a cursory inspection of wires but didn't find any obvious problems. Since it was running just the day before I assume I have spark. And yes, I have fuel - 1/4+ in front and 3/4 in rear. Replaced fuel pumps and sending units 4-5 months back.
Any advice on where to go from here for troubleshooting would be appreciated!
The truck has been running well but wouldn't start a couple of mornings back. It had sat for 1-2 days max. I have battery and it is turning over. The starter had been a little weak at times in the last few months and have one on hand that I haven't installed yet. I can hear the fuel pump whirring when I turn the key. I checked the fuel pump inertia switch and it is fine. I did a cursory inspection of wires but didn't find any obvious problems. Since it was running just the day before I assume I have spark. And yes, I have fuel - 1/4+ in front and 3/4 in rear. Replaced fuel pumps and sending units 4-5 months back.
Any advice on where to go from here for troubleshooting would be appreciated!
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Does the pump run for 1-2 seconds then shut off?
Or does it stay running with the key in the Run position?
A few days ago the truck was running, now it isn't. Never assume. Validate you have spark.
Or does it stay running with the key in the Run position?
A few days ago the truck was running, now it isn't. Never assume. Validate you have spark.
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rla2005-
The fuel pump runs a couple of seconds and then stops. I haven't had time to validate spark yet but appreciate the caution on assuming. If I was working percentages of likilihood, I'd think it reasonable to have spark since it did 24 hours previously but agree it is a good troubleshooting step.
The fuel pump runs a couple of seconds and then stops. I haven't had time to validate spark yet but appreciate the caution on assuming. If I was working percentages of likilihood, I'd think it reasonable to have spark since it did 24 hours previously but agree it is a good troubleshooting step.
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Good suggestion on starting fluid as well - I've had a long work week and only had a few minutes this morning to tinker. I installed the new starter. Sounds fantastic (as they all do when new) but no luck in starting.
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Battery was in the truck when I bought it just a little over a year ago. I double checked today and no one bothered to do the date stamp. It is turning over quite nicely, but no ignition happening. I suppose after checking for spark it will be down to fuel...maybe clogged or bad injector?
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Cargo Master
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If you find you have no spark, most likely the ignition module on the side of the distributor has gone dead.
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Mountain Pass
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Did you check the battery with an actual battery load tester?
It might seem to be turning over ok but if the computer doesn't like a low volts/amps situation it may cause a problem.
I don't yet know as a fact that Ford truck PCMs get flaky in this situation but I do know that other types of FI and Ignition systems get tempermental when the power supply isn't what it wants.
TG
It might seem to be turning over ok but if the computer doesn't like a low volts/amps situation it may cause a problem.
I don't yet know as a fact that Ford truck PCMs get flaky in this situation but I do know that other types of FI and Ignition systems get tempermental when the power supply isn't what it wants.
TG
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Quick update: finally was able to get a few minutes in daylight yesterday and indeed there is no spark - at least in the number one cylinder. The pulled the plug and it looks a little tired too. On to testing the ignition coil and ICM next. I'll go ahead and replace plugs and wires while I'm in there. Hope to do that this Saturday...
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Solved Faulty ICM
Hey thanks everyone. (I did pull SPOUT too). I traced it to faulty ICM. I’d ordered the part in case so was stoked to get it together. Replaced plugs, wires, and adjusted timing. Sounding sweet now!
Grateful for the help!
Btw, I also ordered the ICM tool as recommended on other threads here. Not sure how I would have done without it. Recommend this $5 tool if you’re needing to pull one.
Grateful for the help!
Btw, I also ordered the ICM tool as recommended on other threads here. Not sure how I would have done without it. Recommend this $5 tool if you’re needing to pull one.
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