I have a ford f250 reg cab 4x4 with a 5.4 engine that all the tec's here cant figure out . OK the truck runs for a while but dies after 20 to 30 seconds drains the battery you can jump it and strart but dies after the jumper cables off. OK so i replaced and had two alternaters tested and came back good replaced the battery and still does it However if you replace the battery it will run about a day before it dies. had the volts tested when running and the volts all are right. any idea ????

 

My first step would be to check and determine where the drain is that is causing the battery to go dead,,,,,,,,if that's what is happening. When you disconnect the battery do you get any type of arc then again if its dead you won't get much of anything. Do you get any arc/spark when you try to connect the charged battery? Just speculating at this time, but if the drain/short is big enough the ECM and injectors can't function with insufficient voltage. It will take us a little while , but we will find the problem, we just need to follow a certain sequence to isolate the problem. OK ? ,,,,,hanky

 

ok i will charge a battery and see if i can get a arc off of the charged battery. thanks i will let you know

 

replaced battery and there was no arc and the volt meter does not show anything pullin on the battery i took the hood lite out to make sure ?

 

Since you have no evidence of a large drain at the time you connect the charged battery , this is what I would do next. The fuse panel inside the vehicle, there are rows of fuses,one row is hot all the time with the ign off. Another row is hot with the ign on. With everything connected verify the voltage reading to the row of fuses in the block that are always hot( 12 volts) . If you get a 12 volt reading, good , leave the voltmeter connected there. Now remove some of the fuses that are hot with the ign turned on. (Remember which rating goes where) Now turn the ign on and see if the volt reading drops considerably. If there is no change , start replacing the fuses one at a time and watch the voltmeter You are going to get some lower readings, but we're looking for a big drop.
Just to give you an idea what we are looking for, sometimes the wiper motor will stick when it is supposed to park the wipers and shut off, another could be something like a relay that doesn't return to open when it is supposed to. It's a pain to go through all these checks , but they need to be eliminated so you can concentrate on the real problem. Let me know if you find anything and we can go from there.

 

k it will take me a few days but i will get back to you thanks for the help

 

i checked all the fuses and didn't find anything jump up or down on the volts with the rows in the off or on position ? should i do this agin to make 100% sure i didnt miss anything or you got another idea? thanks hanky
c718a32c-091c-4475-8678-b8b56a982738
1.03.01

 

Mark, just a quick question.
How were the alternators checked?
If you can , what kind of output are you getting from the alternator? It can be charging a few amps and the lite will go out and the voltmeter will read 12+volts with no load.
Do you have access to a clamp on meter that can tell you how much amps the alternator is actually putting out. You have to load the system (headlites + blower), in order to get any worthwile reading.
The alternator may be OK on a test bench ,but if the vehicle isn't telling the alternator to put out max or lots of amps, the battery can only sustain the vehicle until the battery goes dead or the vehicle doesn't have enough juice to keep running. I need to check to determine if your ECM controls your alt output.
Will wait for your reply. Thanks, ,,,,,,,,,,,hanky

 

the alternators were put on so tester at the napa shop. I dont know if thats a good test or half *** test.
c718a32c-091c-4475-8678-b8b56a982738
1.03.01

 

c718a32c-091c-4475-8678-b8b56a982738
1.03.01