Twice now my 2002 7.3 F-250 has been possessed by something that appears to be a short to ground. In both cases, after starting the truck without waiting for the GlowPlug timeout, driving about a mile and after shutting down, the starter solenoid won't engage and crank the engine just a few minutes later.

In the most recent instance, codes P0362, P0381 were tripped as well as System Low Voltage. After the first re-start attempt of maybe 5 seconds, I put a volt meter on both batteries. They were both about 11.5V. When this happened a week ago, after finally getting it jumped/re-started and charged overnight on a charger, it started again just fine with the Alternator putting out 12.64 and the batteries were at 12.4ish. For the last week, the voltage has been steady at 12.4V and it ran fine for a week.

This time (today), as the batteries were recharging from a jump, I was poking around with the Volt Meter --- checking all the terminals on the the two relays near the fuel filter (Starter and Glow Plug, I think). While I was going back and forth checking the terminals, there was a discrete moment in time when the voltage on the aft relay changed (the glow plug relay I think since it had more "hot" terminals on it). Noticing this, I jumped in the truck and it basically cranked right over (other than the batteries having been drawn down a little bit).

Is the relay bad or is something commanding the relay to do something it shouldn't (like dumping all my amps into something other than the starter). Kinda need the glow plugs to start the engine and I thought they energized when you engage starter, but it seems like its just sucking all the juice.

Seems like it will be hard for a mechanic to diagnose if its not actually happening and I don't want to end up just throwing parts at this (I was ready to buy a starter or new cables...but they all seem fine and so are the connections...clean and un-corroded).

Thanks to anyone that can help.

 

I should add, that after 1st instance, ABS light was on and persisted for about 2 days, then went out. And during this time, the "N.C" on the trailer brake controller flashed for about 5 seconds which it doesn't normally do. This time, to eliminate ABS or trailer shorts (which seem to have big fuses), I pulled both fuses for ABS and the trailer brake fuse to no effect.

So, I thought it might be ABS or Brake power draw, but I think it just suffered from the voltage freaking out.

 

And, in addition, after the CamShaftPositionSensor frustration of years ago, I ended up with an aftermarket fuel filter, the casing of which failed and sprayed both of those relays for a couple hundred miles before I figure out what was causing the smoke/leak. So, the relays may have suffered from the soaking in Diesel fuel.

 

Your alternator output is low. It should be at ~14.5 volts. The glow plugs energize when you turn the ignition to ON, and stay on for up to 2 minutes, depending on temperatures. What you saw with the voltmeter was probably the relay de-energizing the glow plugs. I'd have the alternator tested.

 

sounds like you need to get your batteries & alternator tested,them voltages are pretty low.you should see closer to 14 volts after glow plugs time out and engine runs for a few minutes.batteries should read 12.5 - 12.9 after resting over nite from full charge.

 

All measured at battery, at idle , ~12.6V, but 13.6V @2,500 rpm (or wherever my gracious wife actually had it at). I don't think that's the problem...or it wouldn't be intermittent.

 

13.6 is still too low.

 

I guess it could be intermittent if the 'abusive' start overtaxes the lightly charged batteries which then aren't recharged after the mile drive. Will look at belt and maybe upgrade the alternator. Might just need more juice, but I am still a bit perplexed by how this manifests with voltage fluctuations evident in the gauges and even dash lights as it powers up before cranking...must be messing up the computer as well. However, when present, it won't even direct jump start with another F-250 connected. Maybe its the alternator plus something.

 

Look at the voltage from your cigarette lighter while the engine is off and while running, not the batteries. Loose battery cables will change the voltage everywhere on the truck, and not fully charge the batteries.

 

My guess is one or both batteries failed. These trucks NEED two good batteries. I'm on my third set in less than two years. NAPA has a good warranty so it didn't cost me anything. Your truck will act all kinds of messed up with low voltage.

 

If you end up shopping for batteries, I see you're in WA... Costco - big time. Wet or dry side?

 

So, maybe not the safest thing, but I've been checking voltage in the cigarette lighter. It gets to about 14.00 at normal speeds and 1500-1800 RPM. Maybe that $339 alternator will help, but I think something else is going on too. I'll check all the voltage drops on the relay and see if maybe its sticking "on" tomorrow. I wish somebody had an explanation for the intermittent nature of this. Truck runs fine for a week or two and then goes gunny sack for half a day, then fine for a couple days/weeks.

 

That's a bit low... you could have a bad alternator, your batteries might be weak, or you have a heavy draw somewhere (like a stuck Glow Plug Relay).

Did you verify both ends of all your battery cables are clean and secure?

 

In these trucks, things get 'weird' when battery power gets low.

 

Your alternator could be developing an internal short. This just happened to me with the original alternator. Driving to work, headlights and dashlights started to dim, ABS light came on, followed by all other dash warning lights and engine died. Attempted to jump it, but when the last jumper cable was attached it arc'd due to the internal short. Replaced alternator with OEM, charged batteries and now all is well. Voltage rest is 12.6, GRP on 10.9, engine running 14.0. Bought a battery monitor that plugs into lighter at Walmart.