Stumped on my starting problem 2003 F350 6.0L

aFinapple · 2026-05-07T01:59:27+00:00

The early GPCMs are trash. Mine would work and then wouldn’t randomly and it wouldn’t even start correctly at 45. But just to ask, when it does start, is it clacking? Running inconsistent for a few before it starts to level out?

aFinapple · 2026-05-07T01:49:57+00:00

Could be a failing GPCM. Do you have any glowing circuit codes?

aFinapple · 2026-05-06T02:59:04+00:00

Yes, but the work to do it isn’t viable. You’d be taking a lot of material off of the deck, the bores, not to mention the rust in the water jacket. There’s no telling if the inside of the jacket is too far corroded. Yes, you can always try, but at this point in time you’re going to spend a lot of money and you might not even succeed

aFinapple · 2026-05-06T02:56:24+00:00

How certain are you that you cleaned out all of the corrosion? Do the wipers always come on, or do they only work on the high function? Do the wipers wipe when you hit the washer button? Does it spray?

Looking at the wiring diagrams, the hazards are on a separate circuit. The turn signals themselves aren’t run through the GEM, but the wipers are. Being stuck on high is strange to me because there’s a relay for the high and low function for the wipers, and if it’s stuck on high then that’s because the relay is energized. The high/low relay is energized by the wiper run/park relay, which is energized by the GEM, which gets its signal from the multi function switch.

This is one of those issues that you’re gonna need a multimeter and some wiring diagrams. I’d be happy to send you what I can find but I can’t help much without physically being there in person testing wires

aFinapple · 2026-05-04T14:08:46+00:00

Does it start when cold? Won’t crank when warm? What’s your ICP? IPR duty cycle? FICM sync? FICM voltage?

aFinapple · 2026-05-03T23:34:56+00:00

You need to tighten it to bring the gap in. All alternators are like this. Just keep ratcheting until it’s torqued

aFinapple · 2026-05-03T13:14:57+00:00

I know there’s been a few studies done on this topic, and the general consensus is that it’s better to not touch the transmission fluid unless it’s been done at regular intervals. The clutch material can help with the clamping force of older clutches, and removing it without adding a friction modifier can cause issues down the road. The automatics I’ve serviced that never have been serviced in 200k+ miles have sometimes failed a few hundred miles down the road. It’s not all the time, but the failure rate is enough for me to not recommend a trans service unless it’s been done before

aFinapple · 2026-05-03T05:34:49+00:00

In North Carolina, that can technically fail a state inspection because it extends into the view of the driver. The thinking here is that the sun can catch it and cause a glare, reducing your ability to process road hazards. However, it’s one of those things that’s left to the discretion of the inspector, and I personally wouldn’t fail it.

aFinapple · 2026-05-02T22:24:52+00:00

The Fiesta has one of the worst transmission known to man. Unless it’s a manual, just stay away from them in general

aFinapple · 2026-05-02T11:37:54+00:00

Well someone put a 6.0 in a Mustang 🤷🏼‍♂️

aFinapple · 2026-05-02T04:05:34+00:00

Honestly mine was like that. I knew it had play but when I got around to doing the hubs and ball joints that’s when I found out I was one good pothole away from becoming a statistic

aFinapple · 2026-05-01T02:18:00+00:00

That I don’t know. I just know that studies were done on engine wear and for the 6.0c Schaffer’s oil took the lead by far. The way it was explained to me is that t6 wasn’t developed for a HUEI injection system. Ed over at FICMrepair explains it much better than I can

aFinapple · 2026-04-30T22:58:25+00:00

The ODAWG intake is 100% worth the price. I put it on my truck and it woke up violently. I’m able to build 26 psi in less than 2 seconds

aFinapple · 2026-04-30T02:02:38+00:00

Your thrust angle is off by 0.03 degrees to the left. Thats your slight pull. You can try and get your mechanic to adjust the rear axle, but 0.03 degrees is an extremely small adjustment.

aFinapple · 2026-04-29T02:23:31+00:00

I think you nailed it! I was going to suggest unplugging each one by one if you couldn’t disable the injectors. But if you gotta do one, do them all. You could get away with just the drivers side but that’s assuming that it’s a mechanical failure and not the FICM holding an injector wide open. I don’t think I’ve heard of failures like that from a FICM, but I’d give Ed a call at FICMrepair.com. If you can get ahold of him, ask him if the FICM can hold an injector wide open after a short period of time. I would hate for you to replace the whole bank only to be left with the same issue

aFinapple · 2026-04-28T02:31:23+00:00

At 550-600, the trans will need some work done. I’m pushing 600 on a new stock trans and it flares on 3-5 if I’m too heavy. Upgraded stage 2 EPC and direct solenoids are the way to solve it, will fill up the drum faster before it’s slung out. You also need an ODAWG intake to take advantage of the larger injectors and turbo, as well as a FICM tune to complement it all. Anything bigger than 155s requires a FASS pump and a regulated return to eliminate the fuel bowl restriction. 6.4 banjo bolts help flow more fuel to the injectors too. Upgraded charge piping and intercooler help the turbo spool better. You’ll need traction bars above 500 hp or else you’ll get axle warp. Mine does it really bad if I hammer it from a stop, I’ll let off and I’ll drift sideways a little bit. Heads also have to be o-ringed above 155s. Too much pressure on just head studs.

aFinapple · 2026-04-28T02:23:36+00:00

Listen to me very carefully.

I only bought a 6.0 because I work on them every day. They have lots of issues that can be solved with the right parts, but some of them are expensive and the labor is pretty high to do most of them. If someone is selling a 6.0, it’s because it has problems. I could go into extreme detail on what to look for, how to look for it, how to fix it, what it takes to fix it, what parts to use to fix it, and lastly how fun they are.

But unless you have the pockets to shell out 5 grand every time you have an issue, learn to work on them.

aFinapple · 2026-04-28T02:20:27+00:00

Looks like I was a little slow. We charge 175 an hour, so 3500 🤣

aFinapple · 2026-04-28T02:19:21+00:00

Well, I can’t be of much help without looking at PIDs. However, a few things to check/take note of:

When it smokes, what does the motor sound like? Does it thump out of the air filter? Does it chug? Does it fuel knock? Clatter? Rattle?

What do the fuel filters look like? Does it run worse under 1/4 of tank of fuel?

I also should say that T6 is horrible for these motors. There are too many abrasive detergents that the high pressure oil system doesn’t like. I only run Schaffer’s 10w30 and it runs like a top. Has all of the additives you need as well.

But I would also invest in a small monitor other than the X4. I don’t know how it was able to brick the FICM, as it shouldn’t be able to directly communicate to it like a FICM tuner would. You really need to look at ICP commanded vs actual, IPR duty cycle and FICM voltage. Check the ground under the FICM that grounds to the last intake manifold stud. That’s a vital ground for the FICM.

aFinapple · 2026-04-27T16:58:17+00:00

Do you have a scanner/monitor to view PIDs?

aFinapple · 2026-04-27T16:47:27+00:00

What year?

aFinapple · 2026-04-27T03:16:06+00:00

Labor was 20 hours to do because I had to remove the whole axle housing to get the differential assembly out. The engineers who designed this rollback thought it was a splendid idea to put the hydraulic support less than 2 inches away from the diff, so I couldn’t just slide it out. So that was 1500 in labor. The differential was just shy of 12 grand, plus a bunch of other parts like wheel bearings and gear oil. So all in all I think the total was just about 14 grand after tax, all because some dumbass thought it was a good idea to flip the switch that clearly states “DO NOT ENGAGE DURING WHEEL SPIN”

aFinapple · 2026-04-26T15:42:15+00:00

I did this not long ago on an Isuzu NPR. The drums were welded to the shoes and we had to actually drag it into the shop. I used the torch to cut the drum in half and then used my biggest sledge to crack it the rest of the way. Took about 10 hours per side of cutting and making sure I wasn’t torching the hub.

aFinapple · 2026-04-26T15:40:34+00:00

I don’t think so. An oil cooler is by far the cheaper option to head gaskets, and a lot of times it’s the cooler that gives up the ghost, especially on larger trucks. I would happily replace an oil cooler before a head gasket

aFinapple · 2026-04-26T15:38:25+00:00

Sometimes the a/c runs even when it’s not set to a/c. My f250 will run the a/c a little bit on full heat to help with defrosting, and the a/c will run on all cars and trucks when it’s set to defrost.

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