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F150 Intermittent starting issue

We recently purchased a really nice used 2005 F150 for DH new work truck. Truck has 140k on it drives beautifully- when it starts! Less than a week after we bought it he was leaving work it wouldn’t start. It cranks and cranks but won’t turn over. We had it towed and the next morning the shop called that it started right up asked what they were looking for. We brought it home 3 days later it didn’t start again. Hubs brother came over to look it over with him to see if they could get an idea why it wasn’t starting before towing back to the shop. Walked out and it started right up after not starting for 2 solid days. He drove it for about a week and it went dead again. Same thing every time it just cranks and doesn’t turn over. Had it towed and magically again started after being towed again. Back home within a couple days not starting. Had the guy run out and throw the computer on it to read it while it was down he said it had a pats error showing and everyone was sure that was the problem. Truck started again we drove it in and made new keys figured that was the end of it. 3 days later no start. Contacted dealership they stated it wasn’t a key problem we should just start replacing the computer and ECM until we found the problem. That just sounded a bit extreme so we took the keys and went to a different dealership explained the entire situation and they agreed. We towed it to them and of course truck was starting. They kept it for 2 weeks starting it every day because at this point we hadn’t had it for longer than a week without a starting issue at home we all figured eventually it would choke up there. Nope. So after 2 weeks we brought it home and 2 days later it was dead again. Called dealership. They told us that the pats must have been an old code because a vehicle locked out with a pats error doesn’t continue to start it requires a reprogramming which our truck did not. They felt it was in the fuel system somewhere and asked to verify if the fuel pump kicks on when the key is turned- it does. They said that since the truck had been purchased from another area of the country sometimes the fuel grades are different?? Recommended running sea foam through it to clean out any gunk before coming back to them. So the next time we got it started that’s what we did he put gas in it and drove it about 50 miles then shut it off to run an errand not thinking came back out and dead. I don’t know if it would have made a difference to have ran the entire bit of gas mix through it or not but that was the intended plan.
So here we are. It’s been roughly 2 months since purchase and we’ve spent more time arguing about it than it’s worth. Seems like a stupid simple issue to get past? But we’re 2 shops in with nether giving any resolve. Any one else have this issue or can give some insight on how to diagnose at home? 4 times towed 4 times started immediately after it arrives at destination doesn’t lend to wanting to tow it for repairs again. If we can give them something to work with even, just really frustrated and not sure what to do w it. Any advice helps, thanks!

With a live data scan tool and some time studying the instructions you might find the problem yourself. But then there are several possible causes that won’t show up on live data. The problem you are facing is that shops cannot afford to assign a man to diagnose such a problem and you could possibly buy a new truck for the cost of such a diagnosis process.

FWIW I have taken on such problems and installed all manner of test equipment on vehicles and then driven it like it was mine until the problem occurred and when it did I could find what was not functioning and call a wrecker to haul me to the shop and fix it. But that method was costly up front, several hundred dollars before an estimate of repairs could be made, and most people declined. Some actually thought that I should pay them rent for the privilege of driving their vehicle.

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I wonder if this might be an exception to the shotgun rule and throw a new crank sensor in to see if it works.

It needs to be diagnosed in failure mode. Sounds a lot like a failing fuel pump to me.

Along with the fuel pump and crank sensor the fuel pump relay, ECU relay, ignition relay, and ECM come to mind as problems that I have run across in that situation. A live data scanner is a great deal of help and the price isn’t prohibitive but it takes some studying to make sense of the data and the OP could spend a lot on wrecker bills before they solved the problem.

I’m not sure what “DH” means. If that’s a diesel engine truck then the problem is most likely no fuel. Fuel pump(s) or diesel injection pump are the likely culprits. If gasoline engine then the first thing to figure out is whether the problem is no fuel or no spark. If a gasoline engine, either get it to the shop when this problem is occurring or ask your shop to show you how to test for no spark yourself, next time it happens. A faulty crank position sensor is always a possibility for this sort of problem.