Rough Cold Start (v10)

[MadScience]

Ever since I had most of the AC replaced, the van has been starting really rough on initial cold starts. Subsequent re-starts throughout the day are fine. I don't suspect the AC work is related, but the correlation is high.

I checked the fuel pressure at the test port on the rail, and I see 10 PSI if I just turn the pump on without cranking. Once it's running I see a much more healthy 30 PSI. My fuel pump is of unknown age, and of course highly suspect.

I was going to change the fuel filter and re-test before dropping the tank to change the pump. Anything else I should check or try?

I suspect I won't DIY dropping the tank as I'm nursing a broken leg at the moment.

Any recommendations for a pump? -- My default choice here is an OEM spec bosch, certainly cheap enough, but I'd be willing to pay more for something marginally more reliable.

[MadScience]

Swapping the fuel filter appears to have been worthwhile. (And super easy with the tool.) I still only see 10 PSI before startup, but it doesn't drop before it comes up during startup.

After letting it sit overnight, it fired right up with almost no stumble.

I still feel like I want to see more than 10 PSI initially though. While I didn't crack open the old filter, I wonder if it's filled with parts of my fuel pump impeller. I'll probably end up swapping the pump as well soon.

Old filter had 15k miles on it, which seems low, but then I do fill this van up in the sticks and drive it on dusty roads all the time.

Oddly Amazon does not seem to think at the motorcraft FG872 is the right filter for this van, and only shows generic ones as a fit. Fordparts.com only shows it specific to "gas" or the v8s, but doesn't list one specifically for the v10.

[carringb]

Fuel pressure is way too low. Should be 35 when it cycles.

[MadScience]

Thanks Carringb! I mostly figured as much. Mine doesn't even get much over 32 when running.

Anything else worth checking before dropping the tank?

Edit: Will poke at the fuel pressure regulator tomorrow, but the pressure's I'm seeing sound more like a bad pump or clogged screen. Putting together a parts list for dropping the tank...

[MadScience]

Since it's just two nuts and a couple of things to unhook, I tackled this today.

Dropped the tank, and swapped the pump, the sock filter, that little duck-bill valve, all the hoses and the seal. Now I have 38 PSI when it cycles. Still need to let it sit overnight for the real proof.

Stuff I wish I had known that might be useful to someone:

With the battery unhooked, you can power the pump from the contacts on the cutoff safety switch. With a hose connected to the fuel filter output, this is handy for pumping the remaining fuel into jerry cans to reduce the weight of the tank.

When empty the tank really isn't that heavy, a jack was nice to have, and I'd prefer not to do it without one, but jack stands are overkill.

To unhook the remaining stuff on top the the tank, the tank can be dropped almost two feet down. Plenty of room once I realized that.

O'Reilly had the larger diameter fuel filler hose in stock.

Dust from every desert and mountain trail you've ever been on will rain down on you. Wear eye protection. I did and still ended up washing my eyes out twice.

[Jsweezy]

Good stuff to know, thanks!

So is it good now?

[MadScience]

Yup, fired right up today.

Even got the evap self test to pass today, which means I didn't pinch any of the breather hoses.

It also feels like it's running a bit more smoothly under load. There might have been an occasional miss with the old pump, that's distinctly not there anymore.

Glad the pump went out this way, rather than a sudden complete failure with no warning.

[Jsweezy]

Sweet congrats!