Cranks fine, won't start, second time in two months
 

So my truck ('03 FX4 Lariat SuperCrew with the Triton V8) has never had an issue other than battery. Owned since new, about 80k miles. Was a daily driver for the first few years, then an airport car, then just, well, the truck for when needed...

It pulled a large vehicle trailer out to Houston, and added a '69 '442 for the trip back. I had the transmission and coolant systems flushed and filled beforehand, they had no issue. Air still blows cold.

Anyhow, a few weeks ago, it wouldn't start. Turns over just fine, almost like it had no spark or fuel. Then a few days later, it was fine, and I've driven it several times since, including today where I made many stops - some an hour or so long - along the way.

Something I think is relevant - when she's warm and I start her, she fires up almost immediately, literally in half a second or so, sometimes less - so there's no underlying issue like fouled plugs, for example. Always has, still does, even today.

Stopped at a yard sale literally around the corner from home, popped in for 2 minutes - just junk - and she wouldn't start. Same issue - turns over just fine but won't fire.

I prodded around in the engine compartment looking at wiring for the coils and injectors - but an issue with a single cylinder wouldn't prevent starting.

After a while, I tried over and over, waiting a few seconds between, for about 5 minutes. Still cranked strong. A few times, however, she caught, but only for a second, and died. It happened enough that when I heard it, a couple of times I kept the starter going for a few seconds, but she would not pick up and it died again as soon as I released the key.

I am going to search here for similar symptoms. I probably need to get a service manual, but wondering if anyone has any thoughts or suggestions?

I am thinking it's probably a fuel issue - pump, perhaps. A single injector wouldn't cause this. It has coil-on-plug (as you know) so I feel it's very unlikely to be ignition. I have experienced coil failure on 4-cylinder motorcycles, and they still run on the remaining 3 cylinders.

By the way - I take care of my stuff. This was taken a few weeks ago, after a minor body repair thanks to the AAA service location I had the fluid work done, and the idiot that drove it into a pole pulling out of the parking space I had backed into for their convenience. Fluid services were gratis, btw! :D

Check the fuel pressure. It's easy to check at the schrader valve on the fuel rail.

Thank you. I assume I can't use a standard pressure gauge to do that?

I do all my own motorcycle maintenance (down to valve checks) and I have an EE degree, so I'm not afraid of diving in.

Not bragging - the reason I'm saying that is I know the value of a service manual - I have them for my bikes and I guess it's time to get one for the truck. I've just never needed one as it's been totally reliable! ..it's also the first thing one of us says when a new member shows up asking about a particular problem! :D

Parts stores generally have fuel pressure gauges with proper adapters in their loaner tools. When you turn the key on, the pump should prime the rail to at least 28 psi.

When was the last time you changed the fuel filter?

Try this - when it doesn't start, depress the go pedal slightly - does it start? If so, the IAC has issues. If not, press the pedal to the floor. If it starts, it was flooded and you probably have leaky injectors.

If you can't hear the fuel pump run for a couple seconds to prime it and have no or low fuel pressure, turn the key off and back on several times. You can also try banging on the tank with your fist or a rubber mallet.

Never have, but I would think a clogged filter wouldn't have allowed usual performance since the last time this happened. After that happened, I was intentionally a little rough on her, full-throttle acceleration on hills, etc. Nothing unusual. I don't mind changing it out, however.

I tired partial and full pedal several times, didn't seem to make any difference.

Thanks again!

Ha! Well, I went out to pick up some wings for dinner, and stopped by the truck - started immediately. So I drove it home, and walked the half-mile back to my car.

So I guess now I need to wait until she lets me down again to check the fuel pressure. Or perhaps measure it anyway, and see if it's lower than it should be, even while running..

Fuel filter should be changed every 30K.

Borrowed a pressure indicator from AutoZone. Picked up a fuel filter at the same time.

30psi, but *only* after starting (first time after relieving pressure). I'm not confident that the adapter for the valve is working as it should. I didn't do a formal leak-down test, but in a minute or so after turning off the engine, the needle didn't seem to budge. I did a different test - pulled the fuel pump fuse while running - it dies very quickly, and the pressure drops almost instantly. None of that is surprising.

I'll check the connections, and change the filter before I try again.

I pulled the pump relay and took it apart. Contacts are SEVERELY pitted. Working on pics but the "NC" side of the connection is convex, the working "NO" side is pretty much flat at the edges, but the pits are effectively concave and there's enough roughness that I could easily see how the relay would be the issue. I put the trailer battery charge relay in its place (same relay) which I assume is in good shape as it's working fine and I've rarely pulled a trailer with a battery so no frequent load on that.

Hoping the relay swap and a new filter will solve it for good. I'll report back after further testing...

You may need to remove the valve core before the pressure gauge will work correctly.

Relay contacts:

Looks like you found the problem. Congratulations!

No such luck... After a couple of weeks away, with the "spare" relay in place, won't start.

Guess I'm going to drop the tank, or raise the bed.

Question on replacing pump - would you recommend changing the whole assembly, or just the pump?

I've seen no information to help choose between one or the other.

I guess pulling it and inspecting might help, but not sure what I'd look for..