Wife drove her 2010 F150 5.4 home last night. Everything was fine. Now today it won't start. It cranks and turns over great, but won't start at all. Any guess on where to start looking?
Now the starter tries to hang up in the start position.

 

Looks like it was a weak battery. Plenty good enough to turn over the starter, but not enough voltage for the ignition.
I'm sure you all think I suck for starting a thread like this, but a lot of times it helps my old mind to type out my problem and even though I may not get any responses, I may start thinking down another path. And Yes, I always search before starting a thread.

 

 

Hey, just joined this forum and saw your crank but no start for your truck. Let me just pass along my experience. My truck died one day while driving and pulled off to the side of the road and wouldn't start. It would crank just fine. Called tow truck, driver said what's it doing. I showed him and he said, "You got fuel? Sounds like it's not getting fuel." Tank was half full. Towed to the Ford dealer and they kept it for 3 days. Told me that the truck started every time they tried. Couldn't repeat problem. Luckily they didn't charge me a dime caused they said they didn't fix it. That was surprising when they told me that there would be a $150.00 evaluation fee. But anyway...

OK, so for the next couple months this problem would randomly occur. Finally one night out of town I come out of hotel and truck won't start. So I cranked it for two hours thinking it was going to do as before and finally start. It didn't. Towed to Ford dealer. They found that the Fuel Pump Module Relay and wiring harness had corroded and shorted out. Apparently this is a common problem on this truck because of the construction of the FPM. The FPM is constructed of different alloy and it is bolted to a steel brace above the spare tire. This caused a galvanic corrosion issue that ultimately caused the short in the circuit board of the FPM. I was charged $1100 to put in $168 worth of parts.

I found on-line that I could get the FPM for less than $75 and I could have done the repair myself. All kinds of youtube videos that show how its done. Apparently Ford changed the alloy or has a spacer to keep the two different metals from contacting.

If you experience the problem again you might want to check this out.

 

That is a very common problem with those trucks when they see salt in the winter. I don't know why they put it under the truck by the spare tire, but that's where it is. You can usually just look at and tell if it is bad, or will fail soon enough. If there are no codes and you have spark but no fuel that is the first thing I would look at. If it isn't your problem I would still have it looked at , as it might save you from getting stranded or paying a lot to get it done in a time of need.

 

Thanks, I will look at the FPM and fuse 27 also.
So far it is OK. I swapped batteries again and it wouldn't start. Went back to other battery, starts fine. I will just have to watch it.

 

I did get a code when this happened. It was a P0690. P0690 is an OBD-II generic code for a high voltage problem with the power supply to the ECM/PCM. This means the vehicle’s computer is not receiving voltage that is within the manufacturer’s parameters. So there was nothing to pinpoint what the cause was.

A P0690 code can have a variety of causes, but the most common are:

• Faulty ECM/PCM relay
• Blown ECM/PCM fuse
• Bad ECM/PCM grounds
• Bad battery
• Faulty battery cables
• Faulty ECM/PCM

This is what I had to work with.

 

Well it happened again. Guess I better start looking.

 

Checked the fuel pump module plug and wiring. All clean and all looks new. No start.
Checked the ECM plugs and they were all clean and tight. No start.
Removed several relays and made sure they were all tight, clean, and seated. Started right up!
No idea which one is the culprit. Guess I will have to wait till it happens again and try one at a time.

Does anyone sell a set of Emergency assorted relays and fuses for these trucks? Sucks that there are so many different relays!

 

I don't know of an emergency set, but you could buy one of each to keep in the glove box. The chances of more than one relay failing at a time are pretty slim.

If cleaning the relay contacts really did solve the problem, it may have been what's called fretting corrosion. It happens over time as the contacts vibrate when the engine is running and it's solved just as you described it - simply removing a relay and plugging it back in seems to fix the problem. It's fixed because when you remove the relay the contacts scrape against each other and clean themselves, giving the contacts a new surface.

Have you noticed if the problem happens more often when the engine is hot or cold? You need to determine if it's fuel or spark that's getting cut off when the problem happens. Until then, you're just guessing.

 

No more problems yet.
As for the spare relays, I bought a complete used fuse/relay box with all of the relays, fuses, and circuit breakers still in it on the big auction site for $55 this week. Seemed like a bargain to me.

 

What many of us with motorcycles do b/c the connectors, relays, etc. are much more exposed to the elements: dielectric grease. It really works! Advance Auto, Auto Zone, etc. sell little packets of it just for this. Its a corrosion inhibitor and a sort-of sealant and a little dab goes a long way. Since I tend to use more than the little packets I buy 3 oz tubes of heavy duty synthetic stuff, a brand called Super Lube.

Picking nits here but I have found over the yrs that fretting is generally not the cause. Fretting is caused by rubbing and unless contacts tabs are "stretched" to the point of being a loose fit this won't happen. Galvanic corrosion happens when even slightly dissimilar metals are in contact in the presence of oxygen. The wiping action of unplugging/plugging back in removes this oxide layer. Dielectric grease helps keep the layer from forming again.

 

Not always true. Fretting can occur regardless of terminal tension, it's just more often a problem when connectors have been separated, particularly more than once. It's also one of the reasons why air bag connectors are usually gold plated. It's a problem that occurs over time, and there's so many factors that can influence whether or not it's going to occur.

I think that fretting is usually a contributing factor but not the source. A few months ago I was looking at a 2000 Taurus that was brought in for a no start. I found there was no fuel pressure and wasn't hearing the pump engage when the key was turned on. I have a "Relay Buddy" tester kit, so I pulled the FP relay and it tested good. I checked the fuse and it was good as well. I decided next to test whether I was getting power from the relay to the fuse before lifting the car to check for power at the FP. When I turned the key on to do so, I could hear the pump engage and there was fuel pressure. The car started every time after that.

From a diagnostic stand point, fretting was the explanation because all I had done was unplug and plug in the relay and fuse. What I suspect, however, is that there was probably some excess current draw occurring in the circuit that I simply didn't find because I had no reason to keep working on the car after that. It had about 160k on it and was in awful shape - the owner didn't want to take care of anything he didn't have to.

I'm all for the use of dielectric grease as well. I don't know if it's recommended by any manufacturers, but one of my instructors told us that dielectric grease should be applied any time a connector has been opened. I try to use a little more discernment than that - I take into account the condition of the car/engine bay. If I'm unhooking the MAF sensor connector on a 2017 to change the air filter, I'm probably not going to apply grease (especially if it's one of our regular customers and I know they'll be coming back). On the other hand, if I'm doing the same thing on a 2008 that's seen more than its share of road and dirt, I'm not only applying grease but also blasting the terminals with cleaner and compressed air first.

 

I finally found the problem. After the truck wouldn't start Friday, I got around to looking at it again on Sunday. I took each relay out one by one, Cleaned the terminals with a brass wire brush, and used bulb grease on them as I replaced them. Then I moved to the Diodes, Circuit breakers, and fuses. As I was finishing up the last few, I saw a scorched fuse terminal #26 or 27? for the fuel pump relay. Burnt enough to melt part of the plastic part of the fuse, but not enough to burn out the fuse. Looked at that fuse block terminal with a light and magnifying glass and saw no damage, but cleaned the connection anyway, replaced the fuse with a new one and bulb grease, and then it started up! I'm pretty sure that was the problem all along but have been checking it every time it is driven. Marked the inside cover with the number and have a few spare fuses in a couple of unused positions.

 

That is a common problem, you can get a "relocation" kit from Ford. There is a thread on here somewhere about it.