Had trouble starting my 2000 F150 this morning. The engine just spun like it was not getting any gas. There was a buzzing sound coming from the fuze box under the hood. I opened it and isolated the buzzing relay, pressed it in and the truck started and ran fine for 20 minutes while I checked things out. But it would not start a second time. Instead, when you turn the key to on, there's a brief initial buzz from the relay, the odometer turns to all dashes and the "Theft" indicator flashes. I can crank it but it does not start.

Of course I tried swapping out the relay (manual says it's the Fuel Pump relay) with several know good relays including two new ones.

Checked all the fuses both under the hood and under the dash.

Weird thing is, when I remove the fuel pump relay the odometer returns to normal and the "Theft" indicator stops flashing. The only thing I hear under the hood is the ABS module clicking. (Is that normal?)

Reading other posts here suggested some other things to check. I checked that grounding wires were secure. I found 3 on the firewall near the battery plus the engine grounding strap. Two more on the radiator frame, all tight. Don't know where else to look.

Other posts suggested maybe a coil pack failure. I've had coils replaced at least ten times over 14 years and weird things can happen when they fail.

I was hoping to avoid a tow to the dealership. Any ideas, other things to check.

 

Any codes?

 

Thanks for replying DiabloMike

No codes, but I've read that all dashes on the odometer means no communication with the chip.

Anyway, I fixed it this morning (I hope) with about ten minutes work after spending 6 hours and some money on the problem yesterday.

I checked all the ground wires for tightness yesterday. All were tight. This morning I removed two that had a bit of corrosion on them, cleaned them good with a Dremel tool, and reinstalled. The truck started like it was new. It started the next five times too. Hopefully that's the end of the story.

Of the two ground straps that I cleaned, the one on the driver's side of the radiator frame seems the most likely culprit. It had a green/black and a black wire coming off of it that went back in the direction of the fuse box where the Fuel Pump relay lives.

 

Tommy, glad to see you got things potentially fixed. I've moved your thread to the 97-03 forum because it really belongs there and, the people who monitor this section may have some helpful advice.

- Jack

 

Your symptom is of a PCM that cannot communicate with the cluster.

Try a new PCM power relay.

 

Thanks projectSHO89,

Apparently a bad ground wire connection can also cause a PCM not to communicate with the cluster. All fixed now.

 

Anything that prevents the PCM from properly booting up is a likely culprit. Keep that in mind should the problem reappear. Good power and ground circuits for the PCM are mandatory since a PCM that doesn't boot up cannot communicate with anything.

The fuel pump relay was a secondary symptom since it relies on the PCM properly booting up.

 

I used to do my own auto repairs when no start conditions were fixed with new points plugs and wires. Back then there was one grounding strap for the whole car, not one for each electronic subsystem. I stopped trying to fix problems myself in 2000 when I bought this truck new, my first new vehicle. I was a construction manager then. I decided I had better things to do with my time then try to understand modern automobile electronics. Besides, it was new, and I didn't want to screw it up. Ironic since my profession now involves troubleshooting computer problems. Now that the truck is 14 years old, I don't want to give the dealership $150 just to plug in a computer to find out what's wrong. In this case I would have also had to pay for a tow. This forum is such a great resource for guys like me who don't have the knowledge but aren't afraid to dig in and get their hands dirty.

Still baffled however. If the fuel pump relay was just a secondary symptom then why did the dashboard return to normal with the fuel pump relay removed? I have to assume that if the dashboard is normal, the PCM has booted up properly. It makes me wonder if I've really fixed the problem.

 

The baffle is, you not knowing that the PCM must boot up to operate the fuel pump relay.
Fuel pump relay is not a stand alone operation just from the key.
It is done this way for safety reasons. If the motor is not running, the PCM does not receive the crank signal and hence no fuel pump operation.
The safety part is so a fire is not fed gas should there be an accident that might causes gas to pumped out of a leak from the tank or fuel lines.
The double safety is a hard forward motion crash sensor opens the circuit. This is located behind the passenger side kick panel.
I thought you should like to know about all this.
Good luck.

 

That the PCM must boot properly before the fuel pump relay can operate is obvious.
What is the indication that the PCM has booted properly? That the dashboard indicators are clear and normal.
What is the indication that the PCM has NOT booted properly? Dashes on the odometer, "Theft" light flashing.
The baffle is, using the only PCM indicator I had at my disposal, the dashboard, why did the PCM boot properly with the fuel pump relay removed when it could not boot properly with the fuel pump relay installed but with a bad ground. The ground was still bad when the PCM booted properly.
It would seem that the PCM is dependent on a properly functioning fuel pump relay circuit, or the removal of that circuit from the equation by pulling the relay.
I work with computers daily. The whole notion of a computer in a 14 year old truck booting up is laughable to me anyway. The "computer" in my 2000 F150 is little more than a CMOS chip with stored data that's read when energized. It's dumber that the dumbest dumb phone.

 

Everything works.

Multiple possible symptoms including no fuel pump, no PATS proveout, no cluster communications, no scanner communications.

Most likely, the removal and installation of the relay changed an intermittent electrical contact.

The PCM operates the FP relay, the PCM's power-up cycle should be unaffected by the relay.

 

Tom ya got to slow down a bit.
You are not as familiar with modern day computer control of vehicles as you may think.
We are informing you so please listen.
The PCM is alive with standby power called KAM, but not cycling through it's control program until power is applied through a relay via the ignition switch to 'boot' it into operation same as PC does when turned on..
Complete loss of all power to KAM defaults all the 'shift able' tables that had learned your average driving style, ambient conditions etc, as well.
There is a lot that goes on in these PCM so nothing is laughable as you put it.
I hope you don't take this as insult but you indicate you need the information by your responses.
Good luck.

 

I KNOW I'm not familiar with modern day computer control of vehicles. That's why I turned to this forum for help and I appreciate the information. This is the first time I tried to fix anything electrical on this vehicle since I bought it new.

I've been reading up on it here and automobile "computers" are more sophisticated than I originally thought. Still, it is not sophisticated enough to tell me what was wrong with it yesterday. Even if I had the diagnostic computer to plug into the dash, it would just spit out some codes that would have to be interpreted by someone. Could it have even hinted at a bad ground wire as the cause of the problem? I fixed it in a hands on, intuitive way. And I got lucky. The truck's computer only hindered my progress by giving me conflicting information about what was really wrong with the truck's systems.

Modern computers are self contained processors of digital data, ALL digital. The only moving part in my current laptop is the cooling fan. My truck is just the opposite. It's a mechanical contraption on which a series of analog sensors and relays have been applied. The analog devices send and receive analog signals that are converted to digital data that a rudimentary program analyzes to make decisions about which analog signals to sent back to the machine. Comparing it to a PC is still laughable to me. The computer in a vehicle is grafted to the mechanical machine to help control it's function. You say "same as a PC"? Even with a solid state hard drive, my laptop takes 2 minutes to boot up from a cold start. How long does it take for a vehicle's "computer" to boot up? I'd guess less then 1/10th of a second. That's not a computer. Instead, it's is better compared to the CMOS chip on a PC. This is the chip on the motherboard that saves data even when the computer is powered down; the date and time, which device to boot from, what hardware and features to enable/disable, etc. It has a rudimentary operating system of its own that is completely independent of the main operating system stored on the hard drive. The chip in my truck doesn't even save the time. I know this because when I disconnect/reconnect the battery, the clock says 12:00. My 2000 F150 is less sophisticated and has less processing power than a modern refrigerator. Which makes it all the more aggregating when I have to pay hundreds just to get it diagnosed.

I do appreciate the information provided here and am always willing to learn. Ultimately though, I need to get my truck fixed. Having all this information you kind folks have provided about the PCM, how do I apply it when the truck breaks down in the future? What's the minimum I have to spend to get my own diagnostic equipment and will I be able to interpret the cryptic codes that my truck's rudimentary chip divulges? I suspect it's not a viable way to go. So where does that leave me? Stuck like all the other suckers who have to pay a towing company and the dealership to get their "computerized" vehicles diagnosed and repaired.

 

Tom, i'm sorry your taking this attitude.
Until you give in and accept the way automotive systems work, you will, just have to p*ss and moan about it.
There's no more to say that will change your mind anytime soon.
Good luck.

 

It's like we are having two different conversations in two different languages. You're reading my responses the wrong way. I'm not being combative. I'm asking how to approach a repair of this type and you're asking me to accept how automotive systems work. I ACCEPT how they work. Am I also supposed to accept when they don't work?

Your expertise is in automotive repair. Mine these days is in computers. I have not refuted a single thing anyone said about how the system in my truck works. I can't, I don't know enough. I'm merely explaining the difference between a computer and the chip that controls my truck's systems because that's something I have knowledge of. What attitude? Change my mind about what? I don't have my mind set in any particular way on truck repair. I'm looking to this forum to set my mind in a concrete direction.

Can someone please tell me how I can approach a repair of this type on my truck that does not involve tow trucks and dealerships? I can see that everyone who has responded is very knowledgable about how the system works on an F150. You have all related what you know, awesome! I now understand better then ever before how it works, thank you all for that. But what suggestions have I gotten on how to troubleshoot a problem like the one I started with? I got this suggestion from projectSHO89: "Try a new PCM power relay." At that point, I had already fixed it however. What other suggestion did I get? I got descriptions of how it works. Okay, I got that. BUT HOW DO I TROUBLESHOOT IT?

What you are perceiving as "attitude" is just frustration at not getting repair ideas. Is there some inexpensive piece of diagnostic equipment I can get? I'm a clever guy, I like gadgets, they like me, I have a shop stuffed with specialty tools. I'm good with my hands and not afraid to try new things. I've built my own house, I've built everything from custom furniture to complete websites. What can I try the next time something like this happens? PLEASE, give me some suggestions.