Hi Bluegrass, yeah that's the point. I thinking it is something like the crank position sensor since the either doesn't seem to do anything.

So here are my thoughts:
1. turn key to engine on ( NOT engine start) if there is no response from old pump or new pump when attached to the pump circuit.
2. using either and turn ignition key to start, the engine will crank but will NOT fire or start.

then for no known reason the pump will work fine prime and start the truck till the next time it acts up and the pump does not prime on turn key to ignition.

Where is the crank position sensor located and what kind of voltage, contunitity? should I expect.

Is there anything else in the circuit that might cause the same problem beside the crank position sensor? Just in case it isn't the crank position sensor.
thanks for all the help

Walt

 

I mentioned the crank sensor as a reason the motor won't start due to lack of ignition and fuel, but it does not have any control of the pump at 'just' key on before cranking since there is no crank rotation at that time..
If no run at key on, it's still some other fault in the feed circuit.
The crank sensor is rignt behind the A/C compressor behind the crank pulley.

 

Got it, I think. No easy answer to this one huh! Guess I will just have to test every ground and connector along the way to and from the pump.

thanks again

Walt

 

Hi,

Sorry to revive this old thread but did you ever figure out what the issue is? I'm having trouble with the fuel pump right before Christmas. Sometimes I can hear the buzzing/wheezing under the hood, other times nothing. Sometimes she cranks over but won't start, other times starts right up.

Just replaced the starter Saturday, it was the original and finally went out after 13 years so no complains there. But the truck started fine before the starter replacement, only after swap did it have a crank but no start issue.

Thanks

 

Funny you should ask! For the first time in months the friggin thing acted up. I try to start the truck at leat a few times a week. I found? believe? it helps. When I would leave the truck without starting it evey couple of days it seemed to act up. (Lot easier to start often verses dropping tank. Yes seems that somehow by breaking connections??? it fixes problem and yes I haqve checked connections cleaned and found no issues). However, I have been keeping up with the frequent starting routine, letting it warm up to normal drive temperature and then shut off. The other day I went out started it up, ran till warm and then shut down. wife said she wanted to run some errands so I said we should take the truck cause it was already warm, 32F outside that day but when we went to start the truck I turned the key but did not hear the fuel pump hum. I tried a dozen times to turn on the key listen for hum even tried to start with no success. After 10 minutes of trying I heard the familar hum and it started up. Been working fine since then. Only thing I believe I heard was a click under the passangers side where the fuel accident cut-off is located. I played with that the first time I had trouble so long ago. So not sure it has anything to do with it.

Sorry I am still in the dark and can not be of any help. Wish you better luck than I have had and if you ever figure out the problem I for one would be very interested to find out what you found.


Could your fixing the starter and removing battery cables? upset the guizmo under the passanger panel. It is intended to keep the truck from starting if in an accident. Could it have been disturbed by what you did while fixing starter? Think there is a reset? on it somewhere. Don't remember clearly what it all looked like just that there is some way to restore.


Thanks

Walt

 

When difficult problems arise, in depth troubleshooting has to be done to find the cause.
Suppose the pump sticks but the circuit does not open.
A test of current draw would show this up if you don't hear the pump run and a continiuity test shows the pump winding is not open.
A lack of or low voltage at the pump connector.
A poor ground.
Anything is possible and even in combination.
The circuit is powered through a relay because the PCM is not designed to handle high current anymore than is needed.
The relay is operated by the PCM as a low current circuit.
When the ignition switch is set to RUN it powers the PCM first, then a 1 to 2 second solidstate timer grounds the relay operating the pump until the timer times out.
When cranking begins the Crank sensor signal is received by the PCM.
This in turn restarts the pump through the timer, full time.
In the pump circuit is the crash sensor to stop the pump in case of accident so the pump has no chance of feeding a fire situation.
From the above you enough info to see the logic of the total control circuits.
Good luck.

 

I have the same issue with my truck and was about to just buy a pump and strainer and shotgun them...now I'm going to sand clean every electrical ground point related to fuel or starting before purchasing anything. The problem may have began when I replaced the negative battery terminal a year ago.

 

Hi All,

Reviving a old thread.

I inherited a 1999 F150 V8 a couple months ago from my Father In Law. Has about 225K miles on it and the thing was running great. Keep in mind, this is my second vehicle so it gets started about once every 1-2 weeks for home depot runs.

About a month ago, I noticed the car took a couple cranks before starting. I figure it was a anomaly, now this past week I tried to fire it up again and again it cranked but wouldn’t start. It took about 10 tries before it started. I attached jumper cables from my other car, but pretty positive that had nothing to do with it. This past weekend I tried starting again and just kept cranking but not starting. I decided to get the battery tested (O’Reilly charged it up and said it’s at ¼ life). Re-installed it and it still did not start. I ended just buying a brand new battery from costco since it sounded like it would need to be replaced in the near future. After I replaced the batter, same problem…..ok time for some more troubleshooting:

What I have done so far:

1. Gas was just below the quarter from full line so I went and bought four gallons of gas just in case. Didn’t solve the problem.
2. I swapped the PCM and GAS Relay around (didn’t replace). Didn’t solve the problem.
3. I pulled the fuel pump fuse out and took a DMM and measured across both terminals - ~12 volts
4. I got under the car and unplugged the harness going to the fuel pump and noticed 4 terminals. I measured two of the terminals were common to ground.
Pin layout (pin 1 is upper left and pin2 is upper right):
1-2
3-4

a. I unplugged the harness and took measurement across pins 1-3 (~9-10 volts and dropped to zero after a few seconds)
b. I measured 2-4 ~9-10 volts and dropped to zero after a few seconds.

5. Checked fuel cut off reset at passenger kick panel. Pushed down – didn’t seem to be popped out.
6. I borrowed a fuel pressure tester from O’reilly and installed onto the Schrader and stayed at 0 PSI after about 5 tries. Keep in mind, this is my first time using one of these gauges and seems straight forward – but I can’t be positive I did this correctly.
7. I bought starter fluid and sprayed into the throttle body (I didn’t open the throttle body, just sprayed onto the surface) – cranked but didn’t start.

Is the pump very load and audibly noticeable? I am not sure, it sounds silent at the gas tank area. I do hear a buzz from under the hood, not sure if this is the pump sounding or “spark”. Sounds more like electrical spark.

I am not lost, I think it’s the pump – but am wondering if there is more I can do to further isolate the problem. I called around and the shop wants $125 bucks to troubleshoot the problem or $550 to just replace the fuel pump (not guaranteeing that is the problem without them troubleshooting obviously).

Any guidance will be appreciated.

Happy NY

Thanks,

Jon

 

When you turn the key ON, the fuel pump should hum/buzz for a couple seconds. If the gauge showed 0 PSI, the pump is not running. Try banging on the tank with a rubber mallet or your fist.

 

Thanks for the quick reply! I did try hitting the tank with a mallet, but no luck.

The humming and buzzing sound should come from the fuel tank area right?

I can hear buzzing, but it's under the hood. I'll try and get video of it.

 

Start over again because your in confusion with overload from all you have done.
Follow this explanation of how the pump is powered first, then relate what you have seen.
...............................................
Key to Run powers up the PCM.
The PCM applies a ground to the fuel pump 'relay', not the pump direct.
The relay has it's own source of power through a fuse and crash sensor.
This power is connected through to the fuel pump.
The PCM only allows the pump relay to hold up a couple seconds because it is a timer circuit, in the PCM
If you see voltage to the pump for a short time then shuts off, this is the PCM operating the pump relay. So the PCM relay and crash sensor are ok.
If you do not hear the pump run for the short time, it is suspect with no pressure built up.
.
To finish off, the pump is powered full time just after cranking begins because the crank sensor tells the PCM the motor is being cranked and needs fuel full time to run. This causes the timer 'above' to ground the pump relay full time.
.
This is all the info you need.
See what you have and decide accordingly.
.
If there are other issues, we don't know at this time, but get 35 lbs +/- fuel pressure at the test port or the motor will never run.
Good luck.

 

Thanks for the quick reply! I hear a load buzz under the hood when I put the key in ACC, it lasts about 3-4 seconds. I thought this was the pump, but realized the pump is in the back of the car. In that area all I hear is silence. Dumb question, what is the buzz under the hood from? spark?

I'll try to get a video.

 

Video won't be of much help.
Get some one to help and find the noise under the hood.
If it's the pump relay, you need to know that.
Open the fuse box and listen.
Good luck.

 

To give folks an update on my truck, I swapped the fuel pump yesterday and that did it!

I ended up ordering a pump and doing it myself (shop wanted $800!).

The hardest part was getting three buddies to come over to help me lift the bed off. It took a total of about 4 hours from start to finish. Thanks for the help everyone!

 

Congratulations!