No start, had fuel

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Sep 10, 2013 | 10:42 AM

Piffery1

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From: Niceville, FL.

No start, had fuel

2003 F150 4.2L V-6. Cranked ok but no start, no check engine light. Plenty spark and could hear fuel pump running. Thought it might be out of fuel but gauge showed over 1/4 tank . Added ~2 Gals fuel anyway, started immediately- no check engine light, no codes set. Thought- bad gauge sending unit. Dropped tank and found plenty of fuel and sending unit checks good. New pump on order but what else could cause the problem? Thanks,
Piffery1

Sep 11, 2013 | 01:25 PM

Bluegrass 7

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Doesn't do any good to speculate.
The tank level signal is all electronic conversion.
The float changes resistance, the dash processor converts the level into a digital drive signal for the gauge so it's not a direct relationship like old times.
There is dash diagnostics that might tell about what the processor sees as the fuel level.
You would have to know how to enter it and interpret the dash readouts for each function. This is why there is digital conversion involved.
The fuel level is given as an 'Octal' number that relates to fuel level.
I would be looking at fuel pressure first as some indication the pump is not in good health rather than drop the tank, the expense and find out it's not the problem in the end.
Good luck.

Sep 11, 2013 | 11:29 PM

Piffery1

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From: Niceville, FL.

I failed to mention earlier that before dropping the tank I simulated the sending unit resistance with a 15 Ohm resistor (empty) and a 160 Ohm resistor (full) and the gauge worked perfectly After adding the ~2 gallons of fuel the truck started normally, the gauge showed a little under half full, I could detect no difference in the sound of the pump and no check engine light showed. After dropping the tank I emptied about 12 gallons of fuel from it. I have ordered and received a new pump (pump only, no sending unit) but not yet installed it. Don't want to risk getting stranded by putting the original pump back in. Fortunately the failure to start occured in my driveway; I might not be so lucky next time. What worries me now is that I wonder what else could have caused the failure, if not the pump, especially in light that no check engine light (i.e., no codes) showed up. I've read in other posts that this happens on 2004-up trucks due to a bad Fuel Pump Driver Module (FPDM) but apparently my 2003 doesn't have one--at least I haven't been able to find one.
Any and all thoughts on this issue are appreciated. I need to buy a new fuel pressure gauge to have available, my old one only goes to 10 psi. Piffery1

Sep 11, 2013 | 11:38 PM

Bluegrass 7

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The fuel pump system is not monitored by the PCM so you cannot see an codes from a direct failure.
After 03 the fuel system was changed to a single pipe system from a two pipe feed/return, with sensors and a control module that is monitored by the PCM.
This was the beginning of a changeover to Flex fuel capability for the trucks as well as different motor design changes and a different OBDII operating system called 'CAN'..
Hope this clears it up for you.
Good luck

Sep 12, 2013 | 12:07 AM

Piffery1

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From: Niceville, FL.

I would have thought it would have set one or more of codes P0148, P0190-P0198 or P0230-P0232 if there was a pump pressure or delivery problem. If it is actually a pump going out I can't figure why a slight increase in fuel level would cause it to start, There is absolutely no sign of a dirty fuel strainer sock or fuel contamination in tank. And with that much fuel in the tank the pump intake should have been well submerged. I wonder if I should go ahead and replace the frame mounted fuel filter, too, even though the tank looks perfectly clean inside and the truck only has 43K miles. The new pump comes with a new in-tank strainer. Very confusing! Piffery1

Sep 12, 2013 | 12:14 AM

Piffery1

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From: Niceville, FL.

One other question--Can the fuel pressure regulator fail in a mode where no or almost no fuel can flow or do so only intermittently? Piffery1

Sep 12, 2013 | 12:51 AM

Bluegrass 7

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There is .....no pressure sensors to monitor in an 03 or earlier so no codes could be set.
Not all codes apply to all vehicle configurations in all model years.
It's possible for a regulator to stop fuel rail flow but never heard of it.
Most of the time the regulator allows to much pressure as a failure.
After all, the pressure into the regulator can be as high as 90 psi.
It regulates down to the 35 to 40 psi range.
The reason it's done this way is to minimize pressure pulsing changes in the fuel rails affecting fuel delivery pressure changes to the other injectors under the high speed short times they have to operate and service the other cylinders as the fire order cycles them in order.
There is no use going round and round about something you can't find the cause for unless it keeps happening over and over so you have a chance to find the cause.
Good luck.