I am having an intermittent loss of ground in the fuel pump circuit. I have checked all the grounds I can find in the trunk area. I was wondering if there is a list or diagram to show the grounding locations that Ford used in this car. Thanks

 

I believe the scenerio goes like this,
The PCM provides the ground for the fuel pump relay for 2 seconds when you first turn the key on.
Then once cranking the engine and thereafter the PCM requires a crank RPM signal to keep the fuel pump relay energized.
How did you determine the problem to be loss of ground? Could it be loss of power possibly through the inertia switch or the fuel pump driver module? I believe the ground for the fuel pump module may be under the vehicle in the area of the fuel tank using the chassis for the ground. There could be a few reasons for the pump dropping out.

 

The CEL said it was the fuel pump driver module so I replaced it. THat didn't change anything, but when it is cold outside it runs just fine. No CEL or any surging. But when the weather is warm it starts the surging again and the CEL comes back on throwing a fuel pump driver module out of range code. I asked a Ford Mechanic and he said it sounded like a loose ground to him. I had a Ranger once that did the same thing and it turned out to be a loose ground. I am just trying to not have to pay 90.00 per hour for trouble shoooting.

 

Ok I removed all the grounds that I could find and cleaned them up with a file and sand paper until they were shiny. It was warm outside( in the high 40's) and the cleaning didnt help. As soon as it got cold again the surging stopped and after a few starts the CEL has gone off again. THis has me baffled as to what to do next. Any ideas will be greatly appreciated.

 

What was the code received?
Out of range could be voltage too high or too low. The exact code would help.

 

The code was P1235. fuel pump driver module out of range is all they told me at Auto Zone.

 

Depending on what system is used on your particular vehicle, The Fuel Pump Driver Module (FPDM) gets it's commands from the PCM. The PCM gets feedback info from the FPDM which uses info from the Fuel Rail Pressure & Temp sensor on the fuel rail.
A scan tool is required to get the info so a decision can be made as to which part is malfunctioning.
In light of the vehicle temperature having an effect on the engine performance I would be somewhat suspicious of that sensor since it sends temp info to the PCM.

 

I'm sorry to have mislead you, but the vehicle temperature doesn't have any effect. It is the air temperature that has the effect. I work in NC but I live in SC. I go home on the weekends and when I do it starts acting up. The weather is warmer at home. When I get back to NC it stops acting up and after a few starts it clears the CEL on its own. When it is cold at home then it doesn't act up there either. Last weekend it was warm there and it surged the whole time I was home. I left Sunday going back to NC and as soon as the air got colder it stopped surging and has been fine ever since. I will be going back home next weekend and I imagine it will start acting up again. If I need to get a scan tool and drive it hooked up or something I will try to find one. Just let me know what info I need to get and how. Thanks

 

At this point I do not think it will make much difference , because the problem seems to be temp related. There is an intake air temp sensor that reports to the PCM and it could possibly be involved. I don't know how much you are willing to spend on a scan tool, but one that can provide the info you would need will possibly run in excess of $2500.00 or more. Might be cheaper to have a well equipped shop check it out for you.