2007 Ford Sport Trac - hard to start, stalls, and multiple codes setting

Hi all,

I have a mess of a problem in my shop. This vehicle has jumped around to two different shops before I just got my hands on it. The condition as the subject says is a intermittent hard to start and stalling issue. The hard start is more or less just a sequence of long and extended crank times before it fires. Sometimes it will then start and then stall out immediately and then re start. The weird thing is, is that the car could start and run absolutely fine for hours and then suddenly have a hiccup. Before I received the vehicle the customer had told me that the previous two shops had done the following, fuel rail pressure sensor, fuel pump, fuel filter, fuel pressure regulator, throttle body, alternator and a thermostat. The truck also would randomly throw on a check charging system light (even though it is putting out 14+v. The vehicle has several codes: P0191, P0193, P0620, P0740, P0743, & P1235. The transmission codes (P0740 & P0743) I was told have been there for quite some time and is not relevant but am not sure if this is true as it sets with all the other codes. It's just weird that the truck can sometimes start right up and other times not. I put a fuel pump driver module because of how common they are and that's were the codes directed me but still no luck and no changes.  

It is hard to see what I am missing when it does an extended crank as it so random and does not always happen. It is also important to note that once I clear the codes the codes will ALL return immediatly once the first stall out happens.

Could be a crank sensor causing the extended crank. Scope both cam and crank.

Hi,

Appreciate your reply. Ill scope the two sensors but with all of these codes it's kinda tough to see that being an issue...

What does fuel rail pressure read when it’s acting up?

From what i see of this i would test the relays first when cold and then when the car stalls out. To me this sounds like the asd relay is going open circuit when it gets hot.

The other thing i would do is print out the wiring diagrams for the circuits in each of the codes and trace each wire on the paper to see common points that intersect. Green crust in a conector or water intrusion can be a possibility if symptoms are more prevalent when raining/foggy out. Otherwise chaffed/mouse damaged wires is another posibility

I tried bypassing the inertia switch as well. That was one thing I failed to mention

mikeysal12 wrote: The truck also would randomly throw on a check charging system light (even though it is putting out 14+v. The vehicle has several codes: P0191, P0193, P0620, P0740, P0743, & P1235. The transmission codes (P0740 & P0743) I was told have been there for quite some time and is not relevant but am not sure if this is true as it sets with all the other codes.

So, to be clear, if you clear codes then get this thing to act up, all of those codes come back?

I didn't see, but maybe I missed it - which engine is in this Sport Trac?

If all those codes reset when the long crank/hard to start/no start/stall business happens, I'd be tempted to check into the FRP sensor first. It's up front and relatively easy to get to. 5V, signal and ground. I recognize that the P0191 and P0193 might be a symptom of something else, but it'd be somewhere to start. :silly:

Following P1235 might be another option. That code suggests that the FPDM didn't receive the correct signal on the Fuel Pump Command line FROM the PCM. The FPDM then sent the PCM a 25% duty cycle signal on the Fuel Pump Monitor line to signal all is not well. Confirming what's happening on the FPC circuit might help point the way.

Has anyone checked to see what exactly is missing during the symptoms? Spark, injector pulse, fuel pressure?

Something smells like a bad PCM ground here.

Hi Tyler, thank you for your reply...


The sport trac has a 4.0....


The FRP sensor does indeed have a 5v ref. I am going to check all the PCM grounds in the morning and see if any are missing.

It is hard to find out what is missing when it doesn't start because it is so random and unpredictable so I haven't had a good oppurtunity to test it. Do you think testing all PCM powers & grounds in the morning is the correct route?

I tested all grounds to PCM this morning. All grounds tested out good. Still scratching my head on this one

mikeysal12 wrote: It is hard to find out what is missing when it doesn't start because it is so random and unpredictable so I haven't had a good oppurtunity to test it. Do you think testing all PCM powers & grounds in the morning is the correct route?

I think you gotta catch it in the act. Anything you test without the problem being present may show A-OK at the time, but fail under the right conditions.

I'd stick to reproducing the issue, and figuring out what you're missing. Let what's missing dictate your next move.

Intermittents hot to love them. I’d definitely check fuel pressure when it acts up. Scope injectors see if when the extended crank happens you have pulse. MYbe use channel b for the 5 volt ref check. Could be an oxygen sensor sticking rich cutting all the fuel for one bank. Like on the Chrysler’s

I am still fighting this truck. All wires to FRP sensor are good. All wires to FPDM are good. I hooked up my 4 channel lab scope to the FRP sensor but everything looks normal as the vehicle is starting normally when testing as the no start condition is so random.... I need ideas.

Check for excessive alternating current ripple at the battery terminals. Set your DVOM to a/c voltage, anything over .5V is too much. Test at idle and again at 3000 rpm. Too much ac current can cause all kinds of weird stuff.

I will try this, although the vehicle has a new alternator. This thought did cross my mind though. I had a chrysler sebring that did some weird things from a faulty rectifier