Start then stall

Well today I pulled the fuel pressure sensor from another V6 LS I have. Put it in my red one and - SOS. Everything the same. Forscan reads very high fuel pressure, a gauge on the schrader reads <10 psi.
What to do?
Swap out the fuel pump? But engine runs fine when pwr/gnd jump pump motor.
Swap out the REM? (but donor has auto, mine has getrag. Is REM same?)
Look for crimps etc in fuel lines?
Punt?
 
Clearly, something's not adding up here. I don't know what...
 
Is there something else back there that has the same fitting connector plug? I have one but can't see back there up on the lift where it winters. Plus the firewall support bracket and cowl would have to come off to see.
 
You may need to look at the emissions manual to proceed from here. It should have pinpoint tests to verify the wiring and operation of the fuel pressure sensor. I feel like this is somehow (but I don't know how) related to the fuel pump driver codes that you are getting.
 
milehighmikey said:
Are you sure that your fuel pump is compatible with this car?
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Yeah, something doesn't add up all right. I'm pretty frustrated right now. Only clue I have at this time is the high fuel pressure that forscan reports: 4.25 volts, 452kPa = 63psi. Why so high? How is this calc'd? Reads pressure, reports voltage? Wonder if volts signal is shorted thru some resistance to Pwr? Might be time to get out the schematic and the DVM and O'Scope.
I dont think there's a crimp anywhere in fuel lines cause it runs so good with pump motor control bypassed. But then why only 10psi at schrader on normal start? Crank signal must be there cause otherwise PCM wouldn't know when to fire the COPs. MAF on/off makes no diff.

There are two connectors back there - the pressure sensor and the egr diff sensor. But Ford is pretty good about mating male to female connectors so not problem there.
Is pump compatible? Well Spectra says it is. I do have one I picknpulled from a V8 I could swap in. Rock has same PNs for V6 and V8.
 
joegr said:
You may need to look at the emissions manual to proceed from here. It should have pinpoint tests to verify the wiring and operation of the fuel pressure sensor. I feel like this is somehow (but I don't know how) related to the fuel pump driver codes that you are getting.
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Youmean the PC/ED section of the DVD manual? The driver codes are those from the PCM/REM? The PWM signals?
 
heyjewel said:
Youmean the PC/ED section of the DVD manual? The driver codes are those from the PCM/REM? The PWM signals?
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In chart 1 of the symptoms chart, problem stall after start, one of the issues brought up way down the list and specifically for the LS is the AC pressure sensor input to the PCM. This seems like an awfully strange item to cause this problem BUT my AC system is not charged and I dont have the equipment to charge it. Ugh.
 
I don't know what DVD manual you have. From the official source, it is a separate (and quite expensive) manual. It has much more detail than the normal shop manuals.

Edit: sounds like you may have it, or something similar to it. Is it the Helm manuals, or something aftermarket (AllData or such)?
 
heyjewel said:
In chart 1 of the symptoms chart, problem stall after start, one of the issues brought up way down the list and specifically for the LS is the AC pressure sensor input to the PCM. This seems like an awfully strange item to cause this problem BUT my AC system is not charged and I dont have the equipment to charge it. Ugh.
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I'm pretty sure that problem mentioned there would be if you had a fully charged system and the pressure sensor was not correctly reading it. The engine would have a load from the AC compressor that it did not expect. In your case, there can be no load anyway.
 
joegr said:
I'm pretty sure that problem mentioned there would be if you had a fully charged system and the pressure sensor was not correctly reading it. The engine would have a load from the AC compressor that it did not expect. In your case, there can be no load anyway.
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I have the FOMOCO service manual covering all their cars from 96-2002

Yeah I dont want to start chasing an AC goose. I did read the test for this problem and it does try to deterine if a changing pressure can be read. Glad of that.
For future - the charging procedure re adding oil is pretty strange. Tech must drain oil from diff components then add that much plus some more. In my case I had to replace a damaged hose and lost a couple ounces of oil so seems like the right amount of oil to add might be diff to determine. I suppose a shop will have all the info they need ...
Thanks for spending all this brain processing time on my problem folks.
 
heyjewel said:
.. Tech must drain oil from diff components then add that much plus some more. In my case I had to replace a damaged hose and lost a couple ounces of oil so seems like the right amount of oil to add might be diff to determine. I suppose a shop will have all the info they need ...
Thanks for spending all this brain processing time on my problem folks.
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Yep, that's the official procedure, but I think most go by experience instead and take a good guess at it. So far, that's worked for me...
 
joegr said:
Yep, that's the official procedure, but I think most go by experience instead and take a good guess at it. So far, that's worked for me...
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The fuel pump assembly sounds really suspect to me still ...what's the fuel pump assembly # I just put a new spectra in last week I'll compare our part #???
 
heyjewel said:
SP2322M
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That Part # is spot on with mine and you're right it's compatible with both 3.9 & 3.0 engines ...Like you did with fuel pressure sensor I guess the next step is to swap out fuel assembly module and see if the other one changes the situation at all....if not then at least you can rule out the possibility of faulty fuel pump assembly module...the more we narrow this down the better chances of finding the root of the problem
 
Hold the phone - here's an interesting data point for you all:
I pulled the 3 pin connector off the fuel pressure sensor and the car started and idled just fine!! Fuel pressure at schrader went up to about 45 psi. So problem I guess is in that wiring since the pressure sensor has been replaced.
 
heyjewel said:
Hold the phone - here's an interesting data point for you all:
I pulled the 3 pin connector off the fuel pressure sensor and the car started and idled just fine!! Fuel pressure at schrader went up to about 45 psi. So problem I guess is in that wiring since the pressure sensor has been replaced.
Click to expand...
What data is Forscan throwing out when car is at idle?
 
That would seem to narrow it down to the PCM or the wiring between the fuel pressure sensor and the PCM, assuming you don't have two fuel pressure sensors bad in the same way (unlikely). I also assume that you verified the vacuum connection to the fuel pressure sensor. It should be full manifold vacuum at all times.
 
heyjewel said:
Hold the phone - here's an interesting data point for you all:
I pulled the 3 pin connector off the fuel pressure sensor and the car started and idled just fine!! Fuel pressure at schrader went up to about 45 psi. So problem I guess is in that wiring since the pressure sensor has been replaced.
Click to expand...
Stating obvious right now...but you possibly have a short in the wiring...however did you replace the relay just to make sure it didn't get defected somehow along the way of this whole journey of your engine swap?
 
joegr said:
That would seem to narrow it down to the PCM or the wiring between the fuel pressure sensor and the PCM, assuming you don't have two fuel pressure sensors bad in the same way (unlikely). I also assume that you verified the vacuum connection to the fuel pressure sensor. It should be full manifold vacuum at all times.
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I did verify the vacuum at the FPS and it was appx 17inHg
Forscan with the connector off is showing what I'm sure it should - FP square bump up to 75 at start then down to 27 at idle. Of course there is no PWM control.
FRP volts goes to 4.23
FRP kPa goes to 450 which is about 65.
These FRP numbers are the same as what I was getting with the connector on. Yet the FP number is good and the engine keeps running.
 
joegr said:
Maybe the tool is reporting the wrong sensor?
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A little more information here. The tool is definitely reporting the correct sensor. I verified by removing the cover from the 'C' connector at the PCM in the rear of the engine bay. Scraped a little insulation off the wh/gr wire going into pin 49 which is the signal to the PCM from the sensor. The voltage there matches the voltage reported by the Forscan software - 4.9 down to 4.2 The 4.2 is causing the car to stall. There is some info in the DVD about reference voltages at various sensors - cool. The high range it shows for the pressure sensor is about 3.6volts. Normal operating range is around 2.7 volts. Just a short while ago I pulled all the stuff off under the hood of my running LS to get to the sensor connector. I was able to shove a little piece of wire in the output pin and verified that this car starts and idles when sensor out settles to 2.7 or so. Also checked and found that it's operation matches the red (start/stall) car exactly in this way - if I pull the sensor connector off either car and let the pin 'float' open, both cars start and run.
I haven't had time to pull the sensor from the running car and try it in the red one, but I'm either going to do that or order the part called out for the Jaguar S-Type V6 on the net and hope for the best.
Seems to me that since the running and stalling car signals are same without the sensor hooked up, I can only conclude I have 2 sensors that have failed in the same way. Odd for sure.
 
I may be able to get you my redundant sensor left over from my donor engine when I changed engines 3 summers ago. Is it worth it to try a used one (110K mi) to you?
 
***************** Problem SOLVED. ***************

So today I installed the old FPS that mikey, above, was great enough to send me and FINALLY my rebuilt engine starts and runs and sounds GREAT. A few more items to install and clean up and I'll start paying insurance on it again.

So I THINK the cause of this is some gunky additive in California gasoline. My reasoning is that 2 of the LSes I have sat for 3 months or more without being started and with gas in the tank and probably or certainly in the FPS and neither would start. I thought the other car no start was caused by the fuwl pump but when I swapped it's FPS into the red car it failed there as well. Similar thing happened to my motorcycle. Sat for a couple months without being started and then wouldn't start and i found some gunk clogged the jets. So none of the three vehicles would start after sitting with california (ugh) gas in them.

Yet Mikey sent me an FPS from a car in NH which sat for 2 or 3 years and it still worked.

Anyway that's my story and I'm stickin to it. THANKS to all for help.
 
heyjewel said:
***************** Problem SOLVED. ***************

So today I installed the old FPS that mikey, above, was great enough to send me and FINALLY my rebuilt engine starts and runs and sounds GREAT. A few more items to install and clean up and I'll start paying insurance on it again.

So I THINK the cause of this is some gunky additive in California gasoline. My reasoning is that 2 of the LSes I have sat for 3 months or more without being started and with gas in the tank and probably or certainly in the FPS and neither would start. I thought the other car no start was caused by the fuwl pump but when I swapped it's FPS into the red car it failed there as well. Similar thing happened to my motorcycle. Sat for a couple months without being started and then wouldn't start and i found some gunk clogged the jets. So none of the three vehicles would start after sitting with california (ugh) gas in them.

Yet Mikey sent me an FPS from a car in NH which sat for 2 or 3 years and it still worked.

Anyway that's my story and I'm stickin to it. THANKS to all for help.
Click to expand...
Great to hear!!!! Glad you found the solution and nice trouble shooting with sensor...
 
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