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7.3 thread continued?

Swapped the CPS, nothing.
I am not getting a signal at the tach during cranking.ECM? Tried swapping the ecm relay with the horn relay, nothing.
30 amp fuse for the fuel heater/ecm still good.

At this point it’s not even trying to fire anymore. No CEL, never saw one in the truck in the last 25years. Don’t even think it has one.
I tired linking up cheap scan tool, cannot connect to ecm.

Trying to link to the computer with a higher quality scan tool is my next move. I’m guessing the ECM might be done. Dunno?
 
you have a bluetooth dongle? Forscan light app for smartphone will read everything you need and perform buzz tests etc
 
What kind of CPS did you use? There have been some DOA that keep you chasing your tail.

I say that due to no bounce of the tach while cranking which I think if the PCM is good would indicate CPS issues.

Also check the IDM fuse and the simple make sure your batteries and starter are strong and its full of oil.

Bought my truck with the PO convinced it had a bad ICP. Hard to start cold, ran like crap until warm etc... 2 gallons low on oil - fixed.
 
cchambers13 said:
What kind of CPS did you use? There have been some DOA that keep you chasing your tail.

I say that due to no bounce of the tach while cranking which I think if the PCM is good would indicate CPS issues.

Also check the IDM fuse and the simple make sure your batteries and starter are strong and its full of oil.

Bought my truck with the PO convinced it had a bad ICP. Hard to start cold, ran like crap until warm etc... 2 gallons low on oil - fixed.
Click to expand...
Parts store CPS. Duralast I’m guessing. Believe it or not, Ford had to swap my CPS under some NTHA ruling when the truck was about ten years old due to a safety concern. I haven’t changed it since. So I forgot to check the tach for a signal prior to swapping the CPS. Now I have no idea if there was any change. Been so long since I had one go bad I overlooked that.

My IDM has never been messed with either. Years ago guys would crack them open and do the “5k mod” then they wouldn’t seal them up correctly.
Corrosion would destroy them in short order.

batteries are good, oil is full, fuel filter was replaced.

I‘m not aware of a IDM fuse separate of the main ECU fuse but will look into it.
 
Questions about my sons 95 auto transmission. Sometimes at highway speed it seems to go in and out of overdrive, at least that's what it feels like. Has a new parts store speed sensor that seemed to fix it for awhile. Transmission doesn't slip. Any ideas?
Other question is the coolant hose arrangement. One of the hoses going to the heater core has a T fitting in it that goes to the bottom of the radiator . Is this an auto tranny thing? My 97 manual trans doesn't have it. What is it's purpose?
My electric pump conversion is coming along slower than I would like
 
Stock87 said:
Parts store CPS. Duralast I’m guessing. Believe it or not, Ford had to swap my CPS under some NTHA ruling when the truck was about ten years old due to a safety concern. I haven’t changed it since. So I forgot to check the tach for a signal prior to swapping the CPS. Now I have no idea if there was any change. Been so long since I had one go bad I overlooked that.

My IDM has never been messed with either. Years ago guys would crack them open and do the “5k mod” then they wouldn’t seal them up correctly.
Corrosion would destroy them in short order.

batteries are good, oil is full, fuel filter was replaced.

I‘m not aware of a IDM fuse separate of the main ECU fuse but will look into it.
Click to expand...

The only time mine wouldn't start was because of low voltage. The batteries would turn it over fine, even tried bump starting it. Hooked jumper cables to it for 5 Mins and boom, ran great.

Makes zero sense because for one, it started and ran that day, drove to the gas station and died. Plus another time I drove it for a while with a dead alternator. Swapped in vatozone parking lot and the knuckle heads wouldn't jump me. It was so dead it wouldn't crank at all. I was able to bump start it in the parking lot at like 2 mph in reverse :laughing:

So I'd maybe check the voltage or just throw a charger on.
 
6869704x4 said:
Questions about my sons 95 auto transmission. Sometimes at highway speed it seems to go in and out of overdrive, at least that's what it feels like. Has a new parts store speed sensor that seemed to fix it for awhile. Transmission doesn't slip. Any ideas?
Other question is the coolant hose arrangement. One of the hoses going to the heater core has a T fitting in it that goes to the bottom of the radiator . Is this an auto tranny thing? My 97 manual trans doesn't have it. What is it's purpose?
My electric pump conversion is coming along slower than I would like
Click to expand...
Is it the torque converter locking and un locking? Might have a bad tail light. The OBS shares a tail light circuit with the torque converter lock up.
 
I've also seen a bad alternator let a little AC thru with the DC, it can wig out 3-4 shifting. Consider topping off batteries and disconnecting the alt for a test drive
 
6869704x4 said:
Questions about my sons 95 auto transmission. Sometimes at highway speed it seems to go in and out of overdrive, at least that's what it feels like. Has a new parts store speed sensor that seemed to fix it for awhile. Transmission doesn't slip. Any ideas?
Other question is the coolant hose arrangement. One of the hoses going to the heater core has a T fitting in it that goes to the bottom of the radiator . Is this an auto tranny thing? My 97 manual trans doesn't have it. What is it's purpose?
My electric pump conversion is coming along slower than I would like
Click to expand...
Check the tail light bulbs. The trans unlocks when you tap the brakes. Mine would drop out of cruise control if I hit the blinker. Trans would unlock too.
 
Thanks for the replies. The taillights were switched to LEDs.
ABS light is on and cruise control is inop.
Doing some searching.
Truck is in IN, a little SW of Ft. Wayne. He drove it from SE NM to there with just a couple of issues.
 
Stock87 said:
Swapped the CPS, nothing.
I am not getting a signal at the tach during cranking.ECM? Tried swapping the ecm relay with the horn relay, nothing.
30 amp fuse for the fuel heater/ecm still good.

At this point it’s not even trying to fire anymore. No CEL, never saw one in the truck in the last 25years. Don’t even think it has one.
I tired linking up cheap scan tool, cannot connect to ecm.

Trying to link to the computer with a higher quality scan tool is my next move. I’m guessing the ECM might be done. Dunno?
Click to expand...
I would pull the PCM and inspect, it could be dead. Mine did crazy things when it failed; when I pulled it out I found corrosion on the SCRs inside. As soon as they'd warm up they'd stop working properly.
I'll take a look at my EVTM when I get home from work to double check the wiring for the CPS as I don't remember the path the signal takes on it's way to the tach. I'm skeptical of any issues with the IDM because if you're not getting a crank signal it's not gonna fire the injectors anyway.

Both my old PCM and the replacement one have issues with the OBD-II port, and that seems to be a common thing on the 7.3s from what I've read.
 
You getting a WTS light? If not i'd say its possible the ecm is done if fuse & relay r good.
How does your engine harness look overall?
These flow charts work pretty good to narrow most things down quick.

PSD Crank No Start Flowchart.jpg


Ive also read/seen some crazy shit before
An example, no fuel pump, glow plugs working. Oil pressure after cranking. No tach movement. Scanners would not connect to the ECM and it turned out to be a bad ebp sensor.

Unhook the main engine harness on pass V/c with 10mm, if its a bad sensor or short in engine harness your ecm may come alive. if so start narrowing down by pulling plug on sensors one at a time with the main harness hooked back up and key on with scanner connected and see if it comes alive. obviously it wont crank with ipr unhooked (and one other one i cant remember right now)

Somtimes a sensor going bad will shut down the ECM.

Also, Check your grounds!
 
Levigarrett76 said:
Somtimes a sensor going bad will shut down the ECM.

Also, Check your grounds!
Click to expand...

I could see that.

In the 96 EVTM the CPS goes right to Pin 49 (DG, "CAM Position Sensor") + Pin 65 (L/B, "CAM Position Sensor Return") of the PCM. the 3rd wire is the 5v reference (BR/W) , and it also goes to the EBPS, ICP, MAP, BARO & AP (accelerator pedal). So its entirely possible that a shorted power wire in the engine harness, or a shorted sensor could be dragging the rest down.

Edit:
I have the 96 book. if you want/need diagrams let me know, and i can snap some pics of it.
 
You're using the ford A.C. compressor on your build, right?

I wound up with a fleet of obs 7.3 trucks in the last year, I'd take a flat rate box full of rando stuff if its just going to scrap
 
YotaAtieToo
Is the fuel bowl in good shape? My 7.3 sprung a leak yesterday and I think it's the hoses in the valley but I won't know until I pull the bowl out Monday.
 
Projectjunkie said:
You're using the ford A.C. compressor on your build, right?

I wound up with a fleet of obs 7.3 trucks in the last year, I'd take a flat rate box full of rando stuff if its just going to scrap
Click to expand...

Yes, keeping ac compressor

Rockota is getting the injectors, glow plugs, turbo, hpop and a few sensors. Anything else you can think of?

reptillikus said:
YotaAtieToo
Is the fuel bowl in good shape? My 7.3 sprung a leak yesterday and I think it's the hoses in the valley but I won't know until I pull the bowl out Monday.
Click to expand...

Man, I'm not sure, that thing was always the bane of my existence. :laughing:

I can pull it off and take a look, might be a good way to be able to rebuild one with out as much down time?
 
Im figuring either i have a leaky hose, or the bowl is cracked. It runs good just leaks into the valley, and at $5.86/gal thats unacceptable! No rush on it, im not even sure if i need it yet.
 
reptillikus said:
Im figuring either i have a leaky hose, or the bowl is cracked. It runs good just leaks into the valley, and at $5.86/gal thats unacceptable! No rush on it, im not even sure if i need it yet.
Click to expand...

I hate how much shit they crammed into the valley of the 7.3. If I had kept it, I would have done a fuel bowl delete for sure. I'd look into that myself.

I've heard decent reviews on this kit. I'm sure it could be assembled cheaper if you wanted to.

Keeps the stock mechanical pump.

www.ebay.com

1994-1997 OBS Ford 7.3L Powerstroke Fuel Filter Bowl Regulated Return Line Kit | eBay

Find many great new & used options and get the best deals for 1994-1997 OBS Ford 7.3L Powerstroke Fuel Filter Bowl Regulated Return Line Kit at the best online prices at eBay! Free shipping for many products!
www.ebay.com
 
reptillikus said:
oh dude, thats way cheaper than what i was looking at:

www.iratediesel.com

94-97 7.3L OBS COMPLETE FUEL SYSTEM (Includes Regulated Return) NOW WITH NEW BOSCH 464-200 PUMP AND BILLET FILTER BASE! : Irate Diesel Performance

IDP-OBSFUEL-S Continue reading
www.iratediesel.com www.iratediesel.com
Click to expand...

Well thats obviously a much more evolved kit. Full electric conversion for like 500hp.

The one I sent keeps the obs mechanical pump, which is nice for simplicity and will still support "stage 1" injectors fine from what I've read.
 
It’s way to cold outside for me to continue messing with this thing.

I did get the OBD port to work. Same fuse that runs the power port at the dash runs that too. Scanner linked up with no codes found.

it does have a chip plugged into the ECM. (Banks) Been in there for 20yrs. May pull that out to see if it does anything.

Nothing is going to happen til it warms up. 20 degrees with a 20 mile an hour wind does nothing for motivation
 
Definitely yank the chip, its an easy way to eliminate that possibility.

I feel ya on the cold, i was just outside clearing the ice & snow off the cars.

Is the CPS connector ok? Dont remember if this came up or not, but I had to replace mine ~10 years ago because the plug was bad. Its a frequency based sensor, if the pins even look a little wonky theyre probably bad and you wont get a good signal, if you do at all. Ford had a TSB to replace the plug with an updated version with gold terminals. I swapped mine, and sensors that i thought were bad, suddenly started working again.

Ford p/n# 7U2Z-14S411-SA
cps plug.jpg


Technically this p/n applies to 96-97 only, but obviously it will work with all of them.


YotaAtieToo said:
Well thats obviously a much more evolved kit. Full electric conversion for like 500hp.

The one I sent keeps the obs mechanical pump, which is nice for simplicity and will still support "stage 1" injectors fine from what I've read.
Click to expand...
Yeah i like that kit; nothing wrong with my mech pump, and im only running Baby Swamps so i dont need some monster fuel pump.
 
Last edited:
I think i found the source of the fuel leak on my 7.3:
KIMG4932.jpg


Didnt get a chance to drive it, so ill know for sure tomorrow, but im betting my ~15 year old pump was leaking
 
No i was able to get it out w/o bending it :smokin: Fishing that damn banjo bolt in and out under the turbo pedestal kinda sucks!
 
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