Hello,
My 7.3 is an early 99 with 450,000 miles. I decided to perform maintenance yesterday. Here's what I did that now leads to a NO START.
1. Changed oil and filter.
2. Changed air and fuel filters.
Then I decided to change out the top end wiring harness with a new Ford assembly # F81Z-12B637-BA, Used VIN number to verify. So, it begins. I laid out the harness to match up with the old one and a problem quickly showed up. At the GPR, the old harness has 5 extra wires going to it where the new on does not. I could not find what these 5 wires were for. I did a search to no avail. For now, the new harness will not work on my 99 F250. See images attached. Next, I decided to change out all the old sensors. They are all originals with 450,000/20+ years on them except the exhaust backpressure sensor and the camshaft position sensor. These I changed out over 10 years ago.
I replaced the following sensors with Ford Motorcraft replacements.:
ICP
IPR
CPS
EBP + Tube.
MAP
Coolant temp
Engine Oil temp.
Attempted to start the engine, only to find I forgot to tighten one fuel line, and the engine valley got flooded with diesel. Tightened the line, cleaned up the fuel. and refilled the bowl.
Went to start the engine again, there still is a no start condition.
I then replaced the
CPS with the old one, still no start. RPM needle doesn't bounce when cranking with either the old or new CPS.
Removed the lead from the ICP sensor, still no start. Replaced the ICP with old ICP, still no start.
Checked the HPOP oil level and it's full. Fuel bowl is full.
There are no codes set.
I checked all the fuses, and they are good.
I'm at a loss here in moving forward. the only thing I haven't done is to reinstall the old IPR.
I do not have a scan tool to diag PIDS as this truck has been so reliable since 99 with no need for one.
If anyone has had this problem or has ideas of where to continue troubleshooting, I'd appreciate your input.
The new harness image is first, then the old. Sorry for the large images, didn't know how to resize.





To all that respond. Thank you in advance. Jeff



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Do not throw parts...... #1 rule!!!!
Get FORScan or FORScan Lite and the exact OBD II reader they tell you to get.. (( as you did not share what you used))
Pull all codes, clear all codes, pull all codes and share both results.
Run every test FORScan has and share results.
Make sure oil is properly serviced and on the hash marks.
Make sure the HPOP has oil about 1 inch from the inspect port.
Make sure you have well over 1/4 tank of fuel.. See Hutch/ Harpoon mod.
Make sure that over night sitting the batteries are 12.6 volts, key on about 11.5 volts for glow plug cycle, and never less than 10 volts when cranking... If you drop below 10 volts you will fail to start every time.

 

So it cranks but doesn’t fire is what I’m assuming? I wonder if the “Early 99” part is part of the problem. Clearly they aren’t t the same wiring harness and this can get a little tricky replacing parts that are that old. What was wrong with the other one?

 

The old harness is 20+ years old and 450,000 miles. I decided to install a new harness with new sensors to improve drivability.
That's all. I'm not throwing parts at a problem. The problem started after changing the sensors. In retrospect, I should have changed
one sensor at a time, then start the engine to ensure the sensor worked and move on to the next. Lessons learned.

 

my #1 rule along with ForScan codes,

never, change, more than one (1) part at a time, until you verify it will start and run....

change 2 parts or more, and which one or more is Bad???

 

I think that piece with the extra wires was an early version of something where the PCM could tell if both banks of glowplugs were pulling the same amperage. But that’s a far back memory from reading on here so please don’t take that as correct.
@cleatus12r can tell you for certain what it is and it’s purpose. The tag will allow him to see we’ve requested his advice.

I would probably swap the harnesses back and see if that fixes the issue. Not the happiest plan but it’s a large chunk of the changes.

Normally we mention the possibility of the fuel bowl stand pipe check valve getting messed up with the fuel filter change. But you said you had fuel leaking from a line which makes me think you have fuel coming out of the bowl. Was the leak between the bowl and head or elsewhere?

An uncommon but possible issue is getting the IPR and EBPV connectors swapped. They use the same style connector.

Otherwise, getting set up to use FORScan and monitor some things while cranking would probably be the next step short of swapping all the old parts back over.

 

That glow plug relay shouldn't make any difference. The old one has the left and right banks separated but they are still both jumpered to the power lug of the relay. Not sure about the extra wires but I'd guess they don't do much and wouldn't be surprised if they don't all merge into 1 somewhere in the loom. If the 42 pin looks the same then I wouldn't worry much. A multimeter set to continuity might tell you where the extras end up. So which fuel line wasn't tightened? Have you checked the IPR has voltage when the key is on? For giggles check the stand pipe in the fuel bowl. Make sure it's straight and fully seating, or just gut the damn thing to completely rule it out.

 

The fuel leak was from a fitting at the bottom right side of the bowl, just below the inlet line. I forgot to tighten it down.

The old harness has been reinstalled and I still have the no start.

On the fuel bowl standpipe comment. I haven't had a problem with it in the 20 years I've had the truck. If it is messed up, do I just remove it?
Thanks for the info.

 

I haven't yet checked voltage at the IPR. Plan on doing that this morning. I'll check that standpipe as well. Thanks.

 

Morning everyone,
I was looking at the Forscan tool at their website. Which adaptor should I buy? OBDLink EX or the vLinker FS? I would be using the adaptor
with my laptop only.

 

for myself,
I would get the USB wired adapter to your Laptop.

they always work, and the Speed of how the data is transferred to the laptop is noticeably faster.

I saw that myself, when my Bluetooth adapters used to work, they were slow, then I bought the USB version and it was several times faster recording DATA than the BT versions.

 

Your Early 99 is a California emissions equipped truck, having a GVWR below 14K lbs., with a glow plug relay having left and right bank current monitors, which are separated by a power dividing nichrome shunt. In later years, an entirely different set up, called a Glow Plug Control Monitor was utilized, that looks more like a computer module than a relay. But you have the predecessor to the GPCM, which is more like a traditional relay, but with left and right banks divided by the shunt.

Most people in the other states do not have your style of relay. This will frustrate your reading and research of other people' experiences. And it may frustrate their well meaning attempts to help you. When you keep in mind that you have something different than what many others have, you will be able to sort through any misunderstandings they have about what you have.



I wouldn't guess at wiring, especially wires that are routed directly to the PCM.

The left and right banks are separated so that each bank can be monitored separately. The extra wires are how the PCM "sees" what is going on with each bank. Therefore the glow plug relay wiring DOES make a difference, and a mistake in wiring could cause a check engine light (aka Malfunction Indicator Light) that WILL automatically fail emissions testing, and render the truck unregisterable in California until repaired. This would worry me.


The PCM is looking for shorts, opens, relay malfunction, and current levels in each cylinder bank, for applications with this particular type of "California" split bank shunted glow plug relay.

When the glow plug relay is commanded on for longer than 35 seconds, monitoring begins, where the PCM is looking to read a minimum of 39 amps for each bank, and will set a DTC if that fails.

A California emissions PCM (pre GPCM) will utilize both Pins 8 and 9 (instead of just Pin 8) for the left and right relay bank monitoring circuits, as well as Pin 34, whereas 49 state glow plug relays only use Pin 8. In all states, Pin 101 still supplies the ground to engage the GPR relay.

If you pull codes, look for the following DTCs related to the left and right banks:

P1391 Glow plug circuit low input, Bank #1 (Passenger Side, Right) Open/short circuit, relay fault, glow plugs.

P1393 Glow plug circuit low input, Bank #2 (Driver's Side, Left) Open/short circuit, relay fault, glow plugs.

P1395 Glow plug monitor fault, Bank #1 (Passenger Side, Right) One or more glow plugs failed, circuit fault.

P1396 Glow plug monitor fault, Bank #2 (Driver's Side, Left) One or more glow plugs failed, circuit fault.

 

That's exactly what I was going to point out.

 

Ok the leak was from the return line to the tank which is independent of the fuel rails. That supports the possibility of it being the stand pipe. Well maybe not supports but doesn't rule it out. If you remove the black tube that the filter slides onto you should see a small valve assy. in the bottom. You can remove all the pieces and reinstall the tube. If that solves your no start then you can either leave the parts out or reinstall them and be mindful of how the tube installs when changing the filter, If it doesn't fully seat no fuel gets to the rails.

 

Thank you for the detailed explanation.
Jeff