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7.3 Gurus...Got An Issue

catmandu

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You are sure the lift pump is running when the key is on. Check for 12v at the inertia switch, Ford in all their wisdom, put a non serviceable breaker inside the fuse panel,
so even if the fuse is good it will still not put power to the pump. Just a thought
 

TimeBandit

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You said you got 250 psi ICP rail pressure cranking, my research says 500 is needed

  1. IPR (Injection Pressure Regulator) bad, will cause low ICP.
  2. IPR o-rings bad, will cause low ICP.
  3. Injector o-rings bad, will cause low ICP. Should also show up as black fuel (from oil in fuel) in fuel filter canister.
  4. High pressure oil pump bad, will show up as low ICP.
  5. RPM, minimum 100 rpm cranking speed (When warm it should be over 180 rpm)
  6. ICP, minimum required for starting 500 PSI if no rpm signal, ICP won’t go over 400 PSI
  7. Voltage during cranking 7-10 volts minimum depending on year
  8. Pulse Width; 0 ms means no sync, 1994-1997 .42 ms indicates that PCM and IDM are in sync (on 99-03 it should be .60 ms) and the PCM is waiting on the ICP to reach the minimum of 500 PSI. When min. ICP is reached PW should change to 1-6 ms
I really know nothing about these things, let us know what you find!
 
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Mototrig

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So @monkeyswrench I wonder if one of the HPOP lines has popped lose and leaking pressure. Perhaps the one that was replaced? Worth a shot, if low HPOP pressure is indeed the culprit
 

monkeyswrench

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So @monkeyswrench I wonder if one of the HPOP lines has popped lose and leaking pressure. Perhaps the one that was replaced? Worth a shot, if low HPOP pressure is indeed the culprit
HPOP is working great. On the scanner making pressure, and no oil everywhere. Injectors are just asleep.
 

4Waters

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Spray the CPS, ICP and IRP pig tails out one at a time with brake clean, if any of them have oil in them it can cause problems.
 

77 SLEEK

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I was reading this post and thought nobody has brought up that on the 7.3 there is a coiled heater in the bottom of the fuel filter bowl. We would see that the insulation would fall off and the heater coils would short to ground. This will blow the fuse for the PCM power up circuit resulting in a crank no start condition. Maybe something to check out?
 

monkeyswrench

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I was reading this post and thought nobody has brought up that on the 7.3 there is a coiled heater in the bottom of the fuel filter bowl. We would see that the insulation would fall off and the heater coils would short to ground. This will blow the fuse for the PCM power up circuit resulting in a crank no start condition. Maybe something to check out?
All fuses were good. Also checked that wire...only because a couple weeks ago I had a truck leaking fuel from it:oops: Honestly, I wouldn't have even thought to look there if I had recently dealt with that one.
 

ibelio

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250psi toooo looow oil pressure find leak/problem
 

Lumpy

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I`m no expert but know a little bit about various types of pumps and it seams like this revolves around the HPOP. Curious...have you checked the oil level in HPOP itself? I know it ran and all but it just seems odd. Maybe an air lock? IDK.
 

monkeyswrench

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I`m no expert but know a little bit about various types of pumps and it seams like this revolves around the HPOP. Curious...have you checked the oil level in HPOP itself? I know it ran and all but it just seems odd. Maybe an air lock? IDK.
Yep, checked it initially:(
 

SBMech

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I've been looking around since this has got my brain going, leading back around to 500PSI min with ICP plugged in.

You said it's only 250? Something is leaking internally. Injector O-Ring?

Found this handy dandy chart...maybe it will help.
 

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monkeyswrench

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Remember what I told you about the valve cover gaskets??

🤔
Been checked, buzz tested before and after too...actually looked newer.
I've been looking around since this has got my brain going, leading back around to 500PSI min with ICP plugged in.

You said it's only 250? Something is leaking internally. Injector O-Ring?

Found this handy dandy chart...maybe it will help.
I'm gonna print this out...this is freakin' gold here!
Sending a copy to the kid right now too.
 

rivermobster

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Been checked, buzz tested before and after too...actually looked newer.

I'm gonna print this out...this is freakin' gold here!
Sending a copy to the kid right now too.

No clue what a buzz test is, but if say it's good, I believe ya.

I'll text this thread to Jeff. Hopefully he's not too busy.
 

monkeyswrench

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No clue what a buzz test is, but if say it's good, I believe ya.

I'll text this thread to Jeff. Hopefully he's not too busy.
"Buzz test" lights off the injector coils. It buzzes them all, and then each one individually through the firing order. The scanner then will tell you which one didn't buzz, or was out of normal range. It's a quick way to see if you have continuity to the injectors.
 

rivermobster

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"Buzz test" lights off the injector coils. It buzzes them all, and then each one individually through the firing order. The scanner then will tell you which one didn't buzz, or was out of normal range. It's a quick way to see if you have continuity to the injectors.

Can you actually Hear them clicking?
 

monkeyswrench

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They ever try new batteries?
No, not yet. Everything was on hold, snow one night, high winds and cold the next. Today isn't bad, but he's out working. Probably this weekend. Oh, and the truck is not in a garage...wasn't looking to do this in the snow:oops:
 

Flyinbowtie

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500 PSI is required from the HPOP to fire the injectors as I recall. If ECM is not seeing it, no fuel is injected.
Sounds like you have run it down, not IPR or ICP. Look at the UVCH continuity, but I suspect injector O-rings.
If you only have one or two o rings failed, sometimes the truck will pick up the pressure if you can fire it on starting fluid, but this isn't something ya wanna do as a regular thing.

If you decide to do them, get them from Clay at Riff Raff Diesel in Oregon He will know who is building good ones, and there are a ton of junk ones out there to avoid. Motocraft and Alliant were the go to in my day.
Be gentle slipping the injectors and new O rings back in, we always lathered them in a thick coat of STP to lube them up, then changed the oil after start up. It is easy to cut one on the way in and then you get to start all over again.

If the truck hasn't been futzed with, while you are under the valve covers I would replace the glow plugs, and the valve cover gaskets as well.
Again, Motocraft or Alliant parts were my choices.
 

monkeyswrench

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500 PSI is required from the HPOP to fire the injectors as I recall. If ECM is not seeing it, no fuel is injected.
Sounds like you have run it down, not IPR or ICP. Look at the UVCH continuity, but I suspect injector O-rings.
If you only have one or two o rings failed, sometimes the truck will pick up the pressure if you can fire it on starting fluid, but this isn't something ya wanna do as a regular thing.

If you decide to do them, get them from Clay at Riff Raff Diesel in Oregon He will know who is building good ones, and there are a ton of junk ones out there to avoid. Motocraft and Alliant were the go to in my day.
Be gentle slipping the injectors and new O rings back in, we always lathered them in a thick coat of STP to lube them up, then changed the oil after start up. It is easy to cut one on the way in and then you get to start all over again.

If the truck hasn't been futzed with, while you are under the valve covers I would replace the glow plugs, and the valve cover gaskets as well.
Again, Motocraft or Alliant parts were my choices.
Yep, probably going to air check it...something is goofy as hell. The truck has been "futzed" with a lot. That's what makes it so frustrating. It has 200k on it, looks great, but everything has been messed with under the hood.
 

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I know I sound like a broken record but swap the batteries with a known good set. The more you tear into hard parts the more potential you have creating a new problem while figuring this one. Batteries are so simple.
 

4Waters

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Yep, probably going to air check it...something is goofy as hell. The truck has been "futzed" with a lot. That's what makes it so frustrating. It has 200k on it, looks great, but everything has been messed with under the hood.
When my injector o-rings went bad (2 on one side and 1 on the other) I had a long crank, like 8-10 seconds before it would fire, I figure if a second one went on the 1 side it probably wouldn't have started any more.

Has he had a long crank issue leading up to this?
 

monkeyswrench

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I know I sound like a broken record but swap the batteries with a known good set. The more you tear into hard parts the more potential you have creating a new problem while figuring this one. Batteries are so simple.
As I said, haven't even been back out there. It's 30 miles from my house to his. Between weather and my family commitments, not too easy.
When my injector o-rings went bad (2 on one side and 1 on the other) I had a long crank, like 8-10 seconds before it would fire, I figure if a second one went on the 1 side it probably wouldn't have started any more.

Has he had a long crank issue leading up to this?
Supposedly, no...but if he's like any of a million other car owners, they "forget" things.
 

idk

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After reading the first few posts of the symptoms my first thought is injector orings as quite a few have stated. I didn't see that you stated how many miles are on the rig but injector orings are really only good for about 70K miles they still run after that but there efficiency drops off dramatically and if it had a tuner it all goes out the window because they command so much pressure they get hammed, you can pull a fuel filter out on a 7.3 and it will be black that's the oil getting past the orings. I only use the motorcraft oring kits, I've tried most of the different brands and I've had the best luck with motorcraft.
 

monkeyswrench

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After reading the first few posts of the symptoms my first thought is injector orings as quite a few have stated. I didn't see that you stated how many miles are on the rig but injector orings are really only good for about 70K miles they still run after that but there efficiency drops off dramatically and if it had a tuner it all goes out the window because they command so much pressure they get hammed, you can pull a fuel filter out on a 7.3 and it will be black that's the oil getting past the orings. I only use the motorcraft oring kits, I've tried most of the different brands and I've had the best luck with motorcraft.
I did a set on a 450 a couple months ago. The oil was leaking out the top rings only I think. The fuel was clean in the bowl, and not burning or losing any oil. This one may be the same? With that one, o-rings from the Ford dealer. They had them, and I sure as hell didn't want to risk doing it twice.
 

idk

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I did a set on a 450 a couple months ago. The oil was leaking out the top rings only I think. The fuel was clean in the bowl, and not burning or losing any oil. This one may be the same? With that one, o-rings from the Ford dealer. They had them, and I sure as hell didn't want to risk doing it twice.
The fuel will look clean but the element will be as black as the ace of spades.
 

monkeyswrench

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The fuel will look clean but the element will be as black as the ace of spades.
Filter looked good when I pulled it out. Drained the bowl to check volume of lift pump. I have pulled them before and they looked like a 6 liter oil filter:oops:
 
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spectra3279

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Don't know if this will pertain to a Ford but my dodge one time would crank forever before starting but a push start would fire instantly. Come to find out starter was pulling to much power and not enough juice for the injectors.

And no the batteries were fine.
 

AzMandella

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I did a set on a 450 a couple months ago. The oil was leaking out the top rings only I think. The fuel was clean in the bowl, and not burning or losing any oil. This one may be the same? With that one, o-rings from the Ford dealer. They had them, and I sure as hell didn't want to risk doing it twice.
Here is where I get almost all my parts for my 7.3 .
 

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You are sure the lift pump is running when the key is on. Check for 12v at the inertia switch, Ford in all their wisdom, put a non serviceable breaker inside the fuse panel,
so even if the fuse is good it will still not put power to the pump. Just a thought
That sounds like the inertia switch. In the event of a hard impact with key still on, it shuts the fuel pump off so it won't pump fuel into a fire, if there is a fire. The reset switch is inside the passenger side kick panel.
 

Riverfamlee

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This thread is like a good whodonit murder mystery. I keep coming back to see if it is solved and I don't even like fords
 

Havoc Powesports

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Is it tuned chipped? might make sure the chip is fully seated, or uninstall the tune to factory. Had a custom tune drop the ball and left me dead in a 7.3 before.
 

micro525

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This may help you if you're still looking for the problem. Also included a helpful document about the CPS. Best of luck.
 

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monkeyswrench

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Well, I'm thinking the kid's upset that I couldn't fix it...he didn't call me last weekend. I feel like a doctor that lost a patient, "...if I only had more time!"

I'm starting a new 7.3 file...actual paper one. The top drawer of my tool box has different files for stuff I forget. Things like turn signal switch wiring diagrams for 60s-80s cars, and torque sequence and values for those F'd up tty motors. A lot of different info popped up on this thread. Even if it didn't get used on this one, it won't be the last 7.3 I work on.
 

Runs2rch

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Well, I'm thinking the kid's upset that I couldn't fix it...he didn't call me last weekend. I feel like a doctor that lost a patient, "...if I only had more time!"

I'm starting a new 7.3 file...actual paper one. The top drawer of my tool box has different files for stuff I forget. Things like turn signal switch wiring diagrams for 60s-80s cars, and torque sequence and values for those F'd up tty motors. A lot of different info popped up on this thread. Even if it didn't get used on this one, it won't be the last 7.3 I work on.
Kid will be back. Probably has an "uncle" with a sweet set of tools haha
 

81Sprint

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Is it tuned chipped? might make sure the chip is fully seated, or uninstall the tune to factory. Had a custom tune drop the ball and left me dead in a 7.3 before.
Mine did this but would cut out, lose power but wouldn't shut off completely at speed on large bumps, pulled the pcm out and reseated the chip and fixed the problem. Not easy thing to find though I was searching for a grounded or chaffed wire under the hood for a while.
 

4Waters

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Well, I'm thinking the kid's upset that I couldn't fix it...he didn't call me last weekend. I feel like a doctor that lost a patient, "...if I only had more time!"

I'm starting a new 7.3 file...actual paper one. The top drawer of my tool box has different files for stuff I forget. Things like turn signal switch wiring diagrams for 60s-80s cars, and torque sequence and values for those F'd up tty motors. A lot of different info popped up on this thread. Even if it didn't get used on this one, it won't be the last 7.3 I work on.
I don't think he gave you a fair try
 

SBMech

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I don't think he gave you a fair try

I thought it was his buddies kid anyhow?

I would guess that it's a $ issue more than anything. This shit is expensive to play with, and if he's getting shitty advice from others...well there ya go.
 

4Waters

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I thought it was his buddies kid anyhow?

I would guess that it's a $ issue more than anything. This shit is expensive to play with, and if he's getting shitty advice from others...well there ya go.
Don't I know how expensive it is, I became a diesel tech fixing my 7.3, bought some tools and made some, a lot of reading and videos and greasy hands and the truck was fixed. I learned a lot and was really interesting learning how the system works
 

monkeyswrench

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Yep, it's a buddies kid. I was trying to help him out, but no joy. Hell, just diag crap, meters, scanners and gauges, maybe a couple grand in crap? None of the new diesels are "cheap" to work on. When I was young, and working for someone else, my work truck was a Ford Ranger with a service bed...not flashy, but worked good and cheap!
 

SBMech

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Don't I know how expensive it is, I became a diesel tech fixing my 7.3, bought some tools and made some, a lot of reading and videos and greasy hands and the truck was fixed. I learned a lot and was really interesting learning how the system works
I meant if someone is buying parts and throwing them at it, not that Monkey was giving bad advice.

Very few these days can do what you can, teach themselves how to fix their own stuff. It's part of the magic of RDP, there are many members here who are blessed with talent.
 

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Any updates? I really want to know if they ever swapped batteries.
 

rivermobster

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Any updates? I really want to know if they ever swapped batteries.

I was wondering the same thing the other day...

The 8 month old Interstates in my truck BOTH took a shit! Each battery had one dead cell. 🙄

The truck would crank fine, but would NOT start no matter what!

Two new batteries and it's good to go. Freaking Interstates ain't what they used to be. Thank gawd the warranty is solid.
 

monkeyswrench

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Any updates? I really want to know if they ever swapped batteries.
Absolutely nothing. I have not heard from him since the Friday after Thanksgiving. He had written a text previously, and forgot to hit send(?) Anyway, I told him to air check the oil gallies. I'd found out he and his brother had done the injector o-rings shortly before this had started. I have not heard from him since....
 

timstoy

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I was wondering the same thing the other day...

The 8 month old Interstates in my truck BOTH took a shit! Each battery had one dead cell. 🙄

The truck would crank fine, but would NOT start no matter what!

Two new batteries and it's good to go. Freaking Interstates ain't what they used to be. Thank gawd the warranty is solid.
Joe, are your Interstate batteries made in Mexico?
 
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