# 7.3 misfire?



## Shade Tree NJ (Dec 26, 2010)

Have an 03 7.3 with 120,000 miles on her. A handful of times in the last 2-3 weeks she has basically "coughed" or almost died then catches itself at a light or stop. Haven't checked for codes, happens real intermitently, just want to catch it before gets worse. A buddy who is 50/50 on diesel knowledge said was it misfiring but I don't know for sure.


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## Dogplow Dodge (Jan 23, 2012)

I don't own a 7.3, but I get Diesel Power mag and read through some of the tech articles from time to time. (and I stayed in a Holiday Inn Express last night)

So, one of the thing's I've heard about is the CPS (crank Position sensor) tends to go bad, and can cause either a no start,or a rough run . I found a good site that has an entire FAQ section on them, if you want to review it. Once the CPS gets changed, the problem tends to stay away until the next time you need to change it again.... sometimes never. 1/2 hour or so to switch it out from the article I read.

Cold weather, like it's been, I would first replace the fuel filter and put Power Service Red bottle in the tank, and filler up. I had my mitsu gel inside the fuel filter housing last year, and now I run that Powerservice white bottle anytime it's going to be cold. Don't want to relive that again.

Hope this helps. http://www.thedieselstop.com/forums/f47/


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## fatheadon1 (Dec 27, 2007)

Check the oil level my buddys 7.3 would do that when it got low on oil because the injectors are fed off the high pressure oil pump


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## Sprag-O (Dec 31, 2013)

CPS or Fuel delivery... No coils, plugs, wires to worry about.


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## Sawboy (Dec 18, 2005)

CPS is likely culprit


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## Shade Tree NJ (Dec 26, 2010)

Going tom top by auto zone or advance tomorrow or Thursday when get a few free min and have them scan it to see if any codes.

Will swap out filter, changed it about 5k miles ago but a cheap fix, doubt that lucky!

Usually use the dark gray bottle of power servicd every few tanks.

Oil is good, checked twice weekly as has a leak from oil pan ( to much $$ to swap out )

I believe cps was replaced about 2-3yrs/25k miles ago, but again for cheap fix worth the few $$ to see if fix. Again usually not that lucky.
********************************
When cold, won't start in morning w/o being plugged in. Not sure if related or not
Thanks for the quick replies and cheap fix tries (under $75 and some time)....will keep you posted


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## Plowtoy (Dec 15, 2001)

Shade Tree NJ;1897130 said:


> Going tom top by auto zone or advance tomorrow or Thursday when get a few free min and have them scan it to see if any codes.
> 
> *Probably wont find any*
> 
> ...


I think that should help ^^^^^ Worse case, you could have a failing IDM (injector driver module), but usually, those are all or nothing when they fail


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## plowguy43 (Jan 2, 2008)

OP - In the order I listed below is most likely what is wrong and/or what you should check/do first:
#1


fatheadon1;1897040 said:


> Check the oil level my buddys 7.3 would do that when it got low on oil because the injectors are fed off the high pressure oil pump


#2


Sawboy;1897078 said:


> CPS is likely culprit


#3


Plowtoy;1898296 said:


> I think that should help ^^^^^ Worse case, you could have a failing IDM (injector driver module), but usually, those are all or nothing when they fail


#4 would possibly be a bad injector or harness has frayed. Make sure the oil is definitely full though or they won't fire.


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## Mark Oomkes (Dec 10, 2000)

Sprag-O;1897077 said:


> CPS or Fuel delivery... No coils, plugs, *wires* to worry about.


Wanna bet? See #3

Anyways, as the others stated:

1) Oil

2) CPS (should be codes if this is causing it)

3) Injector wire harness. The connectors become brittle from heat over time and cause intermittent runnability issues. This is a known issue.

4) Then something else, like IDM or GPR. A bad GPR is going to cause a hard start issue, not a runnability issue once it is warmed up.


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## plowguy43 (Jan 2, 2008)

If replacing the GPR (Glow Plug Relay) go to a Fisher/Western dealer and buy a solenoid from them for the plow. Its a much beefier round style relay that is much more reliable. My truck went from barely starting on cold days (requiring multiple cranks & glow plug cycles) to a one cycle and starting first try.


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## dieselss (Jan 3, 2008)

Did you get any codes? Till.he replies, were all spinning wheels


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## tjctransport (Nov 22, 2008)

www.ford-trucks.com is a very good source for troubleshooting issues with fords.

there are way too many possibilities for problems to figure out without knowing what codes are present. 
if it is misfiring, it may have a soft code that will not turn the CEL on. 
a very common problem with these trucks is the under valve cover harness.


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## Shade Tree NJ (Dec 26, 2010)

No codes according to guy autozone, however he seemed "annoyed" had to come out in cold even with no check engine light on. 

Good to know about the GPR....even though works may swap for bigger one.

Going to ford in morning for new CPS and fuel filter. Last few times I changed the fuel filter it was like an orange/rust color ( newer to diesels in past few years ). Also going to check the oil in morning before even starting when nice and cold and then again after warms up for a while.

Thanks for all the feedback and comments, much appreciated!


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## 98Chevy2500 (Nov 27, 2005)

AZ's $300 code reader may not be able to read all codes, especially "soft codes" as well as history. Find someone with a real scan tool, a SnapOff unit or Ford Software.


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## Shade Tree NJ (Dec 26, 2010)

Only person I know with "ford software" is the dealer who charges $150 diagnostic fee to take my keys and sign on the line....have to sit and think who I know that may have a "real" scan tool. As mentioned earlier, AZ guy was bothered to come out in cold after told him check engine light was not on.


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## plowguy43 (Jan 2, 2008)

Going to Ford to replace a CPS is also a waste of money. You can buy one and fix it yourself for a heck of a lot less money. Part of the beauty of the 7.3 is that it's a fairly simple diesel to work on.


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## tjctransport (Nov 22, 2008)

where in monmouth county are you? i am just north of Matawan in Laurence Harbor, and have auto enginuity if you want to plug it in.


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## Shade Tree NJ (Dec 26, 2010)

My shop is in englishtown...may take you up on plugging it in.

Not going to have ford replace it, seems easy enough to do from what I saw online so picked up to do tomorrow if get some free time.

Here's a pic of the fuel filter swapped out and the inside of the fuel bowl


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## Shade Tree NJ (Dec 26, 2010)

Nothing in bottom of bowl, wiped down with a clean rag just dirty looking.


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## dieselss (Jan 3, 2008)

Steel tank(s) or plastic?
That is horrible looking. And that "stuff" got past that filter fyi.


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## newhere (Oct 13, 2009)

50 cent repair ? Fixed my hick up


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## Dogplow Dodge (Jan 23, 2012)

Uh..... You've got something wrong there....

Someone, or somewhere you have dirt in your fuel. That's NOT normal. Our fuel is green tinted, and at the most, there would be bits of yellowish chunky stuff in there. 

Brown fuel ? Where do you buy your diesel ? just so I know and I NEVER buy from them...


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## Shade Tree NJ (Dec 26, 2010)

Opened uptop of tank today (on a mason dump so very easy to access ) and fuel in tank was basicaly clear. Nothing even close to color of filter in previous pic. Usually fill up @ QuickCheck in Englishtown, high turnover of fuel as steady flow of diesel customers. 
Had the issue of delaminitating the inside of tank when first purchased truck a few years back. Cleaned fuel sender unit, shop vac entire tank (flakes and little fuel left), wiped clean with rags. Tank was spotless at the time and not a spec of rust inside. As mentioned earlier fuel in tank was clear today, with no new flakes from delamination. Could fuel line be rusted / rusting causing color of filter?


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## dieselss (Jan 3, 2008)

Fuel lines, fuel pump on the rail.


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## Shade Tree NJ (Dec 26, 2010)

Been researching on,kne and came across a few posts that say could possibly be alge in fuel??? 

New fuel lines and rail pump sounds $$


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## Dogplow Dodge (Jan 23, 2012)

Well, I guess it's something else going on, as Quik Check is primarily where I go. My fuel lines are plastic, and I've had my tank (also plastic) out 3 times since I bought the truck 4 years ago. Never anything inside, and the algae thing is usually a different color. Diesel fuel will leave deposits of chunks of whiteish / greenish /black stuff in there, which is the fuel degrading also technically called "agglomeration of asphaltene and the formation of solids in the fuel system". AKA fuel breakdown into waste products..

Read here about it..

http://www.mydieseldoctor.com/FAQ.html

Not a chemist, but all fuel tends to break down over time. Not sure why you have rust color in your fuel filter, but I can only assume the truck's fuel lines from the tank are deteriorating. I'm sure other's here have had similar issues.

Keep changing the filter, more than the recommended 5k intervals, and see what it gets you.

FWIW, I put a quart of 30w in every tank full to add lubricity and keep injectors lubed. Cheap insurance, IMO.


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## Shade Tree NJ (Dec 26, 2010)

Thanks for the info, going to check out that link. Plan on changing the fuel filter every 1k-1500 miles for next 5-6k to see condition of filter. Going to see how much / how hard to swap new fuel lines, see what that brings.

Really...30w in every tank of fuel? Never heard of or even thought of


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## tjctransport (Nov 22, 2008)

i have 12-13 year old fuel and not one bit of algae in it. 
i think that is more of a southern state thing.

i wonder if you had someone put dirt in your tank?


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## Dogplow Dodge (Jan 23, 2012)

Shade Tree NJ;1900120 said:


> Thanks for the info, going to check out that link. Plan on changing the fuel filter every 1k-1500 miles for next 5-6k to see condition of filter. Going to see how much / how hard to swap new fuel lines, see what that brings.
> 
> Really...30w in every tank of fuel? Never heard of or even thought of


Some folks use 2 cycle oil with a rating of NMMA TC-W3® it, again, adds lubricity to the oil whereas the low sulfur oil supposedly is missing. This all has to do with lubrication of the injectors and injector pump.

http://www.cumminsforum.com/forum/a...oils-lubricants/43664-proof-2-stroke-oil.html

IDK, Not a chemist, so I don't know if it's 100% accurate. Still cheap insurance though...


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## tjctransport (Nov 22, 2008)

that is a cummings thing. ford diesels do not need it, all the lubrication they need is already in the fuel as it comes out of the pump.


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## SnoFarmer (Oct 15, 2004)

A myth and a scare tactic ,
A myth that suffer is or was a lube, 
Yes the process of removing the surfer does lower the luberisity.
You can find my home work on fuel on cummins forum also.

They add it back into the fuel before it gets to the depot.
Where a brand specific additive is added then delivered to the station.
And the % of #1 &#2 is adjusted for the climate 

Next even in the winter most states still have a % of bio.
Bio adds even more luberisity to the fuel, more than is needed.

No one needs 10W or 2 cycle oil if they did the trucking industry and the construction industry would be up in arms, they aren't and nether do the 5.9's or the 6.7's

Rust= water 
Old Fuel darkens old fuel will turn your filter black, asphalthaines sp

I use Howes, because it binds with the water to make it even easer for the fuel water separator to catch the water. Stay away form alcohol like you find in 911 or a additive that emulsifies 
But I'd drop that tank and take a look.


Ps if your truck is emission intact do not use 10w or 2cycel oil it will clog up the PDF causing more regens to occur lowering your millage and gum up the 
Exhaust brake and putting you in the shop


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## SnoFarmer (Oct 15, 2004)

So the black build up is normal it iis a sign of fuel decay or that someone in the past ran waste motor oil threw it, you can clean it out.
The red = rust = water. 
I'd be addressing it now if it was mine.
Injectors get expensive and pumps aren't cheep.


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## FISHERBOY (Aug 13, 2007)

A GOOD fuel additive would be stanadyne rev/x or the ford additive, use about every 3,000-5,000 miles


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## dellwas (Oct 16, 2005)

Does an '03 have an electric or diaphram type pump? My '97 7.3 would "stumble" every once in a while, and eventually died. Turned out to be the diaphram type fuel pump.


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## dieselss (Jan 3, 2008)

2 pumps. One on the rail...low psi
And then the high psi gear pump. 

Which pump did they replace on yours?


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## dellwas (Oct 16, 2005)

Were you asking me? The '97 only has one diaphram pump AFAIK. I replaced it myself. It is in the valley between the cylinder banks and is cam driven.

Here's a pic:

http://www.dieselorings.com/21-020-mechanical-fuel-pump-w-banjo-bolt-gaskets-1994-5-1997-oem.html



dieselss;1908708 said:


> 2 pumps. One on the rail...low psi
> And then the high psi gear pump.
> 
> Which pump did they replace on yours?


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