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Discussion Starter #1
Hey guys long time reader first time poster.
I've had this 97 7.3 OBS for just over two years and have been keeping busy doing maintenance items that have been overseen over the years by po.
One thing I noted little after I purchased was the rpms would slightly fluctuate up and down at idle causing you to notice a vibration as the rpms would fall down then start to rise but wasn't to concerned.
Along with the basic other maintenance I've been catching up on I've also delt with all the fuel leaks in the valley such as fuel lines, replaced mechanical fuel pump, replaced fuel filters etc.
Although these leaks have kept my parking spots a lot cleaner they haven't done anything for the rough idle and over time its been getting worse that I'm trying to narrow down what is causing this before it becomes worse and causes damage to my dd or leaves me stranded.
This seems to be getting pretty consistent once engine is warmed up and idled weather in drive or neutral /park and is annoying in drive thrus lol
I've done cylinder contribution test with my scanner and passes no issues but hard to get one to complete being its winter and temperatures drop quickly stopped.
Buzz test also passes and solenoids sound the same from one cylinder to the next.
Disconnected the ICP sensor and seems to fluctuate at idle just the same
I've done some monitoring of data after going for drives and see if I can see anything out of ordinary but hard as this is my first Powerstroke/ HEUI Engine
I have noticed the truck has more of a distinct 7.3 diesel smell to it but it is cold out and will blue smoke just for a little under a cold start but heard thats normal
At this point the truck has 230,000 KM, wondering if its simply time to be going thru these stock injectors but don't like the idea of throwing parts without some insight on guys who have more experience with these heuis.
Would an IPR be causing a rough idle like this or is that just wishful thinking.
Thanks in advance for any advice / help


97 FORD F250 OBS 7.3 POWERSTROKE
STOCK FUEL / TURBO / NO TUNES
 

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230,000 km is not quite ready for injectors on a properly maintained truck. But it would not hurt to send them off to Jim at Rosewood diesel for a recondition.
 

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I think that if you are going to go to all the trouble to pull them out and possibly have them reconditioned I would just get some bigger ones along with a chip to run the new ones.
 

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Discussion Starter #4
I kinda thought low km's for injectors aswell but didn't know being the age of the truck or the nature of these injectors.
Also why I was questioning if the IPR would cause it to fluctuate the way it is or if it made more sense it being more injector related from your experience,
However I am not against going with moderate size injectors to wake her up a little bit but keep things reliable in the future.
What have you guys done in your trucks for injectors if you have?
 

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My truck was horribly neglected for ~300Kmi by its original owner. But I have zero indication that there's any problem with its injectors (which I assume are original, based on the condition of the VCGs).
 

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Discussion Starter #6
My truck was horribly neglected for ~300Kmi by its original owner. But I have zero indication that there's any problem with its injectors (which I assume are original, based on the condition of the VCGs).
Cant say mines been horribly neglected but things have been overlooked to say the least, one thing being assuming from our winters (Salt and moisture) it had an accumulating of rust in the bottom of the filter base that probably hasn't helped any. However besides this rough idle the truck doesn't knock or emit white or black smoke, and doesn't produce an excessive amount of power which sounds on par for an obs 7.3. So was hoping that I'm overlooking something causing it lol
 

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Discussion Starter #7
Figured I'd give an update.
Decided to go back to the basics as I believe it to be getting worse over time and decided to check mechanical fuel pressure.
At idle it fluctuates between 10 to high 22 PSI so definitely out of normal operating range
Time to trace what may be causing this weather its the couple month old mechanical pump or something else
 

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At idle you should be up around 50psi fuel pressure, that 10 to 22 psi is what you should get just cranking the engine over.
 

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Discussion Starter #9
At idle you should be up around 50psi fuel pressure, that 10 to 22 psi is what you should get just cranking the engine over.
I'm gonna start by checking out the fuel pressure regulator to see if anything is hanging up there as the bowl used to be real dirty but I cleaned it out and change the filter with each oil change.
 

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Be careful playing around with the FPR. If you break it you will then be trying to find a new filter bowl, the FPR is not a replaceable item unless you have a spare filter housing.

I would place a actual pressure gauge onto the schrader valve and run a hose on it to where you can read it as you drive down the road. If you do go this route get a glycerin filled pressure gauge to keep the needle from jumping all over the place when you try to read it.
 

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Discussion Starter #11 (Edited)
Be careful playing around with the FPR. If you break it you will then be trying to find a new filter bowl, the FPR is not a replaceable item unless you have a spare filter housing.

I would place a actual pressure gauge onto the schrader valve and run a hose on it to where you can read it as you drive down the road. If you do go this route get a glycerin filled pressure gauge to keep the needle from jumping all over the place when you try to read it.
I agree with checking it mechanically with a glycerin filled gauge as that's what I have done but if I'm running such at such low pressure at idle I'm assuming its not going to get better with load on the engine, but I can take it for a spin.
Besides it being the mechanical pump that I just recently replaced (which doesn't mean much besides doesn't leak lol) I wondered if debris from the previously dirty fuel bowl made it to the FPR and caused the spool body to be damaged and causing it to bind. What should I be careful of before going there? I don't want to throw parts if the mechanical pump isn't the issue.
 

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You may wish to clean the fuel return screen on the drivers side of the fuel bowl canister. This may help with a smoother idle too. Drain some fuel from canister, pull filter, using Q tips, small flashlight and small mirror clean screen. Stainless screen can be found on drivers side inside bowl about 1/3 way down a I recall. Dip Q-tips in fuel and wipe out screen until you see shiny stainless steel. May take a number of Q-tips, typically black keerap comes off the screen.

Next do a search on here called shimming the fuel regulator. Also search on here to assemble a DIY electric fuel system, excellent mod will aid with idle, smoother running to RedLine. Installing injectors is a great mod, will most certainly wake your ride up. 160/30 or hybrids like 205/30s are awesome. Just understand you will need supporting mods like intercooler, electric fuel, Downpipe and tranny mods if an E4OD.
Cheers.
 

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Discussion Starter #13
You may wish to clean the fuel return screen on the drivers side of the fuel bowl canister. This may help with a smoother idle too. Drain some fuel from canister, pull filter, using Q tips, small flashlight and small mirror clean screen. Stainless screen can be found on drivers side inside bowl about 1/3 way down a I recall. Dip Q-tips in fuel and wipe out screen until you see shiny stainless steel. May take a number of Q-tips, typically black keerap comes off the screen.

Next do a search on here called shimming the fuel regulator. Also search on here to assemble a DIY electric fuel system, excellent mod will aid with idle, smoother running to RedLine. Installing injectors is a great mod, will most certainly wake your ride up. 160/30 or hybrids like 205/30s are awesome. Just understand you will need supporting mods like intercooler, electric fuel, Downpipe and tranny mods if an E4OD.
Cheers.
I've cleaned that screen from inside the fuel bowl but was wondering If I should be pulling the FPR off the bowl to be getting behind the screen as well but not sure if that would remedy low fuel pressure?
However I have seen people shimming the fuel regulator and was thinking I should pull the regulator out and inspect being my pressure is so low just wasn't sure as don't want to break anything as Bugman advised.
Upgrades may definitely come in the future but currently its my daily driver and just trying to keep it reliable lol
 

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When my trucks had stock fuel systems I never removed the FPR, just cleaned screen from inside bowl. Shimming the FPR does help on most trucks. Is fuel pressure low on either tank? Thinking you could have debris on the intake screen in tank.
 

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I tried the BB mod years ago and it didn't do that much for me. I then went with the California spring and it helped quite a bit.

Here is the part number for the spring kit. F6TZ-9K061-AA
 

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Discussion Starter #16
When my trucks had stock fuel systems I never removed the FPR, just cleaned screen from inside bowl. Shimming the FPR does help on most trucks. Is fuel pressure low on either tank? Thinking you could have debris on the intake screen in tank.
Just checked to verify and its low on either tank. Removed the FPR and it moves smoothly in the bore so I shimmed it to test the theory and it increased fuel pressure to within spec.
Gonna run to town and get myself an appropriate sized BB to more appropriately shim it up and go from there
I'm thinking it will definitely improve the idle but well go from here.
I tried the BB mod years ago and it didn't do that much for me. I then went with the California spring and it helped quite a bit.

Here is the part number for the spring kit. F6TZ-9K061-AA
And Thanks Bugman didn't realize there was such thing as a California spring. I believe that mine must of just become relaxed over time but might not be a bad idea to put an improved spring but will likely end up going efuel before much longer like Jcart Suggested.
 

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At one point, if memory serves I made an adjustable (cap machine threaded nuts and cap screw) that fit inside the FPR plunger such that I could adjust the FP. Mine seemed to like 62-65 psi at idle.
 

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Discussion Starter #18
At one point, if memory serves I made an adjustable (cap machine threaded nuts and cap screw) that fit inside the FPR plunger such that I could adjust the FP. Mine seemed to like 62-65 psi at idle.
Well got back from town and installed a bb per the mod instructions and pressure was little better but still on the low side 25 - 35 psi, I added a second one to see if that would help with more spring pressure but stayed right around the same pressure with a lot of bouncing around at idle or revved up.
Now I do understand this is a mechanical pump and its normal for it to fluctuate.
Did it take you quite a bit of adjustment to get spring pressure high enough to achieve that pressure or maybe am I up against a pump that can't keep up with flow requirements and dosen't matter how much I shim it it won't be able to make it.
Like I said I replaced the old one a few months ago due to it dumping fuel down the valley but I just got this gauge setup so never checked my fuel pressure following installation.
 

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As I recall on all my trucks (4 now), BB worked ok, however I wanted greater adjustability so I went with a very small machine screw and two nuts in this way could adjust pressure to 60-65 psi. Two BBs would have compressed the spring a lot.... probably would make 70 psi or greater, which is not recommended.
 

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As I recall on all my trucks (4 now), BB worked ok, however I wanted greater adjustability so I went with a very small machine screw and two nuts in this way could adjust pressure to 60-65 psi. Two BBs would have compressed the spring a lot.... probably would make 70 psi or greater, which is not recommended.
Yea I wasn't even coming close to those kinds of numbers. Sitting at the highest 35-38 psi, I've got issues elsewhere maybe its time for efuel like you were saying.
 
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