6.9 idi sputtering, surging and loss of power

Max Harder

Registered User
Joined
Oct 3, 2021
Posts
8
Reaction score
4
Location
Colorado Springs
I recently bought my first diesel truck, a 83 f250 6.9 idi with a 4 speed. It ran great for a month then it started sputtering and surging mostly once the engine got up to temp. I could see diesel leaking from around the injector caps so I went ahead and replaced the o rings, caps, and return lines as well as the fuel filter and fuel/water separator. It seemed to run better after that for a few hours of operating time and then it started again except it seems to be getting worse. It randomly sputters or surges or is completely gutless and in between seems to run fine. On hot starts it dies after a couple seconds but then will start again after 10ish seconds of cranking the motor. The front drivers side of the motor seems to be soaked in diesel and there’s a puddle in the valley behind the injection pump. I have no clue where that fuel is coming from or how that is affecting how the motor is running or why it started leaking. Any help would be very appreciated, thanks
 

IDIBRONCO

IDIBRONCO
Joined
Feb 5, 2010
Posts
9,525
Reaction score
7,708
Location
edmond, ks
Let us know how the paper towel trick works for you. Since you told me that there's fuel around the IP housing and you think it's running down the side of the IP, I would suspect the olive on the return line n top of your IP first. That's assuming that the line is still there. The return system could have been changed to the later 7.3 style that uses a rubber fuel line in place of the hard line.
 

Big Bart

Tow&Slow
Joined
Dec 22, 2020
Posts
1,248
Reaction score
747
Location
Newport Beach, CA
These trucks will surge/buck/stall when you have a lack of fuel. (Clogged fuel line, clogged filter, bad lift pump, stuck tank selector, or air leaks.)

Be sure to take a minute and check all your injector lines are snug. (Don't crank on them, but if they turn easily, they are loose. So make them snug, too tight and you ruin the ends.)

If it was not leaking and now is, perhaps one of the o-rings did not seal, got cut when you put the new return line caps in, or was inbetween and poped up. I often use brake clean and paper towels to clean things up. Then I can see where the leak is coming from. Just know it does like to strip the grey paint off the lines and engine. So use sparingly. I also find Simple Green, a scrub, and a rinse with water works too. Just not always a fan of water around the engine. But if the valley pan and injectors are dry, you will be able to see where the leak is coming from.

So double check your work, but perhaps the additional driving caused a new leak!

Also look around the fuel filter, there several places the housing and filter can leak from.

Send pics and let us know how it goes.
 

chillman88

Supporting Member
Supporting Member
Joined
Feb 22, 2017
Posts
5,335
Reaction score
4,995
Location
Central NY
I'd look the feed over well too. It's possible to be pulling air in somewhere if there's a small leak too.

As said before, clean everything well and place a clean dry paper towel under the IP and see if you can tell where the source of the leak is.

Did all of the caps click firmly when you installed them? Sometimes they don't seat well and will pop back up.

Does this truck have the factory water separator on the firewall still? They've been know to leak and let air in. Once you find and fix what's soaking the engine if you still have issues you may need to look into it.
 

IDIBRONCO

IDIBRONCO
Joined
Feb 5, 2010
Posts
9,525
Reaction score
7,708
Location
edmond, ks
Chris, I had a PM from him this morning. I gave him some things to check and also suggested this thread to get more wisdom than just mine. I believe that he's running a 7.3 style fuel filter with the sediment bowl on the bottom. I'm not sure on the factory water separator. I'm guessing that at least one olive on the IP is leaking fuel.
 

Max Harder

Registered User
Joined
Oct 3, 2021
Posts
8
Reaction score
4
Location
Colorado Springs
Sorry for the late response. I spent a little time this week looking cleaning the engine and looking for leaks. The majority of the fuel appeared to be coming from the back of the ip where the line comes in from the fuel filter. I took the line off and the flare at the end was half broken off and the olives were definitely not in the best condition. I re flared the end and put new olives on both sides and it stays dry in that area now. I did also find that one of the injector o rings is still leaking and the cap is seated all the way so I’m going to need to get a few more o rings to replace them I think. After that I guess if it’s still having problems I’ll have to go through the entire fuel system and fix anything there if there’s anything. Thanks for the help guys
 

Attachments

  • 9C223400-6242-4B79-B587-8E8704304D29.jpeg
    9C223400-6242-4B79-B587-8E8704304D29.jpeg
    241.5 KB · Views: 12

TNBrett

Full Access Member
Joined
Oct 24, 2020
Posts
728
Reaction score
634
Location
Middle Tennessee
That looks like a copper line. That should be steel. I’m guessing someone replaced the original with soft copper plumbing line. There are a few guys selling replacements that use hose instead of a steel hard line. I would do that, or bend yourself up a new line using steel. The copper will likely not hold up to the vibration.

Also, did you find the little piece that broke off of the copper? That probably wouldn’t make for a happy IP.
 

Max Harder

Registered User
Joined
Oct 3, 2021
Posts
8
Reaction score
4
Location
Colorado Springs
I couldn’t find the broken piece. I’m hoping it fell into the valley under the ip and got lost because I can’t imagine that being good for the pump. I was talking with a guy I know and he said that it was soft copper air conditioning line. I’ll be switching to the rubber hose pretty soon here to avoid more issues. Is there anyway to get that copper out of the ip if it did go in there? Or is it just permanently stuck in there causing havoc? Also just some background info, I have daily driven/repaired early 80s ford trucks since I got my license 2 years ago but I’m new to diesel and I’m new to these online forums as well
 

Max Harder

Registered User
Joined
Oct 3, 2021
Posts
8
Reaction score
4
Location
Colorado Springs
I also fixed the o rings on one injector that was still leaking so maybe the lift pump or the ip is bad. Could burning coolant cause this issue too? It doesn’t leak on the ground when it’s parked all day but I have to top of the coolant regularly
 
Top