Noisey Diesel '87 6.9 FOMOCO

Noiseydiesel

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Greetings. My first diesel so far is an '87 F250 with the 6.9. It came home pretty much a non runner and I got educated fairly quickly. It was running when I showed to buy it (never a good sign) and after a short test drive and looking at a few things, it was shut off, I let the previous owner keep the used batteries for another truck and had it towed home.
Sloppy steering column was the largest reason for towing it, and if towing it, didn't need batteries or used ones to start this project.
Engine wise, it got a new controller and Motorcraft, NOT Autolite, injectors. The prior owner had a toggle switch in the dash to energize the injectors.
I rewired it so the toggle switch can now be used to energize the controller when needed for a cold start. The rest of the day, the switch is off and the controller is not needed. This set up is also handy in case the ign switch needs to be turned on and the glow plugs will not be cycled.
Leaving the controller set up as original allows for normal operation when the truck is used by anyone else. Usually I run the glow plugs for 8 to 10 seconds before cranking the engine, then turn off the toggle switch and don't use the controller& glow plugs for the remainder of the day.
One slight oddity is I fired it up a few days ago, not a daily driver truck, and after it ran a short few minutes, the engine got quieter. What? Yep. Noise output seemed to drop no less than 30% and it seemed to smooth out just a wee bit. No smoke from this engine and I never gave the pump or injectors a thought until this happened. I suspect I need to go out and warm it up, then crack fuel lines and see if I can hear an RPM drop. The wife and I took it on a road trip with a 1990's vintage slide in camper the mileage went from about 15 MPG down to about 8 at some times. I am used to gas engines and can feel a misfire easily enough. This diesel routine is a new one and I am still learning a bit.
Other than that, I have replaced the fuel pump, vacuum pump, water pump, fan clutch, coolant.
So what is your opinion? No smoke and varying mileage with excess noise?
Possible injectors? At $35/40 bucks each from Rockauto, I hesitate a bit to drop $340 into this as a SWAG.
Thank you for your time.
Bruce
 

stealth13777

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I think what you heard was the timing advance kick off as your engine warmed up.

One question would be to look at the timing on the engine. It makes a huge difference on these, but unfortunately also requires special equipment. If you do fuel system parts you will definitely want to look at timing.

You also have options, including multiple guys on here who test and/or rebuild injectors and pumps. I personally would buy from one of them if buying fuel system parts, and have. They will probably chime in

There’s guys who know a lot more than me, but my 2 cents is that what you heard isn’t an issue
 

Jason1377

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Your rig will get quit because its warmed up it has both a cold/hot idle most idi's do this n for fuel stuff wes aka @Thewespaul typ4 agem if I got that ma!e right Justin all sell fuel parts glow plug parts turbos pretty much most parts for a ford idi motor I'm a novice n these fine ppl are saviors
 
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