6.9 efficency
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Senior User
Joined: Oct 2007
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From: Sylva NC
6.9 efficency
I have been on this forum before and it got my 1986 F250 ext cab 4X4 on the road shifting, starting, and running just fine. So now I am looking for advice on what I should do to improve efficency. Odometer is showing 48,000 so I assume at least 148,000 miles and best I can tell it is bone stock including the exhaust. I have not run a tank of fuel through it yet so I have no idea what kind of mileage to expect. It has a C-6 with 3:73 gears (I think). I'm not expecting 300hp and 25mpg (honestly probably has plenty of power for my needs) but I would like to get everyones suggestions on how to make the 6.9 most efficent. One more question about glow plugs. When started first thing in the morning it idles rough and a friend of mine said push the glow plug button again until it smooths up the idling. I thought you wasnt supposed to heat the glow plugs after the engine is running. (not gonna try it till I get a second opinion) What do you think? Thanks Joe
Post Fiend
Joined: Oct 2007
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From: Faibanks Ak.
the only mods you need is air intake first cut soupbowl out of top of air cleaner cost nothing.there are several post in here with pictures that people have inlarged the cold air intake sorta like ram air. the cooler the air the better.
the other is exhaust stock form is very restricted larger free flowing exhaust really wakes these motors up.
the other is exhaust stock form is very restricted larger free flowing exhaust really wakes these motors up.
Lead Driver
Joined: Dec 2006
Posts: 6,496
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From: So. Jersey
On the glow plug issue, normal operation when the key is turned on they light for about 10-15 seconds. Then they go into a cycle where they are repeatidly turned on and off for a couple seconds at a time. If you have just a push button you don't want to ever hold them on for more than 15 seconds, these plugs are designed to cycle.
So in other words your friend is right, just count to ten to start then hold for a couple of seconds on/off while running for the first half a minute.
So in other words your friend is right, just count to ten to start then hold for a couple of seconds on/off while running for the first half a minute.
Lead Driver
Joined: Nov 2003
Posts: 6,900
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From: Campbell River, B.C.
Originally Posted by smokey98
I have been on this forum before and it got my 1986 F250 ext cab 4X4 on the road shifting, starting, and running just fine. So now I am looking for advice on what I should do to improve efficency. Odometer is showing 48,000 so I assume at least 148,000 miles and best I can tell it is bone stock including the exhaust. I have not run a tank of fuel through it yet so I have no idea what kind of mileage to expect. It has a C-6 with 3:73 gears (I think). I'm not expecting 300hp and 25mpg (honestly probably has plenty of power for my needs) but I would like to get everyones suggestions on how to make the 6.9 most efficent. One more question about glow plugs. When started first thing in the morning it idles rough and a friend of mine said push the glow plug button again until it smooths up the idling. I thought you wasnt supposed to heat the glow plugs after the engine is running. (not gonna try it till I get a second opinion) What do you think? Thanks Joe
For fuel effeciency, open up the intake with a cold air/ram intake, that mod was worth close to 2 MPG for me @ 70 MPH. Put a minimum 3" exhaust in, but use a muffler, N/A diesels can wake the dead with just a strait pipe.
Aside from that, just make sure everything is in correct tune, and keep your speed at 55 MPH.
I made changes to my drivetrain, but they cost as much as I payed for the whole truck, but I make a 200 mile trip every week running at 70 (and up), so my cost will pay off eventially.
Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
The old style glow plug system on the 86 and older trucks would heat the glow plugs several times after the engine started to reduce smoke until the engine had enough heat to burn the fuel more completely.
When mine was still working back when the truck was much younger, I remember it cycling for over a minute at temps below zero if it had not been plugged in the night before.
As for the rough running my first guess would be a burnt out glow plug, but that guess would be closely followed by an injector that was weak as far as spray pattern went.
Diesel auto ignites at about 475 drgrees.
When it is 40 outside, the engine is 40 degrees as well.
Going from 40 to 475 in one compression stroke is asking a lot from your engine.
Anything that is not working perfectly makes it that much harder.
When mine was still working back when the truck was much younger, I remember it cycling for over a minute at temps below zero if it had not been plugged in the night before.
As for the rough running my first guess would be a burnt out glow plug, but that guess would be closely followed by an injector that was weak as far as spray pattern went.
Diesel auto ignites at about 475 drgrees.
When it is 40 outside, the engine is 40 degrees as well.
Going from 40 to 475 in one compression stroke is asking a lot from your engine.
Anything that is not working perfectly makes it that much harder.
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Senior User
Joined: Oct 2007
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From: Sylva NC
Ok good deal. Is there any way to test the glow plugs idividually or should I just break down and buy a whole new set? Im gonna try to find the pictures that show the air intake modifications on do that. The exhaust, I thinkin dual into a muffler and single 4" out. What do ya think about that? Thanks again, Joe
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Post Fiend
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From: Faibanks Ak.
rough test hook test light to power on batt touch spade to glowplugs if it lights probabaly working this is not fool proof though
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From: New Jersey
If you have a multimeter, disconnect the glow plug wire and run a continuity check between the glow plug and ground. It should be less than 2 ohms.
I upgraded my exhaust to 4" recently. I noticed a good increase in power between 2000 and 2500 RPM, although with normal driving, I seldom get above 2000. I only rev up when getting onto the interstate and I have to get up to highway speed more quickly.
Fuel economy seemed to improve some, my first few tanks showed 17-17.5 mpg, up from 16-16.5. Haven't gotten an accurate measurement since then because I installed a remote starter and I've been using it, so I'm burning fuel when not driving now. I also haven't done intake mods yet, so I'm hoping that will help mileage.
I upgraded my exhaust to 4" recently. I noticed a good increase in power between 2000 and 2500 RPM, although with normal driving, I seldom get above 2000. I only rev up when getting onto the interstate and I have to get up to highway speed more quickly.
Fuel economy seemed to improve some, my first few tanks showed 17-17.5 mpg, up from 16-16.5. Haven't gotten an accurate measurement since then because I installed a remote starter and I've been using it, so I'm burning fuel when not driving now. I also haven't done intake mods yet, so I'm hoping that will help mileage.
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time to wake up the e-350
I just bought a 83 / 84 / 85 ? e-350 cube van 6.9 not run in 3 years
i am - was a cat, cummins, DD diesel tech for a lot of years and have the skills and "some" basic knowledge of automotive diesel with your advise-s posted I'll get'er going my question is with a c-6 transmission what are my options for a "highway" geared differential ...ratios available, and or, possible interchanges with u-pull it wrecking yards ie: will a f-350 diff drop in work in my e-350
this is an additional work van, 400 miles trips don't want the tach pegged all the way there
but for 400$ + make it run costs it is worth a try
i have an 06 e 350 6.0 but can't afford another new one
thanks in advance
tom
i am - was a cat, cummins, DD diesel tech for a lot of years and have the skills and "some" basic knowledge of automotive diesel with your advise-s posted I'll get'er going my question is with a c-6 transmission what are my options for a "highway" geared differential ...ratios available, and or, possible interchanges with u-pull it wrecking yards ie: will a f-350 diff drop in work in my e-350
this is an additional work van, 400 miles trips don't want the tach pegged all the way there
but for 400$ + make it run costs it is worth a try
i have an 06 e 350 6.0 but can't afford another new one
thanks in advance
tom
Lead Driver
Joined: Nov 2003
Posts: 6,900
Likes: 3
From: Campbell River, B.C.
Originally Posted by xoddah
I just bought a 83 / 84 / 85 ? e-350 cube van 6.9 not run in 3 years
i am - was a cat, cummins, DD diesel tech for a lot of years and have the skills and "some" basic knowledge of automotive diesel with your advise-s posted I'll get'er going my question is with a c-6 transmission what are my options for a "highway" geared differential ...ratios available, and or, possible interchanges with u-pull it wrecking yards ie: will a f-350 diff drop in work in my e-350
this is an additional work van, 400 miles trips don't want the tach pegged all the way there
but for 400$ + make it run costs it is worth a try
i have an 06 e 350 6.0 but can't afford another new one
thanks in advance
tom
i am - was a cat, cummins, DD diesel tech for a lot of years and have the skills and "some" basic knowledge of automotive diesel with your advise-s posted I'll get'er going my question is with a c-6 transmission what are my options for a "highway" geared differential ...ratios available, and or, possible interchanges with u-pull it wrecking yards ie: will a f-350 diff drop in work in my e-350
this is an additional work van, 400 miles trips don't want the tach pegged all the way there
but for 400$ + make it run costs it is worth a try
i have an 06 e 350 6.0 but can't afford another new one
thanks in advance
tom
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Joined: Nov 2007
Posts: 175
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87' 6.9 E350 C6 3.31 Srw
2000rpm cruise seems about what is comfortable with
mine- producing 52mph with orignal 3.54 and 31.5 inch
tires 20mpg. With the new 3.31 ring/pinion and 33 inch
tires 6omph is what i'm getting and hoping for a 5mgp
improvement! Beyond the above it might have been
cost effective to replace the C6 with a E40D. I think
thats' possible but what it all entails I don't know :<)
mine- producing 52mph with orignal 3.54 and 31.5 inch
tires 20mpg. With the new 3.31 ring/pinion and 33 inch
tires 6omph is what i'm getting and hoping for a 5mgp
improvement! Beyond the above it might have been
cost effective to replace the C6 with a E40D. I think
thats' possible but what it all entails I don't know :<)
Lead Driver
Joined: Nov 2003
Posts: 6,900
Likes: 3
From: Campbell River, B.C.
Originally Posted by lowell75
2000rpm cruise seems about what is comfortable with
mine- producing 52mph with orignal 3.54 and 31.5 inch
tires 20mpg. With the new 3.31 ring/pinion and 33 inch
tires 6omph is what i'm getting and hoping for a 5mgp
improvement! Beyond the above it might have been
cost effective to replace the C6 with a E40D. I think
thats' possible but what it all entails I don't know :<)
mine- producing 52mph with orignal 3.54 and 31.5 inch
tires 20mpg. With the new 3.31 ring/pinion and 33 inch
tires 6omph is what i'm getting and hoping for a 5mgp
improvement! Beyond the above it might have been
cost effective to replace the C6 with a E40D. I think
thats' possible but what it all entails I don't know :<)
If you like to cruise at or above 70MPH empty, a 3.08/E4OD combo will perform very well, but below those speeds, I can't really use overdrive to much, 2000 RPM or slightly less seems to be best for the 6.9 in terms of MPG. If I'm towing, I run in 3rd gear and the engine is very happy to turn 2200 at those speeds.
Lead Driver
Joined: Dec 2006
Posts: 6,496
Likes: 94
From: So. Jersey
My last consistant driving in my 87, 6.9, dwcc, c-6, 4.10 R&P truck doing 50-55mph @ 25-2700rpm with 6 cetane boost via Diesel Kleen I got 16.5 mpg. Over drive or 3.55 r&p would help alot more. I don't think thats to bad for a 5000lbs+ truck.