bad mpg's

[ilm99cumminss]

I've been driving my 89 7.3 idi and its been sitting on annd off for a year. But I drove it the other day after filling it up and only got 96 miles to a full 18 gallon tank that turns out to only 5.6mpg clearly not right so I started with replacing the air filter. Whatels can I do to gain mpg and maybe make it run a little better? Thanks. Trucks a 89 f350 crew cab long bed dually 2wd auto.

 

[Agnem]

Welcome to the site. I'd check for leaks! Also get your injectors pop tested and your timing set using the proper tool and talent. That cures most MPG ills.

 

[ilm99cumminss]

I've check for leaks I have found none. Also the pump was just put on the truck was timed a year ago and when I drove it this winnter I got 15mpg. Could the injectors also cause a long crank on start up? I have a 800hp 12v cummins I built and have the ability to pop test and rebuild injectors and pumps just the idi is a diffrent animal then the 12v cummins and duramax's I work on every day lol

 

[flareside_thun]

I'd be lookin at running some diesel fuel additive at the very least and maybe even a new fuel filter.

 

[DragRag]

I would be looking at injectors if the pump was recently gone through. I would also check the compression. I have a pig of a 6.9 with low compression and it drinks fuel. mainly because I need to drive it with my foot to the floor to keep it moving, it cranks long to.

 

[ilm99cumminss]

Additives changes nothing. And did I mention the truck has 796k miles!?

 

[Ididriver]

Additives changes nothing.

i woulndt say nothing when i use my diesel kleen i can hear a diffrent tone to the engine and pick up a mile or two

 

[joe f350]

Additives changes nothing. And did I mention the truck has 796k miles!?

that might be the highst millage idi on record

 

[DragRag]

Additives changes nothing. And did I mention the truck has 796k miles!?

With that mileage i would check the compression first, probably low and anything you do will result in nothing. I am with you btw, additives don't do much.

 

[ilm99cumminss]

How do I go about checking compression?

 

[FordGuy100]

Thats the equivilent of 5.33mpg

My guess would be its pulling fuel from one tank, and returning fuel to the other tank.

 

[ilm99cumminss]

No cause the rear tank is empty...

 

[FordGuy100]

That was my guess, its happened in my truck before. Are you sure its empty?

 

[ilm99cumminss]

Now that I think about it I have been haveing problems with the tank valve down on the frame rail... could that be the problem? Also does anybody know where I can get one and not have to chop the lines off and go to rubber lines? I like the clip on lines ford uses

 

[flareside_thun]

Have you checked Rock Auto for your part?