Alright guys I've had my truck since March and there's a few issues I can't figure it out.
1. Speedo is 4 mph faster than I'm going and everything's stock. As of right now it started bouncing and making a chirp noise.
2. If I factor in the excess speedo for MPG I'm getting 12. (It's a 2wd 3/4ton extended cab flat bed with a zf5)
3. Fuel filters are non existent around here fixing leak on two piece today. Anyways i switched tanks and it left me walkin. After messing with it not really changing anything it fired up and switches tanks fine. Only thing I can come up with is little leak on fuel filter.
4. My tanks read way WRONG. When full it's a half inch past full and doesn't drop at a normal "rate" secondly putting fuel in this truck is a b***h. (Flatbed)
5. I need valve cover gaskets bad,
6. Rear axle seal went out.
If y'all get any tips or ideas let me know! Thanks

 

1. was it always that way since you bought it? If yes, then you probably got different sized tires than what your speedo gear is rated for. Buy a different speedogear or get bigger tires.

2. a 7.3 IDI with a manual tranny should AT LEAST you get your 18mpg. Unless you are running duallies or your rear gear ratio is outrageous, you should be getting a hell of a lot better than 12mpg. More than likely, at 3/4 ton is probably a 3.55 or 4.10. To increase your mpg, there are lots of ways to do that. Probably need to have the engine timed, replace injectors, and lots of other stuff. Also, your diesel filter problems are contributing to your poor MPG. Hell, you might be losing MPG to diesel spilling on the ground thru the two-piece filter setup for all we know.

3. Just go online and buy a WIX one-piece diesel filter. Those two-piece units are garbage. While you are ordering it, buy a spare to leave in the cab.

4. Ford 1980's diesel tank fuel level senders are notoriously bad. Mine never work either. And there ain't much you can do about it, cuz they only sell the gasser version. I'm personally converting all my senders to Centroid brand units, but that requires drilling a second hole in the tank, and lots of dudes aren't willing to do that.

5. that's easy. get new valve covers. I forget the prefered gasket, cork or rubber. I think rubber is the one everyone likes.

6. fix that. Find out which Dana axel number you got and buy the seal and fix it.

If your truck aain't starting right, it's probably due to your massive air intrusion from that filter bowl 2-piece setup. That would mean the IP is sucking air and causing all sorts of crap to happen randomly. Also, if you switched tanks and it died, that means either you got a massive air leak in some fuel line BEFORE the selector valve, or you have no fuel in that tank, or you have fuel but the "cone of failure" broke off in the tank and the fuel pick up ain't reaching the fuel level.

 

For #1: The OP may want to check the odometer with GPS prior to replacing the speedo gear. At hwy speeds, about 60mph+, my speed has always read about 4mph fast but my odometer is right on. This was still the case after I replaced the speedo gear when I added my O/D as well as when I replaced it agian when I purchased larger tires. As far as the bouncing, I would inspect and re-lube the cable really well. If that doesn't work just replace it.

For #2: Like Genscripter said, you should definitely be getting better than 12mpg. I agree that you should be getting in the high teen's.......even low 20's on the hwy if you cruise a little slower.

For #4: If you are getting movement/readings from your sender, you may be able to simply pull yours and clean it up. If it always read past full then it usually means it is grounded somewhere

For Genscripter: In testing on my van, the ohm reading for our senders are not the same as the trucks, they are the same as the gassers. With some very minor alteration the gassers work correctly (I have them in mine). The gasser units have a 4 prong plug instead of a 2 prong since they need power for the pump. If you remove the 2 extra prongs and manipulate the plastic around the plug our 2 prong plug from the gauge fits fine. You have to add a length of fuel line to the pick up since it is shorter to accommodate the fuel pump. The other choice it to remove the sender guts off the gasser and attach it to the diesel one. I did it both ways.

 

and your 88 should have a sterling 10.25 rear axle, not a dana.
unless someone downgraded the rear to a dana.

 

Wix fuel filter single piece replacement- either 33417 without WIF sensor or 33617 with WIF sensor. About $45 at the auto parts store or half that on-line.

 

That is good to know. Any links to the gasser senders you used? Any pics of the process? I have run the tank dry twice in the last month cuz of that awful gauge behavior and it's annoying as hell.

 

Thanks for all the replies.
So I got the fuel filter fixed had to buy a fram. I know, I know. So Ima have to order em no one around here Carries them. Checking the odemeter is hit and miss with a GPS. But I'll try the 60mph thing. On the tires I actually put 265/75/16 on the rear for some mud grips.

 

Where do you live? O'Reilly carries Wix but they're almost $50. Here they are online for half but you have to pay shipping so buy 2 or 3 at a time.
Wix 33617