I think that this is the first time that I've actually posted, you guys have answered all of my questions in searches. Well. . . almost.

My fuel mileage has dropped off very suddenly (over the last couple of tanks) from about 22 to 17 mpg. I have been reading this site and have done a few of the tweaks, including adjusting the starwheel, but I don't think that could account for the whole drop.

I was changing the fuel filter last weekend when I noticed a rubber hose hanging out behind where the filter was. It looked pretty dry and cracked, so I came in and found out that this is pretty common for the return line. I am sure that it is at the very least letting air in as the truck is hard to start if it sets over the weekend.

Last night I got down under the truck to check how difficult it was going to be to change (thanks for all the great advice here!) and found that the hose clamp on the return hose wasn't even tightened. The clamp on the other end by the block wasn't exactly secure either. I'm sure that this is at least part of the air problem and will be putting new line on this weekend, but would that explain the drop in mileage? I'm sure they have been loose for a long time and mileage has been good???

I can find both Marine A1 hose and automotive J30R9 hose locally for about the same price of $4.99/foot, which would you guys recommend for replacing my lines? Also, is there anything else that I should be suspect of for taking care of the mileage drop? I am probably due to adjust the valves again and I did back off the starwheel a bit from where I adjusted it to last weekend. Dang, it sure does sound nice and drives a lot better this way, I hope I don't have to change stuff back in order to afford to drive it.

Any comments are appreciated.

 

The marine fuel line is a good choice over the automotive just make sure it is rated for diesel fuel. As for your milage drop it is probably just a heavy foot tring out the new mods, if you see any black smoke out the exhaust thats unburnt fuel if your worried about it just back off your starwheel until smoke stops then you will have complete combustion but your truck will feel like a dog since you have drove it turned up some.

 

Thanks for the reply. The mileage drop actually happened before I started doing anything to it?!?? I'm really not getting much if any black smoke, unless someone is following a little too close and needs a fogging. Otherwise, I have a pretty soft right foot. I think that the marine A1 hose is suitable for diesel, is that correct?

 

USCG A1 will be fine.

 

It's also possible that the timing has dropped off. Might also help to run a conditioner in the next couple tanks of fuel, to give the injectors a cleaning.

 

I generally run Diesel-Kleen in every tank during the winter and at least every couple of tanks in the summer. I have been better about that this winter than I have ever been in the 7 years I've had this truck.

 

I just changed mine last weekend. I bought 15' of each, 5/16 and 3/8. I think it took just about 11'.
So far, my problem with not starting has gone away. But it was a real pain to get it started after I replaced everything.
I used the marine grade diesel hose. It is much larger than the hose I took out.
My original return hose leaked a number of times but I think if you had a mileage loss that great you would definitely see it on the ground.
I also used wire loom on the hose after it was all connected.
If you replace the entire run as many suggest, you will have to remove some clamps and improvise some new clamps.
It wasn't a slam dunk and removing the hoses from the top of the tank is tricky if you haven't done it before. The return line uses a different connection than the supply line. Why? You got me.
Good luck.

Peter

 

yeah I did this also on mine, it was dry rotted enough that it was spewing diesel fuel.
I found the hose was very tight on the metal adapter with the steet braided hose on the end. Some folks here recommended stretching the opening with some needle nose pliers first. I ended up using oversize hose and doubling up the clamps.
Might be a good time to clean and inspect your fuel heater also.
Always good to have a fuel pressure gauge installed, thats a good way to keep an eye on one cause of poor economy.

 

Thanks for the replies. I'm pretty sure that mine is leaking too, I was seeing some wetness along the underside of the engine and onto the tranny that I don't think got there when I was changing the filter. I washed everything under there good last night with my pressure washer so I'll keep an eye out. Nothing on the ground, but maybe it's just hitting something before getting there? Good point on the fuel pressure gauge. I'll have to look into that.