Engine/Transmission (1994 - 1998) Fuel Mileage Woes.....cont'd

[Got Smoke?]

Well back in Janurary some of you may remember my metal fuel return line cracked on me, and I allowed my local dealer to replace it and the rubber line because I didn't have the time to do it myself and the price they quoted me was "right. "



Anyhow ever since I had that return line crack my mileage took a STEEP DROP, and didn't come back with the replacement of the line.



I went from getting around 300-350 miles on 1/2 tank to BARELY making it to 230 miles on 1/2 a tank on consistant driving conditions.



Since all this started I checked my lift pump, and found it to be weak so it was replaced. As well as my over-flow valve, and as recent "last resorts" to help mileage problems I replaced my fuel filter (was due & is usually done every 3-4 oil changes) and fuel prefilter screen.



Something that a fellow member and I discussed was that when I replaced my lift pump one connection had some pipe tape on it, and I did not replace it at the time because I did not have any. We thought that this *might* be a small possibilty of the problem, but after checking my fuel pressure today 15-20psi idle / 25-30psi 2K RPMs (bouncy gauge) I do not think that it could be a lift pump problem.



Something that has since been discussed with some TDR members is that my timing was done 1 & 1/2 to 2 years ago now, and it could be time to have it checked out again. Also I have never been able to find someone to do a valve adjustment on my truck since I've had it, and now I'm ashamed to admit I've put 70K miles on this truck without a valve adjusment. I've been told that these two adjustments could very well be a big part of my mileage woes, but I just wanted to get this boards opinion on them.



I do plan on taking my truck to a friend this week to have the timing checked, and have my valves adjusted and if it fixes my mileage I will make sure to let the board know.



For now I just would like to hear some feedback on this.

 

[Cooker]

This may be a dumb question but are you checking your mileage manually and not relying on the gauge? The reason I mention this is my fuel gauge is terribly inconsistent and worthlees for any type of fuel economy guess.

 

[drrhoades]

You should be able to do the valve adjustment your self it is easy. Just takes some time if you havent done it before.



Doug

 

[Howard Durand]

Not a dumb question at all.



I only check mileage when I fill the tank.

I keep a book and list the mileage and gallons pumped at each fillup. That way the only variable is the accuracy of the odometer.

I try to fill it the same each time.



Nevertheless, if you feel that your references are accurate, then something has changed.

The 300 to 350 miles per half tank would give between 17 and 20 mile per gallon where 230 would only be about 13.

Just to eliminate gauge error use the fillup method a couple of times before making drastic changes.



By your calculations, you have a 4 to 7 miles per gallon loss in fuel economy. That is a lot!

Have you checked the underside for any fuel on the frame. The return line could still be leaking at one of the connections.

And, as Cooker suggests, your fuel gauge sender may be malfunctioning.

Something could possibly have happened to it during the line replacement.

 

[WadePatton]

Yeah, do the valve lash. Simple, I can help you the week after DYNO.



Mileage--DO some MPG calculations! You don't have to convert it for your tire size to compare to yourself.



Have you changed tires or inflation? Is any brake or bearing dragging?

 

[rnolen]

I think my guage is off as well. I can never seem to get it full. It will fill up all the way when i am fueling the truck, but as soon as I pull away it starts dancing between full and 3/4. You guys are suggesting that instead of going with the guage go by miles and gallons. What if you are doing this and for some odd reason your mileage drops (water in the fuel or whatever)? Would you run the risk of maybe running the engine dry? If you are going by the mileage and not the guage what is a safe marker to fill up at.

Thanks and God Bless



Russ

 

[GrantP]

Russ - My gauge is off too. It reads empty long before it actually is. I usually stop around the 400 mile mark and add 24 gallons or so.

 

[edmeyers]

i go to 500 miles and usally add 28-30 gallons which is 16~17 mpg i at one time got 600 miles per tank or 30 gallons but i need my truck timed and need to correct those numbers for the

305 70's but i have never had a fuel gauge that worked on the truck and don't want one i perfer to fill up every time i stop for fuel i mean your going to burn the fuel any way and even if it's $0. 05 higher thats only $1. 50 on 30 gallons that not worth the time it takes driving around trying to find it cheaper.



oh do the valve lash yourself you'll learn a lot and since it needs it every 24k according to cummins you'll save $150 every time just put that towards bombs

 

[bmoeller]

http://www.dodgeram.org/tech/dsl/valve_adj/12_valve.html

 

[Got Smoke?]

Originally posted by WadePatton

Yeah, do the valve lash. Simple, I can help you the week after DYNO.



Mileage--DO some MPG calculations! You don't have to convert it for your tire size to compare to yourself.



Have you changed tires or inflation? Is any brake or bearing dragging?

Wade, I was GOING to call Joe (Mecham's mech. ) today and see if I could just drop the truck off at his house and have him check both the timing and the do the valve adjust. , but I walked out and forgot my cell phone this morning in a rush to work.



The Chevy is dependable enough that I can drive it to work and back so I can manage leaving it with him for a couple of days if he can get to it this week.

 

[Got Smoke?]

Originally posted by Howard Durand



By your calculations, you have a 4 to 7 miles per gallon loss in fuel economy. That is a lot!



Have you checked the underside for any fuel on the frame. The return line could still be leaking at one of the connections.



Something could possibly have happened to it during the line replacement.

The underside of my truck generally stays dirty, but I've also though of a possible extra fuel leak because I washed my tailgate twice right after I got the return line done and it still had the spots all over the tailgate. Took it back to them and they "supposedly" couldn't find another leak anywhere.



I still need to get in there and check those connections to make sure I'm still not losing fuel.



Your correct on the BIG mileage change, that's why I've been so upset over this since Janurary.

 

[WadePatton]

BOOTS!!! Oo.











We found it on the dyno when a lower boot swelled up like a balloon.

 

[thekidfan]

I hope this isn't to silly but, was the boot leaking or what? How could a boot cause that much milage loss and still go undetected ie: gauges. Thanks in advance as mine also gets horrid MPG, for one of these rigs anyway. Jeff

 

[Got Smoke?]

Not only was that boot leaking... ... but all the other clamps were a "little bit" loose. I gave them all a G&T torque'n (good & tight) after replacing the lower right one @ the 'cooler because it had swelled up like Wade said.



Already noticed a mileage improvement, as well as throttle response is WAY up there now.



The funny thing is that there was no hint of a boost leak as "thekidfan" suggested because I could still get 45PSI if I hammered it!



I dunno, but I'm glad the problem is finally solved! Oo. Oo. Oo.

 

[Tmartin000]

Boots??

Now don't laugh..... But how does a boot swell if there is a leak in boost?Oo.



Is there a visual check for me too?



Tom

 

[WadePatton]

Re: Boots??

Originally posted by Tmartin000

Now don't laugh..... But how does a boot swell if there is a leak in boost?Oo.

A 10% leak still leaves 90% to swell the boot. Test your boots by blocking off both ends of the system and feeding 35-45 psi of air into it. Use soapy water on suspect areas. enjoy.