Lousy MPG

[Diesel Dawg]

Picked up my 93 crew cab (turbo 4x4 E4OD 35" tires 4:10 gears) a couple months ago. Flew out to North Carolina to get it and drove it back to Florida. At 65-70mph, I was averaging 11.5-12.5mpg. I thought the engine was running pretty quiet so I assumed that this was due to the timing being out of spec. I bit the bullet and bought a ferret timing adapter and a real nice gun. Set the timing to 9.7ish BTDC. The timing was around 5 BTDC. I noticed a small improvement in economy. I now get 13-14mpg on the highway around 65-70mph. Around town/mixed driving, I get 12-13 driving as easily as possible. I just went on a long haul to get a boat. Big offshore 26 footer. maybe 7000# total weight. I was getting 8-9mpg at 55mph OD off, OD on seemed worse. ***. really? These are some lame MPGs! What can it be? Truck has a very, very slight instability at idle, no smoke or anything. Fires up real easy even on cold days. Doesnt smoke excessively under acceleration unless I am under 1700 rpm, then I feel it is a bit excessive. Any ideas? I'll throw some injectors at her next and see what happens. 170K on the clock....already has BB code injectors. I cant think of anything that would affect the MPG this much??

I got this truck to replace my 92 ext cab NA diesel 4x4 4:10 Manual with 33s. I got 15-16mpg mixed driving and 16-17mpg hwy. Never saw less than 12 towing anything...keeping it floored the whole way just about....
Timed it by ear too!

Is the mpg difference from auto to manual really 20%+?? Thats crazy if it is....


MPGs
Highway: 13-14 @65-70
Mixed: 12-13 Driving like a grandpa
Towing 25' boat: 8-9 @55mph OD off, worse with OD on.

Timing at 9.7 BTDC

What gives????

 

[Silver Burner]

The 35" tires give, I think. Are you measuring your miles traveled off your odometer or Google maps? The 35" tires are throwing your speedo WAY off amd they're also killing your mileage. Put some 235/85-16 stock tires back on and I bet you'll gain 3-4 MPG.

 

[Diesel Dawg]

I'm going by the speedo +10% which accounts for the difference between stock tire size and 35" tires.

 

[Silver Burner]

Try using google maps and plot your mileage and see how close it is to your speedo +10%. Then dump your 35's. I have 285/75's on mine and I see 17-18 empty and about 13 towing a 6000 pound trailer over Mt Hood.

 

[icanfixall]

How many miles are on the injection pump. Not knowing if the Bb code injectors are new or rebulild can make a big differance too. Good thing to have timed the engine but if the pump is shot then that could be the low mileage. If the valley pan under the intake manifold wet looking. Are any of the retuen lines wet at the injectors. Any fluids that drip into the valley pan will drain out the back and down on the starter from the edge of the bell housing. Its the only direction the fluids can flow out of the pan.

 

[FORDF250HDXLT]

Is the mpg difference from auto to manual really 20%+?? Thats crazy if it is....

no.the E40D will get better FE than the ZF5 out on the interstate.

 

[gunz]

no.the E40D will get better FE than the ZF5 out on the interstate.

I dont agree with that statement at all.

 

[FORDF250HDXLT]

I dont agree with that statement at all.

that's ok.you don't have to.but i'll explain;
the reason is because (at around 35mph) the converter locks up (and now has a direct engine to trans connection like the manual trans does.it's just that the locking clutch is in the converter rather than a devoted clutch.)
once in final gear,the E40D can tweak out a bit more economy than the ZF5 because it has a slightly higher final OD gear.

 

[Diesel_brad]

I dont agree with that statement at all.

I dont either. While the E4OD may have a SLIGHTLY Higher OD(.06 difference), the converter does NOT completely lock and there still is slippage Even w a lockup convertor

 

[Diesel Dawg]

How many miles are on the injection pump. Not knowing if the Bb code injectors are new or rebulild can make a big differance too. Good thing to have timed the engine but if the pump is shot then that could be the low mileage. If the valley pan under the intake manifold wet looking. Are any of the retuen lines wet at the injectors. Any fluids that drip into the valley pan will drain out the back and down on the starter from the edge of the bell housing. Its the only direction the fluids can flow out of the pan.

I dont know when the IP was replaced. I assume that it has been replaced due to the fact that the torque screw had a red cap on it. IIRC, only rebuilds come with a cap on the torque screw. The only history I have on the truck is from the past 1.5 months. I know the trans was just rebuilt and TC replaced as well.
There is no diesel fuel down ion the valley pan, bit of oil residue, but thats it. All the returns are dry, no diesel leaks anywhere.

If the pump were shot, wouldnt there be some sort of indication other than poor MPGs?

If the injectors were shot, wouldnt the exhaust be black from all the extra and unburned fuel? At least smoking a bit at idle or something?

I guess I'll pull the injectors and replace them....once new injectors are available that is... start at the cheap end and work my way toward the more expensive!

 

[redmondjp]

Other things to check:

- Tire inflation
- Front-end alignment
- Differential fluids (can go synthetic if you don't have a limited-slip in the back)
- Dragging brakes

Have you checked your engine RPM at cruise to verify that your converter is locking up?

 

[icanfixall]

Before you replace the injectors try running some atf in the fuel. At least one quart is a start in a tank full. Others will chime in if they feel you should run more. I do know these engines can burn straight atf easily. The atf is a cheap injection system cleaner run at high doseages...

 

[Diesel Dawg]

Other things to check:

- Tire inflation
- Front-end alignment
- Differential fluids (can go synthetic if you don't have a limited-slip in the back)
- Dragging brakes

Have you checked your engine RPM at cruise to verify that your converter is locking up?

check
check
check
check

and check

No problemos there my friend, thankfully. Thanks for the suggestions though

 

[Diesel Dawg]

Before you replace the injectors try running some atf in the fuel. At least one quart is a start in a tank full. Others will chime in if they feel you should run more. I do know these engines can burn straight atf easily. The atf is a cheap injection system cleaner run at high doseages...

I had been running a real stiff blend of diesel KLEEN in there since I got the truck. Made no difference. I just changed the fuel filter a couple of days ago and filled the entire filter with Diesel Purge......made no difference. Oh well..........

 

[jhnlennon]

no.the E40D will get better FE than the ZF5 out on the interstate.

I think your not taking into account the efficiency losses of the hydraulic pump and circuit. Automatics have gotten better, but they dont have the energy transfer rates like a standard...