JKM

I have been experiencing TERRABLE fuel milage on my new to me 95 , i'm sitting at 95 miles since fillup , and already under 1/4 tank.

My last tank was down around 1/4 full , and i had 350 miles +/- on it.

I am going to check very closely for fuel leaks , but i have not seen any spots on the ground.

On startup , on cold mornings , it misses badly , very badly below 1200 rpm , but it is smooth above that, and it blows smoke rings occasionally. On the highway , there is NO power on the top end , i'm lucky to pull 2300 rpm on a hill , and i can't hold 70 on any sort of a decent hill, even with the pedal planted to the floor. I tried it on hills i used to drive all the time in the 94 i drove for work (94 , auto , 4x4 ,reg cab) and it pulled the hills MUCH MUCH better than this 95.

I have been driving very easy for this whole tank , i hardly see about 1500 rpm in town , and on the highway , hardly above 2000 rpm , i was just crusing at 60 mph.

I am going to replace the o/f valve (can that cause low MPG?), and as soon as i can afford it, i'm ordering the timing kit from snap on.

What does this problem sound like to you fella's? is it possibly the timing? could it be advanced TOO far? what are the symptoms of too much timing?

It'll probably be after christmas before i can afford the timing kit, and the o/f valve.

My only other though is injectors, could they be bad? I don't see any smoke at all, of the black variety , i see white smoke , but that is normal for these temps, i DO see an unnerving amount of BLUE smoke, but only when the truck isn't under power, and not all the time.

Do i have a candidate for low compression?

MnTom

Other than what you have said (O/F valve, timing) the only other thing I can think of is adjusting the valves. That made a huge difference with mine. Does the truck smoke terrible white when cold and miss 'till it warms some? That would indicate a timing issue and will impact the mileage. When it is warm does it idle somewhat smooth or does it shake a lot? That could indicate a valve adjustment is needed.
Keep us informed
Tom

apache

I have a 95 4x4 5 spd that gets about 18 empty. I fill up at 1/4 tank showing about 350 on the odo, it typically only takes 20-22 gals or so. Id say for one the guages arent real great. Ive had my low fuel light on and still only got 20 gals in it. Regarding power?? My truck is stock, Im lucky to pull 2500 rpm,climbing a several mile long 6% grade floored I`ll hit 75 sometimes. sounds like what you were driving was bombed some or higher HP version?? mine has the 180 pump. The overflow valve can cause the symptoms you describe so definatly change it out along with the fuel filter If not already done. These are also notorious for having fuel line issues between the LP and tank. The rubberlines fail allowing air in and causing problems. You should see fuel leaks though.

mr T

my truck before the gsks couldn;'t pull above 2200 rpms either....ur fuel leak may not be visible...check for wetness on the underbody...to see if it smells like diesel fuel...when i had a leaky fuel filter it didnt drip on the ground ...i just noticed that mileage was awful and then my TAILGATE was greasy form the outside...baffles me too...covered by diesel fuel so dont look just for drips look for a wet fielter and wet parts .....heck start the motor put some cardboard around ur injectors and near ur fuel filter and rev her for 20 sec and then have a look at the cardboard....otherwise ur timing may have actually slipped...is ur fuel shut off solenoid in the fully up position while the truck is running ?

oh yeah and star wheel fully forward or afc fully forward will destroy city fuel consumption...

JKM

I am not so sure about my timing , i'm thinking it may be advanced , advanced way too far that is , smoke rings are usually something i see in pulling tractors , where the timing has been advanced so far ahead that it's a miracle it even starts...

The guages appear to read correct , at 1/4 tank it took 80 or 85L , tank is 130, so maybe it is off some...

My dad gets over 1000 kms to a tank , every tank , on his 97 , i know it is a 2wd , so i expected to lose some milage , but this is way lower than it should be , 95 miles and already used over 1/4 tank!

I forgot about the valves until after i made that post , i think i may check them this weekend.

G1625S

White and blue smoke=retarded timing, as far as I've been told. I've never seen an unmolested p-pumped truck that didn't have slipped timing. Even my weenie 1st gen is louder than all the p-pump trucks around here. I had my pump waaayyy advanced for a couple days and it started great @20*F. The O/F valve sounds like it's worth investing in, from what I've read, but my $$ is on slipped timing...
greg

Fueling around

Start with the basic preventative maintenance
fuel filter
oil change
tire pressure
fuel conditioner with anti-gel

Then move on to the next level
overflow valve
timing
valve lash
boost leak
fan clutch
fuel return line
fuel strainer
fuel heater


Do you run a lot of short trips? Cold engines blow an amazing amount of fuel out the tail pipe.
Do you (can you) plug in the block heater?

My mileage dropped this summer. Then the power went away.
Turned out I got a bad load of fuel and the fuel filter was trashed.

Co-worker notices her mileage drops when the fuel filter is getting due for a change.

TIMMY22

you missed the almighty air filter.




96 stocker


550 miles till fuel light (around town)

700-750 miles till fuel light (highway) Ya baby!

JKM

Start with the basic preventative maintenance
fuel filter-not done , will get one tomorrow
oil change-done
tire pressure-done
fuel conditioner with anti-gel-done

Then move on to the next level
overflow valve-not done
timing-not done
valve lash-not done
boost leak-I don;t think it is this , no black smoke , at all.
fan clutch-i'll check that
fuel return line-check for leaks?
fuel strainer-how to check this?
fuel heater-How to check this?


Do you run a lot of short trips? Cold engines blow an amazing amount of fuel out the tail pipe.
Do you (can you) plug in the block heater?i am goign to start as of tomorrow.

My mileage dropped this summer. Then the power went away.
Turned out I got a bad load of fuel and the fuel was trashed.

Co-worker notices her mileage drops when the fuel filter is getting due for a change.


Thanks for the help.

Fueling around

There's a couple of recent threads on fuel strainer & fuel heater that should help. (The topics even state fuel heater & fuel return so they are easy to find.)
Any fuel restrictions, air leaks, or cold fuel will cause economy issues.

The return line behind the pump is a combination of steel and rubber. Many have air leaks on the rubber part. A buddy of mine has replaced the steel line twice from breaks at the mounting tab.
Infidel recommends replacing the rubber 18" with full rubber all the way back to the fuel tank.

Forgot to mention
I usually remove my fan in the fall, but haven't gotten around to it yet. I noticed today the fan clutch engaged on a cold engine. It is coming out on Saturday.

TxDiesel007

Im in the same boat you are

Im thinking to work on these three things, Timing the pump, valve adjustment, and finally gettin a fuel pressure gauge on there to see if my lift pump is dead or not. dont feel bad, i got mine to 315 miles or so and had 1/4 tank only..

I checked my injectors.. no apparent leaks today...

Tx

JKM

Well , i think i might have found the answer to my highway MPG problem

Pulled out of a driveway today, started down the road , and was counting the shifts , 2nd , 3rd , o/d, then all the sudden , WHOOM! we were off to the races , and the tach instantly dropped at least 300 rpm , probably more like 500 rpm, the TQ locked! I knew that shift into o/d didn't feel right at all compared tot he 94 i drove.

Normally on the highway i cruise just below 2 k rpm , at 100 km/h , if i come to a hill , i can floor it , and the engine see's 2300 or so rpm , but the speed drops , because the TQ isn't locked.

With the TQ locked , i was doing 1750 rpm , and 115 km/h , MUCH better.

The problem is as soon as i let off , it unlocked , and i couldn;t get it to lock again.

So , now , how do i troubleshoot a TQ not locking?

kd460

Do on search on TPS, or Throttle Position Sensor. Sounds like it needs to be cleaned and or adjusted. They technically can not be cleaned, but they can, they technically can't be adjusted, but they can. Do a search and you will get a ton of info on both.

It's still a good idea to do all of the things mentioned to get the truck into shape. Also replace the short sections of rubber fuel lines if not mentioned allready. Good Luck, Kevin

JKM

I just did the TPS last weekend , because it dropped out of o/d on the highway on me, i drilled a little hole in the back of the TPS and squirted contact cleaner in there , it got me back my o/d , but still no lockup , until this week.