Low power and fuel mileage

[JBrock]

I have a 92 W250 4x4 , Auto, 3. 54 gears, and 190 K miles, I have owned this truck for the last 7 yrs. It has always been bad on fuel and low on power. Fuel milage runs around 12 mpg.

I recently tried changing injectors to see if this helped. these were High preformance injectors form our local shop. they are susposed to be good for 30-40 hp I think.

I have noticed a decrease in power and no help on the mileage issue.

The local Shop ( Desert Diesel) say's my pump is shot that I need a rebuilt one , But I want to know how the pump can be shot if it has done this for 90K Miles, that I've owned the truck.

I have turned up the pump some but nothing radical, It wouldn't do 75 mph on the flat freeway with no headwind! the milage was unaffected but power did come up a bit. that was 90 K miles ago.

So do I buy a new pump or look elsewhere?

 

[RGT]

have you ever had the injector pump timing checked? do you have lots of smoke? do you have good boost?

 

[hdm48]

RGT has a good question. How much boost, how high EGTs, when was the filter last changed, what is the timing set at, have you checked for boost leaks, air filter? Some numbers would help us help you. We're not being rude, we just need some more info.



Dave

 

[JBrock]

I just changed the fuel filter, I installed a K&N air filter when I first bought the truck, it has been kept clean, it was washed out about a month ago. I have no boost guage or pyrometer.

I have checked all the flex connections on the tubing to and from the intecooler.

I have not had the timing set by a shop but have tested moving the pump very slightly after marking the original position.

If I rotate it counterclockwise the performance drops considerably,

I ended up with it rotated clockwise a very small amount (I'm guessing about 2 degrees or so)from the original mark. and it seemed to help some. According to the local shop where I have it set should be fine.

I have smoke on startup and when I step down hard on the accelerator for 1-2 seconds. I also notice a very light smoke when I'm pulling a hill lightly loaded, more smoke when heavily loaded.

I feel that I also have a really bad turbo lag it seems to take a few seconds for it to kick in.

I still have the stock exhaust system which I have plans to replace.

 

[hdm48]

Well, with a 92 you have an 18cm housing so that's good. But it sounds like you have a pump problem but, it may be fixable without pulling it. Do you know how to check for fuel pin travel? Have you ever looked to see if the pin is making a mark on the fuel pin? How is the idle and power at partial settings? You could have a bad injector and not know it. Or maybe an imballance.

Can you barrow a boost guage just for testing? This would really help. Have you done a under the truck inspection? Sometimes a fuel supply or return line can be crushed or crimped. This can cause a lot of problems and be overlooked.

Oh, one more thing, the muffler may be plugged. I know this sounds far fetched, but I have run into this many times on trucks, cars, and motorcycles. And don't rule out the exhaust pipe itself.



Now get to work, we'll be expecting a report.



Dave

 

[JBrock]

The truck idled rough and slow with the old injectors. with the new injectors it is idling faster and smoother, but I had an imeadiate reduction in power especially on the top end.

I've also noticed an increase in the diesel rattle when I step down hard on the throttle.

I guess it's time to spend some money on some guages! anyone have a set to sell?

John