Rather Sluggish lately!

[1992tractor]

I have noticed (I think it could be paranoia) over the last several months that my truck becomes sluggish inconsistantly.......I have a 45Km (30 mile) commute every day, one way has 3 or 4 decent hills to pull, and I am noticing some days my truck can pull them usually empty around 80-90Km/h without shifting out of OD but some days my speed falls to 60Km/h before it grabs a gear and gains some speed again . Last night this happened and all I had was 4 sheets of drywall in my box, however the day before I pulled the hills in OD just fine however I was empty but that little bit of weight shouldn't matter. I know these trucks are gutless but I thought a diesel's were meant to pull. I can't image having a trailer on.

I have tried to observe and take note if it is related to a load or not but it usually isn't. One theory I ahve is that my truck is more sluggish when I am running fuel out of my rear tank compared to my front tank. Does this observation hold any water? Do these trucks have a lift pump feeding the injection pump and could it be getting tired? Is it premature for my IP to be tired? Let's hope it is not the IP....$$$

I maintain my truck religiously, therefore my fuel filter is change regularly, and I am running additive also.

Do you guys notice any difference in truck performance from fuel sources?

I know the answer some will say is to turbo my truck but I don't know if I want to spend 2-3K on a turbo and exhaust.

Any suggestions would be apreciated...this is my first Dies and I am slowly learning the ropes. This forum has been great for my learning curve, Thanks!

 

[h2odrx]

Welcome to the site, rear tank? if it was air it would speed up? what rear end? but you said it just started?

 

[1992tractor]

Rear tank is what I think might be more sluggish but I have been driving this week on my front tank. 410 gears in it.....defeinately not a race car but it should be able to pull.

 

[dsblack]

You could have some garbage or alge or a bad hose, in the rear tank affecting the pickup of fuel in the tank. also I wonder if maybe the FIPL is worn and it is not shifting consistantly? Try just running from the front tank and see if the issue goes away. If so, then you may need to drop the rear tank
Just some ideas....

 

[1992tractor]

You could have some garbage or alge or a bad hose, in the rear tank affecting the pickup of fuel in the tank. also I wonder if maybe the FIPL is worn and it is not shifting consistantly? Try just running from the front tank and see if the issue goes away. If so, then you may need to drop the rear tank
Just some ideas....

I had the FIPL adjusted a few months ago as it was giving me weird shift points, and is shifting fine now. As a side note I had a $4000 transmission rebuilt/upgrade due to a misdiagnoses the FIPL needed adjustment too bad the tranney shop guy ripped my tranney apart thinking it was something internal. Needless to say last time he gets my business. so 4K later I have a heady duty lock up converter and a heavy duty shift kit to show for.

I will run on the front tank for a good month and see if i notice anythign different.

BTW if the FIPL needs adjustment every once in a while is it worn and need to be replaced?

 

[Exekiel69]

I would think the tank, the lift pump or something on the fuel. I'm sure the temps are low where You live so maybe You want to check what fuel You're pumping on the tank even though You put additives on it.

 

[1992tractor]

If it is the Lift pump, how do they work, if it's worn does it starve the IP and therefore create a powerloss? Are they expensive and hard to replace? Also is there a seperate lift pump for each tank or is it combined?

 

[bluecollar]

I'm anxious to hear some replies to this question myself. The symptoms you describe have been going on with my 89 dually since I bought it about eight months ago. I've already changed the IP on mine and didn't notice much difference. I'm pulling an 8000 pound camper and truck slows down alot on hills. On one particular occasion coming back home loaded down I climbed a hill that I always slow down on at 70 mph and Old Red pulled like a mule and really brought a smile to my face. That has not happened again. This truck is a lot more stable pulling my camper, but my Chevy 1/2 ton has about twice the power loaded like that.

 

[Exekiel69]

Is easy to replace, is on the pass side of the engine at the bottom. Only thing is to remove on of the two bolts holding it on place then is piece of cake, or just get an electric pump installed and forget about this problems. Very easy to do as well.

 

[Exekiel69]

Usually when the IP is starved for fuel the fuel filter light would light ON. This happened to Me but different reasons, anyway the electric pump conversion is easy and time saver so in Your case I would plan on doing it. Okigringo posted "how to" some time ago.

 

[Agnem]

Fuel pump presure affects IP timing, so any variation in fuel presure can affect your perception of power. Also, as pumps wear, you get a hysterisis effect, where your foot becomes a factor. Let's say you push the pedal half way down and hold it there. Your timing is set at X. Now, lets say you push the pedal down 3/4 of the way, and let it back up to the same half position as in the first example. Even though the pedal and FIPL are in exactly the same position, X in the second example will be a higher value than X in the first. This is due to wear of the advance cam and associated moving parts.

 

[1992tractor]

Thanks for the replies guys! Is there a test or something I shoudl pay close attention too when trying to confirm if it is in fact my lift pump starving the IP or affecting the IP timing......any suggestions?

 

[Agnem]

I'd start with the lift pump test as outlined in the service manual. Sorry I don't have the proceedure handy, but it has to do with measuring the amount of fuel coming out of the fuel filter schrader valve.

 

[dsblack]

Also check it from both tanks. If there is an issue in one tank, it may show up on that test.

 

[jtate]

the answer to your question is both tanks run off the same lift pump. to test the lift pump unplug the wire from your ip so it will not start, remove the valve core from the schreider valve, attach a fuel pressure gauge to schreider valve, crank the motor over for a couple seconds and remember not to crank for more than 30 seconds at a time and let it cool for atleast 2 to 3 minutes afterwards. a good lift pump should regester from 5 to 7 pounds of cranking pressure. if it doesnt replace the lift pump.