Rd 800 losing power in 2nd gear.

[Jeremy Lester]

Hey guys, I am hoping someone can help me out here. I'm a slate hauler at a coal tipple and I've been having some problems out of the RD800 I drive. My boss/mechanic hasn't been able to figure it out yet and I'm hoping someone here could maybe lead us in the right direction.

Basically, the truck just loses power sometimes in 2nd gear when loaded going up the haul road/hill. Some of the grades are too steep to pull the load in 3rd gear, so I pull it in 2nd and when I come to the steeper parts of the hill it begins to lose power and falls on it's face if I don't drop to 1st and even then it still acts like it don't wanna pull it.

However, if I drive up the hill in 2nd gear and when I come to a place on the haul road where it's not so steep, if I upshift to 3rd and then run it up until the next steep part and then drop to 2nd it will run fine the rest of the way and does not lose power.

This is crazy to me and doesn't make any sense at all. Also, it is real hard to start in the mornings after it has sat for a while. I have to crank the heck out of it for minutes before it finally sputters and idles normally.

We've changed air filters, fuel filters, turbo hoses/intake and it's still acting up. I'm not a mechanic at all, I only know how to grease it and throw on fan belts but I'll try to answer any questions you might have for me. Would this be a computer issue, a mechanical issue or maybe some kind of fuel issue?

EDIT: Oh, and it does not show a computer error code when it does this. The light doesn't even come on.

Edited October 2, 2013 by doleo

[j hancock]

Have you checked the fuel lift pump? It maybe going bad and not supplying consistent fuel for the injection pump.

[Jeremy Lester]

Have you checked the fuel lift pump? It maybe going bad and not supplying consistent fuel for the injection pump.

I'll mention it to him tomorrow. Any idea as to why it would do that in 2nd gear and not 3rd?

[MACKTRUCKS4]

If not the lift pump, check fuel lines for a leak, running in second, you may be running a higher RPM which is using more fuel but it does sound like a fuel problem.

[slpwlker]

Just out of curiosity how low are you lugging it before dropping to 2nd out of 3rd. Is it able to pull out of it or just lug till you either get first or finally pull out of it?

[staxx]

sounds like supply pump or overflow valve.

[rsb502]

yep lift pump, also check the pickup tube in the tank to make sure its not gotten loose at the top or cracked and leaning back when going uphill pulling air(experience there). I would try to run iot at a lower rrpm, get it in 2nd and keep it under 1600rpm or so and see if it pulls on out if so your pulling the fuel supply down with the higher rpms and it points to a lift pump.

[Jeremy Lester]

Just out of curiosity how low are you lugging it before dropping to 2nd out of 3rd. Is it able to pull out of it or just lug till you either get first or finally pull out of it?

The curves are numbered, and at the number 6 curve it is not very steep and I can upshift to 3rd and drive about 400 yards or so before I have to drop to second. It doesn't lug at all, picks up speed normally. When I get to the 9 curve, the grade raises and there's no way it would pull in 3rd so I have to drop there. When I go all the way up in 2nd, it's the same curve, #9, where it begins acting up too, where the grade begins to become the steepest.

[rsb502]

When you go all the way up in 2nd at what rpm? It doesn't matter what gear your in as much as what rpm your running. If your dropping to 2nd I'm sure your trying to keep your rpm up, if you pull it all the way in 2nd your probably trying to get it moving pretty good. Try going up in 2nd with the rpm as low as you can so there is less load on the engine and therefore less fuel consumption. If it is a lift (supply) pump getting weak you will pull the fuel faster than it can pump it under a good load.