Power Loss Climbing Hills

florida egg · 07-03-2009, 04:46 PM

Hi All,

We have a 98 36ft Alpine and are experiencing power loss climbing hills. Have taken it to a Cummins shop and they suspected the need for a new air filter. We have replaced the filter and are still experiencing problems and are not in the vicinity of the Cummins dealer. A local mechanic suggested the problem might be with the fuel filter. Our manual gives part numbers for two fuel filters - one with a water separator and one engine mount. I have read other threads here which suggest that this coach only has the one filter with the separator and does not have an engine mount filter. Someone at an O'Reilly's also said that he did not believe the RV would have another filter on the engine. Has anyone here confirmed that the 98 does not have the second fuel filter? Also, is changing the fuel filter something I should attempt to do? If so, should I prime it before installing the new filter?

Thanks for your help. We have a long drive back to Florida and would like to have power when we hit the hills.

Happy 4th

Jeff and Cheryl · 07-03-2009, 05:20 PM

FE,
My '99 has only the one filter. Build date was 5/98. Unless a previous owner added a second filter (unlikely) yours only has the one filter as well. I've seeen previous threads on this forum where folks talk about priming the filter. It does need to be primed.

EngineerMike · 07-03-2009, 05:37 PM

If you can slide under the coach it is easy to check for the filter, or possibly by lifting the bed. The motor-mounted filter will be on the PS at about the front 1/3 point of the engine if you have one. Your filter/water separator is in the aft most PS bay, and you can test the contents w/the little spigot at the base. See what comes out and report back if you have ??
As to priming, yes, you should. Supposably, you can prime by turning the key on but not to the start position and waiting 30 seconds. Then repeat twice more before attempting to start. There may be a bleed screw on the adapter head for the filter which you can unscrew, then shut off when a spritz of fuel erupts. Or there may not be a bleed screw.

Some espouse pre-filling the filter w/fresh diesel fuel thru a paper cone type filter to minimize issues w/priming. Cummins recommends don't, cuz too many bozos don't pay attention, and get junk in the fresh filter where it will go directly into the injection pump. Turn on your bozo-detector, aim it at yourself, and take a reading; if it is in the red, or "danger, he's a bozo" zone, then don't prefill. If it is in the green or "OK, he's not that big a bozo" zone, then pre-fill. If you left the detector back at the garage, ask your wife; I have found that wives usually have an opinion on this point.

Another possible culprit is the fuel Lift Pump, located on the PS of engine behind the big fat plug w/the large wiring loom attached; it has a rectangular flat surface the computer is mounted on and the flow of fuel provides cooling for the computer which otherwise gets hot. Supposedly when you turn the key on, this gizmo clicks away till pressure in the fuel system comes up to 6-9psi so there is a positive pressure on the Injection Pump that then takes it up to ~3000psi on the common rail or in the injector lines if you have pop type injectors (not electronic). If you hear no clicking while a willing accomplice cycles the key and you have your head near the LP (or if you replace filter(s) & they don't fill as above) then the LP is suspect. If no pressure from the LP, the IP has to suck fuel thru the LP and all the way from the tank, and the IP will starve for fuel at high demand situations like hill climbing. Fuel is all that lubricates the high test IP (3000psi), so starving it for its lube will take a toll in addition to causing poor acceleration & maybe even rough running. Judging from the questions, if it is not the filter, diagnosis of a possible LP failure may be outside your comfort zone and you should take it to a shop. If the LP is bad, you will subsequently wear out the IP (which is an expensive ditty) and have to replace both within a few thousand miles or less. Probably in the coupla grand range for a rebuilt IP installed, less than a grand for new LP, maybe even $5-600 (mo bettah fo U).
Hope this helps.

D & D Rich · 07-03-2009, 06:23 PM

If your Air/Fuel filters are up to par, then as eMike said you might also have a bad lift pump. If the LP is ok then I would look at the Turbo system.

If you have a major hole in the turbo system, your coach will hardly go any where even on flat ground. If you have a partial turbo loss that would explain your loss of power on hills. On the boost side of the turbo you have tubing, hoses, clamps and the intercooler. You may also want to check you exhaust manifold from the engine to the turbo. I had a 2001 Alpine with ISC 350 and found a cracked exhaust manifold. (note the replacement manifold from Cummins was a lot better design, so you know they had trouble with their first design). A Cummins shop should be able to hook up a computer to the data port and it should show if you have a loss of boost. Cummins should also test for leaks in the turbo system.

Good Luck
Dan R.
2004, FDTS40