Hi,
I have a 2008 Hino 338. After 480,000 miles the check engine light came on. First it would do this once a month and now it comes on daily after i drive 50-70 miles. No it comes on after only driving 10-15 miles. The engine now is choking up and revs up to 1800-2000 RPMs. Codes show T0087 and T0193 High. I replaced the fuel pressure sensor but this didn't help. The Dealer wants to replace the fuel tanks but I don't think this is the cause of the problem. The check engine light never comes on when the DPR is working.
The second problem I have is with the AC. After 45-60 minutes of working properly, I hear a vibrating noise and it stops working. After I turn it off for 15 minutes, the AC works again. I notice the problem occurs when the air outside is humid or moist.
Any ideas what could be causing these problems? Any insight would be appreciated.
Thanks
Step one: replace fuel filter.
P0087 is low fuel rail pressure. On a truck with 480k, it's likely one of two things: a blockage in a fuel line (happens more often than you'd think), or a failing suction control valve (aka fuel pressure regulator). It's a shiny metal cylinder looking thing on the front of the high pressure fuel pump, and a pain in the butt to get to. Two internal hex screws hold it in. I recommend a 6 inch long hex driver with a ball swivel end. 5 mm, IIRC. Advance Auto sells a metric set for $35, and I haven't broken one yet.
For God's sake, don't strip the screws out. If you do (they can require quite a bit of torque to initially break free), you can run a really long chisel or punch down in there and give the bolt head a little pop with a hammer. Don't beat the **** out of it. Usually a little pop will ease some of the stiction off of the bolt, and it'll crack loose, even if the bolt head is starting to strip a little. Do not ham fist it. Granted, it's a pain in the butt to get to, and ham fisting it is really tempting.
A new scv comes with new bolts. Save the old ones, because inevitably you'll drop one or both of the new ones and they'll go into an abyss somewhere behind the fuel pump and vanish forever, eternally passing through other dimensions, never to be seen again. Forget the magnet, they're made of stainless steel, which laughs at your feeble human efforts of retrieval. Not that I have first hand knowledge of this or anything.
Junk from the fuel tank gets stuck in the elbows at the fuel tank, various banjo bolts between the tank and fuel pump, and check valves in the fuel filter base (depends on Davco or spin on). If you have steel tanks, and they're rusting, the dealer may be on to something. I think all replacement tanks are aluminum.
Not sure what P0193 is off hand, but I kinda think it's scv related too. If so, this whole thing may be a crappy connection in the scv connector. Unplug it (pain in the butt sometimes) and look at the terminals in the plug. If there's evidence of rusty looking powder residue in there, even just a little, it's causing an intermittent bad connection. The dealer can get a terminal body and wire pigtails. Chop the old connector off, splice the new wire terminals with waterproof heat shrink butt connectors, and plug the new terminals into the terminal body and plug it back in. If it's still acting up, the scv could be sticking and failing.
Another test can be to run the truck off of a different fuel source, like a 5 gallon can strapped to the steps. Run it up a hill, foot to the floor. If it's a fuel starvation issue, then it'll run great on an auxiliary tank. Crap in the fuel system fittings. Don't run out of fuel, none will return to the aux tank. You have about ten minutes on a full can.
occasionally the high pressure relief valve starts leaking. It is located on the fuel rail, has a banjo bolt in it, and has a tiny metal line attached. If the scv connector is sketchy, when it breaks contact, the rail pressure goes sky high (like thirty thousand psi). The relief valve opens. The relief valve does not like to open, and if it does too many times, it will start leaking. This can be checked by removing the banjo bolt from it, sealing off the fuel line (I take a nut and bolt, put copper washers on either side, and snug it a bit), then starting the engine. Nothing should come out of the relief valve. Hold the accelerator to the floor for a few seconds. Nothing should come out. If anything comes out, it has failed. Replace it and the scv and the scv connector if it looks the slightest bit damaged.
Worst case, the high pressure fuel pump could be failing. I doubt that though. Usually they just fail outright and the engine dies. These pumps are generally very tough, and if fuel filters are replaced on a half reasonable schedule, they rarely fail. You can probably strike that from your list. Way too many things to check to begin thinking about replacing this. Pretty much, if the truck runs at all, it's probably not the high pressure fuel pump.
Edit: If you ("you" means whoever happens to be reading this) read all of that, and you're thinking, "Oh jeez, why did I buy a Hino?", guess what: Anything with common rail fuel injection is set up in a similar fashion, with similar functions, and suffer similar failures. If you learn how it works, it's pretty easy to figure out, relatively speaking.
The VNT controller on the turbo, or sticking VNT linkage can cause low power situations. Get a can of Loctite nickel antiseize in an aerosol can. Yeah, it's gonna cost around $40. Get it anyway. Best antiseize ever made, especially for the exhaust system anything on these trucks. Spray some on both the upper and lower VNT linkage pivots, then maybe a squirt or two every six months or so. If it was sticking, it won't now. The VNT controller is sometimes damaged by sticking linkage, and it's not available separately, which means you gotta replace the turbo. I'd do this simply for peace of mind.
For your a/c system, assuming that there's nothing wrong with the actual a/c system, I'm assuming the blower motor is in the middle of it's death knell. They don't last forever. When the blower motor gets old and crusty, it takes more current to turn. Not a big deal, but it usually melts the back of the blower switch and the blower switch connector. If you can get the blower switch out and unplugged (pain in the butt [common theme]) if it's melted, you ned to replace the blower motor, the blower switch, the blower switch connector, and any terminals that overheated. It's fixed just like the scv connector I mentioned earlier. Replacing any one of these things and not the others just means you'll fry new parts.
Replacing blower motor=pain in the butt (who saw that coming?) Well, the first time, anyway. Four bolts on the engine side of the firewall hold the blower motor case in place. You can't get the motor out of the case with the case in the truck. Looks like it might be possible, but it's not.
For other a/c problems, it's nothing anyone with some automotive a/c experience can't figure out. The h-block (thermostatic expansion valve) is behind the blower motor case. Everything else is straightforward. On early trucks, the dessicant bag is located in the condensor side tank, but that's on trucks made in 04-05 (in case anyone stumbles across this thread, and happened to be wondering).
That oughta keep you busy for a while. Have fun!
