2008 Hino 338 P0087

[Herc-u-rock]

Tremendous Thanks to All the comments, suggestions and questions on this forum! After reading for months on this forum, may I ask Your help with a P0087 problem... J08E 2008
I'm thrown this code every fresh key start and traveling over 1500 rpm's or above. My Autel Scanner says my "Target common rail pressure" is 26K - 27K during a 'Drive cycle', but "Common rail pressure" top out at only 20K - 21K THROTTLE DOWN... the instance I let off throttle (Manual Tranny), common rail HITS Target and then follows Target back down, common rail pressure follows Target up again until Target pressure demands above 22K, at which point common rail tops off at 21K. When I preform a dedicated SCV test by the recommend rpms, Idle and just above, Common Rail pressures follow Target pressures in all %'s variations in sync. SCV "drive currents" 1440mA - 1667mA, SCV "Feedback 220 - 204mA, Fuel temps never above 148 F. But durring a "Drive Cycle" when common rail pressures top out at 21K, SCV current decreases to 700 - 900mA, Feedback similar, Fuel temps never above 150 F.
Per suggested here, I have 'Isolated' the primary Tank, filter, lines, hoses and fuel pump inlet banjo filter... no change. I've isolated the 'High Pressure Limiter' by removing the banjo return, capping and checked for 'unseating' at the pressure limiter... 5 drops, maybe, in 20 miles. Three SCV replacements, one orignal two new... same results.
DPR Clean... which I belive says my injectors are not bleeding.
Hino dealer say new injectors and / or fuel Pump. I said thanks, but I know a Good Hino Forum... and I'm so Happy to be Here!! Thanks for You Time!!

 

[greasytshirt]

The SCV is asking for maximum fuel pressure but the pump cannot keep up with the demand.

To find out if it's a problem with the fuel supply to the pump, disconnect the banjo bolt and line from the supply port, look inside the port for debris, and if clean, connect a test banjo line directly to the pump and run the engine off an auxiliary fuel source. I use a boat gas tank ratchet strapped to the steps. Go for a wide open test drive. If it maintains pressure during sustained full throttle then there's a supply side problem. If it can't maintain pressure it's likely the pump.

Some fuel systems (like the Bosch system on Cummins 6.7) can have problems with internal injector wear that causes high pressure leakage, but I've never known a Hino to do that. Injectors are not on my radar for this failure mode.

 

[Herc-u-rock]

Many Thanks for You Time sir!! You mentioned this Diagnosis procedure a number of times in previous posts... and I was Sure to Follow every Recommendation "Before" Posting my request for help. I even added steps of my own just to be sure I'm not Re-hashing. And Yes, I did follow Your Recomended diagnosis. Also, tried adding an inline supply pump, as someone else suggested. I Removed the banjo inlet screen, Cleaned / Flushed everything downstream the pump to the fuel cap, Borescoped the fuel tank for "wrappers", strapped a boat tank onboard as well... let me throw a question your way... in one of my experiments I rigged a free flowing filter in the Dayco 232 housing which allowed me to have a "Volume" supply of non-restricted fuel, on that test run 80 - 90 miles, as long as I kept the fuel "Volume" in the filter Housing, the truck could hit 74 mph with power I never felt before, my Cruise Control worked Finally, through the entire trip and Code P0087 Never appeared. When I reinserted the Detroit or Napa Filter ( I've tried both, brand new... haven't tried Hino's yet) or I connect the Boat Tank my P0087 codes sets before I hit 6th gear on a fresh start. I left the 'Primer' bulb connected on the tank on one of the tests to see if it collasped, which would indicate something is Starving my Pump. Is it possible the 5/16 fuel hose connecting the fuel filter or the 5/16th hose to the boat tank is "Choking" my supply "Volume"?

Sorry, I'm chasing any possiblity rather than the pump. One mind said "change" the pump at the start, because each SCV cost us over $400 from Hino... Salesman said the new pump came with the SCV, but he and the mechanics in there didn't know as much as I had learned from Your Posts... so I didn't trust it. Thanks again for your Time!

 

[greasytshirt]

I definitely understand trying to rule out every possibility.

I don't know if your scan tool can access this, but there's a data group called system protection data that has historic things stored, like the highest fuel temperature logged. If this temp is over 200f, it's a good sign that the pump has a high rate of internal leakage.

5/16 fuel line should be fine.

If you want to get scientific, tee a vacuum gauge into the fuel supply line between your fuel source and the pump. The closer the reading is to 0 the better. If there's no restriction, no interruption in fuel flow to the pump, and no air being introduced, the pump looks more likely to be the culprit.

A new pump comes with a SCV. The pump is relatively easy to install on your era of truck.

 

[Herc-u-rock]

Thanks for burning the 'Midnight oil'! Yes, the scanner does has the "History" of the truck "over heating, Start / Run times", etc. The highest Fuel Temp 168F. Neat feature and I Didn't see any red flags to me... it was encouraging that they took care of the truck, thanks for the Insight.

I will get scientific, thanks, I graduated Diesel Tech in 1979 and now a LP - Natural Gas Installer... sizing Piping is very critical - scientific (which gave rise to the thought), with Life in the balance. This too, I don't want to "Blow" something up LOL.

Got another 'Trick' up my sleeve... You da Man!! Thanks for Your Years of Sharing!!

 

[Herc-u-rock]

Greasytshirt, might I trouble you for a Replacement New Fuel Pump Number, Please for this unit? Vin# 5PVNV8JT682S51071
I'm being Quoted now $3553.72 with a $220 core charge.