Engine in question is in my Kenworth, ISC 8.3, common rail, pre-emission engine. Replaced all 6 injectors and HP tubes about 200k ago with Bosch remans. No issue until about 10k ago. After idling for a half hour or more, it’s started falling slap on its face when you first put a load on it, letting out on the clutch when you take off, and between every gear until you get it cleaned out and then it runs great. Any extended idling causes this response. There are times when it pulls it down so bad you have to shut it off and restart to get it to come out of it. There’s roughly 7200 hrs on these injectors, doesn’t seem like it would need another set this quick but definitely seems to be an injector problem. I’ve always ran clean fuel and changed filters every 20k. Curious if anyone else has seen this issue.
Not exactly but just went through a little different problem. Would first want to know rail pressure. Requires a scan tool as it is up around 18,000 + PSI. Also checked for air in supply to primary filter with clear hose. Checked vacuum on supply hose. Checked for supply pressure at 2nd filter, around 80 PSI and steady. My rail pressure was still low. Unplugged sensor on supply pump. No change. Removed line from pressure relief valve on fuel rail. Mine was always bypassing fuel. Replaced that and it was my problem. I am not the 8.3 trouble shoot flow chart but maybe gives you an idea of things to check with what you have.
Extended idle is the only time I have an issue, when I’m on the PTO or just sitting at idle. Once you blow the smoke out of it, it runs fine. The idle is always smooth, usually by the time I hit 10th gear it’s cleaned up and back to normal. It has always loaded up when sitting at an idle and smokes heavy until you get up to speed good, after that, normal again. It did this with the previous injectors also, but never fell on its face like this.
Can the injectors be cleaned? It sounds like the same issue when you last changed injectors but is worse this time. I don't know but maybe a good injector cleaner or fuel conditioner might help. From what I've heard some diesels will get so slobbering up from excessive idling they won't rev up. I know that's not your problem but it could be tied to an issue with the injectors at idle that clears up under higher RPM after 15-20 seconds or longer.
@Welder Dave I definitely agree with you, I’ve ran 3 doses of hot shots through it along with a daily dose of the everyday treatment. Seems to improve it for awhile but doesn’t alleviate the issue. I’m sure there’s no magic sauce to dump in the tank. Unfortunately by the time I down the truck and wait on the injectors to be cleaned, I’ve lost more than what another set cost. Kills me to change them because if all I did was drive it, it runs spot on.
Updating this thread, as the temps cool, the problem definitely lessens. Leads me to think the injectors are getting too hot at idle though I’m not sure what the cause or the solution is to this. Aside from the cooler temps making the issue less frequent, a couple weeks ago I was using the PTO for a couple hours on a Saturday and pulled it in the shop when I was done, when I pulled out Monday morning it was as if I’d not done any idling at all. Seems a cool down keeps it from happening. Continuing to monitor the situation.
Friends FL70 tow truck started the same thing this summer @ 300K, replaced injectors no more issues.
We have an excavator that showed similar symptoms, worse in the heat. I got to looking at things, taking temps etc. Noticed the fuel temp was stupid high, don’t recall the number off the top of my head, but you couldn’t hold your hand on a filter and dang near couldn’t touch the tank. Talked to a Deere tech, he pulled up some info for me. Deere has come out suggesting relocation of fuel cooler and a different “tropical” door with more vents. I said all that to say this, maybe it’s a fuel temp issue? Kinda like the old carbureted cars used to vapor lock.
I ordered a scanner last week, hopefully it will show fuel temp. Maybe that will shed some light on what’s going on.
An update to this thread- The scanner I got doesn’t read much on fuel pressure or temp. I did borrow a diesel laptops computer from a friend and I was able to see some parameters. Since it’s gotten cold, it never has an issue after idling but, when it’s below 40 degrees or so, it does throw a check engine light for rail pressure. Comes up after 10 minutes of driving or so and goes away in minutes and never comes back on the rest of the day. Other than electronic derate, no symptoms leading up to the light. Having the laptop hooked to it, the fuel rail pressure sensor is not acting normal when cold. Has quick spikes up to over 40k psi and back down to normal. Cummins says you can’t buy just the sensor, only comes on a new rail. I scraped the paint off the sensor body and found the Bosch number, roughly $100 vs $1300 for a whole new rail. I’m not sure if this will have any effect on the idling fuel issue I had in summer but time will tell. Hopefully it’ll take care of all of it. Here’s a data line on fuel rail pressure when engine is started cold and idling.
I had a similar issue on one in a trash truck. I could wiggle the wiring harness and make it spike like that, drop to zero, engine would cackle like it was running out of fuel then knock like it was over fueling. Did a sensor and a couple months later the pump died lol. Those trash guys don’t take care of ****.
Do you have the Bosch number still?
Yes, 0281002851 Is the Bosch number. When you run it through, mostly comes up for the 5.9L engine.
What is the source of the $100 part? I did one a while back, only found prices like that for who-knows-what on ebay. It cost a bit more to order the real part but it was a Deere, they list the individual parts, I know some others don't. (I wound up ordering a whole used rail with sensor already in it, contamination was the issue with my job.)
Just a few places I found online. Scheid diesel is local to me and they are a Bosch distribututor so I’ll call them Monday and see what they can do with it.
Scheid came through, genuine Bosch for $110. Updates to 0281006325 I will update when I get it and it’s installed.
Back for an update. Rail pressure sensor made no noticeable difference. A contractor buddy of mine has Cummins insite and brought it over Saturday and we took it for a drive. Rail pressure was 10k psi low under full load until you drove 10 miles or so then it went to normal. Brought it back to the shop and unplugged the Fuel control actuator solenoid on the high pressure pump. Sent the rail pressure to 23k psi. Plugged it back in and everything has been fine for 2 days now. 27k hrs must have had the FCA solenoid feeling lazy. I’m going to order a new one for good measure. Hopefully someone will find this helpful diagnosing Cummins low common rail pressure when cold.
I've replaced plenty of those actuators on Deere engines about the same year model but I think they were Denso. The problem they would have is over pressure thus breaking the rail relief valve into a constant relief state and causing weird hard start and lower than normal power problems. No idea if that has anything to do with your situation, everything is so mysterious on these fancy engines.