Numbers first. Cat988H S/N BXY00384 Engine C18 S/N RHX00979 Electronic Unit Injectors. Engine starts fast in morning but when shut off for break or lunch when restarted 15 minutes later starts good then after a few seconds starts stumbling bad like it is running out of fuel then after several seconds takes off and runs great. I was thinking it was loosing it's prime due to a bad check valve but this seems like it would be worse after setting all night. Usually it is fueled up at night but as it was parked in shop to get new temp. regulators it was not fueled up yesterday and had about 1/2 a tank of fuel, less than it would have when shut down for morning break. While doing some checking for the overheat problem yesterday I checked for active and stored error codes and there were none. Any ideas????
What overheat problem ......? You never mentioned that before. First thing I look at on a hydraulically-driven fan like the 988H is loss of fan speed for whatever reason.
Over heat problem turned out to be bad temperature regulators. I did run the ET to check the fan speed settings and nudged up the high speed to 1100rpm. Pulled the regulators and put in pan of water with one of the new ones. New one was full open at 94ºC while the old ones where just open a crack, barely enough to see. Had advantage of using a digital thermometer at the QC lab for our black top plant. The bad running when started warm has been around before and after the overheating problem surface a couple days ago.
If your overheating problems continue you'll maybe have to look at measuring fan speed externally (i.e. not with ET)
Used ET to adjust speed and checked with photo-tac at fan. Worked hard for 4 hours after installing t-stats and it barely moved off the 12:00 position on gauge.
Back to the OP, is the fuel tank breather OK?
Has it got a fast fill system on it..? If not the tank cap is a vented one with an internal breather (no separate breather). What happens if you pull the cap of right before starting after a lunch break for example..?
Good thoughts, will try to check out later today. Suction in tank would make sense as once it sets over night it would bleed off. No fast fill system. This machine has the cam action fuel cap with the breather in it I try to be sure to check them at every service but it may be getting plugged from spray off front tire. I have a spare breather kit and also, I believe, a spare cap assembly. Might just run down and install a new cap as a test for the lunch time break.
Well I did install a "new" cap with the new filter kit installed. Operator says it still stumbled when restated after lunch break. Maybe first test should be fuel pressure? I'm thinking about making up a test tool with some clear tubing to check for air in fuel. Had this in the past for checking a problem with an old NT855 Cummins. Also might look at hooking a vacuum gauge on the suction side of the system to see if there is a problem there. I might not get to do too much on this machine as long as it keeps starting but will try to do some quick checks when I can, I'll be sure to post back anything I find.
Here's an idea. So long as the engine's reasonably warm when started up after the lunch break try taking it straight to high idle as soon as it fires up and report back what happens. I know it sounds a bit brutal but so long as the engine's warm it won't do it any harm just once as an experiment.
I'll see if I can get down to the pit on Monday and give it a try. When compared to how our old IR DrillMasters were started for years that doesn't sound too hard. But then they were V71 Detroits, mostly 8V-71's. They went right from 0 rpm to 1800 rpm cold. There was a manual governor over-ride but never saw an operator climb up there to engage it.
Yair . . . And gen sets too . . . here it's fifteen hundred (fifty hertz) and full load in twenty seconds at ambient 30 degrees Celsius. Cheers.
Heck those Drill rigs would do it at 30º F! Might be why I had so much experience rebuilding Detroits back then? Starting the 988H after a 10 minute break with a Pre-Lub system to have the oil pressure up before it even starts to turn is nothing!
Yair . . . kshansen . LOL . . . I was just being a smart ass. I ran some 12 and 16v149's and I seem to remember that in the performance specs. Cheers.
I've been told that the two best mechanics in the world are Detroit and Harley mechanics, `cause they have the most experience! Speaking of which I have a Harley Sportster to finish putting together at home this morning! I'll let you guys know anything I find out on the 988H on monday. One thing I should have mentioned right at the start of the topic, this is not something that just started happening this week, been doing this stumble on hot start for at least a year. Operator did mention the other day that it did go away for a time but came back again. Also that it was even worse after being shut down to refuel two days ago when it had been run much lower on fuel than normal, to the point it died and would not restart until electric priming pump was used in the morning.
Sounds like a tank and fuel line cleaning is in order as a first step. Does it have a primary fuel filter/water separator or just a screen..?
I've never worked on one of these engines but was wondering if these are HEUI or MEUI engines. I've heard plenty of stories about the HEUIs not starting because the oil hadn't been changed regular.
The C18 is MEUI
I think I finally solved the problem with this C18. Hard to get access to this machine when it was not needed 100% of the time I was working. As it wwas parked for some dental work on bucket I finally couold install a "sight gauge" in the suction line to primary fuel filter. Once it was primed and air purged from system there was no air in the fuel so problem is past the primary filter. No fuel leaks while using priming pump in primary filter head so I decided to have a look at the secondary fuel filter and the check valve in it. Everything looked good but boss said to replace the check valve as it was under $30. and I think he wanted a reason to take a ride! Put new check valve in and reinstalled filter head assembly. After running to warm up engine a bit let it set shutdown fo several minutes to simulate break time for operator. When restarted it started fine but then stumbled for severral seconds before clearing up. As I only ran a short time to warm up instead of the 3 hours normal use before break time I don't think I improved anything. Next on to the fuel transfer pump. Removed and dissassembled. Gear area had a little wear but nothing I would not think normal and when runnig it had good fuel pressure. Next I inspected the shaft, seals and bearings. Bearings seemed fine. Shaft had wear where the two lip seals ride, enough to catch a finger nail in on the fuel oil side. Seals appeared to be in good condition not hard or torn. So the decision was to put a reman pump on as even if it was not the problem now it would be someday. Well after running for two days with several hot restarts operator says it never skipped or stumbled even for a second on start up. Not 100% sure why this problem was so much worse warm when shut down for only a few minutes than sitting for a two to three day weekend unless the hot fuel oil was just enough low viscosity or the seals a little softer from the heat to cause it to not hold or pick up it's prime when started.
Has there been any change in oil samples over the last year?
Well PPM for iron dropped from 70 to 26 and copper and lead both went down. Viscosity at 100 went up 1.4 cSt. Machine is getting cloase to next service so I'll see then if there is a change. Not sure why the lab we send the samples to does not report anything on Fuel Dilution, they have the column in the report but they are blank on all samples. Lab and the types of tests are determined by corporate but I might send Equipment Supervisor in the next state a email asking about this. Note: We did have an oil cooler failure that resulted in a spike in the copper from the new core.
Viscosity going up almost sounds like soot contamination. What were the soot numbers like and what's your oil change frequency, 250 or 500..? Fuel dilution would cause viscosity to fall, not rise.
Guess I was not clear about the viscosity. It only went up in comparison what it was last year, not in relation to the new oil spec's. I don't have the exact numbers at home but the last sample came back at I believe 12.8 cSt where a couple earlier ones were down to about 11 cSt. This is a little low I believe for Delvac 1300 Super 15W-40 our change intervals on this C18/988H have been set at 500 hours.
We use Delvac 1300 as well, although any 15W40 oil at 500 hours should be around 13.8-14.5cSt. 12.8 is so low it's almost at the start of fuel dilution territory. Are you sure the oil wasn't a 10W30..? IIRC 11-ish is right on the money for viscosity if it was. And I'd sure like to see the soot numbers.