C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Topic: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank (Read 1466 times) previous topic - next topic

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #25 – October 16, 2015, 10:59:35 pm

Quote from: John Duld – October 16, 2015, 06:45:18 pm

Did this start since the last fuel filter change?
JD

I noticed the change when I started allowing the fuel level to stay at lower levels overnight. I can't correlate the slow starting with a change of filters. I can correlate the slow starting to a change in my habits.

It is time for oil and filter changes. We'll see what happens after the fuel filters are changed. I also plan to describe the symptoms to Bernd. He may check some things during the service event.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #26 – October 17, 2015, 09:29:43 am

J.D., you wouldn't necessarily see any fuel leak, when the coach is idle the lines are under suction, not pressure. Any small leak, air can come into the lines, letting fuel drain back to the tank. A low tank increases the problem. Sounds like you're going to be getting your filters changed anyway, if this doesn't cure the problem then the "banjo bolt" on the return side of injector may, as others have suggested, be the culprit. If you do end up replacing this relatively inexpensive part, I'd suggest replacing with one that's tapped to allow a pressure gauge to be inserted or installed. It's possible to tap the stock Bosch part, or purchase an aftermarket unit that is already tapped. If the old one is worn enough to leak down, a new part will probably give you some additional power also.

I know what you mean though. I really like the fact that my C8.3 cranks up instantly, it's like switching on an electric motor.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #27 – October 19, 2015, 09:10:28 pm

A leaking lift pump on mu 95 280 with the 8.3 created the same symptoms that you are describing. An alert mechanic while rebuilding the bracket for the hydraulic pump asked if I would like him to replace the lift pump while the welded bracket cooled off. I told him to go ahead and all the symptoms disappeared. As a side note he apologized when he charged me $38 bucks an hour for labor for the whole deal, wish he was still alive and I still had a FT.
Gary B

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #28 – November 17, 2015, 10:33:55 pm

Here is an interim update on the C8.3 starting issue.

The primary fuel filter was filled with "black stuff." The bottom of the fuel tank was covered with "black stuff." The fuel tank was inspected with a camera and LED on a flexible stalk. Bernd showed how my tank looked compared to another tank that was mostly clean on the bottom, but with some "black stuff" in the corners. In the "clean" tank, we could see reflections from the bottom of the tank, as well as the top surface of the fuel, as the camera was lowered into the tank. In my "dirty" tank, we could see no reflections from the bottom of the tank.

The plastic primary fuel line installed at FOT a couple of years ago had a kink in it at the fuel tank.

The fuel tank has been pulled and cleaned. The primary fuel line will be replaced from tank to primary filter with a new flexible hose.

Bernd thinks the "black stuff" and kinked fuel line are significant contributors to the starting issue. It still puzzles me that the engine starts quickly on a full tank of fuel, but takes 15 seconds to crank at 1/3 full. The slight pressure differential from full tank to partial tank apparently has an effect. The engine has performed well after the first start of the day. Subsequent starts during the day were usually rapid. The issues noted above needed to be fixed. We'll see how things work after I retrieve the coach.

We've had the coach about 5 1/2 years. I've been careful to keep the fuel tank full when the coach is parked. I've bought fuel from high volume stations. I've tried to buy fuel with the least percentage of biodiesel, depending on availability. Between "real" trips, I've driven the coach 20 miles or more every month to exercise and lubricate the systems, and circulate fuel. In spite of that care, we've got a lot of "black stuff." My research indicates that the ULSD fuels are more likely to accumulate "black stuff." Biodiesel is more likely than petrodiesel to introduce water into the system. Biological invaders are more likely to cause problems when the is more water and less sulphur in the fuel. I plan to start using some fuel treatments to avoid the "black plague."

Other issues that are being addressed include: cleaning/treating some rusty areas while the fuel tank is out; replacing a "shrunken" exhaust manifold, cleaning/treating some rusty areas around the radiator and engine compartment; adding some electrical cable to enhance cranking power from the chassis batteries. I plan to report on a couple of those issues in a different thread.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #29 – November 17, 2015, 10:44:55 pm

We get the same "Black stuff" in turbine airplane fuel tanks and it is a growth. Some airplanes have Strontium crystals inside that are changed at intervals as they get used up. In time it corrodes the aluminum fuel tanks. Water is held in suspension in kerosene/diesel/parafin etc. and the growth thrives on it. They use stuff called "Biobore" to clean it out. One application and it evaporates. I would suspect your fuel source.
I cannot answer why it starts better with a full tank although fuel hoses comes to mind from other posts??
Brian

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #30 – November 17, 2015, 10:52:32 pm

It's actually a bacteria growth,is common in the lousy fuel they get on the offshore platforms,been up many a night changing
fuel filters every hour because of the black stuff.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #31 – November 17, 2015, 11:40:31 pm

I always treat fuel with a lubricity/cleaning additive. If stored for a long period of time, I add ILFC 1032. ILFC Ten32<br/>Fuel Inhibitor<br/>Storage Stabilizer, Lubricant — Internation...

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #32 – November 18, 2015, 12:20:55 am

Quote from: speedbird1 – November 17, 2015, 10:44:55 pm

We get the same "Black stuff" in turbine airplane fuel tanks and it is a growth. ... Water is held in suspension in kerosene/diesel/parafin etc. and the growth thrives on it. They use stuff called "Biobore" to clean it out. ...

I found information about Biobor here: Biobor Jf Fuel Additives - Products Biobor was the only additive that I found that has a MIL-SPEC qualification. The specification appears to be primarily related to "stabilization" of diesel fuel. However, the manufacturer claims that it is also effective as a biocide and enhancer of lubricity.

My research indicates that some of the "black stuff" may be asphaltene, a precipitate from degraded diesel fuel. Many of the fuel treatment products claim to "stabilize" diesel fuel, kill microbes, and improve lubricity. I plan to choose an additive and use it regularly. My previous attempts regarding fuel "hygiene" appear to have been inadequate.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #33 – November 18, 2015, 05:03:18 am

If somehow you got some in your tank and/or it grew or got bigger then when/if your additive killed it,its got to go somewhere
and it went in your filters.We would get 500 gal.tanks of diesel on the platforms and for whatever the reason some would be full
of the black junk and some would not.

What I'm trying to say is when you treat it and kill the bacteria it will still be in your tank.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #34 – November 18, 2015, 09:25:18 am

Quote from: J. D. Stevens – November 17, 2015, 10:33:55 pm

Here is an interim update on the C8.3 starting issue.

The primary fuel filter was filled with "black stuff." The bottom of the fuel tank was covered with "black stuff."

JD, did it look like this stuff? I found this in my primary filter last December.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #35 – November 18, 2015, 10:29:39 am

Good info on the forum for recommended biocides if one searches for biocide (particularly any post by wolfe10 (aka Brett Wolfe))

We use it when getting diesel that will be in our tank for more than a month. Then run engine, genset, and AquaHot before sitting to get biocide-treated fuel into all systems.

Of course as John says, if you discover it in your tank, even if you kill it you're going to have to filter the dead bodies out, so it may take several filter changes.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #36 – November 18, 2015, 11:14:12 am

If you can see it in the bottom of the tank, I would recommend you tilt the coach over toward the filler and using a small pump, suck all you can out, drive it a mile, tilt it over again and repeat the process. Cheaper and faster than changing a lot of filters. Then new filters on the generator and engine with several spares available. Check inside of tank frequently for remaining algae on both sides and bottom.

Like I said before, there is not a lot of quality control on diesel once it gets to the service station. Best not to fuel from an above ground tank as daily changes in temperature can cause moisture in the air to condense on the sides of the tank, go to the bottom and provide an interface for algae to grow. Less likely on an underground tank with very little temperature change but old tanks, algae in supply tankers still cause problems.

Pierce

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #37 – November 18, 2015, 11:30:52 am

My 1996 U320 fuel tank has a vent tub at the front centre of the tank which goes over the propane tank and out through the front wall and down behind the front tires.
Not sure if there is a screen on it.
I checked and my fuel caps are vented. I could blow air through both in and out.
Not sure why caps are vented, perhaps PO put them on, when there appears to be a vent tub.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #38 – November 18, 2015, 11:41:55 am

Wyatt,

Your vent may have pressure relief valve set at about 3 psi to avoid tank damage from overpressure. Easy way to tell is after driving for while, remove the filler cap and if you get a puff of air, the vent has a relief valve in it. Ours is like this.

Pierce

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #39 – November 18, 2015, 12:00:53 pm

Quote from: P. Wyatt Sabourin – November 18, 2015, 11:30:52 am

My 1996 U320 fuel tank has a vent tub at the front centre of the tank which goes over the propane tank and out through the front wall and down behind the front tires.
Not sure if there is a screen on it.
I checked and my fuel caps are vented. I could blow air through both in and out.
Not sure why caps are vented, perhaps PO put them on, when there appears to be a vent tub.

I put non vented locking caps to replace the existing ones.

I probably drive my coach harder than whoever installed these as a hard push up steep grades caused fuel overflow out of the vent tube.

Changed to vented locking caps and no more issues. Tanks were full minus 10-15 gallons when they overflowed.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #40 – November 18, 2015, 12:00:59 pm

Quote from: P. Wyatt Sabourin – November 18, 2015, 11:30:52 am

My 1996 U320 fuel tank has a vent tub at the front centre of the tank which goes over the propane tank and out through the front wall and down behind the front tires.
Not sure if there is a screen on it.

There was a screen on the end of the vent tube on the 2000 u270 that I was under a few weeks ago.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #41 – November 18, 2015, 02:27:46 pm

Cummins sells an asphaltine dispersant under their fleet guard label---- it works great and will greatly extend the time period between filter changes with the low sulfur fuels. It keeps the asphaltine in suspension in the fuel instead of clumps in you filters and tank bottom. I have used it with great success.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #42 – November 18, 2015, 02:50:13 pm

Quote from: Kemahjohn – November 18, 2015, 02:27:46 pm

Cummins sells an asphaltine dispersant under their fleet guard label---- it works great and will greatly extend the time period between filter changes with the low sulfur fuels. It keeps the asphaltine in suspension in the fuel instead of clumps in you filters and tank bottom. I have used it with great success.

http://www.cumminsfiltration.com/html/en/products/fuel/additives/asph_cond.html

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #43 – November 18, 2015, 03:50:35 pm

Hi All,
I have used Opti-Lube products. They now have a biocide type fuel treatment.
Raymond

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #44 – November 18, 2015, 07:14:54 pm

Quote from: Lance Camper – November 18, 2015, 09:25:18 am

JD, did it look like this stuff? I found this in my primary filter last December.

No, this the filter did not look at all like that. The "black stuff" looked like a fine black powder. There were no clumps or chunks, and there was no slime. The fuel in the sight glass on the bottom of the filter was clear. There was an almost imperceptible layer of the black power on the bottom of the sight glass. I did not see it until Bernd pointed it out to me.

The filter was screwed on very (too) tight. The mechanic removed it by piercing it with a big screwdriver and using that as a lever. When he pierced the filter, the fuel that came out look like very thin used engine oil. There were no clumps or slime, but the liquid was black. It appeared that the primary filter had captured almost all the black stuff that reached the filter. I think the filter was not clogged because engine performance was good all the way to the shop.

I expect to retrieve the coach next week and will provide more information on what was done to clean the fuel system. I expect to also find out if the "slow start" behavior has been fixed.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #45 – November 18, 2015, 07:51:09 pm

We used big racor cartridge filters where you could see the element ,the whole element was black from top to bottom.
sometimes you could get by by just changing the primary filter.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #46 – November 18, 2015, 08:14:44 pm

Quote from: John44 – November 18, 2015, 07:51:09 pm

We used big racor cartridge filters where you could see the element ,the whole element was black from top to bottom.
sometimes you could get by by just changing the primary filter.

I also use a larger Racor 1000FH filter with a cartridge element, very quick and easy to change.

Re: C8.3 Starts Quickly on Full Tank of Fuel, Slowly on Partial Tank

Reply #47 – November 18, 2015, 09:21:27 pm

My coach had similar symptoms as some of you describe. The biggest being that the coach was VERY difficult to start after sitting in place for two weeks. It was like it was empty of fuel. On occasion, I would pull into a fuel stop and fill up and it would still be hard to start. I never was stranded by the problem but when I returned to Michigan I stopped in for service at Cummins Bridgeway and mentioned the problem to the mechanic who was doing the service. He said it sounded like a bad spring on the fuel return from the lift pump and decided to check it. The spring (as I remember was about 1 1/4" in diameter and maybe 2 1/2" long. I asked the price for a new spring and the price was ridiculously high. He said that he could probably fix the old spring by stretching it out a little if I desired. We did that and it has been working fine for a lot of years. I recently developed the same problem again so I will be getting a $50 fix that I just read about on this particular message link. My coach just turned over 260,000 miles so things are probably getting a little tired, I guess.
Regards,

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