Fuel Filter Maintenance for 8.3 Cummins Mechanical

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Fuel Filter Maintenance for 8.3 Cummins Mechanical

December 04, 2017, 05:59:03 am

This is my first fuel filter experience with the 1997 U270 Cummins 8.3 mechanical system. It only has one filter near the battery bay and an always-on electric boost pump at the fuel tank. A few questions:

1. Draining
Should the boost pump or engine be running when draining the filter petcock?
I don't know what will cause or prevent air to enter the fuel system.

2. Replacing
Should the fuel filter be pre-filled after replacement? What is the best method?
Should the engine be warmed prior to replacing the filter?

3. Are there two filters? I can only find one.

4. Primer
Is there a hand-operated primer pump? Is it effective?

5. What is the best way to purge bubbles from the fuel system?

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #1 – December 04, 2017, 07:13:32 am

You have two filters. You located the first and the secondary is on the block. Look directly up from the lift pump and you will see it.

I use a Parker electric prime. Other than the installer using the wrong threading, we reworked it here at home, it has worked well. You can bleed the air to that point with a Schroeder valve on the top of the unit. Unless something else is admitting air down stream it clears quickly. I also added a vacuum gauge that allows for filter maintenance.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #2 – December 04, 2017, 07:56:42 am

Engine off, it can be cold easier on you, you have 2 filters as OP said. I prefill the filters with clean fuel then turn the key on for about a minute or so to pressurize the fuel system, then start.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #3 – December 04, 2017, 08:05:55 am

Not sure if the 97 differs much from the 96 but you have a mechanical lift pump on the engine block just below the secondary
fuel filter.On mine there is no electric fuel pump.Iv'e always filled both filters when changing and change around 6K miles,why
wait for a problem.Check on the forum and on line,many of us have installed an aftermarket check valve on the bosch fuel
injection pump this will smoothe your idle some.The fuel pressure at idle should be about 20psi, the same place that has the
check valves has a adaptor to install a gauge on the fuel injection pump,if your check valve has never been changed the spring
is weak and you are not getting the 20 psi.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #4 – December 04, 2017, 08:48:35 am

Tim,

You may want to VERIFY that you do have an electric boost pump at the fuel tank. Sure doesn't sound OE.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #5 – December 04, 2017, 11:02:11 am

Yes, two filters. Prefill both then install. Locate prime pump, located on mechanical lift pump, located on passenger side of engine, looking down from above it's easy to see. Turn key on but don't crank. Operate primer plunger or knob repeatedly, probably a min of 50 strokes or so. Listen carefully, you should be able to hear a faint squeak, squeak noise from end of injector pump each time the prime pump is stroked. ( That's the banjo bolt check valve making the noise.) This will indicate that air has been chased from lines. Crank engine. Will probably run rough for a couple minutes, keep rpm up to keep it running, won't hurt a thing. Engine start and run? Good, then done. If it won't start then you need to loosen a couple of fuel injector lines at the injectors, crank and purge air this way. Retighten them when engine is running.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #6 – December 04, 2017, 12:16:48 pm

This pump makes a relatively loud humming noise while the ignition is on, all the time. Two fuel lines are connected.

So, could the boost pump purge the lines if I partly filled the fuel filters, then left them cracked while the pump filled them the rest of the way?

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #7 – December 04, 2017, 12:19:34 pm

Tim,

Definitely not original equipment.

Can you post the model/make on the pump and also where the 12 VDC positive is coming from.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #8 – December 04, 2017, 01:03:17 pm

Looks like they ran the pump hot lead off the fuel gauge sender.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #9 – December 04, 2017, 02:11:12 pm

Quote from: Chuck & Jeannie – December 04, 2017, 01:03:17 pm

Looks like they ran the pump hot lead off the fuel gauge sender.

Ya, couldn't tell whether it was connected to the fuel sender unit or whether the wire just disappeared past it.

I would definitely NOT run a pump on the centroid sender unit. Certainly close enough to the front breaker panel to run a dedicated wire with fuse.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #10 – December 04, 2017, 02:24:24 pm

It should purge all the air through the return line without cracking open a fitting if you let it run long enough. On the ISC, the electronic lift pump only runs when you first turn on the ignition and only then for about 30 to 45 seconds. I find that two or three cycles is adequate to purge air, and that is without pre-filling the secondary block mounted filter. Cummins specifically states to not pre-fill the block mounted secondary filter, something to do with the CAPS injection pump...
Don
"So, could the boost pump purge the lines if I partly filled the fuel filters, then left them cracked while the pump filled them the rest of the way?"

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #11 – December 04, 2017, 05:01:31 pm

That looks like a mighty small pump to deliver the volume normally supplied by the mechanical fuel pump. Are there any valves installed in the line to fuel pump? Kind of wonder if it might be a bypass style prime only pump.

Do you have a mechanical fuel pump as well on engine? Should be a secondary fuel filter close to it.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #12 – December 05, 2017, 07:29:08 am

I believe the model is the Carter 4600. See: https://www.summitracing.com/parts/crt-p4600hp
It is:
- Capable of 100GPH (What is the maximum fuel flow for a C8.3?)
- Wired to the fuel sender +12V
- Replacing/augmenting the lift pump?

I wonder what the motivation was to the original owner:

Better starting?
Easier fuel line purge?
Compensating for a bad lift pump?

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #13 – December 05, 2017, 07:49:28 am

Quote from: Tim – December 05, 2017, 07:29:08 am

I wonder what the motivation was to the original owner:

Better starting?
Easier fuel line purge?
Compensating for a bad lift pump?

Could be any or all of the above. Another thought - if your fuel lines are starting to leak, a small pressure pump (between the tank and the lift pump) could alleviate the problem of air being "sucked" into the lines by the mechanical lift pump. A "band-aid" to avoid replacing fuel lines?

From the comments on the Summit Racing page, it sounds like a pretty good pump! I've often wondered why our coaches, especially the 40+ footers, didn't come from the factory with this type of auxiliary pump. Although I've never had any problem with the stock system (even when changing the filters), it seems like asking a lot of the mechanical lift pump to suck fuel through 30 feet of fuel line + the first filter.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #14 – December 05, 2017, 07:54:30 am

No way this pump replaces the mechanical lift pump,top fuel pressure is 8psi.The bosch inj. pump system with the relief valve
is designed to send an amount of fuel thru the injection pump to cool it.If this pump is an add on and your system is the same as a 96,2 fuel filters and the mechanical engine mounted pump I would remove it.

The aftermarket valve for the bosch pump is made by Tork Tech.
On the air bubbles,I don't think that's even a problem,I read about the carter electric pump and the description does not mention diesel at all.Since some of the mechanical lift pumps are made by carter I would contact carter and ask them about using both
pumps at once.Is a wild guess but is there a chance the electric pump is cavitating and putting air in the line?

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #15 – December 05, 2017, 08:13:43 am

For the newer Forum members who might be following this thread, and perhaps would like more info about the fuel system on the mechanical Cummins engines, see the thread linked below. Several years ago, we had a lively discussion on how to optimize the performance of the stock fuel system. I know I learned a lot from the input of all the participants.

Fuel System Science Project

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #16 – December 05, 2017, 09:01:40 am

Tim,

STRONG suggestion: rewire that pump. The positive wire to the centroid fuel sender unit was never designed to carry the amps to run that pump.

Best way is to use a RELAY, with "ignition hot" to close it. Fuse and wire to relay and then another to the pump.

This way you don't take a chance of harming the fuel sender unit or gauge package AND also insure that the pump has adequate voltage AND will only run when the ignition is on.

Whole thing should cost you less than $20.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #17 – December 05, 2017, 11:15:21 pm

Quote from: George and Steph – December 04, 2017, 07:13:32 am

You have two filters. You located the first and the secondary is on the block. Look directly up from the lift pump and you will see it.

I use a Parker electric prime. Other than the installer using the wrong threading, we reworked it here at home, it has worked well. You can bleed the air to that point with a Schroeder valve on the top of the unit. Unless something else is admitting air down stream it clears quickly. I also added a vacuum gauge that allows for filter maintenance.

Is that water inside the picture of your gauge, and it still works?

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #18 – December 05, 2017, 11:32:48 pm

Oil filled pressure gauges are quite common, I believe it's dampen the needle movement from pulsating.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #19 – December 05, 2017, 11:41:18 pm

Quote from: Old phart phred – December 05, 2017, 11:32:48 pm

Oil filled pressure gauges are quite common, I believe it's dampen the needle movement from pulsating.

Very common in shipboard and oilfield applications. Normally glycerin filled. Prevents damage from vibration and dampens pulsations. About twice the price of standard gauges.
http://www.wika.us/solutions_liquid_filled_gauges_en_us.WIKA

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #20 – December 06, 2017, 12:46:22 am

Thank you Jim, other considerations when buying a gauge for accuracy is 270 degree needle movement, along with buying an appropriate range, for example buying a 250 psig gauge to measure 15 psig is just a waste of money, as +/- 3% of 250 psig is about the best result you can possibly attain on any given day, so buy the 0-25 psig guage. I would venture to say that Any gauge manufactured in China is plus or minus 10%. Digital gauges rely on the same principles mostly, except for the really big buck ones.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #21 – December 06, 2017, 06:38:31 am

Sorry I did not see your question sooner. The gauge is one I bought at Transatlantic Marine Diesel here in Hampton Roads. Yes it is oil suspended, 270 swing with second set arrow for comparative reading. Here is their site. It is a bit dated to say the least.

http://www.designatedengineer.com/

I am relatively new to the MH world and this size diesel. I have never had filter problems on my 5.9 truck but have had several with the 8.3. Both were from changes by techs and my lack of knowledge they had put 5micron filters on as primary. I like being able to monitor my filter rather than guess it's condition. I still change it at 6k. I do carry spares and soon will have a second bowl for pre attachment and a faster change.

One unnecessary change or worse necessary change on the road and I feel I am even.

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #22 – December 07, 2017, 07:15:37 am

Drained the petcock on the primary fuel filter. After about 10,000 miles on this filter, only CLEAR diesel was seen in the glass jar. Wow, I thought there would be water and black stuff collected, but it was an absolutely clean sample. Other observations:

- Without the electric boost pump engaged, fuel trickled out of the petcock
- With the electric boost pump engaged, fuel squirted out of the petcock
- Electric boost pump, shown in a prior post, measured 11.9 volts and drew 2.3 amps

We are about to embark on a 8,000 mile, six month trip across the USA. Should I change the fuel filters now, in my driveway in 40 degree temperatures or wait until the filter has 14,000 miles on it, another 4,000 miles and get it serviced professionally while on the trip? If it ain't broke, don't fix it?

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #23 – December 07, 2017, 08:19:27 am

Tim, does the coach start and run properly? If the answer is yes apply the if it ain't broke don't fixit to it. Having said that given your electrical knowledge, I would do as Brett suggested with fuses and relays when time and weather permit

Re: Fuel Filter Maintenance for 8.3 Cummins Mechanical

Reply #24 – December 07, 2017, 08:29:33 am

Engine starts in one second, without fail. During a 30F start when I forgot to pre-heat, white smoke exhausted for about 20 seconds, then cleared up. I will definitely rewire the pump when able.

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