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Old 09-17-2020, 09:41 AM   #1
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Fuel Pressure Testers/Gauges Cummins 6CTA

I wonder if anyone invested and used the fuel pressure gauges/testers for CUMMINS 450C 6CTA engines. I'm looking for the following info and was hoping that someone here went that route already:

1. What gauge (tester kit) fits the engines to test fuel pressure coming from the lift pump (low pressure side)?

2. What gauge (tester kit) fits to test high pressure pump side?

3. Does anyone have fuel flow ratings for the lift pump and the fuel flow ratings for the high pressure injection pump?

Thanks,
Alex.
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Old 09-17-2020, 10:05 AM   #2
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I have the 250 hp version of that engine and I'm preparing to change the injectors out.

Why do you need these gauges? What are your symptoms?
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Old 09-17-2020, 12:53 PM   #3
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Originally Posted by Xsbank View Post
Why do you need these gauges? What are your symptoms?
I'm troubleshooting an issue on one engine not being able to make over 2350RPMs, with 2600+ expected.

The idea of the gauges/testers to verify that the fuel flow is to the specs. If not, it'll give me a direction.
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Old 09-17-2020, 02:22 PM   #4
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Lots of great help here, but for Cummins help:
https://www.sbmar.com/
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Old 09-17-2020, 07:16 PM   #5
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Interesting. Does it hit the limit without a load? You may find that if it does, the problem is in the running gear, perhaps a wheel is fouled or damaged?

Please keep us informed?
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Old 09-17-2020, 09:23 PM   #6
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Lots of great help here, but for Cummins help:
https://www.sbmar.com/
Yep, I've been using it for years. I posted more details there about my situation, no response yet.

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...You may find that if it does, the problem is in the running gear, perhaps a wheel is fouled or damaged?...
That would be too easy to determine. But, no. My running gear is fine. I dove and made sure all is clear and I can spin my props freely by hand. I didn't have a chance to do much of investigation, but I'm almost positive that it's on the engine side related to some sort of fuel flow restriction, past the filters.

BTW, WOT test in neutral is almost meaningless, as the engine doesn't demand as much as fuel as it does under the load. Since the flow results will be different, it's almost makes no sense even doing it.
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Old 09-18-2020, 08:51 AM   #7
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I don't know what the low pressure side of the pump should be. Don't have the manual at hand. But it is probably the same for all Bosch P7100 pumps, probably in the 10-40psi range. Look that up.

Case pressure is provided by the single plunger lift pump, cam driven on side of the injection pump. Pressure level is determined by a spring loaded relief valve on the top corner of the inj pump. Found this to be a pretty reliable system. Never had to fool with any of this, except leaking primer pumps.

Go ahead and measure the case pressure and compare to your other engine. If they are significantly different, dig into it further.

Measuring case pressure is a bit tricky as there are a lot of pressure pulsations and gauge needle is often a blur.

It absolutely is necessary to know the high idle rpm. I think on the 6CTA 450 it is 2920-3020rpm. But look it up. If that is set wrong, the governor will back off rack position well before the rated 2600rpm. Could absolutely be your issue.

Did this problem suddenly show up? Or has it always been this way in your ownership? Anything done like replacing injection pump? Seen them come back from the inj shop with settings for other ratings.

Also check the simple stuff: Does throttle lever hit the stop at full power?

Edit: regarding your question #2, you don't measure high pressure at the injection pump. It is positive displacement type and if you try to measure that pressure will go as high as the sky until something breaks. The injection pressure is determined by the injector settings, and that can be measured off engine at an injection shop.
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Old 09-18-2020, 09:24 AM   #8
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Give these guys a call, they'll very likely know. Funky website, cool company.

PRESSUREGAUGES
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Old 09-18-2020, 09:50 AM   #9
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Originally Posted by Ski in NC View Post
I don't know what the low pressure side of the pump should be. Don't have the manual at hand. But it is probably the same for all Bosch P7100 pumps, probably in the 10-40psi range. Look that up.

Case pressure is provided by the single plunger lift pump, cam driven on side of the injection pump. Pressure level is determined by a spring loaded relief valve on the top corner of the inj pump. Found this to be a pretty reliable system. Never had to fool with any of this, except leaking primer pumps.

Go ahead and measure the case pressure and compare to your other engine. If they are significantly different, dig into it further.

Measuring case pressure is a bit tricky as there are a lot of pressure pulsations and gauge needle is often a blur.

It absolutely is necessary to know the high idle rpm. I think on the 6CTA 450 it is 2920-3020rpm. But look it up. If that is set wrong, the governor will back off rack position well before the rated 2600rpm. Could absolutely be your issue.

Did this problem suddenly show up? Or has it always been this way in your ownership? Anything done like replacing injection pump? Seen them come back from the inj shop with settings for other ratings.

Also check the simple stuff: Does throttle lever hit the stop at full power?

Edit: regarding your question #2, you don't measure high pressure at the injection pump. It is positive displacement type and if you try to measure that pressure will go as high as the sky until something breaks. The injection pressure is determined by the injector settings, and that can be measured off engine at an injection shop.
Many thanks for helpful tips.

I've owned the boat for the past 10 years. It never had an issue operating to the specs (both engines). I tuned the props to be in 2650-2680 range, so I can keep my engines happy.

Did this problem suddenly show up? - Yes, this is the first time it happened.

Anything done like replacing injection pump? Seen them come back from the inj shop with settings for other ratings. - Never had the need to do anything with the injection pump or the injectors.

The issue is on the PORT engine, while STBD side gets to 2600RPMs as expected.

Hereīs some additional data and symptoms:

1. The engine seems to work as expected until 2300RPMs. Starts fine, idles fine and no hiccups all the way to 2300-2350RPMs.

2. While getting on plane (out of the "hole") I observed NO SMOKE at all.

3. During my preliminary test runs, Iīve noticed that the engine is also experiencing elevated TEPMs. It didnīt take too long for the temp to rise close to 200*. Once I saw the temp go so high I throttled back.

Iīd like to think that high temps and loss of power at WOT are two separate issues. But, I also guess that if thereīs a fuel starvation and the engine is working too hard, could lead to elevated temps.

4. While on plane at 2300RPMs, the Oil pressure, on the PORT engine (the trouble side), registered at about 80PSI, which seemed on the high side, as my STBD side was at about 60PSI. This is on analog gauges at the dash. I didnīt verify the numbers on the engine gauges.

5. The boat is always loaded and during my last run had 3/4 of fuel and full water. Environment - hot summer day, air temp in 90s and water temp in 90s.

6. Preliminary observation showed no issues with raw water flow. Iīll investigate it in great detail when I'm back on the boat, but for now no difference between STBD side.

7. Aftercoolers were fully serviced less than 2 years ago.

8. Itīs not "the boat". Even though I had some growth on the running gear and my bottom wasnīt in perfect condition during the test. I lost couple knots, but there should be no reason for the PORT side perform any different than the STBD side. It was always the same before.

9. Thereīs no issue with running gear. I can freely spin the prop with my hands and thereīs nothing wrapped on the shaft. Some growth on the running gear was the same as on the STBD side and should not prevent the engine going above 2350RPMs.
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Old 09-18-2020, 11:42 AM   #10
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Fuel starvation will not cause elevated temperatures, it will result in less rpms/less power. This is not an old gasoline engine that can run lean and overheat.

When did you last change your coolant? Huge effect on cooling. This is overlooked and misunderstood and made a huge difference on my temps.
If the governor is actually hitting the stop, start with new fuel filters, air filter and while the air filter is off, spin the turbo and check for looseness and cleanliness as well as damage.
Look for too much soot in the intake (might have to remove the turbo).
I'm about to change my injectors - when were yours last done?
When running together, do the two sound synchronized? Tach? Do you have a synchronizer and did you try running with it disabled?
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Old 09-18-2020, 12:30 PM   #11
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Fuel starvation will not cause elevated temperatures, it will result in less rpms/less power. This is not an old gasoline engine that can run lean and overheat....
That's what I think as well and will address this are two separate issues.

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...When did you last change your coolant? Huge effect on cooling. This is overlooked and misunderstood and made a huge difference on my temps....
Coolant was replaced at the same time I serviced the aftercoolers and HEs, less than two years ago. I'm pretty big on maintenance and try doing everything as per the book. That's why I'm not thinking that the issue is caused by the "small stuff".

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Originally Posted by Xsbank View Post
...If the governor is actually hitting the stop, start with new fuel filters, air filter and while the air filter is off, spin the turbo and check for looseness and cleanliness as well as damage.
Look for too much soot in the intake (might have to remove the turbo)...
I'll inspect the racor and will change both filters (racor and secondary), just to rule that out, as it's the simplest and first thing that has to be done before I should be moving on to more serious items.

I'll be checking the governor, the air filter and the turbo.

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Originally Posted by Xsbank View Post
...I'm about to change my injectors - when were yours last done?
When running together, do the two sound synchronized? Tach? Do you have a synchronizer and did you try running with it disabled?
I never serviced my injectors, but I think it might be the time. However, the symptoms are not indicating that this is injectors related issue. High pressure pump?...Possible. That's why I wanted to test the fuel flow rate before the HP pump and after.

I have glendenning sync, but it's irrelevant in this case. My PORT side is the master and STBD side is the "salve". With PORT side having an issue, I don't see how using the sync will add any value in the troubleshooting. The couple test runs I did were with sync off.
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Old 09-18-2020, 03:22 PM   #12
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Originally Posted by Ski in NC View Post
I don't know what the low pressure side of the pump should be. Don't have the manual at hand. But it is probably the same for all Bosch P7100 pumps, probably in the 10-40psi range. Look that up....
I just purchased parts manual and you my friend are spot on. As per PM I should have Bosch P7100 pump.

I also found this interesting site that provides good explanation on the pumps specs and operation:
https://www.4btengines.com/bosch-p71...p-information/

They call for a range of 15-75psi.

Would you happen to know which pressure tester should be used and to which port do I plug it in?
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Old 09-18-2020, 03:59 PM   #13
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Quote:
Originally Posted by Ski in NC View Post
...It absolutely is necessary to know the high idle rpm. I think on the 6CTA 450 it is 2920-3020rpm. But look it up. If that is set wrong, the governor will back off rack position well before the rated 2600rpm. Could absolutely be your issue.....
I'll be following your advice on this. The numbers you suggested are pretty much spot on. I found an older thread on SBMAR site, where Tony said:

"...Pay special attention to the part on throttle linkage and fuel solenoid travel.. Your engine needs to see not less than 2920 RPM in neutral at WOT/NO LOAD.. 3000-3025 RPM is better and more typical..."
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Old 09-18-2020, 06:54 PM   #14
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I looked for mention of vac. guages but don,t see such.

Do you have vacuum guages in your fuel system? The telltale needle type. Designated Engineer sells good ones.
High vac. will starve an engine of fuel which means no dark smoke. , failure to make power and revs.
Even with clean filters other causes can be a problem. Tank venting clogged, fuel line delamination or kink, a screen on the in tank dip tube plugging,. a clog of junk in the feed line or a fitting somewhere.

A vac. guages can help here as many before you have found.
Check fuel system for too much vacuum.

Just remembered Tony Athens has shown exactly where to install pressure gauge on the last filter to check the before injection pump pressure.
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Old 09-19-2020, 08:46 AM   #15
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Thanks George. I'll talk to these guys and see what they recommend.

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Originally Posted by C lectric View Post
I looked for mention of vac. guages but don,t see such.

Do you have vacuum guages in your fuel system? The telltale needle type. Designated Engineer sells good ones.
High vac. will starve an engine of fuel which means no dark smoke. , failure to make power and revs.
Even with clean filters other causes can be a problem. Tank venting clogged, fuel line delamination or kink, a screen on the in tank dip tube plugging,. a clog of junk in the feed line or a fitting somewhere.

A vac. guages can help here as many before you have found.
Check fuel system for too much vacuum...
Thanks for the tip. No, I do not have vacuum gauges. This would be another thing to look into.

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...Just remembered Tony Athens has shown exactly where to install pressure gauge on the last filter to check the before injection pump pressure.
I didn't see that, would you happen to have a link for that article?
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Old 09-19-2020, 11:41 AM   #16
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Do you have a Cummins manual? I will look at mine, it has a troubleshooting table as well as listing all the test points.

There is a final, very small fuel filter on the engine...
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Old 09-19-2020, 09:36 PM   #17
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Do you have a Cummins manual? I will look at mine, it has a troubleshooting table as well as listing all the test points.

There is a final, very small fuel filter on the engine...
I only know of one filter on the engine, which is usually is referred as secondary (spin on) filter. Do you have a picture or any more details about a small filter you're referring to?
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Old 09-20-2020, 09:28 AM   #18
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I think we are talking about the same filter.
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Old 09-21-2020, 10:10 PM   #19
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Thanks George. I'll talk to these guys and see what they recommend.



Thanks for the tip. No, I do not have vacuum gauges. This would be another thing to look into.



I didn't see that, would you happen to have a link for that article?
https://www.sbmar.com/articles/fuel-pressure-test-port/
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Old 09-21-2020, 10:32 PM   #20
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Thank you! That's perfect and exactly what I was looking for.
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