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How does this service work? I have a question regarding the…

Hi, how does this...

Hi, how does this service work? I have a question regarding the Heui fuel system on cat c9

Mechanic's Assistant: What is the complete model and serial number of your machine?

D6r series 2, bpz00208

Mechanic's Assistant: Are you fixing this yourself? What have you tried so far?

Yes, I am a mechanic, it has an engine miss at hi idle. Done cyl cut test with et and can’t isolate to a single cylinder. When I do the iap test and manually increase the pressure I can hear the thing start to miss af idle. I have just fitted a new heui pump, iap sensor, coolant temp sensor and replaced faulty brittle injector wiring harness, still faulting

Mechanic's Assistant: Anything else you want the construction mechanic to know before I connect you?

Yes could the throttle or timing sensors be causing injection actuation pressure fluctuations? I have no active electrical faults also

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Answered in 16 minutes by:
2/7/2018
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
Cat Man
Cat Man, Cat Engine Expert
Category: Construction and Road Equipment
Satisfied Customers: 10,344
Experience: I am ASE Master Certified.
Verified
Thanks for asking your question. I will try and help you out.
So there are no active codes?
The actuation pressure will fluctuate a little.Has the fuel pressure been checked?
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Customer reply replied 4 years ago
When I increase current when doing iap test on et once it gets over 55 on the current I get a 500psi fluctuation (3200-3700psi) and is current fluctuates 53-59. Do you think I am dropping oil pressure somewhere or is it an electrical fault causing it? There is a noticeable miss when doing the iap test, I tested a c7 in a 950h the sane and no miss
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
Thanks for the information.
That’s too much fluctuation.
If you have replaced the Heui and the iap sensor. All that’s left to cause this is a leaking injector. Or sucking air from the pick up tube in the oil pan. I’ve only seen that once. I have seen many injectors leak oil and cause fluctuation
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Customer reply replied 4 years ago
Wouldn’t I pick up a leaking injector by doing cylinder cut test? It passed the cylinder cut test on et. So you don’t think I need to do any further testing on the electrical circuit to eliminate the current fluctuation which would in turn alter oil pressure? If it was oil pressure dropping or cavitation wouldn’t the current still be stable when doing iap test? I need to somehow eliminate elec v oil press fault. But I guess cat et iap test eliminates the elec circuit that’s why changed heui pump. We initially suspected an injector so we got a Reman injector and rotated it through all 6 cylinders to try eliminate the miss but no change. Also ran it with the cover off while doing iap test to try spot some excessive oil leakage but was quite hard with the engine in situ on the dozer.
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
No it will not always pick it up. If it passed the test. The injector must not leak at the test pressure. Most often they only leak at a high pressure.
To test for a leak at high pressure. I like to trick the ecm.
I connect an iap sensor to the engine harness but let it dangle. Do not screw it in the head. Then remove the valve cover and crank the engine. Because the sensor is not reading any pressure. The ecm will send max voltage to the Heui and make max pressure. If there is an injector leaking. You will see it.
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Customer reply replied 4 years ago
Oh ok, will the engine run or is the test done while cranking?? Where will expect to see leakage from? Orings or injector ports?
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
No it will not run. It will not fire the injectors because it sees no pressure. But I’m reality it has about 3200 psi. Leak can come from O ring or spill port.
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Customer reply replied 4 years ago
Ok I will try that, She the leakage should be obvious if there? And it will make 3200psi on the crank
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
If there is a leak. It will be easy to see.
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Customer reply replied 4 years ago
Hi catman, went out and done what we discussed, cranked the engine with another iap sensor dangling (no start) and had a look under the rocker cover. All injectors seemed to be leaking the same out the spill ports and I couldn’t see any excessive leakage around o ring seats. It got me thinking could we have iap oil leakage into fuel system via bottom o rings causing the iap problem?
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
Thanks for the information.
A small amount of leakage is normal.
If oil is getting into the fuel. The fuel in the tank will have a dark color to it.
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Customer reply replied 4 years ago
The fuel sep bowl did have a dark colour to it, I will order a set of injector o rings today. Also just out of curiosity do you know why when we manually increase current using et and the iap increases why the engine would miss when it only needs I think 870psi to idle and it has 3200-3700psi which should be more than enough for it to idle?
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
Thanks for the information.
To be honest. Most often I see the engine miss when iap is raised. Even though the engine only needs 870. The high pressure will cause the engine to run rough or miss when it’s raised.
Please reply back if you need more help or have more questions. I am happy to assist.
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Customer reply replied 4 years ago
Thanks catman, I have been trying to send a video of the dozer exhaust while it is faulting but have not had any luck. I’m struggling to see how the o ring will hold up to 2600psi and then start dumping iap and start fluctuating. What are the possibilities of the ecm being faulty? Only reason I say that is we had to replace the eng oil press sensor as it was pumping oil through the wires to main ecm plug which is apparently common on the c9 also. The ecm plug was full of oil. We also fitted new updated injector harness under rocker cover.
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
You are very welcome my friend. I am happy I could help.
It’s possible it’s an ecm problem but it’s not that common. The bad news is the only way to verify it’s an ecm is to try a new or known hoid one.
Please reply back if you need more help or have more questions. I am happy to assist.
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Customer reply replied 4 years ago
We are just in discussion as to where to go next with this fault. Do you know if it is possible to manually pump up the oil rail to check for the leakage. It is going to be hard to convince the customer to replace a full set of injectors even though I understand that it is a common failure point. Also are there any more tests that you know of that we can do to eliminate the low pressure eng oil supply to the heui pump?
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
Unfortunately there’s not any test. Sorry. But if you have black fuel and the injector orings are ok. All that can be done is to replace the injectors. I am sorry. I wish there was a way.
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Customer reply replied 4 years ago
Ok, do you know where the high pressure relief valve is located after the heui pump? Is it built in to the pump? In the systems operation section it says that it relieves at 100psi which doesn’t make sense.
As when you look at the picture the valve is plumbed straight out of heui out line
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
Yeah he relief is in the pump. The only other Valve is the fuel pressure regulator on the back of the head but it’s for fuel not actuation pressure.
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Customer reply replied 4 years ago
Thanks catman, we haven’t ruled out changing the injectors yet but just want to try check all other avenues before going ahead with it. I am looking at low press supply and was thinking have you seen problems or internal leakage at eng oil filter housing seals or restriction through eng oil cooler? Also we are going to double check eng oil press would we see a fluctuation on the low pressure if it had a flow issue?
Mechanic: Cat Man, Cat Engine Expert replied 4 years ago
You are very welcome my friend. I am happy I could help.
The only issue I have seen is when the oil pick up tube in the oil pan is cracked and sucking air. It’s rare but I have seen it.
I have also seen too high and too low oil level casue air to enter the Heui. Most often when I find this the dipstick is marked wrong and someone is putting the wrong amount of oil in it. Normally when this is the case. The 164-11 only happens when driving.
Cat Man
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