Peterbilt CAT Acert C7 Code 25

350 and 370 for emergency vehicles on highway and motorhomes too. Don't think it's outta line. At 370 it's still not maxed out and blowing smoke either. Did I read right there is no ambient air sensor on your motor? Pretty sure it needs it to calculate egts. They will defuel if it calculates high egts on a hard pull. You almost have to drive it and monitor atmospheric pressure sensor. My bad one gave me fits to diagnose until I saw it live. One mile it was fine next it wasn't. You can unplug it and it will read just above sea level. Light will come on but if you notice more power and consistent power that's your answer.

brickhead said:

350 and 370 for emergency vehicles on highway and motorhomes too. Don't think it's outta line. At 370 it's still not maxed out and blowing smoke either. Did I read right there is no ambient air sensor on your motor? Pretty sure it needs it to calculate egts. They will defuel if it calculates high egts on a hard pull. You almost have to drive it and monitor atmospheric pressure sensor. My bad one gave me fits to diagnose until I saw it live. One mile it was fine next it wasn't. You can unplug it and it will read just above sea level. Light will come on but if you notice more power and consistent power that's your answer.

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According to SIS, the pins that are for the ambient temp sensor, the wires are strung and tied up to the firewall. Nothing connected to the two wire connector. Where does this sensor even go? The intake air sensor is tied up too with plug in intake. Boost pressure sensor is the only sensor on intake.

brickhead said:

350 and 370 for emergency vehicles on highway and motorhomes too.

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I agree, but not if the engine is a KAL prefix. The higher HP versions are a different S/N range, RMF prefix if I'm not mistaken, and have some different iron inside them than cooking models with 300BHP or less.

Nige said:

I agree, but not if the engine is a KAL prefix. The higher HP versions are a different S/N range, RMF prefix if I'm not mistaken, and have some different iron inside them than cooking models with 300BHP or less.

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KAL was old serial number prefix Nige I found wrote down in glove box. I have no clue why this serial number is all numbers...I can't see the number on the block for the frame...

Surely the dealer who sold it will have details of the replacement engine if they installed it before the sale to you..? It's worth a try, because IMHO once we've figured out what you've actually got under the hood we're probably half way to fixing the problem.

Nige said:

Surely the dealer who sold it will have details of the replacement engine if they installed it before the sale to you..? It's worth a try, because IMHO once we've figured out what you've actually got under the hood we're probably half way to fixing the problem.

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They're not offering much help tbh.. I'm going to call them on Monday and try again. The wastegate line is pinched off as well.. The truck ran great the first two months now it's fell on its face. It does run nice though when right.. I've got to get the ambient sensor lined out though to run any tests..

I forgot to add this is a Reman engine..

jlittle2212 said:

I forgot to add this is a Reman engine..

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That shouldn't make any difference. In addition to the Reman S/N a reman engine is usually marked on the S/N plate with something like "for parts and service information use S/N xxxxxxxx". That S/N is either the OEM engine which was used to build the Reman engine or is a typical S/N of an engine arrangement that is identical to the Reman engine.

Looks like the dealer is saying it is an SAP prefix.

Checked fuel pressure today, 73-75 psi at idle. High idle 80-83.

I went through the fuel system, checked all sensors. The only thing i have questionable, is the fuel pressure regulator. What is the proper way to check this regulator?? Is the regulator only for fuel bleed back purposes?

jlittle2212 said:

Looks like the dealer is saying it is an SAP prefix.

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Well that's fine then. It only narrows it down to about 400 or so possibilities........
Is there any chance they can come up with an Arrangement Number...? FYI later KAL prefix engines and all SAP prefix engines pretty much share the same possible combinations of Arrangement Numbers.

jlittle2212 said:

I went through the fuel system, checked all sensors. The only thing i have questionable, is the fuel pressure regulator. What is the proper way to check this regulator?? Is the regulator only for fuel bleed back purposes?

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Correct. The regulator is a spring-loaded check valve set at 5psi. When the pressure in the fuel rail in the cylinder head is lower than 5psi (like when the engine is not running) the spring forces the check valve closed so as to prevent fuel draining back to the tank. If this valve was dodgy IMHO you would be having hard starting issues, especially if the engine sat overnight for example.

Correct. The regulator is a spring-loaded check valve set at 5psi. When the pressure in the fuel rail in the cylinder head is lower than 5psi (like when the engine is not running) the spring forces the check valve closed so as to prevent fuel draining back to the tank. If this valve was dodgy IMHO you would be having hard starting issues, especially if the engine sat overnight for example.

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I found a temp sensor to plug up to the ambient air harness. Hopefully the code will go off so I can run some test on ET. I changed the regulator the tip was sticking out of the end and when I split it, the small o ring inside was cut. Didn't help power issues as known, but it was faulty and needed replaced. My fuel pressures seem to be where they need to be, I'm leaning towards a boost issue. I'm going to hook it to ET and see what I got. If the Huei was bad, would it keep good pressure at low and high idle?

Fuel pressure is generated by the fuel transfer pump which is independent of the HEUI pump, so even if something was out of whack on the HEUI side it shouldn't affect fuel pressure, in the fuel rail at least.

Nige said:

Fuel pressure is generated by the fuel transfer pump which is independent of the HEUI pump, so even if something was out of whack on the HEUI side it shouldn't affect fuel pressure, in the fuel rail at least.

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Which is on the back of the HEUI.. I'm not really familiar with this HEUI setup. I'm about to figure it out though. Thanks Nige!

I wish I was at home. I could download you the complete system operation for the HEUI system an email it to you. Unfortunately for you I'm on a beach somewhere and my options are severely limited. Maybe someone else can help..?

Quite simply the HEUI system has 3 separate components - 2 mechanical and one electronic. First there is the low pressure fuel system supplied from the transfer pump which is mounted on the back of the HEUI pump that keeps the fuel rail in the cylinder head full of fuel at somewhere around 75psi right up as far as the injectors. Second is the HEUI system that is full of oil at high pressure (2000psi+) generated by the HEUI pump. The actual pressure generated is somewhat variable and is controlled by the IAPCV (injection actuation pressure control valve). The IAPCV and the injectors are controlled by the engine ECM which effectively tells the system how much hydraulic pressure to generate in the system and how long each injector will open to supply the necessary amount of fuel at any given time. When an injector solenoid is activated the hydraulic pressure in the HEUI system is what operates the injector to fire in the fuel, it's just a unit injector but operated by hydraulic pressure rather than by a pushrod from the camshaft.

Okay, had a 30 degree day a few days ago, truck was fine. Now it's been in the teens low teens and it's been a struggle! Start, run a few seconds, then shut down. Try to start back, no start just crank. Let sit ten minutes, starts up runs a few then the same. When it does start, it is not idling up for the cold start either..

Now what?

Can you give me any info on the engine temp sensor Nige?

Nige said:

As I said before there are no C7 on-highway engines rated at more than 330BHP. If the dealer is playing fast and loose with flash files and engine tunes by setting an engine up with power it was never designed to have in the first place threaten to spill the beans to Cat unless they pull their finger out and help you. That might just bring them to their senses.

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Their absolutely are 370/1000 tunes out there. Its a souped up cat win flash file

But is it a standard Cat flash file and is it designed to be installed in a KAL-prefix motor.?

It was noted before that higher HP is available but with a different S/N prefix engine that has different iron inside it.