Low rail pressure

[matt2778]

You don't know anything about how the truck is tuned. If you're running more pulse width than the CP3 can support with the oversized injectors, it won't matter what regulator you are running. I can make stock injectors drop rail pressure if I command enough pulse width.

Matt, this is an issue that needs to be discussed with your tuner. You need to provide logs that show exactly what the truck is doing. You may not have a big difference in power between tune 4 and tune 5. If tune 4 is just on the verge of holding 26k psi, it is probably getting the same amount of fuel in the cylinders as tune 5. Was the tune adjusted for the injectors?

The injectors and pump were related to the tuner, who is a reputable duramax tuner. I did call and speak to them and was told if desired was higher than actual by the amount I have I have a mechanical issue causing the drop in rail pressure

 

[CaptPhil]

Whose injectors are they?
How large a pulse are your number 4 & 5 tunes?

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[Dozerboy]

The injectors and pump were related to the tuner, who is a reputable duramax tuner. I did call and speak to them and was told if desired was higher than actual by the amount I have I have a mechanical issue causing the drop in rail pressure

If my tuner told me that without looking at some logs or attempting to help me troubleshoot it. I would find a new tuner, but thats why I do my own. Giving that diagnosis just over the phone doesn't sound right to me.

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[CaptPhil]

If my tuner told me that without looking at some logs or attempting to help me troubleshoot it. I would find a new tuner, but thats why I do my own. Giving that diagnosis just over the phone doesn't sound right to me.

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Exactly. Just because one truck will hold rail with the same setup doesn't mean they all will. Those could be some industrial nozzles that are labelled as 15%s but flow like 30's.

I have had "mechanical" problems turn out to be tune problems on a few occasions.

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[Ne-max]

Exactly. Just because one truck will hold rail with the same setup doesn't mean they all will. Those could be some industrial nozzles that are labelled as 15%s but flow like 30's.

I have had "mechanical" problems turn out to be tune problems on a few occasions.

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Yep. Its easier to blame hard parts then take the time to do "actual" custom tunes

 

[Awenta]

If my tuner told me that without looking at some logs or attempting to help me troubleshoot it. I would find a new tuner, but thats why I do my own. Giving that diagnosis just over the phone doesn't sound right to me.

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Yup :thumb:

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[matt2778]

I changed lift pump springs last night and lift pump pressure went up to 14 psi. Make no change in rail pressure. I guess I'll be giving my tuner another call

 

[IOWA LLY]

What is the supply pressure to the cp3 pump when it's wot, on the tune that is lacking on rail pressure?

You could have 100 psi of supply pressure at idle and it wouldn't mean jack shit if you have no supply pressure when it counts.....

Blaming the tuner, or changing parts blindly, is all pointless.

You have to actually do some diagnosis!

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[WVRigrat05]

I always blame it on society and a bad childhood.