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Fuel Hydrometer Range

jeanne

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jeanne Enthusiast

jeanne

Posted
Posted

Diesel mechanic now says the diesel fuel sampled from my tank has an API reading (aka specific gravity) of 40 to 41 using his temperature adjusted hydrometer and that the GMC spec calls for a range of 34-39 for #2 diesel. The factory tech rep is telling him he needs to drain the tank and replace with diesel that is w/in range. We have already concluded the fuel is not "contaminated" but ONLY has an API read 1 to 2 point outside of the AFPM spec. My only issue with the truck is that the fuel rail pressure running at load is approx half of what it should be (approx 12k vs 26k psi) which is why it threw only the one code P1094 instead of both code for low fuel rail pressure at low AND high rpm.

Question: Can the fuel density (+1-2 API) cause the fuel rail pressure ONLY at high rpm to drop in half?

Draenor Senior Enthusiast

Draenor

Posted
Posted

Wow, I have never heard of such a test. I learned something new today.

 

My theory; Denser fuel would be more difficut to flow thru the filters and injectors.

 

 

 

Now if you want to talk about specific gravity in making your own brew...... :fume:

fbachman Senior Enthusiast

fbachman

Posted
Posted

NOT AN EXPERT.... (full disclosure :fume: )

 

But, a liquid is a liquid. Small changes in a liquid's density should result in small changes in its pressure if run through the same pump into the same volume vessel (rail).....

 

FWIW ...

chris3859 Enthusiast

chris3859

Posted
Posted
Diesel mechanic now says the diesel fuel sampled from my tank has an API reading (aka specific gravity) of 40 to 41 using his temperature adjusted hydrometer and that the GMC spec calls for a range of 34-39 for #2 diesel. The factory tech rep is telling him he needs to drain the tank and replace with diesel that is w/in range. We have already concluded the fuel is not "contaminated" but ONLY has an API read 1 to 2 point outside of the AFPM spec. My only issue with the truck is that the fuel rail pressure running at load is approx half of what it should be (approx 12k vs 26k psi) which is why it threw only the one code P1094 instead of both code for low fuel rail pressure at low AND high rpm.

Question: Can the fuel density (+1-2 API) cause the fuel rail pressure ONLY at high rpm to drop in half?

 

 

OK, this is my first post, but I have been reading for about a month. I am the proud owner of a new 2008 crew cab 4x4 Chevy LT, which I love. Now on to your question.

 

I am in the pipeline industry and am an operator for the Nation's largest petroleum pipeline, so I believe I am qualified to attempt an answer.

 

There are two types of diesels commonly available to the public, 74 grade (high sulphur) and 61 grade (low sulphur). Both can have an API corrected gravity of 30-45 degrees @ 60 degrees F @ sea level. Therefore, a gravity of 40 or 41 is well within American Petroleum Institute's guidelines. I am not sure why this Tech is telling your mechanic that the fuel is not within range. GM is well aware of the API guidelines for specific gravity. It is impossible for a refinery to perfectly blend 61 or 74 grade diesels within a window of 5 degrees (34-39) every single time. This is why the corrected gravity spread is so large. So to answer your question, no. The specific gravity can not cause the fuel rail pressure to drop in half within such a small gravity difference.

 

I hope this helps. Anymore questions just hit me up.

 

-Chris

fbachman Senior Enthusiast

fbachman

Posted
Posted
Diesel mechanic now says the diesel fuel sampled from my tank has an API reading (aka specific gravity) of 40 to 41 using his temperature adjusted hydrometer and that the GMC spec calls for a range of 34-39 for #2 diesel. The factory tech rep is telling him he needs to drain the tank and replace with diesel that is w/in range. We have already concluded the fuel is not "contaminated" but ONLY has an API read 1 to 2 point outside of the AFPM spec. My only issue with the truck is that the fuel rail pressure running at load is approx half of what it should be (approx 12k vs 26k psi) which is why it threw only the one code P1094 instead of both code for low fuel rail pressure at low AND high rpm.

Question: Can the fuel density (+1-2 API) cause the fuel rail pressure ONLY at high rpm to drop in half?

 

 

OK, this is my first post, but I have been reading for about a month. I am the proud owner of a new 2008 crew cab 4x4 Chevy LT, which I love. Now on to your question.

 

I am in the pipeline industry and am an operator for the Nation's largest petroleum pipeline, so I believe I am qualified to attempt an answer.

 

There are two types of diesels commonly available to the public, 74 grade (high sulphur) and 61 grade (low sulphur). Both can have an API corrected gravity of 30-45 degrees @ 60 degrees F @ sea level. Therefore, a gravity of 40 or 41 is well within American Petroleum Institute's guidelines. I am not sure why this Tech is telling your mechanic that the fuel is not within range. GM is well aware of the API guidelines for specific gravity. It is impossible for a refinery to perfectly blend 61 or 74 grade diesels within a window of 5 degrees (34-39) every single time. This is why the corrected gravity spread is so large. So to answer your question, no. The specific gravity can not cause the fuel rail pressure to drop in half within such a small gravity difference.

 

I hope this helps. Anymore questions just hit me up.

 

-Chris

 

 

OK... sounds like I was on the right track then.....

 

I can't comment on automotive Diesel fuels, but I DO happen to have expertise with aviation fuels.

 

Yeah, I know that aviation kerosenes are close cousins to automotive diesel fuels.

 

Sounds like Diesel specs are a lot like JP8, JET-A and aviation fuels standards.... a witches brew of HUNDREDS of compounds to get the fuel to a particular standard, where the standard specifies minimums, maximums and various ranges for various properties. Numerous fuel samples will provide adherance to the standard ranges, but none may be exactly the same, one against the other.

 

:lol:

jeanne Enthusiast

jeanne

Posted
  • Author
Posted
Diesel mechanic now says the diesel fuel sampled from my tank has an API reading (aka specific gravity) of 40 to 41 using his temperature adjusted hydrometer and that the GMC spec calls for a range of 34-39 for #2 diesel. The factory tech rep is telling him he needs to drain the tank and replace with diesel that is w/in range. We have already concluded the fuel is not "contaminated" but ONLY has an API read 1 to 2 point outside of the AFPM spec. My only issue with the truck is that the fuel rail pressure running at load is approx half of what it should be (approx 12k vs 26k psi) which is why it threw only the one code P1094 instead of both code for low fuel rail pressure at low AND high rpm.

Question: Can the fuel density (+1-2 API) cause the fuel rail pressure ONLY at high rpm to drop in half?

 

 

OK, this is my first post, but I have been reading for about a month. I am the proud owner of a new 2008 crew cab 4x4 Chevy LT, which I love. Now on to your question.

 

I am in the pipeline industry and am an operator for the Nation's largest petroleum pipeline, so I believe I am qualified to attempt an answer.

 

There are two types of diesels commonly available to the public, 74 grade (high sulphur) and 61 grade (low sulphur). Both can have an API corrected gravity of 30-45 degrees @ 60 degrees F @ sea level. Therefore, a gravity of 40 or 41 is well within American Petroleum Institute's guidelines. I am not sure why this Tech is telling your mechanic that the fuel is not within range. GM is well aware of the API guidelines for specific gravity. It is impossible for a refinery to perfectly blend 61 or 74 grade diesels within a window of 5 degrees (34-39) every single time. This is why the corrected gravity spread is so large. So to answer your question, no. The specific gravity can not cause the fuel rail pressure to drop in half within such a small gravity difference.

 

I hope this helps. Anymore questions just hit me up.

 

-Chris

 

Chris, Thank you for your reply. I'm not a chemist but instincts were telling me I'm being told a tail. A little more history; I was told they would have to completely drain my full fuel tank ($160/hr * 4 hrs) at my expense of course and refill it with diesel w/in the 34-39 range before the factory tech would allow them to proceed with the warranty work. Chris, could you point me to a website/pdf or such that shows the API's guidelines on this subject? I went to the API website but could not find anything. thanks again for your quick and clear reply

chris3859 Enthusiast

chris3859

Posted
Posted
Diesel mechanic now says the diesel fuel sampled from my tank has an API reading (aka specific gravity) of 40 to 41 using his temperature adjusted hydrometer and that the GMC spec calls for a range of 34-39 for #2 diesel. The factory tech rep is telling him he needs to drain the tank and replace with diesel that is w/in range. We have already concluded the fuel is not "contaminated" but ONLY has an API read 1 to 2 point outside of the AFPM spec. My only issue with the truck is that the fuel rail pressure running at load is approx half of what it should be (approx 12k vs 26k psi) which is why it threw only the one code P1094 instead of both code for low fuel rail pressure at low AND high rpm.

Question: Can the fuel density (+1-2 API) cause the fuel rail pressure ONLY at high rpm to drop in half?

 

 

OK, this is my first post, but I have been reading for about a month. I am the proud owner of a new 2008 crew cab 4x4 Chevy LT, which I love. Now on to your question.

 

I am in the pipeline industry and am an operator for the Nation's largest petroleum pipeline, so I believe I am qualified to attempt an answer.

 

There are two types of diesels commonly available to the public, 74 grade (high sulphur) and 61 grade (low sulphur). Both can have an API corrected gravity of 30-45 degrees @ 60 degrees F @ sea level. Therefore, a gravity of 40 or 41 is well within American Petroleum Institute's guidelines. I am not sure why this Tech is telling your mechanic that the fuel is not within range. GM is well aware of the API guidelines for specific gravity. It is impossible for a refinery to perfectly blend 61 or 74 grade diesels within a window of 5 degrees (34-39) every single time. This is why the corrected gravity spread is so large. So to answer your question, no. The specific gravity can not cause the fuel rail pressure to drop in half within such a small gravity difference.

 

I hope this helps. Anymore questions just hit me up.

 

-Chris

 

Chris, Thank you for your reply. I'm not a chemist but instincts were telling me I'm being told a tail. A little more history; I was told they would have to completely drain my full fuel tank ($160/hr * 4 hrs) at my expense of course and refill it with diesel w/in the 34-39 range before the factory tech would allow them to proceed with the warranty work. Chris, could you point me to a website/pdf or such that shows the API's guidelines on this subject? I went to the API website but could not find anything. thanks again for your quick and clear reply

 

 

 

Glad I could help! My company produces a quality assurance transcript every quarter with API guidelines and our QA guidelines, which are more stringent. Reproducing these manuals with the company header would be a violation of company policy and would reveal trade secrets yada yada yada (fill in legal crap here)!! LOL On a serious note, I believe I have a copy of the 2008 API book at work. I will check tomorrow evening when I get there and see what I can come up with for you.

 

You are being taken on a ride with the bad fuel mess. Don't let 'em do that to you!!!

 

-Chris

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