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Dr. Hamman
Dr. Hamman, Automotive Engineer
Category: Car
Satisfied Customers: 5933
Experience:  30 years experience, Repairing, building, & designing, automobiles.
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Sprinter: what is the tensiel strength of the fuel injector

Customer Question

what is the tensiel strength of the fuel injector hold down bolts in a 5 cylinder 2004 Sprinter
Submitted: 2 years ago.
Category: Car
Expert:  Dr. Hamman replied 2 years ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you. Also keep in mind I don't know if you are a pro or a novice so we may have to fine tune the answer. Feel free to add any additional info you feel is needed as we go on. Always keep in mind that I am here to help you with any questions.



Metric bolts have a different standard than SAE bolts that are grade 8, and 5 on most engine bolts. Metric bolts are graded by “Class”. A class 10.9 is what I have seen in sprinter engines for the injectors. A new copper seal should always be used when the injectors are replaced. The class 10.9 is very close to the SAE grade 8. The minimum tensile strength for a class 10.9 is 1040 Mpa, about 150,000 PSI. If you have any more questions, as always, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer.



I do not get paid for my work unless I am given 3 - 5 stars/smile faces. If the answer is not clear, let me know what additional help you need, and I will assist you further. A bonus and positive feedback are always appreciated, good luck and Thanks.

Dr. Hamman, Automotive Engineer
Category: Car
Satisfied Customers: 5933
Experience: 30 years experience, Repairing, building, & designing, automobiles.
Dr. Hamman and 4 other Car Specialists are ready to help you
Customer: replied 2 years ago.

The hold down bolt is app. 3/16" Are you telling me that a 3/16 bolt has a tensiel strength of 150,000 psi? If not please help me with the math. I have a court date in small claims court for Tuesday. The other guy is trying to say my cylinder pressure was so high that it broke the hold down bolt. How could that be if the tensiel strength is 150,000 psi? The cylinder pressure should never go that high. Please, I need your help. Jerry

Expert:  Dr. Hamman replied 2 years ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you. Also keep in mind I don't know if you are a pro or a novice so we may have to fine tune the answer. Feel free to add any additional info you feel is needed as we go on. Always keep in mind that I am here to help you with any questions.



I think you missed a major point, and that is pounds per square inch, the bolt is nowhere near one square inch, so it wont have 150000 pounds of tensile strength, that one square inch has. Calculate PI x the bolt radius squared, and multiply it times the tensile strength, to get the actual strength of the bolt, It needs to either be done in inches, or all in metric, the two sets of data dint interchange in an engineering type formula like this. The bolts tensile strength also will vary slightly with the temperature of the bolt. The pressure the injector exerts on the bolts wont be the PSI generated in the cylinder either. It will be the same PI x the injectors combustion chamber diameter's radius squared, and multiply it times the maximum combustion chamber pressure. It is sort of like a mini engineering project. BotXXXXX XXXXXne is Sprinters did have excessive problems with the injector bolt failure, and leaking injectors, you can document this with an internet search. If you have any more questions, as always, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer.



I do not get paid for my work unless I am given 3 - 5 stars/smile faces. If the answer is not clear, let me know what additional help you need, and I will assist you further. A bonus and positive feedback are always appreciated, good luck and Thanks.

Expert:  porscheguru replied 2 years ago.

Attachment: 2012-10-01_011426_metric_bolt_properties,_grades,_and_strength.pdf

Here is a pdf document with some very interesting reading regarding fastener strength. Page 3 and page 4 has the detailed tensile strengths of various grades and sizes of metric fasteners.

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