Welcome to Hadit.com Robert Jones,
I did a google search on JP4 and health issues. I found the attached research from https://apps.dtic.mil/ on the subject. GBArmy is correct, if it is not in your Service Treatment Records (STR), then you will need to get an IMO from a Doctor to connect your current condition with a condition/event during service.
Below is something I had put together to help another Veteran:
Make sure you have a copy of your Service Treatment Record, you can order a copy from here: https://www.archives.gov/veterans/military-service-records/medical-records.html
You may need a copy of your Service Records also and you can order a copy from: https://www.archives.gov/veterans/military-service-records
While you are waiting on your records, go to the Doctor to show that you are still being treated for the condition. After receiving your records, go though it and make a copy of anything on this condition. Get a copy of Medical records after Service and make a copy of them also. Go to the 38 CFR here:https://www.benefits.va.gov/warms/bookc.asp#i The 38 CFR shows you how they rate a disability. The Disability Benefits Questionnaire (DBQ) is a form that a Doctor fills out during your Compensation and Pension Exam (C&P Exam) which can be found here: https://www.va.gov/vaforms/search_action.asp?FormNo=&tkey=DBQ&Action=Search Both of these links has good information on what they are looking for.
Then you will need to write a Statement in Support of Claim (VA Form 21-4138). In this statement include a what happen and a timeline of treatment for that condition (attach the copy of your medical records that you made a copy of and referred to them in your statement). You also need to include how this affects your daily life and work.
I would have somebody else read your packet, to ensure that it makes sense and easy to follow. If you have not done so yet, setup a eBenefits account at: https://www.ebenefits.va.gov/ebenefits/homepage You can apply for benefits here or you can find a local Veterans Service Organization (VSO) to submit your packet for you. If you submit it thru eBenefits, it will ask you about submitting a claim for PTSD. A PTSD claim is a lot of work and I would research it before applying. eBenefit will walk you thru the whole process to include VA Form 21-526EZ. If you go thru a VSO, make sure you find one that you feel comfortable with. There are good and bad ones out there. If you do go thru a VSO, they should review all your Medical records, and help you apply for everything that they feel as though is service connected. Also bring any after service Medical records with you as there maybe secondary conditions that you could claim.
Make sure that you keep a copy of everything you do, as you will need them someday.
I hope this information is helpful and if you have any questions, please feel free to ask.
KEROSENE-BASED JET FUEL HEALTH EFFECTS.pdf