Sounds like you have an air leak. Having to prime the system after sitting for a while is usually the sign of an air leak. Make sure all your hoses are in good shape, and the clamps are tight. Does you primer pump squish fuel out when you use it. If so you need a new one and this could be the source of the air leak. If not it could just need a new crush washer. It's also a possibility that the lift pump it toast. This isn't common for most cars, but I've seen it happen a few times on cars that have run WVO without the proper heating.

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