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Old 01-24-2017, 05:45 PM   #6
downplay
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Re: Truck Starts Consistently But Not Like It Should

Quote:
Originally Posted by j cAT View Post
this maybe the fuel pressure or lack of flow. using a pressure gauge measure pressure.
Now I think you guys are right on the money about it being a fuel pressure issue. I got on Youtube and watched some good videos on how to perform the tests.

When I turn the key on (but not the engine) the pressure quickly jumps up to over 50 PSI. But then it very rapidly falls back down to below 10 within just a few seconds.

The same thing happens after the engine is running and I turn the key off. Is this supposed to happen?

It seemed to have the proper pressure while idling, at a constant rev, at quick revs, with the fuel pressure regulator on, and with the fuel pressure regulator off (where it just jumped up slightly). It never went super high or super low during the running tests but stayed in a pretty narrow range around 43 PSI. There was also no fuel in the pressure regulator, in the vacuum tube, and it seemed to have a strong, steady vacuum.

Since it is only losing pressure with the engine off, but pump on, and it happens rapidly, this has to be the check valve in the fuel pump, correct?

Thanks!
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