5.0L with no fuel pressure

MTTod

Registered User
Not an SC question but it's a TBird.

Picked up an 88 with the 5.0 and have no fuel pressure. The pump runs and blows gas out the line at the filter and the filter is new but I only have 3 LBS at the fitting on the fuel rail. How can I test the fuel pressure regulator?
 
switch it out with another FPR

Only 3psi huh well if it was not open or blocked seems like there would be more the 3psi. So if anything it is stuck open but there should still be more pressure than 3psi.. Is there any gas leaking out of it when the pump is running? That is usually the first sign of a bad FPR .. I have yet too see a FPR go bad.. You could have some cloged lines or some pinched lines or a weak pump that was the problem in my case pump was only pushing 10psi....
 
Fuel pressure regulators typically fail through a tear of the diaphram inside them that then allows fuel to flow throught the vacuum line directly into the intake system. That vacuum line doesn't seem large enough to bleed off as much pressure as you feel you have lost.

Just because the pump is able to move fuel, doesn't mean it is able to move it at a sufficient volume to build sufficient pressure.

Maybe someone can post a procedure for testing fuel flow. Typically I've heard of it being taken off the return line from the regulator. Should see over a pint ever 15 seconds. But I don't know exactly.
 
I'm thinking that if you're only getting 3 psi there should be no fuel flow past the regulator. So I'd probably remove the return line and see if any fuel comes out. If so, I think it would be a good bet that either the FPR is bad (and they can stick open just as well as they do closed) or your gauge is wrong and fuel pressure really is OK (might want to double-check with another gauge if possible before spending money on FPR)

If no fuel comes out then a restriction is a possibility, a REALLY clogged filter, or most likely IMO a bad pump. I did once time run into a situation where a pupm had been replaced by a customer but the hose between the pump and the tube going out of the tank had a small split in it which caused a low fuel pressure situation. I've only seen that twice in the last 15 years or so so it's not common by any means, but it will bite you in the *** if you don't check for it :)
 
When the regulator goes it generally peeees gas out the vacum port..Pull vacum line off ragulator and check for gas spewin out when you turn key
 
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