When I pinch off return line I see 25psi on pressure guage so I think I have a fuel pressure regulator problem.

 

I should add it is 11 psi on the feed line.

 

11 psi is right in the middle - spec is 9-13 for TBI.

To determine if the FPR has a problem, turn the key on, engine off (or bypass FP relay with a jumper for a few seconds) and watch the gauge. Pressure should be 9-13 psi and hold steady for at least a few minutes. If it doesn’t hold pressure, pinch off the return line, prime the pump again, and see if it holds steady. If it does, the FPR is faulty.

If it doesn’t hold pressure and you don’t see any fuel dripping from the injectors, pinch off the supply line and see if it holds. If so, the fuel pump is weak or has a faulty check valve.

You should also perform a volume test. Disconnect the supply line at the TB or the filter and use a length of hose to direct the fuel into a container that’s at least 1 quart and has graduations on it to mark volume. Bypass the FP relay and run the pump for 5 seconds, then look at how much fuel was collected and multiply the result by 6.

The general spec is 24 ounces (3/4 quart) in 30 seconds.

 

The 11 psi wouldn't hold for any length of time not 1 second. When I pinched return line it went to 25 psi but wouldn't hold as well for any time. I took it all apart before your post tho so have to do further tests after I get it back together tomorrow.

 

I got the testing process off YouTube howstuffinmycarworks and it said anything over 15psi when return line pinched fpr is the problem. It makes sense to me but not positive they accurate

 

That’s not accurate. Pinching off the return line does not test the FPR - it dead heads (maxes out) the pumps ability to provide pressure.

Consider the fuel supply and return lines are, in effect, a closed loop. Fuel is pumped into the supply line to the TB and the excess is sent back to the tank via the return line. This means, regardless of FPR condition (or even without a regulator), fuel is in a constant cycle to and from the TB.

The FPR is a simple spring type diaphragm designed to regulate pressure to approximately 10 PSI (the spec of 9-13 is there to account for small differences in manufacturing). By pinching off the return line, pressure will build back through the system, but the regulator will still open over about 10 PSI.

IF the pressure exceeded 15 PSI WITHOUT pinching off the return line, the FPR or another restriction in the return line is indicated - but for the pressure to reach 25 PSI with the line pinched off just tells you the pump is capable of delivering adequate pressure.

But again, you need to check volume as well. Pressure can be good and volume not good and vice versa - it all depends on the reason for the pump failure.

 

 

I figured it could be wrong that's the video I watched. It doesn't hold pressure at all

 

I made a video to show how fast pressure goes away

 

I didn’t watch the last couple of minutes of that TBI video, but I agreed with everything he said up until the comment regarding the FPR being bad if you pinch off the return line. It’s just not accurate.

Refer to the “professional rendering” of the fuel delivery system below.

Of course the FPR is part of the TBI but I wanted them separate for the sake of clarity as the direction of flow through the system puts the FPR technically downstream of the TBI, and it will help demonstrate the point.

In the video he states to use an adapter in place of the filter for the gauge - masterfully represented by the “G” above the filter. So if you pinch off the return line downstream of the FPR (point A), everything upstream of the return line is now receiving the maximum pressure the pump can provide, including the FPR.

So what’s the explanation if you cut off flow at points B or C? The gauge will still register the max pressure of the pump, yet at those points in the system, the FPR is fully removed from the test.

However, if you were to pressurize the system and then pinch off the line at point D, then saw a complete loss of pressure, the FPR could be at fault.

Given the difficulty you’ve had in getting the truck to run it wouldn’t surprise me if both the FPR and the pump are bad, but at this point you know the pump is delivering good pressure so tearing down the injector body for cleaning and replacing the FPR is where I’d start too.

If it still loses pressure that quickly with a new FPR, the pump check valve is for sure faulty, but that doesn’t mean the pump itself is bad. For the purposes of getting it to run, I’d recommend turning the key on and off a couple of times to build pressure before cranking.