My initial fuel pressure test readings was incorrect. It was caused by the broken fuel valve at the raid. After I replaced the stem, it started reading some meaningful PSI when I primed the fuel system - key ON, like 35-40 PSI for a second. It would not HOLD the pressure like you said, it dropped pretty quick. When truck was running, the PSI stayed around 35 PSI.

When the car would not start, the pressure still showed 35 PSI when priming.

 

OK, good feedback on the fuel pressure when it didn't want to start. That info would make me want to perform a flow volume over time test, to see if the pump can put out enough fuel Volume. If that were ok, then I'd want to use my inductive timing light to see if the coil was putting out good spark.

 

A flow volume over time test? How to do so?

If the coil was not putting good spark, I would not be able to start cold or hot.

 

With your fuel pressure gauge that has the pressure bleed valve & its hose routed to a volume measuring container + a sweep second hand. 1/2pt-15 seconds pump run time.

Wimpy spark = hard start.

 

Let's focus on why fuel pressure is not holding when priming. I am not worrying about starting or not at this point. Once the fuel pressure is operating normally, I bet we will see the light in the tunnel.

 

I was about to say the refocus thing as you posted.

Why are you so reluctant to perform the return line blow down test to see if it's restricted?

 

I was not reluctant to perform the return line blow down test. As I said, if the return line is blocked, I will have much higher PSI, but I don't see high fuel pressure, so my return line is good. Unless you have something I don't see, please educate me.

 

Pawpaw,

Just a thought, remember one time I connected the gauge directly to the output of the fuel filter, no FPR, injectors, fuel raid (I know you have already warned me not to do do this). However, I learned something from it ... I remember the pressure shot up real high when I turned the key ON, and it dropped back to zero quickly. If the check valve in the pump worked, it should at least held it at certain PSI, but not zero.

In addition, if I have bad injectors (let's say), the pressure will not drop that quick, from 35 PSI to zero once priming is done.

I think I have a defective pump.

Any thought?

 

You get an Attaboy for using your Vivid Imagination. EDIT: I suppose you could have more than one problem though.

 

Well 2046fan how is it going, 1520 curious minds would like to know!!!

 

Sorry I was out of town for the last 2 weeks and did not have a chance to work on the truck.

Anyway, I re-examined the fuel pump again by sliding the bed down a little to gain access to the pump. Took the pump out and applied 12V, it ran fine. Tried to blow air into the pump's output and it's blocked, I assumed the check valve is good. I also removed the intake manifold (upper) to get ready to replace the fuel injectors. Removing the intake manifold was easier than I thought, maybe 30 mins or so. Will let you know what will happen after replacing the injectors. The parts should be here by Tue.

 

While you had the bed back & were at the fuel pump powering it up, did you perform a pressure test to see if it was in range & would hold? Did you check the return line to make sure its open?

 

I did measure the pressure and result was the same. It went up to 40 PSI when priming (for a second) and it dropped back to zero. The return line was open, nothing was blocking its way.

 

Ok, did you replace the pump while you were there?

 

I thought it was the pump six months ago, so I bought a brand new one (the whole thing with the sending unit) and replaced the old one. Issue remained.

Pressure regulator was replaced one month ago (I know you will ask).