So I finally got engine rebuilt and installed in the 97. (4.3, 20 over with 10/10 crank for those who want to know) Turned key a few times to prime fuel only to have pressure climb to 60 and fall right off to 0.
swapped out spider for the other one I have that worked fine and it seemed to fix problem and ran just fine.


Fast fwd a few days and 140miles. I was cruising home at 60mph when it jerked a couple times and died. had to have it towed home and found fuel pressure doing exact same thing. Turn on key it goes to 60 and starts falling off. Got a new pressure regulator and it fired right up, ran about a minute and died. No codes were thrown during any of this. Fuel pressure at that point was 60 when key was turned on, fell off to 40 then fired right up and jumped to about 55-58.

If I spray a lil carb cleaner into throttle body it will fire and pressure jumps to 55 til it dies.


Ive seen posts about spiders and pumps and haven't found any real answers.
Don't want to just throw $$at it so maybe someone can help sort this out.
I think I'm overthinking it again.


Thanks

 

Check the fuel pressure before the fuel filter and not just at the Schroeder valve at the intake. That will tell you if its the pump or not.

 

Fuel pressure readings are all taken with the engine off.

At the service port, key ON, engine OFF, fuel pump running, pressure must be 60-66psi. It must remain above 55psi for at least 10 minutes after the pump shuts off. These readings give you the LOWER of regulated pressure or maximum pump output pressure. For example, if max output is 40psi, regulated pressure will be no higher than 40psi. Using that reading alone, could lead to a misdiagnosis of a faulty fuel pressure regulator. To diagnose the fuel delivery system, max pump output pressure must be tested as well. This is most easily done at the fuel filter outlet. An adapter is necessary between the fuel filter and the pressure tester. All fuel pressure and flow must end at the tester, with no fuel allowed to the engine. Key ON, (engine obviously OFF), pump running, pressure must be 73-108psi. It must remain above 55psi for at least 10 minutes after the pump shuts off.

Check pressure and leakdown at both places, and post the results.

 

Everything from Capt. and Rich are true and pressure dead headed at the filter needs to be and hold those leak down #'s.
My concern is the sporadic nature of your numbers. Fired at 40 psi then to 55-58. Not sure that these will fire at all at 40.
If it was not for the tragic drop in pressure from 60 to 0 I would think intermittent ground from the pump to the frame.
When your under there testing the filter output check your ground, should be less then 5 ohms.
Unfortunately that's not even a good test. Key word, intermittent.
It connects to the top of the back frame rail. I believe from Captains uncanny Jeopardy like knowledge of this stuff it's a 13mm that holds the wire down, try cleaning it. Takes five minuets.
Tried it on mine, didn't do sh*t but it was worth a try before I had to drop the tank, again!
Just thinking??? Take a flashlight and inspect to see if there are any kinks in the soft ends of the fuel lines.
Jeff


Rich is that Rickey Schroeder?

 

I need to clarify it didn't start on it's own when pressure was at 40. I turned key and it primed to 60 then immediately fell off to 40 and stayed there. I gave it a shot of carb cleaner it fired right up and pressure jumped to 55-58 til it died. At that point pressure dropped backed to 40.
I will check the grounds/hoses and pressure at filter fitting as soon as weather allows since it's sitting in my yard and snow is moving in tonight.
stay tuned for results.


On a side note related to problem, here's another question. Which component triggers the spider to fire? It seems like I recall a sensor in the distributor and o course the control module next to coil.

 

Finally got a break in the weather so checked fuel pressure at filter point. First odd thing was gas never did stop running out of line when I unhooked filter. I waited 30 minutes and had a helluva puddle in the dirt so figured I better hurry up. When I got the gauge connected up and turned key it jumped to 60 then dropped immediately to 40. I turned pump on under hood to see if it would climb anymore and it just fluttered from 38-42.


Didn't see anything else out of the norm under blazer so it looks like I need to buy a new pump!

 

Not only buy it, install it too AC Delco or Delphi only for a replacement pump.

 

amazon has good prices on em

 

Yeah I forgot about install it! Hey don't they send monkeys in the box these days to do that?


I'm looking into Delphi but also finding bosch, anyone tried those? It's crazy the price differences between sites!

 

AC DELCO OR DELPHI ONLY.or you may be doing it over again.