Low-ish fuel pressure?

[dlundblad]

I'm currently experiencing a crank, but no start condition on my Blazer. The fuel pump runs with the ignition on, but it doesn't have the usual wine.. sounds very weak. Makes me think it's the fuel pump. I hooked a fuel pressure tester up on the Schrader valve at the plenum and it read around 50 psi so now I am not so sure. I believe this should be at around 60-65 psi.

Would this cause an issue?
Thanks

 

[Donald]

Do you have an OBDII reader. It can trim the fuel to compensate for the slightly low fuel pressure.

 

[Warstud]

Try starting it with the pedal to the floor. If that doesn't work....spray some starting fluid in the throttle body.

 

[spasm3]

Crank no start could be a crankshaft position sensor.

 

[GSCJR]

Try replacing the fuel filter first.

 

[clinebarger]

Those CPI systems can require 66 psi to start in cold weather with OE Poppet Injectors!

 

[14Accent]

Originally Posted by clinebarger
Those CPI systems can require 66 psi to start in cold weather with OE Poppet Injectors!


Bingo, but a CPI system should still run on 50 PSI. Maybe not well, but it should. However, if the injectors are shot they may not work at all on 50 PSI.

What other diagnostics have you done? Have you confirmed spark? The distributor caps on those love to crack and arc inside the cap, causing cross-firing of cylinders. If this happens, often it cranks like it's out of time (bucking against the starter, etc).

Does the fuel pressure bleed down after you pressurize the system? Or does it hold?

 

[StevieC]

Could also be a defective fuel pressure regulator dropping the pressure. Pretty sure it's common on these around this year.

 

[dlundblad]

Thanks for the replies everyone. I'm going to take another look at it tonight.

So far, I've just checked the pressure and bleed down.

 

[Lubener]

Originally Posted by dlundblad
I'm currently experiencing a crank, but no start condition on my Blazer. The fuel pump runs with the ignition on, but it doesn't have the usual wine.. sounds very weak. Makes me think it's the fuel pump. I hooked a fuel pressure tester up on the Schrader valve at the plenum and it read around 50 psi so now I am not so sure. I believe this should be at around 60-65 psi.

Would this cause an issue?
Thanks

The spec for your engine is 50-63 psi.

 

[Lubener]

Originally Posted by StevieC
Could also be a defective fuel pressure regulator dropping the pressure. Pretty sure it's common on these around this year.

If there's a vacuum line on it, pull it off and see if there is raw fuel present. If there is, get a new one. If no gas, look elsewhere it is not bad.

 

[Trav]

Once you have the pressure situation squared away I would seriously look into installing a injector conversion on this one, the poppet valve units get very unreliable as they age.
Rock as an OE GM upgrade module with electronic injectors and bracket for $215, good unit at a good price. This is a really worthwhile upgrade.

https://www.rockauto.com/en/moreinfo.php?pk=984643&cc=1029620&jsn=477

https://www.rockauto.com/en/catalog/chevrolet,1997,blazer,4.3l+v6,1029620,fuel+&+air,fuel+injector,6224

 

[dlundblad]

Finally had a chance to take a look at it.

The fuel pump isn't even making a noise now.

 

[14Accent]

There you go. I would highly consider pulling the upper intake and replacing the injector spider with the updated SFI unit, right now. The original poppet injectors can really tax the original fuel pump, even when they work correctly. You'll be amazed by how much better the truck runs with new injectors, a new fuel pump, and a new filter. Plus, you'll get better mileage to boot.

Of course, with a 4.3 Blazer this means going from probably 15-16 average to 16-17, but it's something.

 

[dogememe]

If you have a Vortec 5.0/5.7/4.3 buy the ACDELCO replacement fuel spider. I had trouble out of the box with a BWD/Standard brand unit.