Electrical Fuel Pump Pressure Problems

[Yellow78]

For years now I’ve use this form to work on my 78. Unfortunately I’ve been sick for the last couple of years and now I have a new LIVER and want to get the 78 back on the road.

Read everything I can find on the form about fuel pump systems I can fine.

 

So here’s what I’ve done.

 

1. Drained old fuel.

2. Remove all old fuel lines with new ones.

3. New fuel pump.

4. Replace all fuel filters,in front of the fuel pump, in before the fuel rail.

5. Replaced fuel rail with new Pallnet rail.

6. Brand new injectors.

7. Car will start with starting fluid and run for five seconds.

8. No pressure at fuel rail.

9. Removed fuel lines from filter before fuel rail and fuel pump pump fuel.

10. Blown compressed air into return line until fuel comes out of filter before fuel rail. (Clear)

 

Have bypass the oil pressure switch for all of these test.

 

If anybody has any advice I sure would appreciate it.

 

 

 

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[Dave WM]

Does the pump run with the key in the start position? is the FPR installed?

Edited October 26, 2018 by Dave WM

[Yellow78]

Yes in the start position I can here the pump. In using the stock FPR


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[Yellow78]

I just clamped off the fuel line after the fuel rail and got pressure up to 30 PSI, cannot understand why am not getting more pressure that 30 PSI. Car will still not start.


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[Jeff Berk]

If you disconnect the fuel line in the engine compartment and run the pump, is there any fuel spraying out? If so, borrow a pressure meter from Autozone and check it.

One issue I'm having is the fuel pickup periodically clogs. I eventually will have to drop and clean up the fuel tank.

[Dave WM]

What Jeff said.

 

Edited October 26, 2018 by Dave WM

[Dave WM]

2 minutes ago, Yellow78 said:

I just clamped off the fuel line after the fuel rail and got pressure up to 30 PSI, cannot understand why am not getting more pressure that 30 PSI. Car will still not start.


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check voltage at pump.

[Zed Head]

1 hour ago, Yellow78 said:

Have bypass the oil pressure switch for all of these test.

I think that you might have got too ingenious for your own good, if you shorted the oil pressure switch to ground.  You want to just disconnect the switch, leave it hanging.  Then the pump should run when the key is on.

Sounds like you're getting a Start because the relay bypasses the switch at Start.  Then when it starts and you let the key back to Run, it kicks off, like it's supposed to.  You could probably just put the oil pressure plug back on and the engine will start and run fine.

Just a guess.  If you do have the plug off, for the "bypass", check that it's not shorted internally.  The relay kicks open when there's a ground at the switch.

[Yellow78]

I have 12 V going to the pomp.
After reading some more I’ve got a G3 between the tank in the pump and I think I may be restricting the pump.
You’re right that bypass on the oil pressure gauge is just to check power not to keep it runing.

Please keep the ideas coming, the soulman’s getting frustrated with this whole car.


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[Zed Head]

2 hours ago, Yellow78 said:

3. New fuel pump.

7. Car will start with starting fluid and run for five seconds.

8. No pressure at fuel rail.

 

I didn't read your first post right.  Are you sure that it's not an injection problem, instead of pressure?  Not clear if you actually measured pressure.  Of course, the cold start valve should get it started even without injection if there was pressure.

Don't overlook that the DC fuel pumps will run backward.  Spinning, but no pumping.

[Yellow78]

Ok after running a unfiltered 3/8” fuel line from tank to pump and clamping off the outlet side of the fuel rail I’m 24 PSI.


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[Zed Head]

That's no good.  Where is your gauge?  What brand of pump?

Sounds like the inlet to the pump might be clogged.  Is the pump noisy when it's running?  That's a sign.

You should have still seen 24 psi at the rail without clamping the return line.  The FPR doesn't open until 36 psi is reached.  It might take a while to get there with a weak pump though, pushing through the filters.

 

Forgot to say earlier, congratulations on getting back to health.   Don't know what ruins a liver but it sounds serious.