low fuel pressure when started and running

[stevek]

My car started having low fuel pressure while i was out running it. At first under boost i started getting kn, then i noticed FP didn't go up as much as boost did. i mean pound for pound. Volts to pump when running are 14.0, I had another pump around so i decided to change it but no luck. I took apart FP regulator I believe it is an old Kenne bell one, all look ok inside , no rip in diaphragm, put back together and turned key and press only went up to 35# then right back to 0, I started it but FP only at 35 # , could not change press by turning down screw then car dies , Before all this happened when i turn key on FP would rise to 50 # then drop to 42 # and stay there till car started. I'm going to change fuel filter next and see. then I guess FP reg. Anyone have any other ideas about this?

 

[rag231]

I second the motion on the fuel filter. Has it ever been changed?

 

[mikestertwo]

Still could be the regulator if the ball isn't seating properly. The fact that the pressure immediately goes to "0" when primed says there is a leak somewhere.

 

[stevek]

Changed fuel filter a few years ago, I will buy one today and see. I don't see any fuel leaking anywhere. If filter doesn't do any thing il'll look at reg again thanks

 

[No disintegrations]

Or it's fine and the gauge is bad. Try at least one more gauge?

 

[steve kowalchyk]

It’s a Hood mountedmechanical fuel gauge from Kenny Bell car only idle for about 30 seconds then shuts off And I also have a fuel gauge right in front of the fuel pressure regulator, Both read the same dirty 35 pound

 

[No disintegrations]

Vac line to reg was dry, no fuel in it?

 

[stevek]

Correct no fuel in it

 

[No disintegrations]

Then suspect it's not sealing off return line, thus low pressure build up.
As a test you can gently squeeze shut the rubber return line near the steering box. Use pliers covered in something to protect the hose. The more it's pinched the high the pressure should rise. Prob need a helper to run the key switch while you watch a gauge.

 

[stevek]

Changed fuel filter and no change couldn't get that lucky, took off return line end and put a clear plastic hose on it then attached jumper wire to FP, then into gas can just to check flow , fuel blew out of hose very strong into gas can, started car again tried to adjust pressure and it still stays at 25 #. I will start car and squeeze return line and see if any change in FP in alit bit heading out now but thanks for all your help thanks

 

[SFITurbo]

Changed fuel filter and no change couldn't get that lucky, took off return line end and put a clear plastic hose on it then attached jumper wire to FP, then into gas can just to check flow , fuel blew out of hose very strong into gas can, started car again tried to adjust pressure and it still stays at 25 #. I will start car and squeeze return line and see if any change in FP in alit bit heading out now but thanks for all your help thanks

I had a leak at the pump outlet in the tank that had similar symptoms. The pump had twisted loose from the short rubber hose connector from torque and would not allow FP to be raised.

 

[dynoman]

I had a leak at the pump outlet in the tank that had similar symptoms.

Agreed , I would check the short hose in the tank , could have come loose .

 

[stevek]

I will check it out tomorrow, I did think about cutting a trap door in trunk to get pump out instead of dropping tank again. This was a new pump i put in after this started but I will check it out, thanks

 

[turbo87adam]

I personally wouldn't cut the trunk floor to save a coupl of hours labor. I have to ask and it has probably been checked but how much fuel is in the tank?

 

[SCOOBY DOO]

Cut a hole in the trunk? Only takes 10 minutes to drop the tank.

 

[stevek]

I took out about 6 gallon still had a little bit at the bottom

 

[stevek]

Yea just kidding about cutting trunk

 

[TURBOELKY]

Interesting thread. I have a buddy with the same issue.
Now my fuel pump is taking a shit, sounds as loud as an external pump. I took was considering a trap door as I'm sick of dropping a tank every time I need to work on the fuel pump. Ugh, good luck

 

[stevek]

Well I found the problem, yes it was the short hose to fp, I did rip it apart to see the split inside . I thought I put a new one on with pump but must of had too many while working on it, lesson learned drink more and don't work on car.Turned key started up FP at 40# vac off at idle. Car off 5 minutes FP at 35# this is good.Thanks for all your help I appreciate it

 

[Lil Truck]

Did you replace it with the correct submersible fuel injection high pressure hose? If not it will blow out again! ...and possibly blow a head gasket as it will most likely happen at high boost fuel pressure.