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Fuel pressure problems please help

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Old Aug 26, 2016 | 10:15 PM
  #1  
pcpotter1023's Avatar
pcpotter1023
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From: Cleburne, TX
Fuel pressure problems please help

This is a little but I'm trying to make sure I covered what I've done at this point.

I have a 1991 F250 7.3 IDI non turbo diesel and I went from the mechanical fuel pump to electric fuel pump using a Carter P4601HP when I turn on the ignition without starting it builds up to 8PSI after I start it drops to near zero and idles rough I also mounted a Carter P74019 fuel pump and got the pressure up to 12PSI after doing this and it idled great after I took it out on the road for a test run the pressure dropped to near zero again and the idle got rough again, once I idle it up with the throttle it levels out but pressure still stays at near zero, here's how I have it hooked up.
Coming from the selector valve to a filter then to the carter fuel pump P4601HP to a check valve all with 3/8" tubing hooked back into the steel line going to the mechanical pump where the steel line normally hooks to the mechanical pump that's disconnected and a 3/8" hose ran to the filter.
Note: I disconnected the Carter P74019 thinking maybe this was restricting the flow, (grasping for straws)

Thanks Patrick
 
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Old Aug 27, 2016 | 01:20 AM
  #2  
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Festus Hagen
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Sounds like an issue on the suction side ...

Like it's sucking air or sucking lines/filters flat.

Unhook the output on the Carter and run it into a jug, what happens?
It should pump the tank dry with a solid stream ...

Personally, I prefer the mechanical pump.

-Enjoy
fh : )_~
 
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Old Aug 27, 2016 | 05:28 PM
  #3  
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pcpotter1023
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From: Cleburne, TX
Originally Posted by Festus Hagen
Sounds like an issue on the suction side ...

Like it's sucking air or sucking lines/filters flat.

Unhook the output on the Carter and run it into a jug, what happens?
It should pump the tank dry with a solid stream ...

Personally, I prefer the mechanical pump.

-Enjoy
fh : )_~

Do you mind me asking why you prefer mechanical over electric
 
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Old Aug 27, 2016 | 09:36 PM
  #4  
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Festus Hagen
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Nope, Don't mind at all ... If you've ever seen a electric pump fueled fire, you'll understand.

I assure you, It's not pretty watching/smelling humans burn ...

I know, not me, it'll never happen, I don't plan on getting into an accident!
That's what we all say ... Until it's to late!

Modern electric pumped vehicles have some sort of fuel shutoff safety, when folks convert manual pumps to electric they RARELY do it correctly, thus in an accident the fuel pump continues to run and fuel the fire!

Safety shutoffs are an added cost and headache.

Not to mention they are cheaper and last just as long if not longer than most electrics.

-Enjoy
fh : )_~
 
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Old Aug 28, 2016 | 08:53 PM
  #5  
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pcpotter1023
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From: Cleburne, TX
Originally Posted by Festus Hagen
Nope, Don't mind at all ... If you've ever seen a electric pump fueled fire, you'll understand.

I assure you, It's not pretty watching/smelling humans burn ...

I know, not me, it'll never happen, I don't plan on getting into an accident!
That's what we all say ... Until it's to late!

Modern electric pumped vehicles have some sort of fuel shutoff safety, when folks convert manual pumps to electric they RARELY do it correctly, thus in an accident the fuel pump continues to run and fuel the fire!

Safety shutoffs are an added cost and headache.

Not to mention they are cheaper and last just as long if not longer than most electrics.

-Enjoy
fh : )_~
You know you're 100% correct: no I don't have a safety switch on mine (yes I agree I should) the only reason I haven't is I could see with my truck being a diesel where this could cause a bad issue because the only ones I could worked off the oil pressure and there is a very short delay between startup and oil pressure buildup but just enough delay to get air in the line between the pump and the engine, not good, after reading your response I'm going to do away with the electric fuel pump besides with all the crap I've tried I could've put 6 or 8 of the mechanical pumps on my truck.

Thanks for the wake/up kick in seat end
Patrick
 
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Old Aug 28, 2016 | 08:56 PM
  #6  
pcpotter1023's Avatar
pcpotter1023
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From: Cleburne, TX
Originally Posted by Festus Hagen
Nope, Don't mind at all ... If you've ever seen a electric pump fueled fire, you'll understand.

I assure you, It's not pretty watching/smelling humans burn ...

I know, not me, it'll never happen, I don't plan on getting into an accident!
That's what we all say ... Until it's to late!

Modern electric pumped vehicles have some sort of fuel shutoff safety, when folks convert manual pumps to electric they RARELY do it correctly, thus in an accident the fuel pump continues to run and fuel the fire!

Safety shutoffs are an added cost and headache.

Not to mention they are cheaper and last just as long if not longer than most electrics.

-Enjoy
fh : )_~
Also wanted to say I'm really sorry if I stirred up some bad memories I feel like I did

Patrick
 
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Old Aug 28, 2016 | 09:37 PM
  #7  
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Festus Hagen
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I wouldn't consider that an issue to worry about, oil pressure switches work fine if the motor loses oil pressure ... What's to say it's going too!

But then a manual pump is no better either!
In fact, in a case like that, an electric with inertia switch is safer.

From a safety point I think they (both) should have several safeties.
From an owner/mechanic stand point I don't want any of them headaches!

So, IMO the lessor of two evils is the manual.

If a person wanted to deal with an inertia switch, I've been told Ford Escort switches are good simple ones to use ... Cheap at the salvage yard as well.

EDIT
It's cool, you know how memories are, they never leave!

-Enjoy
fh : )_~
 
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Old Aug 29, 2016 | 10:47 AM
  #8  
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tjc transport
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the oil pressure switch on an electric pump will not cause an issue with air intrusion. the injector pump is strong enough to draw fuel through the electric pump if the pump should fail while running. i have never had an issue with air intrusion or starting with the oil pressure switch.
i do have a momentary contact bypass wired in the circuit, but i only use it to fill the fuel filter after changing it.
i think the larger issue is in the pump of choice. the carter is a good pump for gas engines, but for diesel engines the only one worth using is the facet duralift.
 
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