Engine won't start until fuel pressure comes up..... advice needed

SoCalHarley

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I have a '96 GT with a full terminator swap done several years ago. I am running the '96 return fuel system. If I turn the key and wait a couple of seconds for the pump to run and then turn to start, the engine fires immediately. If I try to start the engine without doing this it will crank for a few seconds before firing. I have replaced the fuel pump and fuel pressure regulator with no change. Any suggestions would be appreciated. Thanks in advance.
 

01yellercobra

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After I did the PPRV delete in my car it took a couple seconds to build pressure. It just became a habit. I still do it even though my current fuel builds pressure fast.

Maybe you're missing the factory check valve. Otherwise I'd say just wait the second or two before cranking it.
 

CobraBob

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It's in the fuel tank. Circled in the photo.

1669562602623.jpeg
 
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P49Y-CY

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do 96-98 factory return-style fuel systems even use a pprv/check valve?

a quick image seach of their fuel pumps doesn't look like it

perhaps they might not have one since there's a pressure regulator? (just guessing)
 

SoCalHarley

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I do not recall seeing anything like the item circled in the picture when I did the new DeatschWerks 340lph pump recently. From what I have researched the DW pump has an internal check valve. I had a Walbro 255 in the car previously and it worked but I thought the pump might be the issue so that's why I replaced it, plus it was 25 years old and on the edge for the applicaion. I also replaced the Aeromotive fuel pressure regulator thinking that might be the cause but no luck. I have also checked the FRPS to see if there was any fuel leaking into it and that is dry. There is no issue with fuel pressure when the car is running. Again if I let the pump prime for 5 sec the car will start right up. It never did this before so something is causing the pressure to drop when shut off.
 

Bullitt1448

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The function of the check valve is to hold pressure in the system so it doesn’t need to build pressure when you go to start the cat
 

SoCalHarley

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Well assuming the check valve in the pump is working then pressure after the pump is being lost. Where could this be happening if there is no visible fuel leak? I have changed the FPR and no help.
 

olympic

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The check valve in the pump and the FPR are really the only components involved in maintaining fuel pressure when the engine is shut off. The only other possibility is a small leak inside the fuel tank, between the pump and the hat.
 

vr4

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The check valve in the pump and the FPR are really the only components involved in maintaining fuel pressure when the engine is shut off. The only other possibility is a small leak inside the fuel tank, between the pump and the hat.
Or an injector leak but that would manifest as a misfire on startup.
 

SoCalHarley

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I thought about injector but perfect on start up and plugs looked all the same and great when I changed them a few months ago. I guess I'll have to drop the tank and replace the hose from the pump to the hat. The DW pump really didn't fit in the stock assembly and had to modify. Maybe I should use an aftermarket fuel pump assembly.
 

DSG2003Mach1

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It doesn’t sound like you have an actual issue. In my aftermarket return system the pumps stay on with key forward (no 2-3 second time out). If I turn it forward, put my seat belt on, put it in neutral it’s ready to fire up
 

SoCalHarley

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I just spoke with DeatschWerks about the check valve in the pump. He said the check valve is a plunger style and will bleed off about 15psi of pressure as soon as you shut off the car and then additional as the car sits. They changed from a spring loaded check valve to get a bit more flow out of their pumps a while back. We discussed using an inline check valve and he said that would work. He mentioned there is a Ford OE valve that I could get at an autoparts or I may just get an aftermarket one with barbed 3/8 fittings I can splice into the line somewhere. Any suggestions or thoughts on an inline valve.
 

SoCalHarley

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That new pump has plenty of headroom. I was actually OK with the old 255 pump although pretty close to it's limit. I guess I should splice the valve in as close to tank as I can. Have to see where I can access the rubber line back there. Would be real easy to do it in the engine bay. Maybe I'll try there first.
 

DSG2003Mach1

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Ordered a DeatschWerks check valve and will install in engine bay before FPR. I'll report back how it goes.
the problem with that is you'll have fuel at the motor and nothing in the rest of the line, wouldnt be surprised if it fires up then sputters and stalls. If the line isn't pressurized from basically tank to motor I dont think you'll fix the issue
 

SoCalHarley

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I agree and you're probably right but real easy to try it before the FPR under the hood. If it doesn't work I'll splice it in near the tank. We'll see....
 

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