People with return fuel systems

[Gruca]

How long does it take for your fuel pressure to return to 0 after you turn off the car? Mine goes to 0 almost immediately and when I start the car, it takes a little effort for it to turn over.

I’m tuned for E85 and have VMP fuel rails. I’ve checked the connections to make sure they’re tight, both at the engine and on the fuel pump. If I turn the key once and let the pumps prime, remove the key and do it again, it starts fine. So basically, I’m trying to figure out why, after a couple months on this setup, the car is all of a sudden harder to start while only letting the pumps prime once.

 

[ViperRed91GT]

What regulator are you using?

 

[fuelforfire87]

How are you measuring that your fuel pressure is zero? Are you looking at an analog gauge attached to your regulator?

 

[fuelforfire87]

Another thing to mention is to replace your stock starter with the ford performance one. I broke my starter when installing kooks headers so I ordered the FRPP one which has higher starting torque than the stock starter(assuming you're boosted and need to spin a blower). Also check battery. I noticed that when my car has been sitting for a while and not on a trickle charger it takes longer to start. Having to prime twice tho seems like something is up. Pumps should just have to prime once.

 

[Gruca]

What regulator are you using?

An Aeromotive FPR.

 

[Gruca]

How are you measuring that your fuel pressure is zero? Are you looking at an analog gauge attached to your regulator?

The fuel pressure regulator has a needle gauge on it that tells you.

 

[Gruca]

Another thing to mention is to replace your stock starter with the ford performance one. I broke my starter when installing kooks headers so I ordered the FRPP one which has higher starting torque than the stock starter(assuming you're boosted and need to spin a blower). Also check battery. I noticed that when my car has been sitting for a while and not on a trickle charger it takes longer to start. Having to prime twice tho seems like something is up. Pumps should just have to prime once.

My priming comment was wrong. I made it a point to try that again and it still took an extra few seconds to start. So I was wrong about the additional priming.

 

[Gruca]

I also just realized that it only happens when I haven’t started the car in a while. So in the morning when I leave, it struggles. If I stop somewhere for a minute, when I start the car up, it starts perfectly fine.

 

[Riddick]

Sounds like a tune issue. E85 can be a little tricky to dial in on cold starts.

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[ViperRed91GT]

Aeromotives are known for not holding a prime. I’d bet that when you shut the car off, the pressure drops to zero almost immediately, where most regulators will hold pressure and slowly bleed pressure.

 

[Gruca]

Sounds like a tune issue. E85 can be a little tricky to dial in on cold starts.

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Oddly, it was fine for the first month and now I'm having the issue. Granted, the car always starts, it just takes 2-3 more turns before it does.

Aeromotives are known for not holding a prime. I’d bet that when you shut the car off, the pressure drops to zero almost immediately, where most regulators will hold pressure and slowly bleed pressure.

By the time I get out of the car and look under the hood, it's at or very near 0.

 

[4VFTW]

mine takes a crank or two extra to fire when cold which isnt uncommon with E85 and my aeromotive regulator slowly bleeds down. You could have your tuner look at your cranking fueling but I wouldnt be concerned.

 

[stang910]

Without a check valve or pumps that don't bleed down this is normal. My fuel pressure goes to 0 as soon as my pumps turn off. When starting the car the pumps have to fill all the lines and fuel rails again. You can have your tune set to keep the pumps running during the prime this way you can turn the key and let the fuel prime for as long as you need before you start the car.

 

[11Sec_Lx]

Adding a check valve from Fore, cured this for me.

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