sefi fuel pressure regulator problems?

[Silverhorse]

Still hard to start after warm-up. I have about 35psi when running and when I shut down the motor the prssure goes to 0. Is this normal?
After the motor warms up and she becomes hard to start I noticed my fuel pressure was around 41 and when I turn off the key the pressure did'nt drop down? BTW it's a stock explorer regulator with a non stock motor

 

[Dave]

Is that the one line (no return line) system? I know that the 94 Mustang system holds pressure after shutdown and regulates very consistantly at whatever psi the book says. (think its something like 38)

 

[Silverhorse]

Is that the one line (no return line) system? I know that the 94 Mustang system holds pressure after shutdown and regulates very consistantly at whatever psi the book says. (think its something like 38)

No. It does have a return to the tank

 

[72ford]

I'm having similar problems with mine, hard cold start, warm starts not a problem. My fuel pressure runs about 38 psi, I thought I read somewhere that cold starts should have 45 psi

 

[Dave]

I'm having similar problems with mine, hard cold start, warm starts not a problem. My fuel pressure runs about 38 psi, I thought I read somewhere that cold starts should have 45 psi

I might be wrong but I believe that is is a simple diafram pressure regulator that has a vacuum line to reference it to manifold pressure so it should be pretty constant. You can disconnect the vacuum line to it and it should sit right at 38 (check the manual) psi. Check your engine temprature sensor and circuit. The computer uses it to determine the mixture for cold starts. You can pull the sensor and put it in water with a thermometer and use a ohm meter to check the value vs. temp against the book.

 

[jurob]

39 psi with vacuum plugged and off regulator will drop to lower to mid 30's when you reattach vacuum. since its a stock reg and not adjustable there will be variation from 39 and that is no bid deal.

i've had many fuel injected fords and some bled pressure immedialtely and some held it for bit, never has made a difference in drivablility for me.

nothing wrong with a stock regulator as they have been used on many high hp vehicles. if my memory is correct, the explorer 5.0 reg is the same as the 94-95 mustang regs (2 bolt).

give a little more detail on what you mean about hard start when hot. takes 4 seconds? 10 minutes or?

 

[Silverhorse]

39 psi with vacuum plugged and off regulator will drop to lower to mid 30's when you reattach vacuum. since its a stock reg and not adjustable there will be variation from 39 and that is no bid deal.

i've had many fuel injected fords and some bled pressure immedialtely and some held it for bit, never has made a difference in drivablility for me.

nothing wrong with a stock regulator as they have been used on many high hp vehicles. if my memory is correct, the explorer 5.0 reg is the same as the 94-95 mustang regs (2 bolt).

give a little more detail on what you mean about hard start when hot. takes 4 seconds? 10 minutes or?

When it gets warmed up I have to press down the accelerator to get it to crank

 

[Dave]

The fuel system pressure leak down test says that the fuel pressure should remain within 5 psi of the maximum for at least one minute after shutdown. If it leaks down immediatly it indicates a faulty regulator which can lead to hard starting. Fuel pressure range should be 35-40 psi. The pump has a check valve that sould keep the pressure from leaking back through the pump (at least on the stock Ford pump). The regulator will keep the pressure from bleeding down forward through the return line.

With the vacuum line disconnected the pressure shouldn't fluctuate more than 3 psi while running from idle to hard accelleration. With the vacuum line attached you should see small pressure fluctuations as the regulator maintains pressure relative to manifold pressure. Constant and consistant regulation is very important to the opperation of the whole system. Mixture is determined by the ECC controlling the pulse width to the injectors and relies on the pressure being accuratly controlled by the regulator. If your regulator is allowing the pressure to raise too high (over 40 psi) It could cause too rich of a mixture for start with the idle air valve in the start position. Thus you have to open the throttle to get it to start after it gets partially flooded.

One other thought. If your fuel pressure is within range and you have leakdown, it could be an injector that is leaking. This is a bit more of a pain to isolate and generally manifests itself as a puff of black smoke and rough idle for a couple of seconds after start. They usually start ok as only one cylinder is effected.

Hope some of this is usefull.

Good Luck

Dave...

 

[Silverhorse]

The fuel system pressure leak down test says that the fuel pressure should remain within 5 psi of the maximum for at least one minute after shutdown. If it leaks down immediatly it indicates a faulty regulator which can lead to hard starting. Fuel pressure range should be 35-40 psi. The pump has a check valve that sould keep the pressure from leaking back through the pump (at least on the stock Ford pump). The regulator will keep the pressure from bleeding down forward through the return line.

With the vacuum line disconnected the pressure shouldn't fluctuate more than 3 psi while running from idle to hard accelleration. With the vacuum line attached you should see small pressure fluctuations as the regulator maintains pressure relative to manifold pressure. Constant and consistant regulation is very important to the opperation of the whole system. Mixture is determined by the ECC controlling the pulse width to the injectors and relies on the pressure being accuratly controlled by the regulator. If your regulator is allowing the pressure to raise too high (over 40 psi) It could cause too rich of a mixture for start with the idle air valve in the start position. Thus you have to open the throttle to get it to start after it gets partially flooded.

One other thought. If your fuel pressure is within range and you have leakdown, it could be an injector that is leaking. This is a bit more of a pain to isolate and generally manifests itself as a puff of black smoke and rough idle for a couple of seconds after start. They usually start ok as only one cylinder is effected.

Hope some of this is usefull.

Good Luck

Dave...

Thanks very much for the info Dave! I'll try and check it out ASAP.

 

[Silverhorse]

Dave, Do you think I need an aftermarket FPR?

 

[okorangebrnco]

I had, in essence the same problem on my 94 GT. I changed the regulator from a stock to a barry grant and my bleed off and hard start problems subsided. the Barry Grant is typically about 20 bucks more than the other, but I put a few other makes on, and the BG's craftsmanship is alot nicer.

 

[Silverhorse]

Just checked the FPR- When vaccum lined removed pressure stayed at a constant 41.

 

[Dave]

Just checked the FPR- When vaccum lined removed pressure stayed at a constant 41.

That is a little higher than my book says it should be but not high enough that I would expect starting problems. If you have any u-pull-it yards around you can probably find several regulators for a couple of bucks. Does it leak down after the pump is off?

 

[jurob]

more info is still needed. non stock motor, what does that mean? which mass air meter and eec, etc....did this just start happening or has it always been happening.

first thing i would do is after you shut the motor off after its to full opertating temp, wait as long as you can so that i would still have the problem then start pulling plugs. i would guess that your motor is running rich and when you shut it off the plugs are fouled or fuel soaked.

which heads and plugs? you can try a hotter plug, or??

also 41 psi of fuel pressure is fine.

 

[Silverhorse]

That is a little higher than my book says it should be but not high enough that I would expect starting problems. If you have any u-pull-it yards around you can probably find several regulators for a couple of bucks. Does it leak down after the pump is off?

If I get your meaning, the fuel pressure goes immediatly to o when I turn off the ignition!

 

[Silverhorse]

more info is still needed. non stock motor, what does that mean? which mass air meter and eec, etc....did this just start happening or has it always been happening.

first thing i would do is after you shut the motor off after its to full opertating temp, wait as long as you can so that i would still have the problem then start pulling plugs. i would guess that your motor is running rich and when you shut it off the plugs are fouled or fuel soaked.

which heads and plugs? you can try a hotter plug, or??

also 41 psi of fuel pressure is fine.

351w,FMS y-303 heads,216/224 duration hyd. roller cam,gt-40 intakes, 30lb.injectors,mustang computer with chip,65mmTB, 75MAF. Newly built not driven yet. Still working out all the bugs!!

 

[jurob]

sounds like my old lunati 51014.

since you have a 75mm maf i guessing its a bullet. is it cal'd for 30's? who burnt you a chip before it was running? what was done to the chip?

if its a sct chip ask them to email you a copy of a program and i can tell you what they did if you don't know.

first thing i would do if your meter is cal'd for the injectors is pull the chip and see what happens!

your car is running rich from a overly rich condition most likely caused by your meter. if you know a stanger in your area with a known good meter cal'd for 30's give it a shot.

you honestly won't need a chip to get the car running on your relatively mild combo as long as the meter is cal'd correclty. once they can tune then you will benefit with the chip by adjusting your air fuel and timing. if its just a hot start problem your tuner can adjust your crank fuel pulsewidth via chip for you.

 

[jurob]

ignore my previous post about the plugs now that there is more info.

 

[Dave]

If I get your meaning, the fuel pressure goes immediatly to o when I turn off the ignition!

It shouldn't do that. Should hold pressure within 5 psi of max for at least a minute.

 

[Silverhorse]

sounds like my old lunati 51014.

since you have a 75mm maf i guessing its a bullet. is it cal'd for 30's? who burnt you a chip before it was running? what was done to the chip?

if its a sct chip ask them to email you a copy of a program and i can tell you what they did if you don't know.

first thing i would do if your meter is cal'd for the injectors is pull the chip and see what happens!

your car is running rich from a overly rich condition most likely caused by your meter. if you know a stanger in your area with a known good meter cal'd for 30's give it a shot.

you honestly won't need a chip to get the car running on your relatively mild combo as long as the meter is cal'd correclty. once they can tune then you will benefit with the chip by adjusting your air fuel and timing. if its just a hot start problem your tuner can adjust your crank fuel pulsewidth via chip for you.

It is Cal for the 30's. SCT chip, no idea what they did to it. I did try with computer only with same results. I'm thinking I might need new injectors. They are the only used part on the motor.