Long crank issue - fuel pressure question

[Hoffbrohaus]

I have problems starting from time to time and was wondering if it's the fuel pump check valve. Per a search:

The check valve in the fuel pump goes bad over time. When the valve fails, it allows all of the fuel in the injector rail and supply line to drain back into the tank causing longer cranking times. A dealer can order a repair kit which consists of a new section of rubber hose with an imbedded check valve. It costs about $5 and takes only a fuel minutes to install."

I have a fuel pressure gauge, how long is the pressure supposed to hold in the rail after the car turns off? I figure if it's not holding for the specified amount of time then it's the check valve right?

[spdracrm3]

most new car diagnostic's give a spec of 20min to 1/2 hr for any significant bleed down , i would say not more than 10 pounds loss in 2 hrs is good , but you also need to watch how fast it resumes normal pressure on cranking which should not take more than 1-2 seconds to reach full pressure

[andrewill]

Do you have problems starting when the motor is cold or still warm??

I had long crank issue with mine when the motor was still warm, the problem was the coolant temperature sensor. If your problem occurs when the motor is cold, then you can skip my suggestion.

[jlevie]

If the FPR and pump is good and the injectors aren't leaking the rail should hold pressure for more more than a day. I'd seen pressure in the rail over a week after the engine was last run.

[Hoffbrohaus]

Do you have problems starting when the motor is cold or still warm??

Seems to happen randomly. I swear I have had it in the morning after sitting, and sometimes after a quick run to the store. I will pay more attention.

If the FPR and pump is good and the injectors aren't leaking the rail should hold pressure for more more than a day. I'd seen pressure in the rail over a week after the engine was last run.

FPR is new and tested pressure was in spec. Injectors were cleaned and new o-rings installed so I don't think they are leaking. I will check residual pressure tomorrow but pressure in the rail for a week that would be surprising to me.

[digger]

I have problems starting from time to time and was wondering if it's the fuel pump check valve. Per a search:

does it take a while to crank when the engine is warm and the car has been sitting for more than 5 or 10 mins?

what about stone cold in the morning

[Hoffbrohaus]

Finally attached a fuel pressure gauge. Hot or cold, pressure drops to 0 as soon as pump turns off. So I guess I need that check valve huh? Or would it just be better to get a new fuel pump?

[Cephas]

Could this also be leaking injectors?

[Hoffbrohaus]

I don't know what do you guys think? I don't think so because I just replaced the injector o-rings. I installed an air fuel ratio gauge and my ratios look good all the way up the rpm band. It idles fine, maybe a little lumpy like a big cam but I figure that is more likely valve lashing.

[Hoffbrohaus]

Anyone know the new part number for the check valve kit? Every post references part #16 14 9 068 988 Pelican, BMA, & Real OEM says that does not exist anymore.

[Cabriolet]

try another crank position sensor. i've seen this happen is the KPS is going bad.

[digger]

Finally attached a fuel pressure gauge. Hot or cold, pressure drops to 0 as soon as pump turns off. So I guess I need that check valve huh? Or would it just be better to get a new fuel pump?

i always thought the check valve was in the pump?

[spdracrm3]

yes the check valve is in the pump assembly to control pressure on feed side and the FPR stops flow to hold pressure on the return side

to test which is allowing bleed down pinch the return line after the FPR after cycling pump and if pressure still drops pump check valve is bad ,if it doesnt bleed down until you release pinched hose regulator is bad (it has a spring loaded seat that sets hold pressure inside it )

[Hoffbrohaus]

yes the check valve is in the pump assembly to control pressure on feed side and the FPR stops flow to hold pressure on the return side

to test which is allowing bleed down pinch the return line after the FPR after cycling pump and if pressure still drops pump check valve is bad ,if it doesnt bleed down until you release pinched hose regulator is bad (it has a spring loaded seat that sets hold pressure inside it )

I'm assuming I need to put the fuel pressure gauge inline on the delivery side, before the fuel rail, not in the return line after the FPR right? I have a new FPR so I'm pretty sure it's the check valve but good double check.

[spdracrm3]

"I'm assuming I need to put the fuel pressure gauge inline on the delivery side, before the fuel rail, not in the return line after the FPR right?" YES

you wont see any pressure downstream of FPR its open all the way to tank, pinching this line works to test as noted