check valve vs regulator

[acarr6]

So, I’m chasing down a long crank cold start issue. I’ve replaced injectors, sending unit, plugs, fuel pressure sensor.

The only logical thing to replace would be the actual fuel pump itself which has the check valve in it.

However, I’m getting conflicting info. I know the regulator is in the fuel sending unit, which is what I initially replaced. The system is still bleeding pressure after everything I’ve replaced (at a fairly slow rate). Goes from full pressure to 0 over the course of about 1.5 days. Just want to confirm from the experts the actual fuel pump unit (not the sender unit side) has a check valve in it.

[deansbimmer]

Yes, the fuel pump (right well) has a check valve built into the motor. It's really the only component that goes bad in the pump assembly.

[acarr6]

Originally Posted by deansbimmer

Yes, the fuel pump (right well) has a check valve built into the motor. It's really the only component that goes bad in the pump assembly.

Good to know.. so in all likelihood after replacing every component, the last one is the culprit for my pressure loss lol

[jhu321]

Originally Posted by acarr6

Good to know.. so in all likelihood after replacing every component, the last one is the culprit for my pressure loss lol

sorry to bring up old thread, i'm chasing the same thing.. i thought i had a fuel injector leak because on cold start only i would see the fuel pump pressure start at 6.9 and over a period of 5 minutes drop to 5.9... but after the car has been running and warmed up and i do a stop and then start again, it'll hold 6.9 and actually increase to 7.2.

with that i assumed my check valve was okay and it was thermal related so i concluded it was my injectors. however after replacing my injectors its still doing the same thing... so i'm thinking its check valve now? were you successful with your check valve replacement? thanks

[e36mikee]

Originally Posted by jhu321

sorry to bring up old thread, i'm chasing the same thing.. i thought i had a fuel injector leak because on cold start only i would see the fuel pump pressure start at 6.9 and over a period of 5 minutes drop to 5.9... but after the car has been running and warmed up and i do a stop and then start again, it'll hold 6.9 and actually increase to 7.2.

with that i assumed my check valve was okay and it was thermal related so i concluded it was my injectors. however after replacing my injectors its still doing the same thing... so i'm thinking its check valve now? were you successful with your check valve replacement? thanks

Did you ever fix this? Also chasing a similar issue. I noticed it after changing injectors, but then realized my fuel rail hoses were leaking. After then changing that and then changing o rings on injectors it seems to still be happening albeit under slightly different conditions. It sseems to only leakdown pressure after cars hot and initially after shutoff and reprime it holds pressure really well until about 1 hour after shutoff in which it bleeds down to 0 in a few hours. If i restart it seems to run fine and doesnt seem like injectors , as they are also new. They for sure dont leak when its cold.

[jhu321]

Originally Posted by e36mikee

Did you ever fix this? Also chasing a similar issue. I noticed it after changing injectors, but then realized my fuel rail hoses were leaking. After then changing that and then changing o rings on injectors it seems to still be happening albeit under slightly different conditions. It sseems to only leakdown pressure after cars hot and initially after shutoff and reprime it holds pressure really well until about 1 hour after shutoff in which it bleeds down to 0 in a few hours. If i restart it seems to run fine and doesnt seem like injectors , as they are also new. They for sure dont leak when its cold.

So the thing I was looking to solve was long crank on cold start. And it turns out the fuel pressure leak down isn’t an issue. It would leak down and it was fine. It builds pressure really fast so the cold start low pressure leak down was not the root cause. It turned out to be a sensor thing. I want to say camshaft or crankshaft I can’t remember which one i kinda threw the kitchen sink at it until i got it solved. Basically the theory was it was taking a bit longer on cold star to sync the camshaft position.

[e36mikee]

Originally Posted by jhu321

So the thing I was looking to solve was long crank on cold start. And it turns out the fuel pressure leak down isn’t an issue. It would leak down and it was fine. It builds pressure really fast so the cold start low pressure leak down was not the root cause. It turned out to be a sensor thing. I want to say camshaft or crankshaft I can’t remember which one i kinda threw the kitchen sink at it until i got it solved. Basically the theory was it was taking a bit longer on cold star to sync the camshaft position.

Ok gotcha makes sense. My issue actually started initially as a slighly long crank a few times after not driving(i dont daily) which led me to check pressures, which led me to discovering the physical leak on the hose. Now im not even sure if i have an issue. Im doing more diagnosis to determine the parameters of when it loses pressure but i dont really have any issues and it seems to hold fairly well. I cant find actual specs to compare to, maybe its fine.

[jhu321]

Originally Posted by e36mikee

Ok gotcha makes sense. My issue actually started initially as a slighly long crank a few times after not driving(i dont daily) which led me to check pressures, which led me to discovering the physical leak on the hose. Now im not even sure if i have an issue. Im doing more diagnosis to determine the parameters of when it loses pressure but i dont really have any issues and it seems to hold fairly well. I cant find actual specs to compare to, maybe its fine.

Yeah long crank isn’t an issue. My fear was hydro locking the cylinder these engines are known to do that. You prob don’t really have an issue. The only other thing was I noticed my secondary air pump came to life after I fixed the sensors too. Now it’s very prominent when I cold start.

Once I confirmed I don’t have a risk of hydrolock it wasn’t a big deal anymore.