jllphan

Car in question is a 2003 C4s w/ 105k mi.

Car runs great, no CELs and no issues passing emissions. Other than the same issues i have at the pumps with all my cars, i have no issues fueling up. Battery and starter are good. Ignition switch is good. Purge valve in engine bay has been pulled and checked w/ a 9v source and works as it should. Short and long term fuel trims have been mapped and aren't making me think i have leaking injectors -- you can view what I've mapped here and here.

But, during ONLY warm weather and ONLY if the engine has been brought up to temp and then sat for at least 1h but no more than 3hr it sometimes takes a few cranks to start. Additionally, i just got back my first oil analysis (which you can see here) and looks like I have a fair amount of fuel dilution in the oil. So all things pointing towards round cylinders if i don't get on top of it.

I'm not one to just buy parts and throw them on the car hoping it will fix it, but seems like it has to be one of the following:
-Barely leaking fuel injector
-Some part of the EVAP system is not working right
-The fuel pressure sensor is bad (this seems possible based on this thread given they were having essentially the same issue)

So, if the fuel trims don't point toward a leaky injector issue, the purge valve works fine, i have no CELs or issues putting gas in the car (making me think the rest of the EVAP system is functioning) -- where would you look to fix the issue? What am i missing?

Mark I

Your Oil analysis shows fuel dilution? It reads negative, which according to the legend means OK, right?

jllphan

Well heck Mark, you're right about the analysis -- got a bit mixed up with the viscosity and fuel dilution boxes, so all good there -- thanks for bringing that to my attention!

But still have the warm start issue in the summer time, so most of all posted above is still relevant. would to hear from the peanut gallery on what to do next. I'm assuming there is no way to bench test the rest of the EVAP system or fuel pressure sensor?

If not, i guess i can pick up a fuel pressure test kit and hook it up to the fuel rail, just leaving that as a last resort if the aforementioned bits can't be tested to prove faulty or not.

DBJoe996

How about the fuel pressure regulator? I don't know of a good way to check it, but if it is stuck it will bleed off fuel in the fuel rails when they are hot.

Mark I

Other than what you've mentioned, what leads to a fuel issue as the problem? Does the tach bounce slightly while your cranking (re failing crank position sensor)?

Mike Murphy

jllphan

FPR would be inspected if/when i start poking around the injectors.

The fact that it seems flooded when experiencing the warm hard start issue (more on that below). Tach does not bounce. Been thinking about a CPS if/when i change o2 sensors (both would be out of PM not necessity though).

It does indeed. Starts right up. Which as i understand it, going WOT at start introduces more air, not fuel-- making me think there's additional fuel where it shoudn't be at start up. What does that have you thinking?

hatchetf15

Mike Murphy

If the engine is flooded with fuel, then yes, WOT at start will help clear it out for a faster start. I guess you might check to see if dense fuel cloud exits the exhaust for this step.

Otherwise, I did a search with your symptoms, and lots of different responses that include:
Impulse sensor
Fuel Pump Relay
Fuel Tank Pressure Sender
Crank Position Sensor
Fuel pump/filter
Vapor lock recovery valve located on the fuel tank might be stuck
Fuel tank breather - might be the same thing as the above ^^

Other things to check:

Check fuel pressure at the fuel rails
Check if the tach need bounce when you try to start during turnover

Looks like most people reported the crank sensor.