'98 SOHC hard start

[Kevin Hawkins]

I know it's been discussed and I have searched the forum for a satisfying answer without luck.
Here is what I am experiencing: 1998 Explorer SOHC 5r55e with 215k miles, Hard to start when the engine is cold (first start). If I cycle the key a few times it will 'hit" a few times but not start. If I treat it like a flooded carburetor, meaning hold the pedal to the floor it will start and run bad for about 3-5 seconds and then smooth out as it should. The truck runs great after it starts, no stumbling, and will restart just fine after it is driven. Even if it is off for a few hours it starts right back up. I've checked my fuel pressure and initial key on it goes to 35psi and will not drop much in 15 minutes(29psi). Revving the engine the psi goes to almost 40. I have cleaned the IAC and haven't seen and difference. Could it be the fuel pump is just tired and weak? I wouldn't think a tune up would help (wouldn't hurt). The only thing I have changed lately is the newer version of the t-stat housing and timing chain tensioners (slightly modified).
Thanks for your time and thoughts.

 

[Kevin Hawkins]

I know it's been discussed and I have searched the forum for a satisfying answer without luck.
Here is what I am experiencing: 1998 Explorer SOHC 5r55e with 215k miles, Hard to start when the engine is cold (first start). If I cycle the key a few times it will 'hit" a few times but not start. If I treat it like a flooded carburetor, meaning hold the pedal to the floor it will start and run bad for about 3-5 seconds and then smooth out as it should. The truck runs great after it starts, no stumbling, and will restart just fine after it is driven. Even if it is off for a few hours it starts right back up. I've checked my fuel pressure and initial key on it goes to 35psi and will not drop much in 15 minutes(29psi). Revving the engine the psi goes to almost 40. I have cleaned the IAC and haven't seen and difference. Could it be the fuel pump is just tired and weak? I wouldn't think a tune up would help (wouldn't hurt). The only thing I have changed lately is the newer version of the t-stat housing and timing chain tensioners (slightly modified).
Thanks for your time and thoughts.

Really? Nobody has any ideas? Suggestions?

 

[koda2000]

Kevin, we see this same issue so many times people get tired of responding.

The SOHC engine typically suffers from hard starting when cold because the intake gaskets/O-rings shrink and leak air, especially when the engine is cold (like the first start of the day). Typically your CEL will also be on when this happens with P0171 and/or P0174 codes. Often once the engine warms up it runs okay, as the parts expand with heat and seal better. If your upper and lower intake manifold gaskets have never been changed, they're certainly due/suspect.

There are other things that can cause hard starting when cold. Have you replaced the coolant temp sensor? When the engine cold it tells the computer to richen the fuel mixture to help the engine start.

 

[Kevin Hawkins]

Just done the t-stat change with new sensors. The only cel code that shows up is o2 sensor slow response. I did a search on the forum and got nothing on this issue. This hard start just showed up all of a sudden. I will check the intake gasket soon but i have my doubts. No lean codes. I have been fooled before.