My grand cherokee is getting hard to start when it has been sitting over night but after that it starts up ok. Also, it is very sluggish when I get on the skinny pedal. It does have a new fuel pump. Any suggestions on what to check?

 

When was the last time it had a full tune up???

 

Sounds exactley like a fuel pressure problem. Do you by chance have a fuel pressure guage you can screw onto the fuel rail to check leakdown? When you replace the pump, did you replace the whole assy, or was is the individual pump motor? The reason I ask is you can do them both ways and the fuel filter/regulator is the round can on top of the module that the fuel line plugs into. This regulator/filter also has a check valve in it to prevent fuel pressure from leaking back into the tank. It is also possible that the new pump could have a failed check valve assy though that would suck but I have seen it before.

If not fuel pressure it could be a number of things or multiple problems. IAC and throttle body could be dirty for the hard start concern (this is a free step to check with a can of carb clean), if dirty this usually causes idle quality issues too.
Tune-up/ignition components- plugs, wires, cap & rotor, even air filter, these things if bad/worn would make the engine run sluggish and could have a start issue too. Maybe check for codes, a faulty sensor could cause these issues too.

 

I checked the valve on the fuel rail and there is very little pressure even after cycling the key on/off several times. I guess the fuel pressure regulator or the check valve is bad. I replaced the whole sending unit/pump with an airtex brand pump. After doing a little research online I found that these pumps are pretty crappy so not really sure what I am going to do now.

 

i just replaced mine with an airtex a couple weeks ago and it works fine, if it has a warranty i would just replace it again and the fuel regulator while your at it

 

I bought the pump off of ebay and it has a warranty but to get it replaced I have to have a receipt from a professional mechanic which I don't because I installed the pump myself. Also I'm pretty sure the fuel pressure regulator is built into the sending unit.

 

The regulator check valve is the round can looking thing on top of the fuel pump where the fuel line snaps on. This is also considered the filter.

 

ahhh i just put an airtex in...

 

The warranty instructions say I have to return the pump with receipt showing installation from a professional mechanic. I wonder how much they look into that. Maybe I could make up a receipt.