My brother in laws 98 grand Cherokee is having a starting issue. Truck runs fine but has a hard time starting. It will crank and crank without starting. Has spark and fuel according to a local shop he took it to, they have no ideas as to whats wrong. Most times if you hold the pedal down it will fire up and run fine after that. Its has a six cylinder. Any ideas on what to check?

Just had one yesterday (a 99)had a bad ignition coil. I was suspecting it to be a crank sensor but it had cranking rpm.crank sensors are a fairly common problem with those. ;-)

Don't get the coil? Cheap enough to try though.
I was thinking something with the TPS since putting the pedal to the floor makes it fire up.

Replace the Crakshaft Position Sensor.