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chrkjpn
01-27-2010, 08:07 PM
Got 90 xj 4.0 built motor, The jeep always takes a long time to first start after sitting. Prob 15 seconds. When it does it acts like it is coughing or trying to crank then will fire up. If i shut it down and start again it will fire right up in prob 3 seconds. It just does this on the first startup. Any ideas?

Mudderoy
01-27-2010, 09:52 PM
Have you ever replaced the CPS?
Have you checked and cleaned the CPS connection?
Fuel line pressure checked?
Fuel line filter changed?

If you turn the key on and let it sit for 15 seconds, then try to start it does it start up quicker?

BlueXJ
01-27-2010, 11:12 PM
All good questions and we need to hear your answers before proceeding further. Many times the Throttle Body is very nasty and can be a contributor to a slow start up too.

TheWeiss
01-28-2010, 01:30 PM
What is a CPS?

Mudderoy
01-28-2010, 02:00 PM
What is a CPS?

Crankshaft Position Sensors


Some 1989 and early 1990 vehicles equipped with the 4.0 liter engine and automatic transmission may experience an engine no-start, hard restart, or an engine die-out. This condition may be caused by low signal strength from the Crankshaft Position Sensors (CPS) due to a larger than desired distance to the flywheel sensing ring.

What you need to do is check to see if the vehicle has a slotted crank position sensor. If the vehicle is equipped with a slotted crank position sensor, Figure 1, check to see if the CPS grommet on the top of the transmission bell housing has been updated,see Figure 2. If the CPS grommet has not been updated, replace the CPS grommet.

:link: (http://autorepair.about.com/cs/faqs/l/bl557h.htm)

kryptonitexj
01-28-2010, 03:03 PM
My '91 does this but I know the problem is the fuel pressure regulator. Its $60 from the parts store I just haven't gotten around to it (I just cycle the ignition a few times to prime the rail before starting it after its been sitting for a while, this normally help it start quicker ). If you have a fuel pressure tester put it on the rail and take a reading before you start it up in the morning you should have 39psi at all times on the rail. If you don't the the regulator is bleeding back down into the tank. hope this helps.

Mudderoy
01-28-2010, 03:21 PM
My '91 does this but I know the problem is the fuel pressure regulator. Its $60 from the parts store I just haven't gotten around to it (I just cycle the ignition a few times to prime the rail before starting it after its been sitting for a while, this normally help it start quicker ). If you have a fuel pressure tester put it on the rail and take a reading before you start it up in the morning you should have 39psi at all times on the rail. If you don't the the regulator is bleeding back down into the tank. hope this helps.

Could a leaky injector(s) cause the same problem?

chrkjpn
01-28-2010, 04:56 PM
Yes everything is bran new, New motor, whole fuel system. Tps,cps everything new. I tried it today and pressed gas pedal a few times b4 starting and it fired right up. Also ne fuel pressure regulator,injectors, everything pretty much new.

96xj
01-28-2010, 06:09 PM
What is a CPS?

http://i642.photobucket.com/albums/uu147/96xj/good.jpg

http://i642.photobucket.com/albums/uu147/96xj/2-1.gif