Getting fuel and Spark no start

[nmcommando]

Well I currently replaced the motor on my 1994 jeep cherokee. but for some reason the it just wont start and stay running.

Some background for you i put it in and made sure all the pieces were in right it wouldn't start so then i threw my codes and got my throttle sensor and map sensor replaced them both. After i did this it started but ran really rough it would overheat just driving 4 or 5 blocks at 35 mph. My jeep had been sitting for a while so i figured it might be running rough because of bad gas so i dropped the tank and it had water in it emptied all the water and gas and put fresh premium in it. Then i went to start it again and there wasnt any spark i replaced the coil because it had gone bad and magic it had spark again. But now it's getting spark and fuel and when i go to start it after a couple try's it will jump up to about 1000 rpms but die right away i mean not even long enough to know it's running.

Thanks any suggestions

 

[jfiscus]

map sensor & cps are about all that'll cause it not to start if injectors are firing & fuel pressure is correct.

 

[winterbeater]

Do you have the ballast resistor going to the fuel pump on your year? If so, you can jump around that. When you go from start position to run position, the ballast resistor comes in to the circuit. I'd pull a spark plug too, just to verify that they aren't fouled.

 

[nmcommando]

Ok the spark plugs are brand new i forgot to mention that but it's my second set and both times after a couple try's to start it the spark plugs are black and kinda carbon fouled does that help any Thanks again

 

[winterbeater]

Is that a rebuilt or a JY motor? Have you checked the compression? Spark plug and injector wires on in the right order? Maybe you should clean the plugs again. Spray them good with spray start and put them back in.

 

[jeepster_259]

computer? when my comp. went bad the jeep would run for 20 sec. or so and die. replaced the comp. and has run fine since.

 

[gradon]

Did you sync up the cam position sensor when the engine was installed?

 

[CharlesS]

IF you Jeep has the factory tachometer...; what is the tach doing while starting the engine....
IF the tach is not registering RPMs... then I would look at the CPS and its connector....
IF it does register RPMs....; then I would check the other engine sensor connectors for debris on the terminals and proper insertion....
Pay close attention to the MAP, IAC and TPS....

 

[nmcommando]

Ok the spark plugs when i pulled them were carbon fouled a little and it's all in the right order how do u sync up the cam position sensor

 

[winterbeater]

For more ideas please see PM.

 

[birchlakeXJ]

You really gotta verify fuel pressure at the fuel rail. If you have good spark, fuel is suspect and takes all of 5 minutes to verify fuel pressure. If you don't have a gauge, rent one. This is a methodical process of elimination; test your way to a solution.

 

[nmcommando]

Ok i got it running but now it's running rough and has almost no power; it idols really well but if you leave it in neutral and rev it up to about 2500 rpms it really rough getting it there and when you take your foot of the gas a sound almost like a backfire but it's just air shoots out the exhaust any ideas

 

[winterbeater]

Was this a JY motor? How does the compression check?

 

[89xj]

Ok i got it running but now it's running rough and has almost no power; it idols really well but if you leave it in neutral and rev it up to about 2500 rpms it really rough getting it there and when you take your foot of the gas a sound almost like a backfire but it's just air shoots out the exhaust any ideas

that souds like a timing issue:

the dizzy may be off a few teeth or 180 out.

bad cps

 

[winterbeater]

Make sure spark plug wires are in correct order and position on the cap.

 

[jfiscus]

What did you do to get it to run????
Are all the injectors firing?
Is the fuel pressure correct?
Is your timing right?

 

[gradon]

Check this pdf out to learn how to sync up the cam sensor:
http://motorage.search-autoparts.co...estandard//motorage/292005/169830/article.pdf
In summary, pull spark plug #1, Have a helper put their finger on the hole, rotate crank pulley until it's @ 0* and air is blown out #1(If it didn't happen the first time, rotate crank another 360* to get to the end of the compression stroke). Next pull out distributor, remove distributor cap and rotor, once rotor is off you can remove the cam position sensor plate. Align the outer hole in the ring(by the vertical metal half circle thingy, as there is a 2nd one that is used for 4cyl) with the hole in the housing and put the toothpick in. Set the oil pump to 11-o'clock, start rotor at 4-o'clock, and drop the dizzy.

 

[nmcommando]

To get it to run i replaced the cap and rotar and the crank postition sensor then it started right up but now it's is running really rough so i thought the problems might come from my exhaust so i took the catalytic converter off and then it runs a little better but not a big enough deference to really count and sometimes it seems to have good power but then will go away almost instantly, it has good fuel pressure seems to be coming out well i dont know if the timing is right or not but the number one is in the right spot

 

[winterbeater]

Good to check compression before chasing more parts.

 

[ChevelleSSLS6]

From a sorta kinda noob-
Check fuel pressure and flow. Just because you have fuel, doesn't mean you have pressure and the flow needed at higher rpms.