90 XJ Hard Start

I've got a cherokee that has an intermittent starting problem, and its been getting worse and worse. Checked the battery and its good, the starter spins and the engine turns over but it just won't start for a few seconds, starter gets slower and slower.

So I looked up the Crankshaft position sensor and it seems those are the likely culprit when this happens. I checked out the resistance of the sensor and it seems to be in speck. Did the AC voltage test accross the sensor and it doesn't seem to be putting out a voltage, but it could be my meter isn't working right, since the smallest setting for AC is 750V.

So are there any idea's on how to confirm that this is the problem? I don't want to spend the money on a new one and it doesn't do anything.

There are many threads on this. What's your fuel pressure?

On my 97 (slightly different fuel system), it's most likely a bad check valve that is allowing fuel to run back into the tank. The way I tested it was turn the key to run, hold for a second, then turn off. Repeat about 3 or 4 times and the jeep fires up on the first crank.

First, Renix have to crank more than other xj jeeps.

Second, if your battery has full charge and passed a load test, but your starter quickly slows in its cranking speed, your cables are crapping out or the starter is crapping out.

The CKP is pretty much start/no start, however I have read posts here where some state that after changing the CKP it would start sooner. That said, I would fix the slow cranking issue. Renix has to crank up to 300 rpm before it is going to start, so that needs to be fixed first.

Ok thanks for the pointers. I am sure this has been asked a thousand times, but I was too lazy to search through all the posts.

I think its just cranking slowly because the battery is drained. I don't think its a fuel thing since it doesn't matter whether I turn it to key on. Seems to make no difference.

Is there any way to positively tell its the starter that is causing the problem. One thing I noticed was that the fuel pump ballist resistor was broken. I grabed one out of a 94 XJ and no noticable difference.

Before any other diagnosis, take apart all the battery connections, starter connections and grounds you can find under the hood. Clean corrosion off with scotchbrite or sandpaper, clean debris off with electrical contact cleaner, brake cleaner or spray start, and reconnect. If you really want to, the starter can be tested for a current draw test. I'd clean the circuit criticals first, just because it should be done anyway.

Thanks alot for the help guys. And sorry about asking a much overasked question. So I swapped out the starter from a wrecked xj that I have around and it starts up great now. It wasn't the sensor after all. I banged on it while trying to crank and it gave it new life for a second. So thats an obvious bad starter.

I took it apart and it was really dirty and greasy inside, and the brushes looked kind of worn. Do you think it would work again if it was cleaned and put back together?

I have opened up starters, cleaned out all the debris (brush particles, etc) and had them work for a long time. New brushes would help if you can get them. Usually you just get a rebuilt. Depends on how tight your money is. Personally, right now, I 'm patching together whatever I can to conserve short term cash.