my 89 xj has an issue i cant figure out. it will not start without some help. a spritz of carb cleaner in the air inlet tube and a few cranks, it fires up. its a 4.0L automatic. ive changed the crank position sensor (fixed part of my original issue), coolant temp sensor (on engine block behind exhaust mainifold, plugs, wires, cap, and rotor.

once i get it started it idles and runs fine...its just the initial starting thats the problem. you can hear the fuel pump turn on and run, and theres fuel pressure to the injectors, and has spark....

any ideas? any help is appreciated

 

When you start it, try priming it 2 or 3 times and see if it starts easier. Your fuel pump could be on its way out?

 

Has great fuel pressure...would it still have good fuel pressure when the pump is going bad?

 

Try the "poor man's prime" as krazyness suggests and report back.

 

turn the key on and allow the fuel pump to prime for a good few seconds like 5-10 then turn off and repeat a couple of times before u try to crank it

 

I have noticed that if I have the fuel rail disconnected and turn the key on no gas pumps out but wen I crank it gas pours out

 

Ill try it...see what happens. So if it starts after the "poor mas prime" my fuel pump is bad or going out?

 

Im going to work on the xj a little tomorrow...ill give it a try..

 

Going out but it could be fine and could be something else

 

Hmm...ok ill post after i give it a try later on today...

 

Ok...tried the poor mans prime...no go. My buddy said he wants to try a volume test before i go buy a new pump.

 

It will start when its nice outside. 60 some degrees the other day..after i got it started initially..it would start like normal after that....man im confused...

 

Test your CPS output even though it makes no sense that it will start with starting fluid. We need to know it's output. It could be borderline, and they are affected by temperature.

Renix CPS Testing and Adjusting
　
　
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
　
Revised 11-29-2011

 

mine did this on cooler mornings ended up being map sensor

 

How about a temerature sensitive fuel pump relay? Just for fun, juggle the relays in that pack of four on the passenger inner fender so they're all in a different place.