Hard starting issue

[djcherokeexj]

1992 Cherokee Sport, 4.0, 5-speed.

Been having issues with hard starts ever since I owned this Jeep for about 4 months now. It starts every time, but takes about a decent 5 seconds or so of cranking for it to fire.

Goes something like this: turn key, cranks for a second, does a quick sputter like it's about to start but doesn't, continues to crank for a few more seconds, then fires. I replaced spark plugs, wires, cap, rotor, coil, fuel filter, and air filter. Cleaned the throttle body, checked for vacuum leaks and even seafoamed the engine. Still starts the same way.

Did a quick search and it seems I may need to replace my cps sensor. Could it be my o2 sensor? Figured I'd ask before I keep throwing parts at this problem. I hope it's not the fuel pump.

Thanks for any help guys.

 

[krelja]

I was having an issue similar to yours and it looked like it was the check valve for fuel. I never fixed the problem but have seen write-ups about using bmw ones and other fixes. A way to check and see if thats it before you crank the heep over cycle the key in the ignition a few times to prime the fuel pump and get fuel to the rail. If you cycle the key on off on off start slowly and it still doesn't work hopefully someone else will shime in before you throw to much money at it

 

[wim hoppenbrouwers]

Hallo '92 Jeeper.
Time to buy a fuel pressure gauge. You can see very easy or the pump is keeping the pressure in the fuelrail on the right PSI value.
To change the O2 sensor is always a good idea for the fuel consumption.
To change the CPS sensor is an important maintenance item after many miles of duty.

Greetings '92XJ Wim.

 

[birchlakeXJ]

You are most likely experiencing a loss of fuel pressure somewhere in the line. The extended crank times is the time it takes to get the pressure back up to a point where the engine will start. WM is right in that a fuel pressure gauge can be helpful in isolating your problem.

Try this procedure. It's called "the poor mans prime".

1. Turn key to ON position. DO NOT CRANK THE ENGINE. Fuel pump should energize and run for 2 seconds
2. Turn key to OFF position
3. Turn key to ON position again.
4. Repeat above one more time for a total of 3 ON/OFF sequences
5. NOW crank the engine.

Does it start quickly and cleanly? If so, you've verified the loss of pressure.

An extended crank time where the engine eventually starts and not having any other symptoms is not the crank sensor.

 

[silverlakexj]

I have sort of the same thing on my 99, I just turn the key and let it build pressure for a few seconds and havn't had a problem

 

[heyhar]

Sorry to resurrect an old thread, but I may have the same problem. My '96 just began needing a lot of cranking to start first time of the day. This morning, I checked at the Shraeder valve, and had nothing. Primed the pump, plenty of pressure. Started a little quicker. Once it starts, it will start and run the rest of the day just fine. Does the pump have a check valve? Or, at 146k and 14 years old, is it time to replace the pump? Thanks!

 

[joe_peters]

Sorry to resurrect an old thread, but I may have the same problem. My '96 just began needing a lot of cranking to start first time of the day. This morning, I checked at the Shraeder valve, and had nothing. Primed the pump, plenty of pressure. Started a little quicker. Once it starts, it will start and run the rest of the day just fine. Does the pump have a check valve? Or, at 146k and 14 years old, is it time to replace the pump? Thanks!

I always get confused on the change over years. Does your 96 have a fuel pressure regulator with vacuum line attached at the front of the fuel rail? If not, does it have a round disc-type dampner mounted on the fuel rail?

Asking because if you have the pressure regulator on the fuel rail then there is no problem adding an in-line check valve between the tank flange and the external fuel filter, 3/8" line, seller on eBay jbass195 sells them for $14 plus $2 s/h.

Now, for the questionable part--I was told by another poster here that he installed an inline check valve on a later model XJ, one without the pressure regulator on the fuel rail, and his dampner blew off the fuel rail. Another poster later said that couldn't happen, no way, no how, and that an inline check valve on the later XJs is fine.

So, search, and make up your own mind.

 

[heyhar]

Joe-The '92 and '95 have the vacuum fitting and black disc (return line?) but neither of the '96s do. Kastien suggested on a thread I started that '96 is a stand-alone year-no regulator on the rail, but different than '97+. How long can I go with it in this condition? My '98 ZJ 4.0 started acting like this, and in a few days it was toast, although it was most likely due to the plastic tank. It was dissolving, clogging the screen and overheating the pump motor. I've got the time, as I'm laid-off, but don't want to throw the money into the car right now....

 

[joe_peters]

Joe-The '92 and '95 have the vacuum fitting and black disc (return line?) but neither of the '96s do. Kastien suggested on a thread I started that '96 is a stand-alone year-no regulator on the rail, but different than '97+. How long can I go with it in this condition? My '98 ZJ 4.0 started acting like this, and in a few days it was toast, although it was most likely due to the plastic tank. It was dissolving, clogging the screen and overheating the pump motor. I've got the time, as I'm laid-off, but don't want to throw the money into the car right now....

Well, other than taking longer to start there is nothing going to be damaged, as long as you don't crank the engine for more than 15 seconds at a time--more than that it will heat up and shorten the starter's life. Using the poor-man's prime, turning the key ON, wait 3 seconds, repeat 2 more times before cranking works well, it may lead to a switch failure prematurely.

You could try the inline check valve, noting the caveat about the fuel dampner on the fuel rail, or pull the pump assembly and install one of the BMW inline check valves in the fuel pump assembly.

This is a judgment call for you. Wish I had a more definite answer for you.

Good luck.

 

[5-90]

My thoughts?

Many automotive electrical issues come back to failed/contaminated grounds. Have you checked yours lately? A bad main ground will cause a slow crank, a bad chassis ground will cause dirty signals (and a dirty CKP signal is often a problem. RENIX had a TSB for rewiring the CKP directly to the ECU for severe cases, when everything else had been seen to...)

A refinement of "hard starting" may be in order tho - are we talking about simply long crank times, or is it slow cranking that winds up before the engine starts? Both are different problems, and usually have different causes...