Engine just cranks sometimes.

I Just bought this Cherokee 3 days ago, it is super clean and runs good. It had a few little problems but no big deal right? Well...........Problem One is sometimes it will just crank and no start. When it does start it runs great. I figured it was the CPS so i go and pick one up and put the new one in. I noticed that the old one looked pretty clean when i took it out so i started getting leery and sure enough after a couple of starts it it just cranked. So i took the new CPS out and put the old one back in(needed my ninety bucks back). So then i put a test light on the plugs and i have good spark when it just cranks. Then I thought maybe it was a fuel problem. I checked the schrader valve with my finger nail and no fuel Sure enough I sprayed a little ether down the throttle body and it fired right up and ran. Now i'm stumped it runs great once it starts and the issue with it cranking only happens every once in a while(mostly when I try to start it after its sat a while). It's defiantly starving for fuel on start up but WHY? Problem 2 the dealer i bought it from said the fuel gauge is inaccurate it is on empty at around 1/4 of a tank (i haven't ran it enough to find out for sure). Problem three the exhaust pipe hits the transmission mounting cross member(barely) the pipe is new is there a difference between the exhaust for a automatic and a 5 speed, maybe they put the automatic exhaust on the Jeep on accident(mine is a 5 speed)? Problem 4 the clutch pedal seems stiff it could be I'm just not used to it the clutch seems to operate fine. Any help would be appreciated.

P.S. It's a 1998 Jeep Cherokee 4.0 5-speed 121000 on the ODO No Check Engine light No codes checked with Acutron

There is a check valve made in to the fuel pump do a naxja search on the fuel pump but it has been kown to leak and the pump has to reprime

as far as the gas gauge get you a gas can with gas and just drive till it runs out and see how far it will go that way you will no for sure

wf_s10 said:

as far as the gas gauge get you a gas can with gas and just drive till it runs out and see how far it will go that way you will no for sure

Click to expand...

That would work for the short term but I would like to fix it, I'm kinda anal like that. I was think that this maybe part of just cranking problem, or it could just be the resistance of the sending unit is off.

Alright, A little update. Now the cranks won't start has turned into a sometimes it will crank and not start other times it will crank, start and run rough. I managed to get a fuel pressure gauge on it tonight while it was running rough and the fuel pressure was all over the place. When the pump primed it was at 45 psi then it would go to 20 then 15 then 30 and well you get the idea. Also after I drove it about 25 miles today. I shut it off and could hear a strange gurgling coming from the gas tank.

Okay starting to get this narrowed down. When the engine just cranks the pump is not priming so it's intermittent. Sometimes when the the key is on the pump primes sometimes it doesn't. When the vehicle starts and runs rough I'm assuming the pump is running intermittently. So what is controlling power to the pump? The ECU? My understand of the system ECU provides low amperage power to the fuel pump relay the relay closes providing high amperage power to the pump so maybe its the relay? Any Ideas? Not many responses to this thread; Does anyone have any ideas?? Anything?? What is the strange gurgling coming from the tank?

Are all your tune parts fresh ? Used some fuel injector cleaner, and cleaned the Throttle Body ?

The gurgling is the failed check valve. You can replace the fuel pump and ASD relays.

You have to pinpoint the no-start to either the CranKshaft Position Sensor, The Camshaft Pickup Sensor or the Neutral Safety Switch (NSS) by testing. The NSS can be cleaned and adjusted. The CPS can be tested and it has other visible symptoms besides a no-start.


Check Valve

When your 1997 to 2001 Cherokee won’t start on the first try day after day, the first thing to suspect is a failed check valve on the fuel pump. The fuel pump check valve is supposed to hold pressure in the fuel line while the engine is off. The check valve is located on the fuel pump and located in the gas tank. A failed check valve allows the fuel to drain back to the tank. This results in the following symptoms:

SYMPTOMS

• Longer than normal cranking times
• Never starts on first try, almost always starts on the second try
• Rough idle for a few moments of idling
• Rough running for first ½ block of driving
• Little or no fuel pressure at the fuel rail test valve similar to this -

1- Key in on position; fuel pump primes for 2 seconds then stops. 0 PSI
2- Cranking over the engine. 2-3 PSI
3- Engine starts and idles for 20 seconds. < 5 PSI
4- Engine idles and fuel pressure creeps up to 45-50 PSI.


POSSIBLE CAUSES

• Failed check valve on the fuel pump in the gas tank.
• Leaky fuel injector(s) may be the true cause of your problem, but more likely they are simply contributing to the check valve issue.

Testing of the fuel injectors should show if any are faulty and are allowing fuel to drain into the cylinder. Either problem can allow heat soak to vaporize the remaining fuel in the fuel rail and you may be dealing with a bit of vapor lock as well, especially in warmer weather.

1. Connect the gauge at the fuel rail and start the engine. The gage should read 49 psi plus or minus 5 psi.
2. Turn the engine off and immediately clamp the fuel line just ahead of the fuel tank. Watch the pressure gage and see how long it takes to loose pressure.

If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - probably the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky injector.

There are a few solutions to the problem –

1. Turn the key to ON for 5 seconds and let the fuel pump prime. Turn the key to OFF, turn the key back to ON for 5 seconds, start the engine.

2. Crank the engine for 3-5 seconds, pause, and crank the engine again. It will almost always start on the second try.

3. Replace the fuel pump assembly in the gas tank. The check valve is not a separate part and cannot be serviced. This is both expensive and time consuming because you have to remove any hitches and skid plates and then remove the gas tank from the vehicle.

You can use solutions 1 or 2 for as long as you want to, they do not harm anything and the fuel pump will continue to function for many more years.

If you do replace the fuel pump assembly, purchase a high quality OEM style unit. Some cheap aftermarket fuel pump assemblies, like Airtex, don’t hold up and fail completely within 12-18 months.

The gurgling noise is from the filler neck check valve. It's a very common issue on '98
model XJs. There's a TSB on this. The original spring is a bit weak to hold the float ball
tightly. A revised spring is available from your local Jeep dealer. It's basically harmless
and many owners will forgo or delay fixing it because of the hassle of having to drop the
tank to access it. My car does this also, but I'm waiting until I need to swap out my fuel pump to do this as I've got a dodgy fuel gauge sender.

I didn't know about the check valve in the pump thanks Tim_MN but this still doesn't tell me why sometimes the pump kicks on when the ignition switch is keyed on and sometimes it doesn't. Hopefully, I get a chance to work on it this weekend.

Before performing any major surgery - have you tried swapping the fuel pump relay?

It's located in the fuse box on the starboard side of the engine compartment. It's location
is indicated on the inside cover of the fuse box. The part is a generic relay that can be
had at most auto parts stores (~ $10).

Double-post erased.

It looks like replace the fuel pump relay has fixed the the issue I was having some of the with the pump powering intermittently. Now to begin with some of the other problems.