I have a 2000 Grande Cherokee Laredo. Auto. 4 litre. I did a search but couldnt seem to find my exact problem.

It started getting hard to start a few weeks ago when it is cold. You have to crank it over for a few seconds stop and repeat until it fires up. You can cut it off and it will start back just find within say 5 minutes. Any longer and same issue.

I hooked up my fuel pressure gauge to check the pressure. When you turn the key the pump does not come on. I verified this by getting underneath and listening for it to kick on. No matter how many times you cycle the key, nothing. After turning it over a few cycles it will kick on jump up to pressure and fire up the engine. Runs fine no stumble. No pressure flux. Turn the engine off but leave key on and pressure slowly drops to nothing. Cycle key and pressure jumps back to 50 and slowly bleeds off.

So, I am thinking fuel pump. I replaced the filter this morning to no avail. Any suggestions before I drop the tank?

 

Only other thing I can think of is to get into the power distribution center (black box under the hood) and swap the fuel pump relay with another.

When you turn the key to the ON position, by design, the fuel pump should immediately kick on and run for about 2 seconds. Yours isn't doing that. The relay is a long shot, but should be ruled out by a simple relay swap before dropping the gas tank and replacing the fuel pump assembly.

The "bleeding off" of fuel pressure though is likely one of the check valves on the fuel pump assembly. A VERY common problem on your vintage. But a bad check valve in and by itself should NOT prevent the pump from immediately energizing when you turn the key to the "on" position.

So I think you have 2 things going on.

 

Thanks I will go check that now.

 

Sounds to me like you have two problems. The long start/no start/no power to fuel pump could be being caused by your CPS. The fuel pressure bleed down is likely from the check valve in your fuel pump. In either case, you will likely be changing a fuel pump, then onto the CPS. I will be changing the fuel pump on my 92 tomorrow. I did a pressure test today, and it dropped almost 30psi in 30 minutes.

 

It was not the relay changed them out and have same issue. CPS as in the main computer? Going to hit the web and find a fuel pump deal.

 

Pump Assembly is $164 at Advance. Anyone know of a better deal online? That's for an Airtex.

 

Don't let price drive the bus here. You get what you pay for with fuel pumps. Big time.

I will not install nor will I recommend Airtex. Search for Jeep Cherokee and Airtex fuel pump and you should be able to find plenty of other supporters.

Bosch is my favorite brand. Carter is my second favorite. I don't have a third favorite.

 

Found a Bosch online. Going with it.

 

Very wise choice.

 

CPS = Crank Position Sensor. It's mounted up top of the bellhousing in back. You might barely be able to see it by looking from the driver's side down the back of the engine where the bellhousing attaches.
It's function is to tell the PCM which cylinder to fire, by sensing flywheel/flexplate position. If you have consistent spark, it's working.

 

Let me share an update with you guys. My 92 has been acting very similar to his and I have replaced the CPS (Crank Shaft Position Sensor)again, then today changed the fuel pump (which is a good thing because turns out there was no pre filter on the pump or in the tank and when I tested the pressure it dropped from 35psi to 11psi in about 30 minutes). After changing the pump, I drove about 10 miles, highway city and backroads. The vehicle performed great. We let the kids take the jeep out tonight, and it started stumbling and stalled a couple of times all over again. Turns out it is the camshaft position sensor (not crankshaft position sensor) also known as the distributor pickup coil. Its about a $60 part. I know it is bad because with the engine running I started checking wires. As soon as I lifted up on the wire from the cps (thin flat wire that comes out of the distributor and plugs into a harness on the firewall going to the computer)the engine stumbled and stalled. I repeated this 4 or 5 times. I know exactly what the problem is now.
I hope this will help others.
**Note** Changing this part is a bit involved for a newb, but the Haynes Jeep manual outlines the procedure fairly well.

 

I see that too.
The PCM is supposed to command the Fuel Pump on for about 5 seconds when the key is turned to "ON", then hold it on while the key is in start. Only then does it look for the CPS signal, if it sees a rotating engine it holds the pump on when the key is released back to "ON". Else it shuts it off again.
I'd put a DVM or test light on the fuel pump power connector and see if power is there when the key is first turned "ON". There should be. If there isn't there is a problem other than the pump itself.