Cranks forever until starting

I have a 1995 Jeep cherokee, It will just crank over for way to long until it fires up. Then sometimes it starts great. I replaced the Fuel pressure regulator and that didn't help. Also once its running it runs great with no missing or anything. Could it be a relay or a loose connection or something?

Thanks guys

Colin

CPS

Check battery cables too as slow cranking will make it take longer too (esp on a Renix).

Jeep cranks very strong and fast as it should. It also has a brand new battery.

badgator said:

CPS

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x2

Check/clean/repair/replace grounds (a failing ground can cause long cranks due to shonky sensor signals.)

Check/replace Crankshaft Position Sensor.

I'd put my money on the grounds first, tho. There are, I think, four that should get your main attention:
1) Ground strap from engine block to firewall (both ends)
2) Ground connection from battery to chassis at fender liner
3) Ground connection from battery to engine block at dipstick bracket (near distributor)

Clean chassis parts down to bare metal (small patch - about the size of a postage stamp - will do) and apply corrosion inhibitor on reassembly.

Also, check the make sure the braided ground strap between the engine and firewall isn't itself dirty - this can cause "signal drain," and give you all sorts of headaches. It's OK to replace this with a proper cable - I do it all the time (the braid is cheap, and bad to use. But, it's cheap.)

Also check your fuel pump, I had this problem, changed many parts and a new pump solved it, although it had to die before I figured it out.

Other times the Jeep will start just fine when I let the pump prime for a second or two. Could it be the fuel pump relay?

Thanks

not sure what year they stopped this configuration,but on my 92,the check valve in the fuel pump was bad,letting pressure bleed out of the lines and the engine would crank until fuel got to the injectors. you can check this by hooking a fuel pressure gauge up to the shraeder valve on the fuel rail. it should hold pressure after the key is shut off. my 92 would drop pressure almost as soon as the key was turned off. a new fuel pump fixed the problem for me. start in less than 3 seconds now most times I start it.

The usual suspects have been identified.

Check and clean the connector for the CPS near the back of the valve cover. The connector can be problematic even if the CPS is good.

Ground issue are notorious for causing intermittent problems.

A quick check on the fuel pump it so turn on the key and let the pump run up the pressure. Turn it back off for a 30 seconds and turn it back on. It should run for a shorter time as the line should maintain the pressure from the first time.
If it run the same amount of time it could mean the back flow valve is gone or you have a leak.
To check for pressure at the fuel rail you will need a fuel pressure tester. There is a valve on the fuel rail for that. But if it does run good when started I do not expect that to be the problem.

I can almost GUARANTEE that it is your full pressure regulator. Put a fuel pressure gauge on the check valve on your fuel rail. Start your vehicle. Check the pressure (should be about 32psi). Turn off your engine. If you now have 0 pressure, it's your regulator... an extremely easy to replace and relatively cheap (~$70) part to replace.

I will try checking the pump and cleaning the CPS, I already replaced the regulator and it didn't fix the problem so I returned it.

Thanks