sandstone

3 times over the past 3 weeks ( about once every 10 starts ) my stock '96 4.0 cherokee cranks but won't start until I depress the accelerator pedal about 1/2 way. All the other times it starts right up. Runs fantastic once started. I've owned it for 5 years and had no problems. No recent changes or work. No key codes and no codes or pending codes via Actron scanner. Any ideas?

98 JeepJeep

If no codes present verify condition of plugs/cap/rotor/wires and then move on to Fuel pressure.

BlueXJ

Evaluate the CPS connection. Do you notice any other similar circumstances when it won't start? Things like very humid or when warm or cold or maybe first start after sitting for two days?

Read this>>>>https://www.cherokeeforum.com/showth...ed=1#post73869

sandstone

The 3 times that it was hard to start were all humid days with temps in the 50s. However, there have been other days with identical weather when the cherokee fired right up. Today its 35 and snowing, and it fired up right away. Each time it was difficult to start, the cherokee cranked fine but wouldn't start till I depressed the accelerator more than 1/2 way down and kept it down for a few seconds. Runs great otherwise. Very smooth. As I said, this happens only intermittently, like 1 time out of 10. Still no codes via CEL flash or with Actron scanner. Also no pending codes.

Distributor cap and rotor have been on for about 40,000 miles, so I'll be buying an Accel set tomorrow.

sandstone

Thanks. I'll be getting an Accel cap/rotor set tomorrow since the cap and rotor have about 40,000 miles on them. I'll be checking fuel pressure too.

BlueXJ

If you will take a few minutes to check that CPS connection it will probably cure your problem. I sent you the write-up and a description ofwhere it is located is there too. Might take 5 minutes to locate clean and replug it. Humidity may be your connection problem.

gearheadette

Blue is 100% right, if your Cps "crank positions sensor" is not working then your engine will just crank and crank and crank, it wont allow the spark plugs to fire, cause your computer doesnt know what stroke, what cylinder is on, hense for if your cps doesnt work neither will any of your ingnition circut until you fix it. so dont waste money being a parts changer, fix it right the first time!

sandstone

I did unplug and replug the CPS. It wasn't wet or dirty. I didn't do any tests on it however. I will do so later this week. Wouldn't a bad CPS trigger a code, though?

sandstone

But why does it start as soon as I depress the accelerator a little?

gearheadette

Then you got a fuel issue, to double check, this is what i do, i spray a little starting fluid in the intake and if it starts up everytime that i do that, then it's lean, so first thing you would need to do after you do that is clean the intake, fuel rails, injectors, or if its a carb, the carberator. If it isnt your dd, when was the last time you were at the pump? Gas has a 28 day shelf life, doesnt matter how often you start it up, if the gas has been in their too long. just some suggestions.

BlueXJ

The CPS is getting and receiving a +/- 5v signal so anything that moves the connection in the slightest can effect the signal. Gas pedel can be one of them.

sandstone

It's my wife's dd. Out of about 30 starts over the past 2+ weeks, it cranked but wouldn't fire only 3 times. Each time, however, it fired up as soon as I depressed the accelerator a little. Its EFI and the TB is clean.
I use fuel system cleaners about every 3,000 miles. Last fill-up was 10 days ago with 87 octane.

I will check fuel pressure and check the CPS later this week. I'm also putting on a new distributor cap and rotor because the old ones have 40,000 miles on them.

sandstone

That might be the case. I'll check it when my wife returns with the cherokee later today. Thanks!

BlueXJ

If you do that and it cures the problem post that, so that everyone knows you have cured the problem. If you find another culprit post that as well so that we can all broaden our knowledge base.

sandstone

Will do, but it'll be a while before I know if the problem's gone, since it is very intermittent.