I have a 1996 Cherokee that takes from 4-10 minutes of intermittent cranking to finally start. Replaced injectors, fuel pump and filter. Replaced crankshaft position sensor last summer when the truck died. Auto zone checked battery, alternator, starter with their diagnostic tool. The garage says they checked for spark and no problems. After the vehicle does start, it will run just fine.
What should I try now?
Thanks
So…after one shop had the Cherokee for 2 weeks and changed the fuel pump, filter, and sending unit, I have moved to a different mechanic. The new mechanic tested everything and settled on the ECM. We got a new ECM and the Cherokee starts immediately and runs like a dream. However, the ac doesn’t work. The second mechanic reinstalled the old ECM and the ac works just fine. So ordered a new ECM and the ac still doesn’t work. The ECM does not send enough voltage on the ground circuit to start the compressor. We’re now looking for an ECM from a different company hoping that it’s just a programming issue. I prefer to have the vehicle start every time and do without the ac, but would like to have both. I would never have considered the computer. Hopefully this will give others another idea on what to check. Thanks for the help and I will continue to update.
Did you use an OEM crank sensor or, if not available (they may have been discontinued), a leading brand such as NTK? Those vehicles don't take well to most aftermarket sensors but there have been reports that the NTK brands work OK.
How old are your plugs, wires, and distributor cap?
Any codes?
Did you check the starter itself? That could be the culprit.
Auto zone says starter, battery, alternator all good
Not sure which sensor brand was used. A shop in the middle of Kansas changed it. At that time, the truck stalled on the highway and would not start. Not sure about the age of plugs, etc. But the mechanics are assuring me the spark is ok. This morning it took 14 minutes to start. I can hear the fuel pump running when the key is turned on. Once it gets started, it will start and run fine unless parked for longer than an hour. No codes are being thrown.
Not sure which sensor brand was used. A shop in the middle of Kansas changed it. At that time, the truck stalled on the highway and would not start. Not sure about the age of plugs, etc. But the mechanics are assuring me the spark is ok.
If the engine is in good condition internally and you have fuel, spark, and air in correct measure the engine pretty much has to start. So on a cold start you are missing at least one of these items. You hear the fuel pump running but have you checked pressure at the fuel rail? How old is your fuel filter? Are your fuel injectors clogged or dripping? How old is your air filter? Do you have any vacuum leaks leaning out the mixture? (Cold start requires a rich mixture and fuel injection runs open loop when cold.) How old are your distributor cap, rotor, and wires? Have you checked for codes and suspicious readings in live data? (1996 is first year for OBD2.) That thing is going on 27 years old and almost anything could be wrong with it.
You can verify if spark is actually OK by spraying some starting fluid into the intake when the engine is cold and crank it. If the engine briefly fires up you have spark. If it doesn't, you don't have spark. You should also verify condition of the spark plugs. You didn't specify whether you have the 2.5 or 4.0 engines but plugs are easy to get to on either of them.
Not sure of the age of spark plugs, wires, distributor as we bought this used 2 years ago. Tried spraying crc jump start fluid and tried pouring a cap of gas into intake, and those didn’t do anything. I can’t Find any vacuum leaks so far. The fuel filter, pump, and sending unit are all brand new. New injectors. 4.0 liter 6. The garage says that the fuel pressure is just fine. There are no codes, though there might be if the garage had a “real time” reader.
The only way this cold starts is if we leave the ignition key on to “prime” the system and try cranking every minute or so. It took 14 minutes this morning before I took it to a garage. This garage has thrown up their hands and says they will give back the money I’ve spent so far (around $700).
If it will not fire up with starting fluid that strongly suggests an ignition problem.
So, spark plugs, wires, etc…tune up? This sort of happened over night and has progressively gotten worse, that’s why I thought the injectors might just be getting more and more clogged
So, spark plugs, wires, etc…tune up? This sort of happened over night and has progressively gotten worse, that’s why I thought the injectors might just be getting more and more clogged
It really should fire up with starting fluid if you have spark. It would not be a bad idea to test if you're getting spark when cranking. However you could certainly have an injector problem, that's where live data might give some indication in the fuel trims. Of course you could check with noid lights to see if injectors are firing and physically check their spray patterns to see if they're clogged or leaking.
It is preferable to diagnose the actual cause of the problem rather than throwing parts at it. Since the engine runs OK once it starts we can assume it's mechanically in good condition. If your air cleaner and intake are good the engine is getting air. So logically you're either not getting spark, or fuel, or both when cranking.
https://www.fixjeeps.com/jeep-ignition-coil.html
https://axleaddict.com/auto-repair/How-to-Test-Fuel-Injectors-3-Simple-Methods