Should the tach move while cranking?

[tommy54]

I have a no start condition on my Jeep and am trying to figure out what is normal and what isn't, since I have spark, fuel, and compression.
The tach doesn't move while cranking, and seems to me that it should register something? Jeep is a 2000 Cherokee sport automatic.

 

[Johnnie Walker]

I'll have to check tomorrow when I start my renix, but I do not recall seeing it move while cranking.
The IP is electrical. So, I would say they don't.
Have you checked your CKP? Most common crank/no-start for XJ's. 3-pin connector, dirver-side, rear of head/valve cover. Disconnect and reconnect it. See if it starts. If so, there's your problem. Once every few months my heep crank/no-starts, so I discon-recon. and it starts right up.

 

[Ecomike]

If you have spark, it is not the the CPS (CKP). More likely it is flooding, too much fuel, leaking injector(s), or too little air. Press the accelerator to the floor, and see if it dries out and fires up. WOT shuts off the fuel injectors, to unflood it.

 

[djgrayxj]

Note from DJ
Is your no start problem when hot?

 

[tommy54]

No start at all, anytime. New CPS, airbox is clear, flooring it while cranking doesn't work. Starting fluid doesn't work, but maybe there's too much fuel in there already.
I'll try pulling the relay for the fuel pump, clear things out, and try starting fluid. I know I have spark, so clearing out fuel and putting some starter fluid in should get it to pop.

 

[Lowrange2]

How long did you try with the flooring it?

I had the same issue... Floored it for about 10-15 revolutions.

This may seem like a stupid question but give it a shot.

How is your battery? Are you having to try to jump start it?

When I bought my 98 it wouldn't run. The guy had thrown every part at it he could think of and couldn't get it to run. The engine would turn over on it's own and seemed plenty strong to start the engine but it wouldn't.

I put a new battery in it and it fired right up and I haven't had an issue yet. I'd suggest testing the battery voltage while attempting to start it. Betcha it's dropping out.

 

[Ecomike]

On the older Renix jeeps, 10 V while cranking is critical to get it to start, probably under 10 V the spark is too weak and or the engine speed to slow for Renix to spark the plugs. I have read that Renix has a minimum crank rpm below which it refuses to spark. Long story short, a too cold spark is also possible, plug gap to large, warn, dirty, weak spark coil, low voltage...

 

[ktwalker01]

Tach moves while cranking my 99 4.0 sport

 

[tommy54]

Anyone know why my tach might not be moving while cranking? I have spark, but I'm trying to figure out if the ECU is malfunctioning and not sending it at the right time, thought a lack of tach signal may be related.

 

[Ecomike]

My 89 tach does not move while cranking at all, but works fine.

My 87 will jump about once by no more than 1/8" about every 3 seconds of cranking, then drop back to zero.

 

[XJosh95]

Sounds like you've got no spark. If you know your CKPS is good, an easy check would be to pull off the cap and check the contacts on the cap and rotor. If there's some corrosion, using some sand paper or emery cloth to clean up the contacts will serve as a good bandaid.

The harder checks would be to pull out your spark plugs and check for fouling. But if you haven't replaced them in a while, now is a good time to go ahead and do that. Plugs and wires. If they look good, move on to the coil.

As I was typing this, I looked up and read this. Why do you believe you have spark? If you've tried starting fluid and had spark, it would have ran...

Anyone know why my tach might not be moving while cranking? I have spark, but I'm trying to figure out if the ECU is malfunctioning and not sending it at the right time, thought a lack of tach signal may be related.

I would hate to condemn a ECU so soon in the diagnosis...Also, your ECU shouldn't be getting confused about spark since you have a distributor telling the spark plugs when to fire. Unless you have jumped teeth on the timing chain or sheared teeth on the distributor shaft, your timing shouldn't be an issue.

Edit: 2000...is that coil on plug? Then your computer would control spark...and my advice for looking at the contacts is moot.

This is just odd all around.

 

[tommy54]

The 2000 is DIS, no distributor. I tested for spark by removing the coil rail, putting a plug in the boot, grounding the coil rail and plug, and cranking the engine. Good spark on every boot. Man, what I would give for this to have a dang distributor.
I have spark, fuel, compression, and air. There is no way to put a timing light on the motor to make sure the spark is happening at the right time. I also can't get a code reader to communicate with the TCM. All seems like some computer glitch.

 

[XJosh95]

So it cranks normally? It doesn't sound choked or anything?

The only other thing I could blame before an ECU would be a camshaft position sensor. But it still wouldn't get spark IIRC.

 

[old_man]

Wet fouling the plugs is a chronic problem with XJs in a no start situation. I would pull all the plugs, hold your foot to the floor and crank it over several times. I also recommend a fresh set of plugs.

 

[tommy54]

old_man: I will be trying all of that, I have put in a new set of plugs even though the other plugs still seemed fine. I need to figure out a way to make sure that my spark timing is correct, once I know that I will know that I've either got weak spark, or a fuel problem.

XJosh: It doesn't sound choked. I pulled the airbox tube off and am going straight to the TB. Cam sensor supposedly only affects injector timing. Nobody has ever officially stated the other things that a cam sensor signal affects. It is aligned, and seems to be working.

 

[Ecomike]

The 2000 is DIS, no distributor. I tested for spark by removing the coil rail, putting a plug in the boot, grounding the coil rail and plug, and cranking the engine. Good spark on every boot. Man, what I would give for this to have a dang distributor.
I have spark, fuel, compression, and air. There is no way to put a timing light on the motor to make sure the spark is happening at the right time. I also can't get a code reader to communicate with the TCM. All seems like some computer glitch.

You said TCM, I assume you ment PCM?

If the code reader can not communicate check the fuses, and see if an ignition or computer fuse is blown. My daughter's Saturn was a no start recently, and code reader could find the PCM, the PCM and 2 other fuses were blown from trying to jump a dead battery...long story....kids...

Are the injectors actually firing?

 

[tommy54]

Code reader can communicate with the engine, but when it tries to read transmission codes it says that it can't communicate. I know this model has a TCM, so I assumed that it must communicate with a code reader independently from the PCM. Anyway, maybe there is nothing wrong, and the particular code reader is trying to do something the jeep can't do. I don't know for sure, I'm just trying to track down any little things that might lead me to the cause of the no start situation.

 

[Ecomike]

All the automatics since 1987 have TCMs. But communication proto-call is another issue. Not sure if the OBD-II can chat in 2000 models or not

 

[crimsondragon]

When you initially turn it on, the CEL comes on then turns off. Is it coming on?

I don't recall the tach suppose to move as all power is closed off and sourced to the starter.

 

[tommy54]

Yeah, looks like all the lights go on, then go off, like they are supposed to. I think you're right about the tach not working until the engine starts. I just thought maybe I wasn't getting a tach signal(ECU maybe not interpreting crank sensor signal) that I should be getting. Looks like this has nothing to do with my no start problem.