93 Jeep Grand Cherokee Cranks, But No Start

rifleman did pass the time by typing:

Delays like that sound like thermal or leak current. Dirty connectors can cause similar problems.

Did you pull trouble codes when the lamp didn't light?

There are quite a few relays in the vehicle, apart from a smattering of relays under the dash, the primary center is located in the glovebox. It holds relays for Interior lights, power door locks, horn, power antenna, heated rear window, and the security alarm relay that flashes the lights and beeps the horn.

I'm running out of ideas, short of having a local dealer put a scantool on the system and run a full diagnosis. Most sensor faults are stored but on the 93 there is limited testing ability.

Failure to start can be the camshaft position sensor or the crankshaft position sensor. It can also be the coil. Anything that causes a no-start after a couple of engine cranks will turn off the ASD relay and remove power to the ignition coil. IF you have a test lamp, backprobe the coil wire that runs to the relay center. The lamp should light when you turn the key ON and stay lit while the engine cranks. It will go out if the engine doesn't start after a couple of revs. If it never comes on then there is another issue. (dead sensor/ECU fault) but most of those should be in the diagnositc codes.

One thing you might try though is to clean the ECU connectors. (disconnect the battery + before doing this)

You will have to remove the overflow bottle to gain access to the ECU. in the center of the large connector is a bolt, this has to come out. Turn it out, wiggle the connector, turn it out, wiggle the conector..etc. Don't use this bolt to force the connector on or off, it will crack the ECU! take the bolts out that hold the ECU to the firewall then rinse out the ecu with a plastic safe contact cleaner. Do the same to the connector. A bit of sandpaper on a stick can be used to clean off some of the connectors. Put some dilectric grease (sparkplug boot grease) on the connector before you put it back.

Again, when you put the ECU back. Don't crank on the bolts that hold it down and don't use the connector bolt to suck the connector on. Press, tighen, press tighten, etc.

Also, when cleaning the connector, don't forget to clean the wire side, that's where 90% of the buildup accumulates.

I've been pulling and cleaning anything I find as I go along and no change.

There are no trouble codes. The only thing the system is holding atm is the battery has been disconnected because it was during tests.

I'm not certain the clicking I occasionally here is related to this problem or not, but since I'm not positive of whats behind the glove/dash, I thought it a possible important note. I know the fuse box has four circuit breakers in it and that one is for the alarm. Since I can hear the rear window defrost relay "click" when I turn it on and off, I was hoping the alarm circuit might do the same, but it's the only one and it appears to be working.

I've talked to a few people and the concensus is this isn't a senor problem.I'm just hoping it's not the ECM.

But would any of these cause the dash "Check Engine" light to fail to light or delay it to light?

Is the ECU the only thing that sets the "Check Engine" on and into it's diagnostic mode? I was hoping for some more light on these areas.

Um, I think the fact that it consistantly starts when the "Check Engine" light comes on on the dashboard indicates this is not a mechanical problem. The engine is sound, cept for an oil change, and no point in doing that until I can resolve this weird issue.

sounds like an intermittant connection.

could be a ground or a wire or a connector.

when the light is out, start wiggling wires.

Casper did pass the time by typing:

The ECU (engine brain) is what does all the testing and lights the Check Engine light.

Here is a few things that might help you understand how things hook up.

SBECii (the computer) pdf file.

I am back a page still, or want to be....

First off you say there is a failure issue or fatal error with the alarm. It does 'not' work because you cannot program the second key and the idiot light is flashing failure at you or not flashing when it should which is a failure. Something has to be 'broken' in that situation.

Then you said you have power at the fuel pump relay but no power back at the fuel pump.

Now you say the key sometime turns on everything properly, but most times doesn't.

I think these are related.

I would be running a booster cable from the negative battery post to something metal on the firewall to see what happens just because I live in the rust belt and see too many 'rotted where you can't see them' connections.

Then I would be trying to find out if I could bypass the alarm and security key.

Next I would be physically tracing the power from the fuel pump relay to see what is between that and the pump itself. I would just take a wild guess and figure the alarm has a cut off relay in there.

Could it be a bad ignition switch causing everything?

Or could the $tealer have screwed the alarm setting when they failed to program the second key?

Mike

I figured as much. I know the ECM is the CPU (or brain) of the Jeep. I just try to avoid talking about it because it ain't cheap to replace.

I have a few books here that contain a number of wiring diagrams, but yours are definitely easier than thumbing thru the manuals.

Thanks for the info. I am going to do a more testing this weekend.

Couple more questions...

Should the fuel pressure be exactly 31psi? When we tested my neighbor's 95' GC Laredo, his was about 20-21Psi. We expected 30, but it only went up after starting, and then to about 40-41Psi.

He replaced his ECM last summer because he thought the tranny might be getting improper signals. As it turned out, one of the tranny connections had some broken magent pieces that were the culpprit to his gear switching issues. Once he cleaned that up, it shifts fine. But it may be that his starting problem began after he replaced the ECU. He plans on swapping the old ECU back in to test. He offered me his spare to test but not sure it would work in my 93'GC Limited. (*Ref Post: 95' GC Laredo - Odd Power/Start Problem)

And your website is cool. :-)

Tough to "wiggle" the wires because the light seems to only remain off for a few seconds.So far, the longest it's been off has been about

Oh, the only two engine codes that show up are 12 and 55. I've been checking those about every three to four days and no changes. Unfortunately I do not have an ODBC checker to connect to my PC.. tho I am giving it some serious thought as of late. Thanks again!

Actually, I never said there was a failure here. Sorry if I have confused you. Let me try to set this straight...

First, neither the alarm nor the security light comes on when I attempt to start the Jeep, which is normal. Only once did it ever come on since this start problem began. I believe that *may* have been a fluke, and I only say that because I do not know enough about the system and how it all interconnects.

Second, I tried to get a second IR fob over five years ago. I think IF that were related to this start problem, the problem would have happened long before now.

Correct. Tested near the fgas tank using an OHM, both off, in RUN position and during cranking and no voltage at any time. Repeated several more times and results all the same, no voltage. But, someone said it may be that it should not have voltage, which IMHO, doesn't sound right. As for the engine relays and box, they all have voltage. My neighbor and I tested the relays and they all seem to work (click on/off normally).

When you turn the key to RUN, the four dash lights should come on...

IF all these come on when I turn the key, the Jeep starts.

IF the "Check Engine" light does NOT come on, the Jeep does NOT start.

SOMETIMES, if the "Check Engine" light does NOT come on, BUT you leave the key in the RUN position, the light EVENTUALLY comes on and the Jeep starts. So far, no way to predict if the"Check Engine" light will come on or not until you turn the key and watch the dash.

Yesterday I had a hard time getting the "Check Engine" light NOT to come on. Yesterday it seemed to want to work. Today I can't get it to come on at all... YET.

As I said, I do not know enough of the system to be certain, but my intuition agrees with you. At least so far.

I will try this over the weekend. But just to let you know, both I and my neighbor have gone over the wires several times and have not, as of yet, found or resolved anything via wires.

I asked this question earlier but only received info on how to test the security system. No replies on how to disable it.

I "heard" that the dealer will turn it off for $30 but I really want to avoid spending $60 to turn it on and off if they are not related.

IF anyone knows how to disable the Alarm/Security System, I would GREATLY appreciate the info!

Both my neighbor and I traced the wires from the engine relay compartment back and everything seems fine. We also traced forward from the connection near the fuel tank where we got no voltage but that line disappears over the axle and into the cabin and we could not follow.

I never rule anything out, but it seems tight. I have tried "wiggling" these wires (as "Scott in Baltimoe" stated), but everything remains consistant. I tend to think, and I may be wrong, but if it were the ignition, then the reults and the dash light would be responding differently. I had a bad ignition once before on a '84 Olds and that ignition was very loose. That had no bearing on the dahs (idiot) lights. That's when the dealer told me how many people screw up their ignitions with heavy keyrings. Ergo, I have split keyring... one side is Jeep only and the other everything else and the two parts come apart (Thanks Snap-On!) so weight it minimal.

Always a possibility. Since it was over 5 years ago, I really think I would have seem something occur long before now. Also, the dealer said they never checked the system in the Jeep, just worked with the IR fob and I never took it back because it didn't seem worth it since I only really needed one fob back then. It's rare my spouse uses my Jeep.

When I HAVE gotten the "Check Engine" light to come on, the only test codes have been 12 and 55. Obviously if the light is not coming on, I cannot test.

So far, the only information I have been able to find, other than all the MUCH appreciated suggestions and information here, is from this link:

Check out my next post for some more info...

~Casper

Since my last post was pretty lengthy, I decided to put my last comments in a new post along with a couple of small pictures...

Five are post-accident photos. The damage doesn't appear to be very much, but turned out to be over $3500 to date.

One is pre-accident (and clean!). I was actually taking photos that particular day of the two spare overhead consoles I have so I could put them up on eBay. They will soon go on eBay.

I do not want sympathy, but so you understand the basics of my situation, a year ago I was rear-ended and am still having physical issues (long boring story here) that make working in some positions very painful, which is why I love my neighbor's help!

Yes, the vehicle was the Jeep I am having the start problem with, and it's only been since after the accident that this start problem began. However the Jeep was repaired. The shop said "bad gas" (crapoline as Doug calls it) so since I have freshened the tank.

The worst part is while I was recuperating, my employer replaced me, so for now, the budget is really tight until I once again have gainful employment. Not having a working sucks, especially to get work.

So, when my neighbor pointed out this group, I jumped at the chance to get some Jeep info and hopefully save me some labor hours if I could fix things myself. Again, thank you all for all the suggestions!

~Casper

Photos usually can't be sent to this group, my server will kill your post because this is a text only group.

Your last and this post helped me think about things.

Impact damage changes everything!

Your Jeep wasn't 'repaired' properly, they missed something..... Bad gas my ass.

There are a mess of small black wires bolted to the engine block usually on the passenger side near the dipstick. I would check there for a broken wire also. I for sure would do the booster cable trip on the body. There might also be a ground inside above the gas pedal on the firewall.

I do not know where your fuel pump ground is located. The YJ has it on the firewall by the emergency brake pedal bracket. I would be looking 'close' at the wires in the back near the pump for signs of a pinched or flattened wire.

Does having your foot on the gas or brake make a difference. (ground theft issues)

The relay to tank connection seems to be one/the issue. If there is power at the relay for a second or 2 when the key goes to run, there 'must' be power at the pump. When you go to start, there must be power at the pump as well as the relay.

If the body ground is bad or intermittent, then you are putting the meter leads on the body to pump power at the back and you will see no power.

I run the booster cable back there from the battery negative for a clean ground tag when testing sometimes. If you have power that way, then for sure the ground is dead.

If no differences, then I would have my finger on that relay when the key was turned to see if it clicks every time. If it does, the trouble is downstream. I then would pierce the pump power wire just below the relay box to see if it has juice coming out of the relay box. I use a dab of 'sensor safe' RTV after on the pierce holes. If it doesn't click every time, then I might be thinking keyswitch, but.....

Hope some of this helps.

Mike

Sorry, wasn't sure. One day I will have to make a personal web page for just such things/occasions.

Cool!

That was another suspicion of mine, but I wanted to rule other potentials out first, if possible.

I said the same thing to the guy at the repair place but he didn't seem to get it. heh..

I plan to this weekend.

I'll ask my neighbor to see what he can see for me.

Nope, not at all.

Everytime we go to test, we get no power, but that's when there is no "Check Engine" light on either. No voltage when I crank either. Just been odd luck that the "Check Engine" has been off every time, but I'll try to get it to come on again over the weekend.

Been connecting the leads only to the terminals. Even added paperclips so they would go into the terminals better.

Gotcha.

Will try this too over the weekend

Sure does.. thanks again Mike! :-)

Btw.. I once worked with a Mike Romain at Six Flags. Any relation?

~Casper

You can post photos over in alt.binaries.pictures.autos.4x4 if your server carries that newsgroup. It is pretty empty and a bunch of us post there. I use Sony's imagestation site for my off road albums.

I am not likely the same Mike because I have no idea where Six Flags is....

Good luck,

Mike

Casper did pass the time by typing:

The 93's diagnosic system is OBD-III, not OBD-III compliant, so the modern code scanners don't work.. You have to buy a $peical one from one of a few vendors.

Casper did pass the time by typing:

No problem, hope it helps.

Thanks. :)

Just got thru posting them there. I will check out the Sony site. Thanks for the info!

Six Flags is all over. Multiple theme parks across the US. They are second to Disney. But if you've never heard of them... different Mike... but nice to meet you!

Thanks again! ~Casper