93 Grand Cherokee Startup Issues

[Bad_Wing]

Hi all,

Recently I have been having problems with my 93 Jeep Grand Cherokee.

Specs:
6 cyl. 4.0
4x4
A/C
MFI

It progressively needed more cranking time for startup in the mornings. So I reacted with a simple tuneup, consisting of plugs, wires, cap, rotor, air filter, and a fuel filter. Although this clearly improved performance while running, the startup issue stayed the same, if not, got worse.

I did the "key switch to run 3 times" fault code check. No error codes.

I noticed the Jeep did not seem to have proper fuel pressure in the mornings, so I figured it is the anti-drainback valve in the pump assembly. I decided to put in a new fuel pressure regulator and a fuel pump (thorougly cleaned the tank using an approved antibacterial soap before reassembly). No change in startup performance.

I checked all connectors and ground locations and saw nothing visibly wrong.

I figure it must be a sensor that the control module is looking for before startup. I replaced the crankshaft sensor, making sure it is mounted as close to the flywheel as possible. I also tested the camshaft sensor, it seems to be performing as expected. No change in startup performance.

I downloaded a schematic from Autozone.com and reviewed it. The problem is neither my schematic nor Hayne's repair manual clearly defines the logic to the startup process.

During some of my wrenching, I did notice two things:

First, if I leave the key in the "run" position for a varying amount of time, the fuel pump will suddenly cycle and deliver pressure to the fuel system. After this occurs, the jeep fires up like it was brand new.

I can force this condition, by turning the key to the "run" position and disconnecting the negative (-) battery cable and reconnecting it. Every time I do this, the jeep will cycle the fuel pump and start perfectly.

My theory for why this works is that if I disconnect the negative (-) cable and reconnect it, the control module doesn't have time to go through it's software and is tricked to latch the fuel pump relay, allowing the jeep to start...neat huh? I dunno?!?!

My question is, does anyone know precisely what the control module looks for before startup?

Help me guys, don't let the dealers win...keep me out of there!

[dksob81]

ok does ur CHECK ENGINE light come on, when u try to start the jeep.

email me and let me know, Joe [email protected]
and include ur list of problem, just copy/paste it from here so I don't forget what ur problem was. I get alot of email and it's hard to keep them sorted

[tdenkler]

Your coil is getting weak. exact same scenario on my 93.. these need/produce hot spark, hard on coils. hence when you reconnect battery, you surge coil too

[Bad_Wing]

As soon as I reconnect the negative battery cable, I hear the fuel pump relay latch and I hear the fuel pump charge the fuel rail. It seems to me that it's a component that the ECM is looking for before startup... I am suspecting that one of my sensors is not providing a strong enough signal...

I will still test the coil as you suggest. I'll let you know in the morning how it goes. Thanks for your help! I'd love to get this thing back to its old reliable self..

[The_Penguin]

Originally Posted by dksob81

ok does ur CHECK ENGINE light come on, when u try to start the jeep.

email me and let me know, Joe [email protected]
and include ur list of problem, just copy/paste it from here so I don't forget what ur problem was. I get alot of email and it's hard to keep them sorted

I'm a newbie here, so forgive the question..

I've seen a lot of "email me" replies here, and it strikes me as odd.
Isn't it better to keep information exchange happening in the forums, so everyone benefits?

[dksob81]

Yes this is a good idea, but u can't send pictures thru here, and it is easier to type something up especially if it is a long explaination in an email.
I always recommend to ppl when they figure out what the problem was to post the FIX on here so if anyone has the same problem they will have a good place to start

[The_Penguin]

Ahh ok. I didn't realize you couldn't post pictures.
Makes sense now, thanks.

[Caribbean ZJ]

Have The same problem, but just after replacing the pressure regulator due to gas leakage. Mines a 93 4.0 as well. takes a few seconds longer to start but runs fine. keep us posted

[Bad_Wing]

After Doing the Following:

Plugs
Wires
Cap
Rotor
Fuel Filter
Crankshaft Position Sensor
Switching Relays
Inspecting all the wires and connectors
Checking grounds
Testing the coil
Fuel Pressure Regulator
Fuel pump
Distributor/Cam Shaft Sensor

I'm extremely tired...lol
I'm having a dealer test the module.

I'll keep you all posted...thanks for your help.

[Christen]

Hi,
I'm having the same exact problem...but I think it may have something do to with the security system. Couldv you post an update on the results of taking it to the dealer? I am interested to see what the problem was....thanks!
Christen

[Bad_Wing]

Well I took the Jeep to a shop and they told me it was the PCM. So I dug deep in the wallet and had them replace it. Upon receiving my jeep the guy told me that he tried to start it about 4 times during the day, he said half of the times he tried it seemed like the timing was off. As soon as he would try again it would startup fine. He suggested I drive it for a few days and see if the computer would "learn" and make the necessary adjustments. After a week it hasn't improved so it goes back in the shop Monday. I will keep you posted.

[Dale Aeppli]

Originally Posted by Bad_Wing

Hi all,

Recently I have been having problems with my 93 Jeep Grand Cherokee.

Specs:
6 cyl. 4.0
4x4
A/C
MFI

It progressively needed more cranking time for startup in the mornings. So I reacted with a simple tuneup, consisting of plugs, wires, cap, rotor, air filter, and a fuel filter. Although this clearly improved performance while running, the startup issue stayed the same, if not, got worse.

I did the "key switch to run 3 times" fault code check. No error codes.

I noticed the Jeep did not seem to have proper fuel pressure in the mornings, so I figured it is the anti-drainback valve in the pump assembly. I decided to put in a new fuel pressure regulator and a fuel pump (thorougly cleaned the tank using an approved antibacterial soap before reassembly). No change in startup performance.

I checked all connectors and ground locations and saw nothing visibly wrong.

I figure it must be a sensor that the control module is looking for before startup. I replaced the crankshaft sensor, making sure it is mounted as close to the flywheel as possible. I also tested the camshaft sensor, it seems to be performing as expected. No change in startup performance.

I downloaded a schematic from Autozone.com and reviewed it. The problem is neither my schematic nor Hayne's repair manual clearly defines the logic to the startup process.

During some of my wrenching, I did notice two things:

First, if I leave the key in the "run" position for a varying amount of time, the fuel pump will suddenly cycle and deliver pressure to the fuel system. After this occurs, the jeep fires up like it was brand new.

I can force this condition, by turning the key to the "run" position and disconnecting the negative (-) battery cable and reconnecting it. Every time I do this, the jeep will cycle the fuel pump and start perfectly.

My theory for why this works is that if I disconnect the negative (-) cable and reconnect it, the control module doesn't have time to go through it's software and is tricked to latch the fuel pump relay, allowing the jeep to start...neat huh? I dunno?!?!

My question is, does anyone know precisely what the control module looks for before startup?

Help me guys, don't let the dealers win...keep me out of there!

HI, CHECK AND SEE IF YOUR JEEP HAS THE FUEL PUMP RESISTER ON THE DRIVER SIDE INNER FENDER IT'S A WHITE CERAMIC BLOCK WITH 2 WIRES TRY JUMPING THE WIRES IF YOU HAVE ONE THEY USED TILL LATE 93 DALE [email protected]

[oglalaed]

Originally Posted by Bad_Wing

Well I took the Jeep to a shop and they told me it was the PCM. So I dug deep in the wallet and had them replace it. Upon receiving my jeep the guy told me that he tried to start it about 4 times during the day, he said half of the times he tried it seemed like the timing was off. As soon as he would try again it would startup fine. He suggested I drive it for a few days and see if the computer would "learn" and make the necessary adjustments. After a week it hasn't improved so it goes back in the shop Monday. I will keep you posted.

Newbie alert!!! I just registered and have been riveted by this site for over an hour now. Mostly because I am getting desperate and broke due to this exact same scenario. My 94GC has had the following replaced to date and still no help.
Fuel pump, Fuel filter, CKP sensor, Distributer, Spark plug wires, Starter and Plugs. Still I have the exact same issue. Mine will not start on the first 3 revolutions (sounds like a revolution anyway), but if I let it do that then turn it off and then try to restart it... VROOOOM almost every time. Try it. The problem is that I am sure it had something to do with the premature death of my starter. I am very anxious to hear the end of this story. I would actually chip in for the cost of the dealer mechanic if it will save me a trip to the dealer, which is my next step if I can't find something out on this site. Which is pretty awesome, due to the people of course. keep us updated please!!!

[Dale Aeppli]

[quote=oglalaed]Newbie alert!!! I just registered and have been riveted by this site for over an hour now. Mostly because I am getting desperate and broke due to this exact same scenario. My 94GC has had the following replaced to date and still no help.
Fuel pump, Fuel filter, CKP sensor, Distributer, Spark plug wires, Starter and Plugs. Still I have the exact same issue. Mine will not start on the first 3 revolutions (sounds like a revolution anyway), but if I let it do that then turn it off and then try to restart it... VROOOOM almost every time. Try it. The problem is that I am sure it had something to do with the premature death of my starter. I am very anxious to hear the end of this story. I would actually chip in for the cost of the dealer mechanic if it will save me a trip to the dealer, which is my next step if I can't find something out on this site. Which is pretty awesome, due to t

he people of course. keep us updated please!!![/QUOTE


Sounds like the fuel pressure regulator maybe going bad and gas is returning to tank. When you try to start it has to reprime the fuel line and fuel rail before it starts. try turning the key on and wait 30-45 seconds then try starting. If ti starts then the fuel pressure is leaking. try it and give a holler i can't send thru the forum i'll tell you how to change it give a holler at [email protected] Dale

[djeep]

Hey Everyone.
I'm new to this site and have been reviewing different threads for the past hour or so...and decided to join and kick-in my 2 cents!
I'm convinced that a bunch of these similar threads have to do with a power drain and random alarm problems. My 94 GC 5.2L started giving me issues last winter and they went away all summer. Now that we've returned to the cold (I live in Northern Ontario) they're back!
Twice this month I've gone out in the morning to a dead vehicle. Yesterday was the latest...I was able to hook it up to a spare battery. As soon as this is done the alarm system triggers. I try to disarm this by turning the key in the passenger door and it appears to work. However, when you attemp to start it the beast will fire and then stall. It needs repeated coaxing to keep going and idle and then it ran rough. This is probably the 6-7th time something like this has happened (only in the winter!). In the past it usually takes several days before the throttle response returns to normal.
I also can't lock the doors and then unlock them with the driver's door; this always sets off the SOB alarm. Recently, my tailgate lock stopped working properly. I can lock and unlock it with the power locks from either door arm but can't do it with my key.
Everytime I have to disconnect the battery to do any work the hard starting and rough running thing returns to make the next couple of days a real treat.
Yesterday I had it back in the shop and my mechanic said that the battery was holding charge and that there didn't seem to be a drain...
I've also seen, however, the symptom described elsewhere with the voltmeter dropping significantly when at lower engine reves, almost as if the alternator is bad (I don't think mine is, as this is the second alternator I've seen this with). The voltage drop on the meter isn't always consistent, either.
I wish someone could help with these issues. I love this vehicle when it's working and am almost ready to give up hope. I put a new fuel pump in it recently because that's what the dealer said ...I'm $600 poorer and no further ahead!
Any ideas would be great and I will post any ideas or solutions that are offered by my new service shop (no more dealer!!)
Thanks,
Derek.