1993 5.2, hard starting

[ericsyzf]

New member here but I've been using the site for great info for some time.

I have a 1993 GC 5.2 that has had poor starting and idle lately. I have done 2fuel pumps in the past and did replace it last week under warranty to rule that out. Also did the fuel pump relay and fuel filter. When I turn the key to "on" I dont always hear the pump priming up right away. I turn it off and on a few times until I hear it and it pops right off. If I just go in and start cranking it before I hear the pump it will take a long time to start up.

What have I missed? Pump is new. Relay is new. Filter is new.

Any other ideas? I guess the pump could be bad out of the box..?

Not sure what else to look at.

Thanks, Eric

[JimHefToo]

Always can suspect a dirty throttle body and a bad idle air control. Throttle position sensor is another, along with crankshaft and camshaft position sensors.

[tiki2569]

my 94 5.2 was starting after a couple long cranks also with a rough idle. ended up being a bad coil

[2470commando]

Something else to think about is where do you get your parts? Autozone or other cheap parts stores parts can sometimes make a vehicle run worse on new parts than it did on the old ones.
Good Luck With Your Project.

[ericsyzf]

Thanks for the feedback.

I did already put in a new IAC and cleaned the throttle body well. It starts and runs great when I hear the pump priming before I start it. I am pretty focussed on fuel supply from the pump. Anything else that can keep that pump from priming when key is on?

Thanks for any help, Eric

[joegibs]

im still having the exact same problem, i however have only changed the filter and done some simple tests, but cant figure anything out. the only way i get mine to start easy is to turn the key forward, and let it sit until i hear the pump kick in and see the check engine light come on after about 15 seconds

any help on the subject would be appreciated.

[dyneq]

Originally Posted by joegibs

im still having the exact same problem, i however have only changed the filter and done some simple tests, but cant figure anything out. the only way i get mine to start easy is to turn the key forward, and let it sit until i hear the pump kick in and see the check engine light come on after about 15 seconds

any help on the subject would be appreciated.

Same problem here with a 93 GC Laredo 5.2.:fatkid:

I am thinking it is the PCM (computer) based on some other posts I've read.

[joegibs]

shouldnt the fuel pump be priming itself immediately when the key is turned forward?

[dyneq]

Originally Posted by joegibs

shouldnt the fuel pump be priming itself immediately when the key is turned forward?

I'd like to know the answer to that question too. I believe the answer is yes, because that is the only condition in which my 93 v8 will start.

If I put the key into the on position, AND the check engine light goes on, I will hear a relay clicking rapidly from the engine compartment and then shortly after, I'll hear the fuel pump run for about 2 seconds. If I then crank, it starts right up and runs great. Lately that only happens about 1 time in 12.

Tonight, I tried something different. I turned the key to on the first time and just left it there (I usually give up if I don't see 'check engine' and turn back to off and try again). An interesting thing happened after about 30 seconds. The 'security' light lit up. The vehicle is new to me, and I didn't even know it had an alarm system. Anyway, soon after the security light came on, I got the relay/pump operation and was able to start. I don't usually see the security light in any other circumstance.

I found this related thread which goes on for a bit, but FWIW a couple of people solved similar problems with a new PCM (computer).

[joegibs]

i'd rather put up with this problem then spend several hundred on a new computer

[Taz]

Originally Posted by ericsyzf

New member here but I've been using the site for great info for some time.

I have a 1993 GC 5.2 that has had poor starting and idle lately. I have done 2fuel pumps in the past and did replace it last week under warranty to rule that out. Also did the fuel pump relay and fuel filter. When I turn the key to "on" I dont always hear the pump priming up right away. I turn it off and on a few times until I hear it and it pops right off. If I just go in and start cranking it before I hear the pump it will take a long time to start up.

What have I missed? Pump is new. Relay is new. Filter is new.

Any other ideas? I guess the pump could be bad out of the box..?

Not sure what else to look at.

Thanks, Eric

done a tune up on it lately?

[ericsyzf]

Well this really doesn't present itself as "tune up" issue or even ignition related at all for that matter. It runs great otherwise.

The real question is whether or not something else is involved in sending power to the fuel pump. Does the pump get powered directly via the relay? Probably so. So what's telling the relay to energize? Just the key? Or is it computer controlled even after the key is turned on?

???Eric

[dyneq]

Originally Posted by ericsyzf

Well this really doesn't present itself as "tune up" issue or even ignition related at all for that matter. It runs great otherwise.

The real question is whether or not something else is involved in sending power to the fuel pump. Does the pump get powered directly via the relay? Probably so. So what's telling the relay to energize? Just the key? Or is it computer controlled even after the key is turned on?

???Eric

Here's a link with detailed startup info. My problem is exactly like what he describes.

The bad thing is that his solution involved 2 fixes, so it's hard to say what actually fixed the problem! I have tried wiggling the wires going from the door into the door jam while turning the key with no difference, but I need to read my manual and see how the alarm system is supposed to be working. I did notice that there are 2 sensors that monitor if the door is closed, so one of them must be for the alarm and the other for the dome light?

[Taz]

bad fuel press regulator?

[dyneq]

All,

In the hope that this thread may help others in the future, I wanted to post what worked for my 93 GC Laredo.

After checking all relays and fuel pump, I came to the conclusion that the issue was the PCM. To recap, if I turned the key to 'ON', I would not always get the 'check engine' light to come on (maybe 1 out of 10 times). Once the light did come on, I could hear the relay chattering rapidly for about 6 secs. then the fuel pump would kick on for about 3 secs. Then turn the key and it would fire right up and run great until I turned it off.

So, I decided to buy a Cardone reman. PCM. I have not changed anything else. It now starts up every time on the first try.

Now I have to fix the *$%** vacuum line I snapped while shoehorning the old PCM out! Only affects the cruise control, though.

John

[joegibs]

Wow, just as i was going to search for the thread to kick it back to life, someone already did

With my zj, i would turn the key forward for about 15 seconds, and every time after that 15 seconds the relay would kick on and the check engine light would come on shortly after. over this last weekend, it took a turn for the worse, and i have to literally wait 5 minutes before that damn relay starts clicking. the relay also now clicks for about 30 seconds before i start to hear the fuel pump start to click, and then after about another 15 seconds the fuel pump finally kicks in and allows me to start.

i'm confident that mine is also the pcm causing problems, so i'm willing to purchase one to get the POS running properly again. where, and how much for either a brand new or refurb?

i've also found someone who has a 93 that they're parting, and he is willing to sell his to me, but neither of us know what a used one is worth, any suggestions as to what price should be for a used one?

[dyneq]

Originally Posted by joegibs

i'm confident that mine is also the pcm causing problems, so i'm willing to purchase one to get the POS running properly again. where, and how much for either a brand new or refurb?

i've also found someone who has a 93 that they're parting, and he is willing to sell his to me, but neither of us know what a used one is worth, any suggestions as to what price should be for a used one?

Well, I can't comment on where you might find a brand new PCM. I was only available to find a reman. I think that Cardone is the only place that remans them, but I didn't do an exhaustive search. I ended up going to partsamerica.com because I liked the idea that I could return the core to my local Advance Auto.

As far as the used one goes, it's obviously up to you. I decided that since I'd be using my Jeep for its intended purpose (to travel to remote areas), it was worth it to just get the reman. If I was short on funds and had to get the used PCM, I would try not to pay more than 33% of what the remans cost.

That all said, it sure feels nice having it start right up every time! It sure sounds like you have the same symptoms as I had. Let us know how it turns out.

John

[Taz]

i've heard and seen more bad PCM's on 4.0's than 5.2's...

[joegibs]

im looking up used ECU's from a parts website, for the 5.2, its asking me to choose between two identification codes.

ident #56028011
ident #56028012

and each have an option of w/ or w/out security. my zj has the alarm, and has the keyless entry/remote locking. so i'm assuming i'd want the security option.

where do i find the identification number on my zj?

[dyneq]

On mine, there was a white sticker right on the PCM with the number printed out on it. The PCM is located on the firewall behind the coolant reservoir. I think I was able to read the number without removing the reservoir.

John