Bought an MJ today - Now it won't start

[dbkirkp]

Today I bought an '88 long bed MJ. 4.0 5 speed. It is in pretty good condition (body and everything). It has a 4.5" lift on it and I thought I got a good deal on it. I knew coming into it that it will require a bit of maintenance ...

 

I test drove it, it started right up (seller was putting new spark plugs in it when I drove up). Drove it around and it seemed like the engine ran smooth etc. It had 165k on the 4.0 which shouldn't be a problem at all. It was well cared for. 

 

I negotiated, bought it and had the title/bill of sale in hand when I went to drive it out of his driveway and it wouldn't start. We opened the hood and I put as much accelerator as I could into it to start it. He grabbed the throttle body and pushed it all the way down and ... vroom. It started. 

 

I have started it now multiple times this way. It also seems to have a low idle when it is started. Any idea what could be wrong. Someone suggested fuel pump ... but I would think that would be an all good or all bad situation. Anything else?

 

-Happy to Join the MJ club!

 

 

[87MJTIM]

Other than a lift, you did not say what, if any, modifications/changes were done to the MJ.  Since it is an 88, I assume it is still a Renix.  Before anyone else chimes in, you should perform Cruiser's Renix Tips.  http://comancheclub.com/topic/48463-cruisers-mostly-renix-tips/

 

Put in your signature a description of your MJ (Yr, eng, trans, mods done) and your location.

[dbkirkp]

Thanks for the tip. It sounds like grounding issues might reduce the spark sent to the engine. I can work on that. Always interested in other possibilities though. 

 

It is still original Renix. (I am guessing that means pre 91 Chrysler HO). Not too many mods have been done to it. I was told it had an xj rear axle. I was assuming that was to help with the lift more than durability. It was repainted the stock gray, but it is pretty standard besides the lift and wheels. No aftermarket bumpers etc. 

 

As for the photo, I am working on getting a photo small enough to fit in the profile pic. 

[cruiser54]

Tips 1 through 5 before you load up a parts cannon. 

[onlyinajeep726]

Thanks for the tip. It sounds like grounding issues might reduce the spark sent to the engine. I can work on that. Always interested in other possibilities though. 

 

It is still original Renix. (I am guessing that means pre 91 Chrysler HO). Not too many mods have been done to it. I was told it had an xj rear axle. I was assuming that was to help with the lift more than durability. It was repainted the stock gray, but it is pretty standard besides the lift and wheels. No aftermarket bumpers etc. 

 

As for the photo, I am working on getting a photo small enough to fit in the profile pic. 

 

When you say XJ axle, did the PO just slap it under the rear springs, or were the spring perches relocated to the correct spots so that the leaf spring bushings aren't in a bind?  The below graphic illustrates what I mean (no to scale):

[Ωhm]

Doesn't Renix have "clear flood"? That is, when holding the throttle to the floor (WOT), the injectors shut off during crank, in order to clear any flooding that might have accrued in the manifold. 

[cruiser54]

Doesn't Renix have "clear flood"? That is, when holding the throttle to the floor (WOT), the injectors shut off during crank, in order to clear any flooding that might have accrued in the manifold. 

Yes it does. 

[dbkirkp]

Ok, I am going to start going through Cruiser's list tomorrow morning, but I have some new information that might help in the diagnosis. 
 
1. It has no problem starting when cold and it runs once started, but once warm ... it won't start. 
 
Also, I don't see too much torque on the rear leafs to make it seem out of position on the rear axle. The axle doesn't look modified though. PO said that the person that had it before him put an XJ rear axle on it. I don't know how to identify an axle and currently I don't know how to post pictures on this forum. Once I have that identified, I will post/update the rear axle thing. 

 

Is that something that I should have fixed, or is it something that can pass, but just isn't optimal?

[cruiser54]

Ok, I am going to start going through Cruiser's list tomorrow morning, but I have some new information that might help in the diagnosis. 

 

1. It has no problem starting when cold and it runs once started, but once warm ... it won't start. 

 

Also, I don't see too much torque on the rear leafs to make it seem out of position on the rear axle. The axle doesn't look modified though. PO said that the person that had it before him put an XJ rear axle on it. I don't know how to identify an axle and currently I don't know how to post pictures on this forum. Once I have that identified, I will post/update the rear axle thing. 

 

Is that something that I should have fixed, or is it something that can pass, but just isn't optimal?

Next time it won't start warm, wiggle the connector on the ICM and the coil wire and see what happens.

 

You need to get the Tips done though. 

[onlyinajeep726]

 

Doesn't Renix have "clear flood"? That is, when holding the throttle to the floor (WOT), the injectors shut off during crank, in order to clear any flooding that might have accrued in the manifold.

Yes it does.

 

 

I was not aware of this... That explains why there have been times that that is the only way I was able to get mine started... Cool info.

 

Also, I don't see too much torque on the rear leafs to make it seem out of position on the rear axle. The axle doesn't look modified though. PO said that the person that had it before him put an XJ rear axle on it. I don't know how to identify an axle and currently I don't know how to post pictures on this forum. Once I have that identified, I will post/update the rear axle thing.

 

Is that something that I should have fixed, or is it something that can pass, but just isn't optimal?

If it is in fact an XJ rear axle that was swapped in without relocating the perches, then yes, it'll have to be addressed. If it is bolted in like below, it has not been modified and your bushings will hate you.

 

 

Oh, and here's a How-To on uploading pictures on a thread on CC: http://comancheclub.com/topic/37727-how-to-post-pictures/

[cruiser54]

 

 

Doesn't Renix have "clear flood"? That is, when holding the throttle to the floor (WOT), the injectors shut off during crank, in order to clear any flooding that might have accrued in the manifold. 

Yes it does. 

 

 

I was not aware of this... That explains why there have been times that that is the only way I was able to get mine started... Cool info.

 

Something is causing it to run real rich. That's why.

 

How's the hose going from the throttle body to MAP? 

[HOrnbrod]

 

Doesn't Renix have "clear flood"? That is, when holding the throttle to the floor (WOT), the injectors shut off during crank, in order to clear any flooding that might have accrued in the manifold. 

Yes it does. 

 

 

That's how you clear any flooded fuel injected engine. Carburetted engines too.

[onlyinajeep726]

 

 

 

Doesn't Renix have "clear flood"? That is, when holding the throttle to the floor (WOT), the injectors shut off during crank, in order to clear any flooding that might have accrued in the manifold. 

Yes it does. 

 

 

I was not aware of this... That explains why there have been times that that is the only way I was able to get mine started... Cool info.

 

Something is causing it to run real rich. That's why.

 

How's the hose going from the throttle body to MAP? 

 

 

It's good.  I'm running 24 lb Mustang injectors on a 4.6L stroker. 

[cruiser54]

 

 

 

 

Doesn't Renix have "clear flood"? That is, when holding the throttle to the floor (WOT), the injectors shut off during crank, in order to clear any flooding that might have accrued in the manifold. 

Yes it does. 

 

 

I was not aware of this... That explains why there have been times that that is the only way I was able to get mine started... Cool info.

 

Something is causing it to run real rich. That's why.

 

How's the hose going from the throttle body to MAP? 

 

 

It's good.  I'm running 24 lb Mustang injectors on a 4.6L stroker. 

 

Minor detail..LOL.

[87MJTIM]

Ok, I am going to start going through Cruiser's list tomorrow morning, but I have some new information that might help in the diagnosis. 

 

1. It has no problem starting when cold and it runs once started, but once warm ... it won't start. 

 

Also, I don't see too much torque on the rear leafs to make it seem out of position on the rear axle. The axle doesn't look modified though. PO said that the person that had it before him put an XJ rear axle on it. I don't know how to identify an axle and currently I don't know how to post pictures on this forum. Once I have that identified, I will post/update the rear axle thing. 

 

Is that something that I should have fixed, or is it something that can pass, but just isn't optimal?

 

The PO may have installed a later model XJ axle - Chrysler 8.25.  This is considered a better axle than a Dana 35, that most likely came from the factory.  (A Dana 44 was an option for MJs).

 

Additionally, the factory gear ratio for a 4.0, 5 speed was 3.07.  You should check the current gear ratio.  If the XJ axle came from an auto trans, then the ratio would be 3.55.

 

The front axles used for MJs and XJs was a Dana 30.  If the rear axle changed to 3.55, make sure the front axle matches that ratio.

[dbkirkp]

 

Ok, I am going to start going through Cruiser's list tomorrow morning, but I have some new information that might help in the diagnosis. 

 

1. It has no problem starting when cold and it runs once started, but once warm ... it won't start. 

 

Also, I don't see too much torque on the rear leafs to make it seem out of position on the rear axle. The axle doesn't look modified though. PO said that the person that had it before him put an XJ rear axle on it. I don't know how to identify an axle and currently I don't know how to post pictures on this forum. Once I have that identified, I will post/update the rear axle thing. 

 

Is that something that I should have fixed, or is it something that can pass, but just isn't optimal?

 

The PO may have installed a later model XJ axle - Chrysler 8.25.  This is considered a better axle than a Dana 35, that most likely came from the factory.  (A Dana 44 was an option for MJs).

 

Additionally, the factory gear ratio for a 4.0, 5 speed was 3.07.  You should check the current gear ratio.  If the XJ axle came from an auto trans, then the ratio would be 3.55.

 

The front axles used for MJs and XJs was a Dana 30.  If the rear axle changed to 3.55, make sure the front axle matches that ratio.

This is a Chrysler 

 

I found an Axle Identification guide, and I do have a Chrysler 8.25. The gearing is really tall (Also they have 33" wheels on it, so it might just bee the wheels). I will need to take a look at that. My truck's rear end looks just like Onlyinajeep726's photo. I will need to address this so it will drive a bit better day to day. Also if the gearing on the front and rear axles are different, wouldn't that be really rough in 4 wheel drive? Makes me shutter! Is there a what to test that without pulling the gears for inspection?

[yxmj]

You do not have to "pull the gears"

 

But since this is a "NEW"(to you) truck why not be sure and do some simple preventive maintenance at the same time. Remove the diff covers and drain the fluid,,,,the gear ratio is stamped on the large ring gear.

 

This way you will have no doubt as to the ratios....you will have had the chance to give each diff a personal visual inspection .....and you will know that in the end they are running fresh correct fluids. Instead of 20+ year old possibly incorrect juice.

 

Why guess when it it as easy as that.  :dunno:

 

As for the no start.....the comment you said about it starting cold but not starting hot brings to mind a CPS failure.....I have had a couple do this.... I might be wrong but it is worth a look...one fast trick i found by accident was when it warmed up and will not start try spraying the CPS (as best you can) with brake or carb cleaner.....if that cools it down enough to restart...that narrows it down... :???:

[Rockfrog]

As for the rear axle, obviously the rear was done as a spring over axle conversion. Simply look down the springs, if they are in line with the spring hangers, all is fine, they moved the perches. If the springs are tweaked outwards about 3/4 inch, on each side, you have something to address.

 

Sent from my SGH-I337M using Tapatalk

[G O B]

'Leaky'  injectors or pressure regulator will cause a flooded condition on hot starts. I changed the pressure regulator on mine and it cured the problem. There is also a shut down relay that presets the IAC, make sure that it is there and working.