Hard Start Up In The Morning

[TheDirtyJeep401]

When I start my truck in the morning or in the cold it starts up but you have to give it some gas in order for it to not die. Also the transmission is also harder to shift when it has been sitting or is cold, but when it warms up, its fine. Just trying to see if i can just easily fix this or not. Thanks 

[Thomas]

My jeep did this when the coolant temp sensor went out. I would try that first because it's only like a 20 dollar part.

Does your electric fan constantly run?

[TheDirtyJeep401]

Mine dosent have an electrical fan. And ill have to look at the coolant sensor 

[cruiser54]

Before throwing parts at it, do some simple stuff.

 

Are your intake manifold bolts loose?

 

Those hoses to the intake manifold below the throttle body-are they rotted and leaking?

 

Have YOU ever put in new copper spark plugs, cap and rotor with brass terminals, and some premium ignition wires?

 

Done a ground refreshing and C1o1 refreshing as outlined in "Cruiser's Mostly Renix Tips" that you can click on in my signature?

[onlyinajeep726]

My jeep did this when the coolant temp sensor went out. I would try that first because it's only like a 20 dollar part.

Does your electric fan constantly run?

The 4-banger doesn't have a stock electric fan.

[TheDirtyJeep401]

I haven't checked the bolts or the hoses, but i will look. I did replace the spark plugs but am planning to buy new wires and a cap soon. 

[HellCreek]

I have nearly the same problem.  It is very hard to start - sometimes - when the engine is cold.  Sometimes it starts right up and always starts good when it is warm.  After it starts it runs great and has plenty of power for a 2.5L, so it is probably not a CPS or TPS.  Also, because it runs good, it is probably not a ground issue.  What would be the most likely culprit in this case.  Most of the threads on the forum deal with the Renix 4.0, but mine is a 1989 2.5L.

 

Thanks,

Tom

[big66440]

I have nearly the same problem.  It is very hard to start - sometimes - when the engine is cold.  Sometimes it starts right up and always starts good when it is warm.  After it starts it runs great and has plenty of power for a 2.5L, so it is probably not a CPS or TPS.  Also, because it runs good, it is probably not a ground issue.  What would be the most likely culprit in this case.  Most of the threads on the forum deal with the Renix 4.0, but mine is a 1989 2.5L.

 

Thanks,

 

I have this exact same issue and yes mine is also a renix 4.0, when engine temp is cold it takes a good 15-20 seconds if not more of intermittent cranking for it to start, once it's just a little warm it fires right up I have also replaced the engine coolant temp sensor and it didn't make a difference

[54bobby]

my 2.5 has the same problem. intake is snug but the exhaust mani has both front and rear studs broken off. been like that since before this problem. starts right up with some feathering of throttle when cold and will stall out when pulled into gear unless you ride the brake while giving her ever so lite throttle. very low loping idle till she starts to warm then she purs and runs great with no starting problems. only when cold.

[HellCreek]

Hi,

 

Nice to know that mine isn't the only one with a hard starting problem.  Does anyone have any solutions?  Like I said, it runs fine after it starts, it's just very hard to start -- sometimes.

 

Thanks,

Tom

[HellCreek]

I have nearly the same problem.  It is very hard to start - sometimes - when the engine is cold.  Sometimes it starts right up and always starts good when it is warm.  After it starts it runs great and has plenty of power for a 2.5L, so it is probably not a CPS or TPS.  Also, because it runs good, it is probably not a ground issue.  What would be the most likely culprit in this case.  Most of the threads on the forum deal with the Renix 4.0, but mine is a 1989 2.5L.

 

Thanks,

Tom

Hi, Guys,

 

I hope everyone had a great Christmas and New Years.  I am going to assume that everyone was busy and didn't have time to help with this issue.  I still need help, and I'm hoping that someone has an answer.  My truck is my daily driver, and I need it to be dependable, so I really need this fixed.  Someone must have a solution to this. Please help.

 

Thanks,

Tom

[Dillithium]

Well, if you can't find the direct cuprit, let's try to look at it systematically.

You want Spark. Spark would be given from the CPS, to the coil, rotor, leads, spark plugs and boom. You have spark. How are all of these parts looking? Corroded/shiny? New/old? Electricity can pass through corrosion, but it meets more resistance at first, possibly making it harder to start.

 

Secondly, fuel. You say grounds are not an issue, how is the tail light ground looking? That ground is responsible for the fuel pump, could induce performance issues there. Could it be possible you have sediment in your gas tank, clogging the strainer/fuel filter during first start up during the day? That sediment collects at the bottom of the tank, effectively choking the strainer before fuel is slushed around while driving.

 

Last, air. Not much to say about air, renix has a closed loop system when cold so the sensors are indeed not suspicious here. 

 

How fast does it crank during a cold start? Normal or slower?

How long does it take you to crank for it to start during one of these episodes?

[yxmj]

You can tell by my avatar we have almost the same MJ  :thumbsup:

 

One thing about the older 2.5 is there is a goofy water line that runs under the TB ( maybe to preheat it???)......this is probably the culprit because you say once it warms up you have no problem.

 

Easy fix up here is plug it in......Do you have a factory block heater? If not there are after market ones available.

 

Mine is a hard starter when not plugged in but 2 days ago it was -47 C (-52.6 F) MJ was parked with the nose into the north wind......but it was plugged in.....Started right up.

 

You only need to preheat it for about 45 min. prior to starting to get good results.

 

My guess for the trans would be that the fluid is just thicker when cold and warms up with use making shifting easier.

[HellCreek]

Hi,

 

Thanks for the replies.

 

I replaced the CPS last year, so that probably is not it; besides, if the CPS were bad, it most likely would be hard-start or no-start all the time, not just when it is cold, which is why I replaced it last year.  I'm guessing that any electrical culprit would act in the same way, i.e., trouble at any temperature.  I could probably use new spark plugs, but, there again,  that would manifest itself in poor drivability at all times.  Bad plug wires or rotor/caps usually show up in the form of ignition misses or back-fires, neither of which I am experiencing.

 

The tail light ground looks o.k.  Also, the fuel pump gives that reassuring hum every time the key is turned on, even when the engine doesn't start.  Dirty fuel filters would affect drivability and performance at any temperature and, basically, all the time, and my little 2.5 idles and runs great after it is started.

 

It acts as though the engine is flooding, although I can't smell fuel, and it doesn't help to hold the accelerator down to the floor, as you would in a carburated engine.  What makes this totally aggravating is that the problem is intermittent; sometimes it starts right up.  I am thinking it might be the TPS going bad, but I don't want to replace it unless I'm sure.  I don't want to just start throwing money at the problem, until it is finally fixed.  I would like to only replace the bad part.

 

I live in Mississippi, so I don't have a block heater, and probably don't need one.  The last time this happened, it was near 70 degrees.  When I say "cold", I mean that the engine has not been started in several hours.

 

Thanks for the suggestions,

Tom

[54bobby]

are you getting spark when the problem rears its ugly head?

[Jeep Driver]

Hi,

 

Thanks for the replies.

 

I replaced the CPS last year, so that probably is not it; besides, if the CPS were bad, it most likely would be hard-start or no-start all the time, not just when it is cold, which is why I replaced it last year.  I'm guessing that any electrical culprit would act in the same way, i.e., trouble at any temperature.  I could probably use new spark plugs, but, there again,  that would manifest itself in poor drivability at all times.  Bad plug wires or rotor/caps usually show up in the form of ignition misses or back-fires, neither of which I am experiencing.

 

The tail light ground looks o.k.  Also, the fuel pump gives that reassuring hum every time the key is turned on, even when the engine doesn't start.  Dirty fuel filters would affect drivability and performance at any temperature and, basically, all the time, and my little 2.5 idles and runs great after it is started.

 

It acts as though the engine is flooding, although I can't smell fuel, and it doesn't help to hold the accelerator down to the floor, as you would in a carburated engine.  What makes this totally aggravating is that the problem is intermittent; sometimes it starts right up.  I am thinking it might be the TPS going bad, but I don't want to replace it unless I'm sure.  I don't want to just start throwing money at the problem, until it is finally fixed.  I would like to only replace the bad part.

 

I live in Mississippi, so I don't have a block heater, and probably don't need one.  The last time this happened, it was near 70 degrees.  When I say "cold", I mean that the engine has not been started in several hours.

 

Thanks for the suggestions,

Tom

 

 

 

Image Not Found

 

As you will see here, just to the left of my thumb, the idle control motor.

 

I guarantee you that yours does not work or does not work properly.

 

 

My engine has always started up on a cold morning, even before I replaced the ICM. 4-5 revolutions, feather the throttle twice....starts right up.....feather the throttle two more times and let it warm up for 5 minutes....good to go.

 

 

The ICM never worked from the day I bought the truck, I manually adjusted the idle at the adjustment screw at the end of the push rod, set at around 750rpm, engine ran smooth at idle.

When I replaced the AC compressor and got my AC working I wanted it to idle up as it's supposed to, so, I replaced the ICM. You will not find one listed for the Comanche, you'll need to get one for a '84 Cadillac.

 

 

Once replaced, I thought I would be able to do the same as before, set the idle...doesn't work that way. No matter where I set the screw the idle returned to the same spot, low, around 250-300 rpm, this is where I discovered I had a mechanical problem but that's another matter.

Originally, I thought the ICM only bumped up the idle 2-300rpm when the AC came on to compensate for the drag. I was confounded as to why I could not set the idle to a fixed rpm until I realized that the ECU takes the readings of the TPS and the MAP and likely reads the rpm to continually signal the ICM to adjust idle rpm.

 

FWIW-

Most of my OE vacuum lines are gone. Once my new engine is installed the only vacuum that will be connected is- brake booster, MAP, PCV to VC, and one line to the heater control.....I'm considering even getting rid of the vacuum ball if the heater control works without it.

 

As a side note and probably unrelated- Saturday night I cut out the vent line to the charcoal canister and replaced my canister with a homemade unit at the tank, I also replaced the lines to the new canister. My idle bumped up to around 600rpm and has smoothed out a little. I still have low compression and a miss at idle but idle does seem a little stronger now. I'm wondering....convinced.......that the vent line was clogged and not venting at all.

 

My next move will be to cut out the C101 connector and I have an expectation that my idle will improve again.

 

 

To answer your question- You'll need to consider ICM, TPS, MAP, temp sensors, electrical, EGR........basically the entire system if you want to fix this problem.

 

My new engine has a new NOS TBI on it with factory TPS and ICM......at that time I will dig further into.....spend more time fine tuning my idle.

[Jeep Driver]

It's 28 degrees here this morning.
 

I turned the key twice without touching the throttle, both times it fired right up but died, third time I just barely cracked the throttle and it fired up and stayed running, ICM took over.

 

Most days I can reach in and start it without my foot on the throttle (this after I replaced my ICM).

[cruiser54]

Grounds "look" okay? Nah. Refresh them unless you can SEE electricity flowing.

[HellCreek]

Just an update.  I refreshed the tail light ground, and that didn't help the problem.  I removed the coil and cleaned the terminals yesterday.  This morning it started normally (5-6 turns).  I went to the parts store to get some antifreeze for my son's CJ-7, and when I got back into the truck, it wouldn't start.  I tried several times and almost ran the battery down,  After about an hour of waiting, I turned the key and it started normally.  What do I try next?   By the way, my truck is a 1989 and doesn't have a C101.

 

Thanks,

Tom

[HellCreek]

By the way,  What is the flat center terminal on the coil used for?

[54bobby]

crank position sensor

[cruiser54]

crank position sensor

Test it. 

 

Renix CPS Testing and Adjusting

 

 

 

Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark. 

 

Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.

 

The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark. 

 

Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected. 

 

You should get a reading of  .5 AC volts. 

 

If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs  (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!!  That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.

 

Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off. 

 

A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8” from the stock 5/16”, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.

 

 

 

 

Revised 01-26-2013

[cruiser54]

Tom, of my Tips, which have you completed? 

[HellCreek]

Hi, Cruiser,

 

I was doing them one at a time so that I could pinpoint the cause.  If I did them all at once, I wouldn't really know what the problem was or what fixed it.  So far, I have refreshed the grounds and the coil connections.  I am leaning on the CPS next, as 54bobby suggested.  Since the engine was warmed up this morning when it wouldn't start, I can rule out cold start as an exclusive issue.  As I said, I don't have a C101, so I can rule that out as well.  I will keep you posted. 

 

Thanks,

Tom

[cruiser54]

Hi, Cruiser,

 

I was doing them one at a time so that I could pinpoint the cause.  If I did them all at once, I wouldn't really know what the problem was or what fixed it.  So far, I have refreshed the grounds and the coil connections.  I am leaning on the CPS next, as 54bobby suggested.  Since the engine was warmed up this morning when it wouldn't start, I can rule out cold start as an exclusive issue.  As I said, I don't have a C101, so I can rule that out as well.  I will keep you posted. 

 

Thanks,

Tom

Do 3, 5, and 7. In that order.