4.0 renix no start when cold

[Jeffery Starn]

Hey guys I have a 90 Comanche 4.0 renix 5speed 4x4 and for the last few weeks it’s been below freezing in the mornings and has a really hard time starting up and today it didn’t start at all until it warmed up, any ideas what could be causing this? I’m going to replace my map and crank sensors soon.

[JMO413]

Have you done cruisers tips yet?

 

[87MJTIM]

How old is your battery?

[gogmorgo]

X2 on Cruiser’s tips. www.Cruiser54.com. 

Have you done any diagnostics at all before deciding to throw parts at it? Crank and map sensor control two very different aspects of engine management and have very different symptoms if they fail.

When you stay it doesn’t want to start, do you mean you turn the key and it doesn’t want to crank the engine, or does it crank over just fine and never fire? Have you checked for spark? Fuel pressure?

 

One of mine sometimes struggles at low temperatures, cranks just fine but doesn’t fire. Old temp sensors get funky at the edge of their range and it runs way rich, floods out. A little throttle and it fires up every time... but we’re talking -30 or colder, not just “below freezing”.

[omega_rugal]

try some starting fluid, see if it helps, does the engine crank at good speed? the old renix usually needs good cranking RPMs before it starts pulsing the inyectors and spark

[Jeffery Starn]

No I haven’t done any diagnostic on it yet, yes it cranks everytime and has a good crank to it just first thing in the morning when it’s below 30 degrees it won’t fire, I was watching some videos on the crank no start and people suggested to do the map and crank sensors which wouldn’t hurt the old girl has 413000 miles on her lol

[Jeffery Starn]

1 hour ago, 87MJTIM said:

How old is your battery?

I just put a brand new optima in it 

[JMO413]

3 minutes ago, Jeffery Starn said:

No I haven’t done any diagnostic on it yet, yes it cranks everytime and has a good crank to it just first thing in the morning when it’s below 30 degrees it won’t fire, I was watching some videos on the crank no start and people suggested to do the map and crank sensors which wouldn’t hurt the old girl has 413000 miles on her lol

I would refresh the grounds before I did anything else. I believe Renix had to reach 300 RPM before it will have spark. Test the crank sensor before you replace it. The new parts store junk tend to be worse off than a wore out Factory one.

[Jeffery Starn]

Just now, JMO413 said:

I would refresh the grounds before I did anything else. I believe Renix had to reach 300 RPM before it will have spark. Test the crank sensor before you replace it. The new parts store junk tend to be worse off than a wore out Factory one.

Okay thank you I’ll try it out tomorrow 

[omega_rugal]

last but not least... at such low temps all cars struggle to start, cover the engine bay at night and or use a block heater...

[omega_rugal]

also don't step on the gas pedal while cranking, it doesnt help, also try to not crank the engine for long periods, cold air makes difficult for the fuel to ignite and you end up flooding the engine, its best to do it in 2 or 3 attemps at the time

[Jeffery Starn]

22 minutes ago, omega_rugal said:

also don't step on the gas pedal while cranking, it doesnt help, also try to not crank the engine for long periods, cold air makes difficult for the fuel to ignite and you end up flooding the engine, its best to do it in 2 or 3 attemps at the time

Ya I don’t ever use the gas pedal and I won’t crank longer than 4-5 seconds 

[gogmorgo]

If the crank sensor fails you lose spark. It’s all or nothing, if you’ve got spark, you’ve got a functioning crank sensor.

Check fuel pressure with a gauge.

 

For mileage that high, cruiser’s tips are definitely in order. It’s also worth looking into the Renix Engine Monitor (REM) or some other kind of scan tool that can read your sensor data to confirm it’s reading as it should.

Its also worth doing an old fashioned tune-up if it’s been a while. Plugs, wires, cap and rotor. 

 

37 minutes ago, omega_rugal said:

last but not least... at such low temps all cars struggle to start, cover the engine bay at night and or use a block heater...

 

Any car that struggles to start without a block heater above -20°C is broken, and the cold has very little or nothing to do with it. The coldest it’s been at OP’s location in the last few weeks was -5°C. It’s barely even cold enough to be concerned about any water that might be in the fuel lines freezing. 
Stepping on the gas will definitely help if the engine is flooding out. It’s a mechanical throttle that allows more air into the engine. Maybe it helps atomise and distribute the fuel better, I don’t know. What I do know is that on the -30 mornings when the breaker tripped on the outlet my block heater was plugged into, less than 1/4 throttle was the difference between firing right up and not even coughing.

 

But at this point it should be treated as a regular no-start. 
 

4-5s isn’t very long crank time. 15 second crank intervals, 1 minute cool-down in between. After 5 attempts, give it a ten minute break.

[Jeffery Starn]

10 hours ago, gogmorgo said:

If the crank sensor fails you lose spark. It’s all or nothing, if you’ve got spark, you’ve got a functioning crank sensor.

Check fuel pressure with a gauge.

 

For mileage that high, cruiser’s tips are definitely in order. It’s also worth looking into the Renix Engine Monitor (REM) or some other kind of scan tool that can read your sensor data to confirm it’s reading as it should.

Its also worth doing an old fashioned tune-up if it’s been a while. Plugs, wires, cap and rotor. 

 

 

Any car that struggles to start without a block heater above -20°C is broken, and the cold has very little or nothing to do with it. The coldest it’s been at OP’s location in the last few weeks was -5°C. It’s barely even cold enough to be concerned about any water that might be in the fuel lines freezing. 
Stepping on the gas will definitely help if the engine is flooding out. It’s a mechanical throttle that allows more air into the engine. Maybe it helps atomise and distribute the fuel better, I don’t know. What I do know is that on the -30 mornings when the breaker tripped on the outlet my block heater was plugged into, less than 1/4 throttle was the difference between firing right up and not even coughing.

 

But at this point it should be treated as a regular no-start. 
 

4-5s isn’t very long crank time. 15 second crank intervals, 1 minute cool-down in between. After 5 attempts, give it a ten minute break.

ya as soon as i got the truck about 6 months ago i did a tune up plugs, wires, cap, rotor, thermostat, waterpump, belt, injector upgrade to 4 port, cold air intake, oil change, new battery, throttle position sensor, new valve cover and gasket, new clutch and master slave, it has ran like a dream and have had no issues at all it fires right up within a couple seconds everytime except when its cold out and i also have an issue with the idle on occasion it will rev up and back down when I'm stopped thats why i tried the throttle position sensor, i am looking into the REM for it, i will check my fuel pressure this weekend thank you.

[gogmorgo]

Revving up and down at idle could be a vacuum leak, or an issue with the idle air controller (IAC). I think Cruiser’s got a tip for the IAC, I think just giving it a good clean. Cleaning the whole throttle body will be good for it.

Check your intake/exhaust manifold bolts. They like to wiggle loose, could cause a vacuum leak.

[Jeffery Starn]

6 minutes ago, gogmorgo said:

Revving up and down at idle could be a vacuum leak, or an issue with the idle air controller (IAC). I think Cruiser’s got a tip for the IAC, I think just giving it a good clean. Cleaning the whole throttle body will be good for it.

Check your intake/exhaust manifold bolts. They like to wiggle loose, could cause a vacuum leak.

okay ill look into that thank you 

 

[omega_rugal]

cold, humid air makes starting difficult, gasoline doesnt vaporize, instead turns into tiny droplets, it won't ignite properly in those conditions.

 

another thing that may be bad are the temperature sensors, try disconnecting them, this forces the ECU into believe that is deep cool outside and adjust the fuel accordingly. if it starts with the temp sensors unplugged then one or both are defective, just try to no leave them unplugged when it reach operating temp or the mix will be too rich

 

 

16 hours ago, gogmorgo said:

Stepping on the gas will definitely help if the engine is flooding out. It’s a mechanical throttle that allows more air into the engine. Maybe it helps atomise and distribute the fuel better, I don’t know.

 

it helps by shutting down the injectors so air push the excess fuel out

[JMO413]

8 hours ago, Jeffery Starn said:

ya as soon as i got the truck about 6 months ago i did a tune up plugs, wires, cap, rotor, thermostat, waterpump, belt, injector upgrade to 4 port, cold air intake, oil change, new battery, throttle position sensor, new valve cover and gasket, new clutch and master slave, it has ran like a dream and have had no issues at all it fires right up within a couple seconds everytime except when its cold out and i also have an issue with the idle on occasion it will rev up and back down when I'm stopped thats why i tried the throttle position sensor, i am looking into the REM for it, i will check my fuel pressure this weekend thank you.

How much of a fluctuation in RPM do you get when it revs up and back down? The REM is awesome! It was 17° here this morning and mine fired right up. What condition are your battery cables in?

[gogmorgo]

2 hours ago, omega_rugal said:

 

it helps by shutting down the injectors so air push the excess fuel out

Only if you put it in “clear flood” mode by holding it wide open. Less than 1/4 throttle doesn’t shut down injectors.

[EUREKA]

On 12/1/2020 at 4:46 PM, Jeffery Starn said:

Hey guys I have a 90 Comanche 4.0 renix 5speed 4x4 and for the last few weeks it’s been below freezing in the mornings and has a really hard time starting up and today it didn’t start at all until it warmed up, any ideas what could be causing this? I’m going to replace my map and crank sensors soon.

So did you get it figured out?