1994 Aerostar with a 4.0L won't start when it's cold.

[clockhill]

My 1994 Aerostar 4L AWD runs perfectly but it won't start when it is even a little cold ie 0C or 32F. When it has been left overnight it turns over fast, fires now and then and backfires through the intake. If i plug in the block heater for 15min or so (a little longer when it is very cold) it fires right up. Once it is started you can drive all day leaving it sit for 3 , 4 ,5 hours and it still starts right up. Once it sits overnight it won't start again.

The vehicle has 275000 km on it but it runs so well I hate to give up on it.
I changed spark plugs about 70000 km ago and wires about 40000 km ago. After it stated acting up about 2 months ago I ran some concentrated injector cleaner through - no difference. I cleaned the MA sensor and then swapped it with another. No difference. When it does start the fast idle works as it should and there is no black smoke to indicate flooding.


It seems when the block is cold I don't get fuel. I tried spraying starter fluid into the intake but it made no difference. Is there a sensor that tells the computer extra fuel is needed for start up?

Has anyone got any ideas on what to check next?

 

[crazymind]

Have you tried priming it? Turn the key in the on position a few times to see if it starts?

 

[BrooklynBay]

Welcome to this forum! Do you have a check engine light with a code? Did you check the engine coolant temperature sensor to see if it's out of spec?

 

[clockhill]

Have you tried priming it? Turn the key in the on position a few times to see if it starts?

I have checked to make sure th fuel pump runs when the key is turned on and I have tried turning the key to on several times before I try to crank the engine. Doesn't seem to make a difference. As far as priming, because it is fuel injected I could only think of spraying into the intake. I propped the throttle plate open and sprayed in starting fluid. It didn't have any effect.

 

[loosenut349]

When you changed the plugs, what did you gap them to? The normal gap for the 4.0 is1.32 mm (.052 thousands of an inch). When these engines get some mileage on them, they tend to be hard to start, hesitate and stumble on acceleration. One fix is to close the plug to 1.016mm (.040 thousands of an inch). Closing the gap will have the effect of a hotter spark. My 4.0 had similar problems and this method cured most of it.

 

[clockhill]

Welcome to this forum! Do you have a check engine light with a code? Did you check the engine coolant temperature sensor to see if it's out of spec?

I have the digital display. There has been no check engine warning so the scan thinks everything is normal. The digital temperature guage shows 6 bars at operating temp - the same as it has since new.

I tried disconnecting the battery for 20 mins to rest the computer. No change.

This morning it was 5 above celsius. Van started perfectly.

 

[clockhill]

plugs

When you changed the plugs, what did you gap them to? The normal gap for the 4.0 is1.32 mm (.052 thousands of an inch). When these engines get some mileage on them, they tend to be hard to start, hesitate and stumble on acceleration. One fix is to close the plug to 1.016mm (.040 thousands of an inch). Closing the gap will have the effect of a hotter spark. My 4.0 had similar problems and this method cured most of it.

I would have set the plugs to original spec so i could try narrowing the gap on a couple. However there is no stumble once it starts . he motor runs and idles smoothly. This morning it was plus 5 celcius and the van fired right up afte sitting all night. Block temperature seems top be the major factor.

 

[BrooklynBay]

The temperature sending unit for the temperature gauge is a different part than the engine coolant temperature sensor.

 

[loosenut349]

If you disconnected the battery then the pcm has been reset and it will have to re-learn the drive cycle parameters. this can take anywhere from 6-20 miles to occur. if the check engine light is not on, it does not mean that there is not what is known as a "soft" code. this type of code will not turn on the check engine light, but it will have a noticable change in engine performance. take the van to a local auto parts store or a good repair shop and see if they can hook up a scan tool to check for any codes. most places will do this for free.

 

[clockhill]

temperature sensor

The temperature sending unit for the temperature gauge is a different part than the engine coolant temperature sensor.

Thank you,

That sensor must be the one just behind the thermostat housing. I hope it can be checked while still in the block - I will look it up. Space is so tight it is hard to remove most Parts i would like to check.

Recently remperatures down to -4 C and the van is starting well. I am hoping the injector cleaner and sensor cleaning has made a difference but will need cooler temps to tell. I was thinking i might clean the IAC as suggested on another thread

 

[BrooklynBay]

It's been an average of 15* - 20* F in Brooklyn all week. My van refused to start a few days ago. It sounded like it was about to catch, then it missed each time. I kept cranking until it flooded, and the battery died. I pulled out the front spark plug, and it had the usual carbon deposits. I cleaned the plug, bent the tip closer to the electrode, then connected a battery charger. It started right up, and continued to do so all week after this. The spark plugs tend to get a wider gap as they deteriorate. There won't be enough spark energy if the gap is too wide, and they are fouled up.