My 1995 Ford Aerostar won't start when it rains.

[perlsu]

We love our Ford Van-roomy, runs great, but just will not start when it rains, or when it is forecast to rain.

Does anyone have any suggestions as to what might be the problem? We have taken to the garage, but if it's not raining, they can't find anything wrong.

 

[BrooklynBay]

Welcome to this forum! My 95 van does the exact same thing. One time when it happened, I removed the front driver's side spark plug, and found moisture on it. I cleaned the plug, and it started right up. I still have this issue since I've never replaced the spark plugs. When this issue occurs, I connect a big battery charger on wheels, and have it charge the battery for a few minutes to get extra starting voltage & current. It usually won't start unless I do it or wait until the sun comes out, and the humidity drops.

 

[loosenut349]

If I remember correctly, there is a barometric sensor on the intake manifold or somewhere along the intake run between the air box and the upper half of the intake manifold. That could be causing a problem if it is out of spec.

 

[BrooklynBay]

The 1995 with a 3.0L only has a mass air flow sensor. The original poster didn't say which engine he has. He might have a 4.0L.

 

[loosenut349]

OH REALLY, only a maf and no TPS,IAC,IAT or MAP sensors? That's funny, no matter what engine the van has, it still has most of these sensors.

 

[BrooklynBay]

When I was referring to only a MAF sensor, I meant that it would have either a MAF sensor or a MAP sensor (not both). Don't confuse a DPFE sensor with a MAP sensor. It obviously has the usual sensors such as a TPS, coolant sensor, etc.

 

[jlh3rd]

i had this problem with my 92 3.0......once, it was the platinum plugs that went 100,000 miles and the gap was too big, so replacing them fixed it....another time was bad spark plug wires, but that had other symptoms also...

 

[Adam_tinkerer]

Could be bad plug wires. I had the same problem with a 78 Volare. It turned out to be a bad coil, you could see the spark jumping from the center to the outer terminal. Of course, newer vehicles have a much more complicated system, but it could be a spark jumping to a shorter wire or something. -Adam

 

[loosenut349]

How could you confuse a differential pressure feedback EGR sensor with a Manifold absolute pressure sensor? They do two different jobs. The intake air temp. sensor works in conjunction with the mass air flow sensor to control fuel flow and mixture, which is also monitered by the O2 sensor in the exhaust stream. the map sensor is a BAROMETRIC sensor that moniters atmospheric pressure going into the intake. The DPFE monitors exhaust pressure and tells the PCM when the EGR valve needs to open or close. exhaust gas recirculation is used to keep combustion temps. down to prevent pinging and detonation. it also helps reduce nox, oxides of nitrogen, a by-product of gasoline after it is ignited.

 

[jlh3rd]

the maf would have nothing to do with a no start in wet/rain conditions only....disconnect the maf.....the van will start/run but roughly.....like Brooklyn Bay and my experience,...I will wager the problem is ignition related only . .....never ever heard of any sensor in any car called a barometric sensor
I don't think Brooklyn bay is the one that's confused.

 

[loosenut349]

Ok, a bad MAF will cause a no start/hard start condition and yes if it disconnected, the vehicle will run rough, but it will run. if you look up some ford literature, you will see that they classify a barometric sensor as a MAP/BARO sensor. it is the same thing, it measures manifold absolute pressure, BAROMETRIC pressure to regulate fuel/air mixture. years ago, ford had problems with the ignition system getting moisture, specifically the distributor cap, into it and causing a no start condition. while most vehicles no longer have distributors, I do agree this problem could be ignition related but, if that was the case the van would run rough after it did finally start, at least until the wires dried out. the original poster stated the van runs fine once it starts so, that makes me think it has another issue.

 

[BrooklynBay]

We need to hear from the original poster of this thread. It's important to know the engine size, trouble code numbers (if applicable), and if he started to do any troubleshooting (examine vacuum lines for cracks, plugs, cables, sensors, etc).