94 XLT no start in high humidity

[juggernaut2874]

My 94 XLT with 180K miles is having problems starting after it rains or when there is high humidity and since I am on the coast that is always. There are no KOEO or KOER codes and I have new fuel filter, clean K&N air filter, plugs, wires, and battery. When it is sunny and hot out, I have no problem firing it up. I put water remover in the gas tank every so often. Could moisture be getting into the coil pack or somewhere else? Could it be the FPR or a vacuum leak? Have not had a noid light on the injectors because none of the old plugs were fouled and it runs just fine when it starts. I'm at a loss.

 

[gsmaclean]

On a dark night, start it up, then take a spray bottle of water (one that makes a fine mist) and start spraying it around in the engine bay. When you start seeing sparks, you've found your problem area. Chances are it's coil, wires, or other high-tension component.

 

[juggernaut2874]

Spraying the running engine with a fine mist of water showed NO problem areas last night...not even a shudder. So far I have found no vacuum leaks other than the seal on the hard plastic input to the throttle body from the air cleaner is a little damaged. Anyone else have this happen or have an idea what to check next?

 

[quicklook2]

was this a hurricane damaged vehicle?

was it ever flooded when offroad?

 

[juggernaut2874]

No it was not flooded at anytime. During Katrina, the Marine Corps had me on the other side of the world and the X was in TX.
I got it to start by spraying ether into the throttle body last night. Ran KOEO, CM, and KEOR codes again and all passed. After it started with the ether it was able to be started over and over again for a couple of hours. I let it sit over night and it won't start on its own unless I give it ether again.

 

[juggernaut2874]

I'm going to verify what the fuel rail pressure is from the Schrader valve. I hear the fuel pump engage when the key is turned and know that fuel is getting to the rail when it starts with ether. The fuel pump relay is working. Maybe the Fuel pressure regulator is bad. If I pull the vacuum hose off the FPR, should fuel be in the vacuum hose?

 

[quicklook2]

no, if it is you need a new fpr.

when you turn the key on engine off, how long does the fuel pump run?

if it is running for a long time, like a half minute, the computer may be bad.

 

[juggernaut2874]

No the fuel pump runs for the normal ~2 secs after the key is turned on. Computer is good to go since it is running just fine once it starts. Idles at 600 rpm, not sluggish or hesitant. The only problem with the X is that it has trouble starting on some days. I'll crank it over and over (moreso on humid days or after it rains it seems), get frustrated come back to it a couple of hours later and it usually fires right up. Right now the truck is working just fine but I don't know for how long?

 

[juggernaut2874]

The truck is back to not starting...just crankig over and over and it hasn't been humid out or raining. No fuel was in the vacuum line of the FPR - assume FPR is good then. Could this be a bad/dirty Engine Coolant Temp sensor, IAC sensor, Cam Position sensor, weak starter? What can I check?

 

[quicklook2]

does it start if you spray ether in the intake?

codes?

does it have spark when it does not start?

 

[juggernaut2874]

Yes it does start if ether is sprayed in the intake. No there are not any KOEO, CM, or KoER codes. It just cranks over but does not fire up sometimes. Today right now...it starts up just fine.

 

[Jcnbama]

If you can spray ether into the intake and it fires up it would see like its not getting the fuel it needs to start, May sound crazy but maybe your reading too much into the whole " humid environment thing " My 94 xlt about 195k fuel pump just went out and it was acting similiar only it was running rough intermittently and cutting out sometime.Did you say you had a new fuel filter? Installed properly? Have you tried fuel system cleaners etc?

 

[explorer pilot]

Two things I would check. When it does not start are you sure the fuel pump is running? I would replace the fuel pump relay and the eec relay both under the hood on passenger side. If memory serves me correctly they are the same relay. I had something similar happen 25k ago, random wouldn't start(once running good to go). Started off being weeks between problems, then days. I have 177k on my '94. I repaced the fuel pump relay and it went away for a couple of weeks. Replace EEC relay, no more prob. Relays are cheap.

 

[juggernaut2874]

Possibly fixed...time will tell

I am certain that it is not the fuel pump relay (45-50 psi on fuel rail). I have interchanged all of the relays to no avail. I just replaced the crankshaft position sensor and it seems to have fired right up. We'll see if it works. I'll post with new news later.

 

[juggernaut2874]

Been a little over a week since the crankshaft position sensor was replaced. Have not had a problem starting the truck at all no matter what the weather condition is. I consider this fixed but will post if the problem reoccurs.

 

[mikeinri]

Glad you got it fixed. Just out of curiosity, what led you to the crankshaft position sensor as the root cause?

Mike

 

[juggernaut2874]

Explorer still starting just fine and runs great. What led me to the crankshaft position sensor was more curiosity than anything. It is cheap to replace, easy to get to, and knowing that if the PCM doesn't know exactly where TDC is then it won't send the right info to start. When it did start before, I guess it was by luck or the sensor worked just enough to send the proper signal.