I have a 94 ford ranger. when it is hot out (80 degrees +), and only when it is hot it burns rich. While driving, fumes will come in through the vents when the a/c is on. After running it in hot weather and turning it off, it will not start easily and you can smell fumes. I've replaced the oxygen sensors. I was told today that it could be the fuel pressure regulator...haven't replaced fuel filter or pump. Like I said this only happens in hot weather, no problem in fall/winter/spring.
94 ranger 4.0
265,000

 

Welcome to FTE.

Which engine do you have?????

Did this problem come about suddenly after some event, or slowly over time????

Do you have a CEL lit?????
If so, have the computer scanned for trouble codes & post ALL the code numbers found & the sequence (KOEO, KOER) in which they were found.

Most autoparts stores will do it at no cost.
If your ride is ODD-1, with the computers diagnostic port underhood, ask them if their scantool will hook up to it.

If it's OBD-1 you can also pull codes yourself, by using the directions in the "Tech Info" thread located atop this forums thread listing page.
Lots of other good repair info there too.

Are the fumes you smell of raw unburned gas?????

If so, maybe suspect a problem with the vapor recovery system, as it stores fumes from the gas tank in the charcoal canister & purges the tank via a rubber vacuum line on start up, using the fumes to start the engine easier. So any leak in dryrotted vapor recovery system components, or vacuum lines can cause a big stink!!!!

Those fumes are highly flamable/explosive, so you'll want to find out where they're coming from & put it right without delay.

It could be a faulty fuel pressure regulator as has been suggested & if your engine has it mounted on the fuel rail, pull it's vacuum line & see if any raw gas is in the line, if so, the regulators diaphragm is leaking & the regulator should be replaced.

If the fuel pressure regulator is in the tank as part of the fuel pump assy & if you suspect the regulator is acting out, check the fuel pressure with a gauge attached to the fuel rail to see if you have a over pressure condition.

If you don't have a gauge, most autoparts stores have one to loan on their "Loan-A-Tool" program, for a refundable deposit.

A bunch of trouble shooting thoughts to get you started, or for pondering.
Let us know what you find.

 

No matter how rich the engine is burning, you should not be able to smell it inside the cab. This is the whole reason there are law and regulations about where tailpipes can exit the vehicle. If you can smell it inside the cab, it is a possible indication that there is an exhaust leak in the forward section of the exhaust system. A leak in such a location would cause the vehicle to run rich. However, ambient temperature would have little effect on an exhaust leak, and you should be able to smell it all the time.

Since you reported the problem is occurring at warmer temperatures, I second the purge canister may be leaking. Warmer temperatures reduce the vapor pressure of gasoline and other liquids, which results in greater evaporation. In warmer weather, this might result in enough evaporation to produce a strong smell. I would agree, this is a dangerous situation, since a potentially flammable, maybe even explosive mixture could form.

 

94 ranger
V6 4.0

checked codes (obd-1):
KOEO: none
KOER: i couldn't get this one to give me any reading (the parts store i went to just loans the scanner). i'll try again tomorrow

yes, the fumes are of raw, unburned gas

I took it to a repair shop to check it over. They said pressure regulator and vacuum modulator for tranny??? Now, they weren't too certain on exactly what the deal is (I had told them when I brought it in that I thought it might be the fuel pressure reg.). I'm confused. Would the vacuum modulator have ANYTHING to do w/ this or is it something completely seperate that needs handled. I feel like they are just throwing parts at me. I'm still going to do the pressure regulator myself, just looking for any suggestions...

 

IMO, a bad tranny vacuum modulator wouldn't cause you to smell raw gas fumes.

BUT, do you have a auto tranny????
If so, is it's shifting acting out, or is it sipping/using tranny fluid, but you can't find an external leak????
If so, suspect that the tanny vacuum modulators diaphragm may be leaking, such that it's sucking tranny fluid back through the modulators vacuum line that connects to the intake manafold.

SO, pull the modluators vacuum line at the intake manafold connection & see if it has tranny fluid in it, if so, the modulator also needs to be replaced.

Did you pull the fuel pressure regulators vacuum line & find it wet inside with raw fuel, or do a fuel pressure check, to prove that the fuel pressure regulator is bad & needs to be replaced????

 

My votes are for purge valve stuck open and/or a leak in the gas tank. My old F150 had both.