Help! On the highway and need some info

[rockwerks]

Im in the middle of the deserts of Nevada between LV and REno. Im having major fuel smell and loss of MPG, no visable signs of leaks etc. The smell only happens on heavy load while pulling steep grades. The next town of any size is 90 miles north and IM going to limp it in tomorrow AM early but any thoughts would be a big help

current mileage around 8 mpg towing a trailer, yesterday 20 mpg same trailer

4.0 1994 Mazda b4000
auto rebuilt with HD cooler

any thoughts?

TIA

Brian and Ali and the dogs too!

 

[Wicked_Sludge]

fuel pressure is increased as engine load increases...it sounds to me like you have a leak before (or at) the fuel pressure regulator that is only leaking under the high pressure caused by high loads....this is why you cant see the leak at idle (fuel evaporates quickly, especially on a hot engine in the desert).

i would try pulling the vacuum line off the regulator while the engine is idling (this closes the regulator, thus increasing fuel pressure) and see if the leak exposes itself. specific areas to check include fuel injector o-rings, fuel rail quick disconnect fitting, and the crossover line between the left and right side rails.

 

[rockwerks]

well I was able to get hold of a scanner and got a 176 code when KOEO, but not KOER. anyone? need help here

 

[Wicked_Sludge]

176 is a stored lean mixture code...most likely because all your fuel is leaking out onto the ground rather than going into the engine. this must be a hell of a leak...

 

[rockwerks]

176 is a stored lean mixture code...most likely because all your fuel is leaking out onto the ground rather than going into the engine. this must be a hell of a leak...

the 176 is a drivers side o2 sensor correct?

 

[rockwerks]

fuel pressure is increased as engine load increases...it sounds to me like you have a leak before (or at) the fuel pressure regulator that is only leaking under the high pressure caused by high loads....this is why you cant see the leak at idle (fuel evaporates quickly, especially on a hot engine in the desert).

i would try pulling the vacuum line off the regulator while the engine is idling (this closes the regulator, thus increasing fuel pressure) and see if the leak exposes itself. specific areas to check include fuel injector o-rings, fuel rail quick disconnect fitting, and the crossover line between the left and right side rails.

I will check this in the morning, any other ideas?

 

[Wicked_Sludge]

if you smell fuel, then it is leaking somewhere...and quite a bit to lower your economy that much and set a DTC. the fuel is probably evaporating before it makes it to the ground.

yes 176 is the drivers side bank.

 

[rockwerks]

if you smell fuel, then it is leaking somewhere...and quite a bit to lower your economy that much and set a DTC. the fuel is probably evaporating before it makes it to the ground.

yes 176 is the drivers side bank.

Thanks again, Ill check it out in the morning. I can find the tps. the maf, iac. where is the fuel regulator?

 

[Wicked_Sludge]

its the shiny round thing mounted right on the fuel rail. it has a single vacuum line plugged into the top of it.

 

[shadetree]

its the shiny round thing mounted right on the fuel rail. it has a single vacuum line plugged into the top of it.

The fuel rail on the 4.0 (at least on my 94 Explorer) is sandwiched between the upper and lower manifold. It's not actually a rail. The regulator isn't shiny. It is on the right front of the intake manifold, and hard to see. It also doesn't have a rubber hose for control. It is a solid flex hose. He may have a problem checking the regulator itself. He can do a pressure check if he has the equipment. The pressure valve is right behind the regulator.shady

 

[MAKG]

The DTC and smell HAVE to be separate issues, unless the fuel smell is coming out the tailpipe. Internal fuel leaks make for lean codes (rich missing), and external leaks make fuel smells. If the fuel leak is bad enough to make a lean miss, it's gushing out, and will make puddles, even in the desert. Note that an exercise I had trying to figure out how to install injector O-rings on a 4.0L without cutting them (hint: Vaseline) made huge fuel leaks, and didn't trip any codes.

It's not always hot in the desert (even in summer), especially once one gets well out of Las Vegas and into some altitude. First thing in the morning, start the engine, remove the FPR line and cover the nipple, shut it off after 30 seconds at most (you don't want the engine to warm up), then go looking over the engine for wet spots.

Note that MOST fuel leaks on the engine do NOT leak onto the ground, but rather onto the top of the intake manifold. It does form puddles there, but they are often very hard to see due to shadows. Get a bright flashlight. Leaks around upper injector O-rings and the FPR O-ring are common. It would take a disconnected pressure line to leak enough to make the engine lean out.

Lean codes can be tripped by a lot of things, including rich misses. If your engine is rich missing, you can get raw fuel out the tailpipe, and a lean code at the same time (HEGO sensors only measure oxygen, and don't care if there is fuel there, too). The cat may never warm up enough to do anything about it, but if it does, it will often glow bright red. This is not a broken cat.

How far are you from Tonopah? There are several garages there.

 

[rockwerks]

well there where no issues with the rig today, we put it under some heavy loads and the truck got 27 mpg today, the difference was the fuel. the gas I bought the day before was contaminated and 91 octane. I ran all that fuel out that day put in 87 octane full tank and no issues today. no gas smells at all today and we drove over 400 miles. I have had gas smells before on cherokees and know the drill, there is no evidence of a fuel leak on this rig, my thought is the excess fuel was causing the charcoal canister to be overwhelmed and hence the fumes.

I found the fuel reg and did the requested tests, no leaks, all the fuel was running through the engine and out the pipe.

 

[MAKG]

Well, that sucks.

Keep in mind that you don't need 87 octane at high altitude. The thinner air will keep it from detonating. A good rule of thumb is that the lowest pump grade available is probably adequate. You'll find 85 octane over much of the Great Basin. Not in California, though (and perhaps not in Reno), as it's just too easy to drive down to sea level in well under a tank, and detonate like mad when you get there.

I'd siphon the tank out if I thought the fuel was bad. Where did you pick up contaminated fuel? The Nevada Test Site? Does your truck glow in the dark now?

 

[rockwerks]

Well, that sucks.

Keep in mind that you don't need 87 octane at high altitude. The thinner air will keep it from detonating. A good rule of thumb is that the lowest pump grade available is probably adequate. You'll find 85 octane over much of the Great Basin. Not in California, though (and perhaps not in Reno), as it's just too easy to drive down to sea level in well under a tank, and detonate like mad when you get there.

I'd siphon the tank out if I thought the fuel was bad. Where did you pick up contaminated fuel? The Nevada Test Site? Does your truck glow in the dark now?

Kingman AZ where else............In Carson city now truck ran great all day without any issues at all. but we did run the truck nearly dry the day before and most places in the west 87 is low grade gas. On to Oregon tomorrow.. The army was testing drones as we went by nellis test range.

As for Tonopah garages most where not open when we past through at 9:00 am this morning and the guy who was said he might be able to help on Tuesday next week