Losing fuel somewhere, thoughts?

[locovaca]

So I'm still trying to figure out my low MPG situation (low 20's with nearly all interstate driving). The last few weeks I went and retrofitted an Explorer Message Center and Taurus Digital Cluster to my Ranger (more on that in another thread). Both of them come with MPG calculations, which are made by using the speed sensor signal (which I have confirmed is 100% spot on) and the fuel flow signal from the computer.

The Taurus Cluster has average and instant MPG, and the Explorer MC has both of those and a feature which shows the amount of fuel consumed. I did a fill up today; the MC said I had used 13.3 gallons of fuel, and I filled up with 14.7. That's a 10% difference. The important thing is that my average MPG according to both was 25.1 MPG, based on that 13.3- that's more of what I am expecting. With the real fuel used, it was 22.7.

From what I've read on FordFuelInjection.org, the Fuel Flow signal is 100% dead on. It is an absolute value of the number of times it opens the fuel injectors * the number of injectors, so there isn't any compensation needed for an I4 vs V6 vs V8. So I'm operating on the assumption that the computer is right and I'm losing fuel somewhere on the line.

I need to get a pressure tester, but checking pressue is on the list. My next thought is maybe someone swapped in an injector or two which was a higher flow than stock. Which comes to my first question- how do you identify the injectors?

The next question is, any other ideas? The regulator seems ok, but I'll get that fully tested when I get my pressure gauge. No leaks that I can see/smell... the truck overall runs fine, it just gets poor mileage.

 

[SykoRanger88]

i would check the fuel filter, the lines going in and out of it might not be on there right or something.

 

[Mark_88]

Short of other places, is the fuel tank new? I had a leak in mine about half-way down and it would dribble out when I filled it up until the time it reached the leak...then it'd be ok till I filled it up again...

I didn't notice mine even because most of the time I was highway driving and I wouldn't fill it up on the way home...only on my way to work...and by the time I got back home it was usually below the leak...it was only when I took it in for E-testing and filled the tank then topped it up with that E-Test Pass stuff...they noticed it right away and said they couldn't test the truck until the leak was fixed...

If you're not sure...put a piece of cardboard under the tank and check it in the morning for gas smell...

Other than that...are you saying you used a gas mileage sensor from a vehicle that had a V6 or V8? Would that not somehow be off if it was expecting 6 or 8 injectors?

I have no idea about these things...just wondering if that might be part of the problem...

 

[locovaca]

Other than that...are you saying you used a gas mileage sensor from a vehicle that had a V6 or V8? Would that not somehow be off if it was expecting 6 or 8 injectors?

It doesn't work that way. The EEC sends a signal every half second that says "In the last half second, this total amount of fuel was used." The EEC does the adjustments/calculations for the number of injectors when it generates that signal.

And even then, the instruments came from different cars with different engines (Digital cluster is from a 3.0/3.8 Taurus, Message Center from a 4.0/5.0 Explorer). If there was some built-in compensation I would expect the two separate calculations to be off, but they're not, they are exactly the same. That supports that documentation on FFI.

The fuel tank is not new, probably original. I just filled up yesterday so I'll get under and check everything, although I haven't had a gas smell since I capped off my evap system.

So does anyone know how to identify the injectors?

 

[mrcarcrazy]

Injectors are typically identified by color. Mine are red.

 

[locovaca]

So, a couple of things:

1. Maybe I'm not looking at the right place, but my injectors have a gray plastic ring on them... Is that right?

2. I hooked up the pressure gauge. I'm not 100% on how to interpret these results, but something does seem off from what I've read:

* From 0 psi, priming the pump 5 times brings the pressure only up to about 12 psi.
* Starting the engine, the pressure slowly rises to about 25 psi- maybe of the course of 30-45 seconds. It wouldn't go above 25 psi on its own, even with goosing the throttle.
* Taking the vacuum off of the regulator, psi rises relatively quickly up to 40 psi (this was the only part that seemed normal)
* After putting the hose back on the FPR, the PSI very slowly trickles back down mid 30's psi.
* Goosing the throttle, with or without vacuum on the FPR, does nothing (I saw several sites that said the pressure should rise 5 psi or so)
* After running the engine the pressure holds at its last mark consistently, so there don't seem to be any injector leaks.

Does that all sound correct?

 

[feellnfroggy]

10 percent? I dont think you are losing fuel. If its showing a fuel loss and its a return style system then you have the fuel in the hoses unaccounted for. But I have seen on way too many occassion where the instant MPG and hte AVG MPG are wayyyyyy off in the ford vehicles. If your fuel pressure is as consistent as you say it is then no probs. Keeping in mind that when your needle is on the E you should have another 20-30 miles you can drive, ford has always left that room for error in their gauges. Same with filling up. 3/4 is not 3/4 cuz the needle stays on full for way too long. Its stays on full for about 4-5 gallons in my ranger.then starts moving at a steady pace as I drive.
Again I don't think your losing fuel anywhere I think its just the electronics playing Fords Calculation games.
You can always pull your tank and weigh it full, put it back drive around and pull it weigh it again and compare the weights to the computer numbers LOL but I dont recommend it.

Edit:: My mustang has a rubber grommet where the filler neck enters the gas tank. This grommet is busted on my car so I cant fill up beyond 1/2 tank. Every time I turn right my fuel sloshes out the filler hole in my tank and I lose fuel all the time. This is the exception to everything I said above. You might be losing fuel this way.

 

[Caulk04]

Definetly check for leaks. Especially with original parts on a 93. My 97 has a split in the filler neck that I patched up with some silicon since I don't want to spend the fortune on a new neck. It still leaks a bit when full, but not much.