Fuel Consumption: Next Imponderable

[imp]

Lots of today's vehicular wonders display read-outs telling the mpg, or fuel being consumed, at any moment. My question is are the sensors used to power these displays generally-available? Could a guy rig one in his fuel line and view fuel flow rate continuously, as he drives along?

Second thought: Realization that one's car is using too much fuel, more than usual, can't account for a reason, beyond the operating reasons, injectors, plugs, pedal-foot fell asleep, etc., what about fuel leaks?

My wife says she smells gasoline. I'm getting really horse gas mileage. Connection?

Throw a fuel pressure gauge on the Schrader valve, turn key on and off a few times, observe gauge. Pressure drops steadily? Fuel pressure regulator leaking internally, bleeding pressure away to tank. OR, leaking externally, the source for the gas odor.

How about leaks in the fuel line delivery system? At filter, observed pressure would drop as described above when key turned off. But, in RETURN LINE, which is isolated from feed line by a nice spring-loaded valve in the regulator, a leak anywhere is undetectable by the pressure-drop check. You could be driving along losing fuel via a return line leak, it simply vaporizes (if, hopefully it does not catch fire), and is gone. You've already paid for it in mpg lost.

Just sayin' that a fuel leak causes low mpg. If in pump to eng. feed line, detectable by gauge. If in Eng. to tank return line, NOT DETECTABLE except by nose or maybe fire.

Check it out. Just sayin'. imp

 

[Black1987]

Lots of today's vehicular wonders display read-outs telling the mpg, or fuel being consumed, at any moment. My question is are the sensors used to power these displays generally-available? Could a guy rig one in his fuel line and view fuel flow rate continuously, as he drives along?

Second thought: Realization that one's car is using too much fuel, more than usual, can't account for a reason, beyond the operating reasons, injectors, plugs, pedal-foot fell asleep, etc., what about fuel leaks?

My wife says she smells gasoline. I'm getting really horse gas mileage. Connection?

Throw a fuel pressure gauge on the Schrader valve, turn key on and off a few times, observe gauge. Pressure drops steadily? Fuel pressure regulator leaking internally, bleeding pressure away to tank. OR, leaking externally, the source for the gas odor.

How about leaks in the fuel line delivery system? At filter, observed pressure would drop as described above when key turned off. But, in RETURN LINE, which is isolated from feed line by a nice spring-loaded valve in the regulator, a leak anywhere is undetectable by the pressure-drop check. You could be driving along losing fuel via a return line leak, it simply vaporizes (if, hopefully it does not catch fire), and is gone. You've already paid for it in mpg lost.

Just sayin' that a fuel leak causes low mpg. If in pump to eng. feed line, detectable by gauge. If in Eng. to tank return line, NOT DETECTABLE except by nose or maybe fire.

Check it out. Just sayin'. imp

You probably smell gas due to a few things, without knowing the specifics of your model or set up...shot in the dark:

1. What kind of exhaust do you have? Non-tailpipe cars aka with dumps/turndowns will have a heavier gas smell because the exhaust gases are under the car.

2. The smell also may be related to a clogged or absent charcoal canister. Without this functioning, our cars will smell like gas unless it is vented towards the back of the car or something creative.

3. What is your fuel pressure at idle and does it hold after you shut off the car? Should be around 38-40psi.and should not be bleeding off that fast. Sounds like the diaphragm may be going to bad.

4. Is there fuel gauges for MPG, probably, but it would be simpler to run a wideband O2 and see what's going on. If there are no irregular A/F readings like going super rich, then that will help narrow it down to a leaky system.

5. Lastly, wouldn't hurt to have it tuned also.

 

[Noobz347]

Get an electric car.

 

[jrichker]

The Right Foot-O-Meter is usually the source of low MPG in an otherwise properly maintained car.


To help diagnose this problem, an old fashioned vacuum gauge attached to one of the spare vacuum port will tell you when you are in the gas gobbler zone...

 

[Mustang5L5]

I GPS log my drives, and then do basic math when I fill up the tank.

I'm averaging 6.7 MPG. It's great

 

[vristang]

Lots of today's vehicular wonders display read-outs telling the mpg, or fuel being consumed, at any moment. My question is are the sensors used to power these displays generally-available? Could a guy rig one in his fuel line and view fuel flow rate continuously, as he drives along?

Not with fox generation computers.
And it typically isn't calculated by 'fuel flow', but rather by injector PW, rpm, gear ratios, tire size, etc.
It could be done with something like an Arduino though...

Second thought: Realization that one's car is using too much fuel, more than usual, can't account for a reason, beyond the operating reasons, injectors, plugs, pedal-foot fell asleep, etc., what about fuel leaks?

My wife says she smells gasoline. I'm getting really horse gas mileage. Connection?

Throw a fuel pressure gauge on the Schrader valve, turn key on and off a few times, observe gauge. Pressure drops steadily? Fuel pressure regulator leaking internally, bleeding pressure away to tank. OR, leaking externally, the source for the gas odor.

How about leaks in the fuel line delivery system? At filter, observed pressure would drop as described above when key turned off. But, in RETURN LINE, which is isolated from feed line by a nice spring-loaded valve in the regulator, a leak anywhere is undetectable by the pressure-drop check. You could be driving along losing fuel via a return line leak, it simply vaporizes (if, hopefully it does not catch fire), and is gone. You've already paid for it in mpg lost.

From what you are describing... leaking regulator or sticking injectors come to mind.
The regulator can develop leaks between the fuel side and vac side, which leaks fuel into the intake manifold. Usually there will be a fuel smell/trace coming from the vac ref port of the regulator in this case...

 

[General karthief]

.
The gas smell your wife complained about is because your charcoal canister is missing/not hooked up, you mentioned this in another post.
And those 'miles left till empty' numbers on the newer cars are not accurate, I've had cars run out while the readings said '25 miles to emply' had one that made it 7 miles to the auction with '0 miles' indicated.

 

[imp]

.
The gas smell your wife complained about is because your charcoal canister is missing/not hooked up, you mentioned this in another post.
And those 'miles left till empty' numbers on the newer cars are not accurate, I've had cars run out while the readings said '25 miles to emply' had one that made it 7 miles to the auction with '0 miles' indicated.

@karthief
Your memory is remarkable! I will try to live up to your expectations regarding over-thinking in my reply to @Black1987, who took the time to also do some thinking! imp

 

[imp]

Not with fox generation computers.
And it typically isn't calculated by 'fuel flow', but rather by injector PW, rpm, gear ratios, tire size, etc.
It could be done with something like an Arduino though...


From what you are describing... leaking regulator or sticking injectors come to mind.
The regulator can develop leaks between the fuel side and vac side, which leaks fuel into the intake manifold. Usually there will be a fuel smell/trace coming from the vac ref port of the regulator in this case...

@vristang
Not on dashboard readouts, of course. After about an hour looking over too-numerous offerings of small fuel flowmeters using turbine, gears, suspended steel balls (!), etc., I gave up to seek more info.

I've installed a new pressure regulator, take-apartable, BBK, diaphragm nice and clean, strong, center ball seats cleanly on outlet seat, seals well enough that my 5 psi of spit can't be forced past it. (forked-tongue won't work). But, yes, big regulator leak would cause rich-running; would PCM cut back inj. time to compensate? That would go outside look-up table, ought to throw CEL (?).

Leaky injector(s), why not? Good point. Rich-running, same question as above, I dunno. imp

 

[imp]

You probably smell gas due to a few things, without knowing the specifics of your model or set up...shot in the dark:

1. What kind of exhaust do you have? Factory OEM, never been touched, except air feed from smog pump closed-off.
2. The smell also may be related to a clogged or absent charcoal canister. Without this functioning, our cars will smell like gas unless it is vented towards the back of the car or something creative. Canister missing, nylon vapor line to canister was hidden away in fenderwell, contributed to fuel odor, it's now capped off. (creative?). Canister solenoid missing, too. This subject is worth a thread of it's own, IMO, though @karthief will proly disagree!
3. What is your fuel pressure at idle and does it hold after you shut off the car? Should be around 38-40psi.and should not be bleeding off that fast. Sounds like the diaphragm may be going to bad. Problem was new pressure regulator leaking fuel to outside, leak was improper seal of inlet tube (the larger with 2 O-rings) to housing. Anyhow, OEM regulator showed 35 psi idling with vac. tube disconnected, 30 connected. New reg. adjustable, BBK 1707, nice looking, piss-poor workmanship, sealed leak myself, rather than mess with return. Truly interesting, this. One website showed the bottomside of the reg, it had a rubber seal encompassing both fuel tubes, to solve their leak problems! Mine came without it, old stock?
4. Is there fuel gauges for MPG, probably, but it would be simpler to run a wideband O2 and see what's going on. If there are no irregular A/F readings like going super rich, then that will help narrow it down to a leaky system. Not literate enough to understand exactly, substitute different HO2S, view outputs??
5. Lastly, wouldn't hurt to have it tuned also. No question! But, what? Has new plugs. Could check initial timing, advance, if I knew how.

 

[jrichker]

The initial timing is whatever you set it at - see below


Putting the distributor back in and setting the timing.

Revised 15-Apr-2016 to add fix for TFI hitting the thermostat housing while trying to set the base timing at 14°.

You can forget about anything beyond this point if you don't have access to a timing light. You will never get the timing set right without one.

Note: If you don't have access to a timing light, most of the larger auto parts stores will rent or loan one if you have a credit card or leave a cash deposit.



Putting the distributor back in is fairly simple. Pull #1 sparkplug, put your finger in the sparkplug hole, crank the engine until you feel compression. Then line up the TDC mark on the balancer with the pointer on the engine block.

The distributor starts out with the #1 plug wire lined up at about 12:00 with you facing it. Align the rotor to about 11:00, since it will turn clockwise as it slides into place.

Align the distributor rotor up with the #1 position marked on the cap, slide the distributor down into the block, (you may have to wiggle the rotor slightly to get the gear to engage) and then note where the rotor is pointing.
If it still lines up with #1 position on the cap, install the clamp and bolt. If not, pull it out and turn 1 tooth forwards or backwards and try again. Put the #1 spark plug back in and tighten it down, put the clamp on the distributor, but don't tighten it too much, as you will have to move the distributor to set the timing. Note that there is no such thing as one tooth off on a 5.0 Mustang if you follow the spark plug wire order on the distributor cap. If it doesn't align perfectly with #1 position, you can turn the distributor until it does. The only problem is that if you are too far one way or the other, you can't turn the distributor enough to get the 10-14 degree optimum timing range. If the TFI prevents the distributor from being turned enough to get 14°, there is a simple fix. Pull the distributor out and turn the rotor 1 tooth counterclockwise Don't move the wires from the positions shown on the cap on fuel injected engines!!!! The #1 position cast into the cap MUST have the spark plug wire for #1 cylinder in it. Do it differently and the timing for the fuel injectors will be off. The computer uses the PIP sensor to time injector operation by sensing the wide slot in the PIP sensor shutter wheel. If the injector timing of #1 and the firing of #1 do not occur at the right time, the injector timing for all other cylinders will be affected.

Setting the timing:
Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

10 degrees BTC is towards the drivers side marks.

Note: setting the timing beyond the 10 degree mark will give you a little more low speed acceleration. BUT you will need to run 93 octane to avoid pinging and engine damage. Pinging is very hard to hear at full throttle, so it could be present and you would not hear it.

Simplified diagram of what it looks like. Not all the marks are shown for ease of viewing.

ATC ' ' ' ' ' ' ' ' ' '!' ' ' ' ' ' ' ' ' ' BTC
---------------- > Direction of Rotation as viewed standing in front of the engine.

The ' is 2 degrees.
The ! is TDC
The ' is 10 degrees BTC
Set the timing 5 marks BTC. Or if you prefer, 5 marks towards the driver's side to get 10 degrees.

To get 14 degrees, set it 7 marks BTC. Or if you prefer, 7 marks towards the driver's side to get 14 degrees.

The paint marks you make are your friends if you do it correctly. They are much easier to see than the marks machined into the harmonic balancer hub.

At this point hook up all the wires, get out the timing light. Connect timing light up to battery & #1 spark plug. Then start the engine.

Remove the SPOUT connector (do a search if you want a picture of the SPOUT connector) It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT
Warning: there are only two places the SPOUT should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.

Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

 

[Black1987]

The capping off the vent line does more harm than good IMO. The fuel pump has a specific pressure range it needs to run efficiently. When you cap the line now there is going to be a build up of pressure in the tank which can cause the fuel pump to fail prematurely. If when you go to fill up and unscrew your gas cap and it sounds like a big rig air brakes discharging then you are asking for an ill timed static spark or idiot with a cigarette near by to cause a fire (is it likely no one knows). Sticking something in the hole isn't creative. This could end up being a situation where sticking something in the wrong hole could lead to Darwinism.....(marriage joke)

The OEM exhaust with no air pump may also being causing a smell issue. The air pump is used to recirculate air into the catalytic converters. This allows them to function appropriately and extend their life. Without this, the catalytic converters are prone to clog and fail, which would lead to poor gas mileage and smell....just a thought.

Lastly the MPG question, the wideband O2s (google is your friend) would tell you if the car was not running optimal in real time and some have a function of data logging. No this will not tell your MPG like a new car, but this can show you if you car is running pig rich, too lean, and driving habits. Once you narrow out your car is running fine, then mpg can be calculated the old fashion way: how many miles/how many gallons.

If your odometer doesn't work they have GPS apps for this as well.

 

[vristang]

@vristang But, yes, big regulator leak would cause rich-running; would PCM cut back inj. time to compensate? That would go outside look-up table, ought to throw CEL (?).

Leaky injector(s), why not? Good point. Rich-running, same question as above, I dunno. imp

In either case, the ecu would reduce injector PW's to correct the AFR as seen at the O2's.
However, the ecu is only allowed to adjust the PW's 12.5%...
If the AFR is still rich after reducing PW's by 12.5%, then the AFR stays rich.
I don't recall if this triggers the CEL, or just logs the code.

Do your plugs indicate rich condition?

 

[imp]

The capping off the vent line does more harm than good IMO. The fuel pump has a specific pressure range it needs to run efficiently. When you cap the line now there is going to be a build up of pressure in the tank which can cause the fuel pump to fail prematurely. If when you go to fill up and unscrew your gas cap and it sounds like a big rig air brakes discharging then you are asking for an ill timed static spark or idiot with a cigarette near by to cause a fire (is it likely no one knows). Sorry, I have to disagree on this. Here's why: there is no difference between a capped-off vapor line without a canister, and the presence of one. Both are un-vented, both allow vapor pressure to remain stored within. That pressure level is strictly determined by the temperature of the tank and it's fuel. I see no correlation to fuel pump life expectancy. Anyways, when I unscrew my fill cap, there is no discernible puff of vapor present.
Vapor pressure always seems to be a much misunderstood concept, yet we all know it's there, and what it's like.

The OEM exhaust with no air pump may also being causing a smell issue. The air pump is used to recirculate air into the catalytic converters. This allows them to function appropriately and extend their life. Without this, the catalytic converters are prone to clog and fail, which would lead to poor gas mileage and smell....just a thought. This one I can't argue about, but recall my Foxes had a single air pipe which entered the exhaust system behind the right-hand side cat, had no affect on the cat operation. My SN95 I am not certain about, but noted the replacement exhaust systems marketed have a stub nipple welded on the SIDE of the RH cat, thus allowing smog pump air to enter the cat. So, I dunno. Except that, those baby solenoids connected in the smog air circuit allow ALL pump output to go to the exh. pipe when the engine is idling, and direct that air into the cyl. heads when running under power.

Lastly the MPG question, the wideband O2s (google is your friend) would tell you if the car was not running optimal in real time and some have a function of data logging. No this will not tell your MPG like a new car, but this can show you if you car is running pig rich, too lean, and driving habits. Once you narrow out your car is running fine, then mpg can be calculated the old fashion way: how many miles/how many gallons.

If your odometer doesn't work they have GPS apps for this as well. Ya know yer old when "APPS" mean Employment Applications! imp

 

[imp]

In either case, the ecu would reduce injector PW's to correct the AFR as seen at the O2's.
However, the ecu is only allowed to adjust the PW's 12.5%...
If the AFR is still rich after reducing PW's by 12.5%, then the AFR stays rich.
I don't recall if this triggers the CEL, or just logs the code.

Do your plugs indicate rich condition?

@vristang
I replaced the plugs awhile back. The old plugs were in excellent condition, could not have been extremely high miles, my guess, checked gap on one, ~ 0.060". Their color was light brownish-gray on the electrodes. A guess, not extremely rich running. Of course, I had to blab about rebates on Platinum plugs, which started a whole debate..... imp