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Ive done improve my mpg,,After replacing intake gasket throttle body gasket & aalmost every concievable trick the MPG seems to have dived to 16??Ive noticed that the trip odometer seems to stick sometimes..
I have a spare 94 speedo which I will swap out,,Ill try to see if the improves,,last pring I replaced the axle wires & used heat shrink coating but still occasionally the needle bounces
I m wondering if anyone else w has similar experiences???
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i fixed it!!! not sPEEDO AT ALL!!! i GOOFED UP HEN LAST CHANGING THE FUEL FILTER & LEFT OFF 2 CLAMPS OR SOMEHOW THEY CAME LOOSE!!!
i FILLED TANK,,,AFTER REPLACING THE CLAMPS & GOING 71 MILES 1/2 AT 75 MPH...I FILLED TANK & IT TOOK 3 GALS,,,24MPG!!
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Can someone post a pic of the Fuel pump housing as it sits in the tank. to the lower right there appears to be a broken rubber cap. I got a new cap & am going to replace. hopefully that is the leak,the fuellines all seem to be tight & nt leaking,,,
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Im trying to figure out how to condense this.At some point th vapor canister to tank line was plugged off at the canister & at the fuel pump sender!! I shouldve studied the setup to 4 yrs ago when I bought the car!!!
Ill have to see whether my mechanic for the hard stuff can reinstall it...
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As Spook writes you providing wise guidance.
A cause of low fuel economy, as Nantanha indiates to you, is the failure of the fuel injector fuel pressure regulator (FPR).
At high air intake manifold vacuum (negative pressure we can call it? I dunno.), such as when you foot is off the gas pedal, the FPR opens allowing fuel to pass to the low pressure fuel return, lowering fuel rail pressure. The fuel ECU also changes the injector pulse duration. When you floor it, the intake vacuum is lowered closer (more pressure, yet a vacuum, usually, and the FPU responds by closing, reducing the amount of fuel to the low pressure return, increasing manifold pressure.
Blindboy, I'm unsure of your 1993 940 Wagon is Turbo or not. Bosch or Siemens / Bendix Rex (ignition) / Regina (fuel control). (Bendix Rex / Regina is like Bosch D-Jetronic a wee bit! Maybe with less fuss!)
Your 1993 940 includes the OBD-1 test ability. May want to check for fault codes as in in the FAQ for both socket 2 (fuel and emissions) and 6 (ignition and emissions). Does your instrument cluster display an illuminated CHECK ENGINE light?
One cause of fuel enrichment is a vacuum leak at any vacuum line connection at the manifold downstream of the throttle body (as well as upstream) as such a vacuum leak lowers the vacuum, so the FPR raises injector fuel rail pressure and injector pass more fuel into the engine.
The PCV on my factory stock (as I love it!) 1992 green 240 GL has been a vacuum leak headache since 2007. In the final round some months ago, I used new not the best quality PCV piping in the up to 1988 iPd relocation kit, a section of coolant line to secure atop the PCV breather box to the flame trap. I used hose clamps gently tightened.
Also, you may want to verify miles traveled using a cheapo GPS device or a mobile phone app.
I found odometers tend to lose accuracy with age and use, clocking more miles than actually traveled on RWD Volvo with electronic odo / speedo. I'm not sure of the 700-900 instrument cluster speedo / odo performance changes through age and use.
16 MPG in mixed use is a significant reduction in fuel economy in mixed motoring.
If you suspect leaks at the closed pressure side of the fuel delivery system, the leak would be significant and possible dangerous. You could wire the fuel pumps to run with engine off and body raised to see any fuel drips. You can wipe fuel line unions with a dry paper towel and check for gasoline wetness. Observe safety! I can suggest ways to jumper the Bendix pump or Bosch (both pumps) as you like.
Another cause for reduced fuel economy are faulty emissions control sensors:
- Oxygen sensor if exhaust header pipe outlet to catalytic converter union intake leaks. May not hear it. Yet between exhaust pulses, external air gets sucked in, the oxygen sensor encounters more 02 than should be normal with a properly sealed exhaust, and the fuel ECU enrichens the fuel to air ratio. Can also cause limp home mode. You can the the oxygen sensor using your digital electric multimeter (DMM). The 700-900 Series FAQ describes this procedure.
Yet do not test the ECU side of the oxygen sensor connector as cheap DMMs may not present the minimal resistance to do so and can cause fault in fuel ECU.
- Check Oxygen Sensor
Using a DMM with a disconnected 02 sensor connector and grounded to the engine, test the 02 sensor per the FAQ. Steady above .5 VDC indicates a rich exhaust. Steady at .5 VDC is a failed or failing 02 sensor. Below .5 is a lean exhaust. I'm better with Bosch than Bendix yet the values may be the same between the two. Bendix uses a very different 02 sensor.
- Check grounds and power.
Low voltage from the alternator, an old battery that does not hold a good charge or presentr improper load to the alternator, as in an old battery present very low resistance, reduces fuel economy. Poor found connections between the alternator, batter, and engine can be a fault.
On the engine control system side, poor signal, ground, and power connections can also limit fuel economy.
I guess that's all I got.
Hope that helps.
Questions?
Hope that helps.
Yes, practicing my tech writer skillz in these posts. Sorry for the long post.
Buttermilk MacDuffy's Tavern
(Glad and pleased and grateful Uncle OldDuke is BACK!!!!
OldDuke reminds me of Hunter S. Thompson and Charles Bukowski a bit, and some other literary heroes of mine!)
--
Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity
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no codes n no chk engine light ill get a gauge from autozone n chk the pressure to thanks
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as soon as my SSD check arives Ill get another FPR,,valve,,Ive tracked down every possible leak I can trace,,& Ill get fr guage ffrom Autzone then too,,,But Im pretty sure the weak link is the old fuel lines,,,leading from the tank forward
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Dear Blindboy,
Hope you're well. Put clean white paper towels around or under any place, from which you think fuel may leak. If fuel wets the paper, it will discolor the paper towel. That discoloration will remain, once the fuel evaporates.
I recall a post by the late "Lucid" that described replacement of the fuel pipe, from the tank to the fuel filter. If I recall correctly, replacing this pipe involves dropping the fuel tank.
This fuel pipe is part #3507548. It may still be had from a U.S.-based Volvo dealer. The cost will be about $90.
It might be easier to replace the metal pipe with fuel injection-rated hose.
I suggest checking the banjo bolts, that connect fuel pipes/hoses to the fuel filter. Those bolts are fully exposed to underside hazards. A heavily-corroded banjo bolt might "pin-hole". While the engine is running, a "pin-holed" banjo bolt will leak or spray fuel.
Hope this helps.
Yours faithfully,
Spook
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How old is your fuel filter ?
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Hiya Blindboy,
Sorry for the slow (ice) flow tardy reply.
Can you put some dry cardboard under your 1993 940? Can you run the pumps at the fuse and relay board socket behind the ashtray?
Can you find a pal with a good oldfactory (olfactory) sense and sniff about your 1993 940 Wagon.
If you believe leaks are the cause to get such an MPG, the fuel loss would be catastrophic and a grave danger of fire and worse.
Can you use a hand held GPS device to track miles traveled and compare with your speedo / ODO?
Is your 1993 940 Turbo or no? 1992 940 was Bosch fuel control (with intank and main inline pump). Last year of Regina in non-turbo 940 was 1991 or 1992?
Please advise.
Thank you.
--
Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity
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still trying to figure out,,,put a new plug on the plastic nipple on the fuel sender,,drove 100 miles & used 5 gals,,,20 mpg,,,so it improved,,,then drove it 86,,miles & it dropped down to 13 mpg seems like every fix works for a little while...& then the reverse happens..its been raining alot in NJ..so when it clears up ill jack it up & get a closer look underneath
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Having perused this whole thread - seems more likely to me that the problem lies with calculation of the fuel mileage, rather than with the fuel mileage itself. The tell-tale is this latest "it went from 20 to 13" post. FWIW - My daughter's 760 wagon (loaded with every option known to man) never got better than 15-16 mpg around town, and 20-21 on the highway. This averaged over many tanks with miles traveled verified by GPS.
Because of variations in the way different gasoline pumps (or even the same pump at a different time) shut off flow -- you have to be really careful trying to determine fuel mileage --- especially for a relatively small number of miles (like 100 or 86). It doesn't take much variation in the fill amount to really skew the mileage number. If the fuel shutoff cut off a bit early, 5 gallons might have turned into 5.5 gallons -- and now your 20 number becomes 18. It takes the average of many tanks over a long period of time to get a good handle on what the actual fuel mileage is.
If you have such a significant leak that it's causing these problems, I've gotta think you'd see evidence of it on the ground -- and you (or someone) would smell it.
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Amen.
We have a long established habit of keeping the pump receipt with mileage and trip odometer noted. One receipt doesn't tell much of a story, but several in hand are revealing.
Lacking a good sense of smell would seem to me to be a serious disability when owning a 30-year-old vehicle. All the fuel leaks I've had were identified by the smell long before any MPG issue was noticed. Smell, and melted undercoating.
Been a while since I tallied up the receipts, but when I did, the effect of winter-blended fuels was clear.
--
Art Benstein near Baltimore
What engineers say and what they mean by it:
Engineering says: "The designs are well within allowable limits"
Engineers meant: We just made it, stretching a point or two.
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I've always kept close track on all of our vehicles. Because nerd.
The newer ones have the handy/dandy computer on board. Once I established how close the computer was to actual (On both the Subie and the Mazda, the computer reads out about 2-3% better mileage than actual), I stopped keeping track of miles/receipts.
The Volvo/LS3 combo has been interesting. Coming up on 4 years since the conversion. Like clockwork my around town tanks have been 19-20 mpg. Pretty amazing for a 430HP engine. Haven't had multiple good long highway runs, but have had some loops around the city. Looks like 25-27 on the highway is going to be repeatable. About the same mileage as my daughter's 76 242 got back in the early 90's.
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That kind of mileage on your V8 is impressive. I wonder how much might be attributed to the difference in driving style maturity brings. I barely remember what a V8 feels like or the 50-cent gas that made it inconsequential.
--
Art Benstein near Baltimore
What engineers say and what they mean by it:
Engineering says: "Test results were extremely gratifying"
Engineers meant: It works, and are we surprised!
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2 CLAMPS CAME LOOSE AT THE HOSES ON THE FUEL FILTER,,NOW IM GETTING 24 MPG,,, .
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I was thinking 29 cent gas....
The new stuff is SO much more efficient. Pretty amazing - the average new V6 (or turbo 4) Accord or Camry will outrun the average muscle car from back in the day, outhandle it, outstop it, run for 250,000 miles with a little care, all while quieter and more refined and knocking down 30+ mpg. Never a better performance time than now.
No doubt driving style plays importantly in mileage. Although I’d point out that a naturally aspirated 2.1L 76 Volvo itself seems to bring about a certain maturity in driving style regardless of the age of the driver.
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Dear kittysgreyvolvo,
Hope you're well. According to Volvo VADIS - a superseded dealer parts/service database - the Rex/Regina engine/ignition management system was used up to and including the 1995 models. These cars had a single, in-tank fuel pump. The 940 was not marketed in the U.S. after 1995.
In 1995 models with Bosch engine/ignition management, there was a single, in-tank fuel pump.
Hope this helps.
Yours faithfully,
Spook
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Im pretty sure this screwup was created by MOI!! when I last replaced the fuel pump MOI!! shouldve took a cell pic of the arrangement of the hoses.
there is the fill hose,The return hose the the fuel delivery hose & the vapor hose from the charcoal canister.That was never on the fuel sender top.I guess it had been left off by whoever worked on the car from the prior owner
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I think I may have screwed up when I replaced the pump!! under the quick disconnect is that the vapor line??? maybe this unit is the wrong 1 for the car & THATS the problem//.there is a sealed /craked 3/8 inch rubber cap instead of the return or vapor line!!!
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Most of these things I have done...Its a Base model,Rex Regina,,,,,replaced the FPR w new about 1=1/2 years ago..i dont think its bad but Fcp guarantees all parts so i may order anther &replace it.
i think as I see a leak in the line that runs along side the fuel tank..Ill have to see if I can get it on a lift t get a better look..
does anyone have a pic of the routing of the fuel line??
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Get
a reading on your.fuel pressure. Regulator could be faulty.
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Getting a reading on your.fuel pressure. Regulator could be faulty.
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it was new last spring,,Car runs great accelerates really well.Starts up immediately,,no bogging down ever at all!!!
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I changed the speedo out & no difference,,,Ill have to get it on a lift & replace gas line,,,I think that must be the problem for 15 mpg,,,
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Dear Blindboy,
Hope you're well. Before you dismantle the fuel pipes/hoses, pull the oil dipstick, and see if the oil has the aroma of gasoline. If so, a faulty injector is dribbling gasoline into the oil. The could explain a down-trend in miles/gallon.
If the oil smells "just like oil", inspect the banjo bolts at the front and back of the fuel filter. If those bolts are badly corroded, there could be a pinhole leak. Turn-on the engine and see if fuel leaks from a banjo bolts. If so, saturate banjo bolts with penetrating oil (e.g., Kroil or PB Blaster) and then replace the fuel filter. You'll need copper crush rings to ensure the new fuel filter seals completely.
As to the speedo, if the "new" speedometer needle "bounces", check the wiring connector to the speed sensor, mounted at the top of the differential cover. Over time, those wires - fully-exposed to road splash, etc. - deteriorate. If the wires are corroded, that could explain intermittent signal from the sensor and thus a "bouncing" speedo needle.
To ease removing the wiring harness connector from the sensor, apply penetrating oil and give it time to work. If the wiring harness connector is corrosion-bonded to the sensor, you may need "to sacrifice" the wiring harness connector. Once you've removed the plastic housing, the harness connectors female terminals could remain bonded to the sensor. A bent-tip needle nose pliers will help you to grip the harness connector's female terminals, and so remove them from the sensor.
I'm not sure where to find a replacement section of wire with the proper connector: a salvage yard in the desert southwest might have a section that is not heavily corroded. Coat the sensor's metal contacts with di-electric grease (inhibits corrosion), use crimp sleeves to connect the replacement wires, and cover the splices with heat shrink tubing.
Hope this helps.
Yours faithfully,
Spook
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Ill have to get a friend to smell the dipstick.I have very little smell ability from taking asthma drugs,,I ve run loads of injector cleaner through & the oil is pretty clean,,,not any visible defects
Im pretty sure that the fuel supply line is leaking & thats my problem,,,Il try to get it on a lift to eyeball
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Noleaks onthe fuel line,, fuel sender assemly has an extra plastic nipple sticking, out under the vapor return line,,there was a cap on it & it was cracked & bent,,so I replaced & now ill gas up drive 60 miles & check the MPG,,,
Praise Doggies!!
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My laptop skips around a lot & sometimes I fail to check it..Ive done loads of improvements to my 945,,,replaced intake manifold gasket,,the o rings,,new plugs, nw cap & rotor,sealed & or replaced all vacuum hoses,,installed new hose 1/4 " hose clamps.new 90 degree ,,plastic line fittings,,
Ill have to chk if by some chance thereare pinhole leaks in the fuel lines,,although I did replace them 3 yrs ago when I bought the car,,,
so now Ill switch out speedo s w a 94 940 spare & see if the figures change.
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Dear Blindboy,
Hope you're well. I, too, noticed a drop in miles/gallon in a '93 940. I tracked it to a faulty injector, that was dribbling - rather than spraying - fuel. I changed the oil - which smelled of gasoline - and replaced all four injectors. That has helped matters.
If a speedo needle "bounces", that's a sign that the speedo is "on the way", most likely because capacitor leakage has damaged the circuit board.
Hope this helps.
Yours faithfully,
Spook
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