bad gas mileage.

[Shran]

Larger injectors and "upgraded" ignition stuff is really going to help your gas mileage.

The first thing that comes to mind here is your fuel pressure regulator. It can be bad even if you don't see fuel in the vacuum line although you usually do. Get a fuel pressure reading and see if it is in spec.

Bad FPR is the cause of about 90% of poor mileage/hard starts/fuel smell in my experience.

 

[broncobuckinaround]

thx shran. i did do a pressure test and it was just under what spec is supposed to be.

im not to familiar with FPRs. didnt know they can control the pressure before start up. just after.

the guy i bought it from let the car sit for 2 years so it probably got rotted. i know i did my best to clean any old gas out but dont know if that worked.

 

[Shran]

They work off engine vacuum. There is a diaphragm inside it that opens to let more fuel through the rail. Yes, they control pressure before the engine is started and should not allow more than 40psi through with the engine off and fuel pump running.

Spec is about 30-35psi at idle and around right at 40 when you crack the throttle open. More indicates a bad FPR, less indicates a bad high pressure pump. Fluctuations could be either one.

If you are smelling fuel it is either leaking somewhere or running super rich.

 

[broncobuckinaround]

i believe it is running super rich. iirc the fuel psi when off was but pump on was around 38. and when running it was about 33.

ill rent me a fuel pressure tester and get you a better reading.

 

[broncobuckinaround]

hey guys finally got some more info. i got some codes, code 21 25 32 34 74. i know what they all mean. but now for new parts. ive allready replace the temp switch cuz it was way out of range it wouldnt switch cold or hot. i bench tested it with cold water then torched it and the values didnt change. so i swapped it out with a new one. but the codes didnt go away.

im not really concerned about the 74 iirc it was the knock senor issue unless it messes with the engine performance.

i will be replacing the egr as soon as i can afford it. i took it off and that sucker is suck good. is there a way to clean them

also i need to know, i used a multimeter to check th ects switch, single wire. i was reading voltage coming from it. it was high than low, kept fluctuating. is there supposed to be anything at this one wire.

 

[wildbill23c]

Not sure you can do it on the 2.9L but I unplugged the EGR and plugged the vacuum line on my 2.8L and it runs great, was having issues with it not wanting to run, and just started looking around for vacuum leaks and don't remember why but I pulled the vacuum line off the EGR and my B2 started idling nice and running better, so I never bothered trying to replace the EGR because its expensive and didn't see where it was really needed considering the rest of my Emissions system is MIA.

 

[ab_slack]

I would think this would have already been sorted....the miles per tank thing...I know my fuel gauge doesn't read right and if I go by empty indication it is only about 200 miles. Of course it doesn't take 20 gallons like I would expect from a truly empty tank.

So like has been said, make sure it is really full and look at miles driven since last fill and number of gallons put in the figure the MPG. My 88 and 89 B2s I got solid 22mpg which yielded better than 440 miles per tank. My current B2, an 87, I been getting a crappy 18mpg to 19mpg.

From what you are saying you must be getting 10mpg if you are indeed filling the tank. Like others said, it seems improbable to get this kind of mileage without a leak. Hence the question of how many gallons are these fill-up after 200 miles.

I am hopeful the new O2 sensor I put in brings up the fuel economy. It sure seems to be running smoother. But maybe the engine coolant temp sensor is a problem cause that could fit symptoms of mine too.

 

[wildbill23c]

Something else to check too, that I just remembered from my 84 Ranger, it got to the point where the automatic shut off on the fuel nozzle would trip, but the gas tank wasn't even close to full, I think it was due to a vent line issue, but I'd definitely check that out as well, I had that happen and realized down the road the tank was only about 3/4 full.

 

[chazzone]

As was mentioned before, "miles per tank" is a worthless number that tells you absolutely nothing. Mileage is figured in miles per gallon. The only way to actually know what the mileage is, is by dividing the actual miles traveled by the gallons used.

Not very hard to do.

You said that you would simply disregard the knock sensor code. The knock sensor picks up detonation. It will definitely affect the performance of the engine, and suggests either a lean condition, or too much timing.

Have you checked the timing with the spout out?

I'd also make sure that the idle bypass is clean and functioning properly. If this is clogged or sticking, it will also cause a rich condition on start up.

 

[broncobuckinaround]

ok for the math for the tank since youve been asking me to death about it. every time i fill it, it takes 20 gallons at around 200 miles. i know my gauge is off about 3 gallons. cause its a 23 gallon tank. now that that has been said we can move on.

i replaced the other ects, the one that is a two wire one. im getting a lot less pinging now and the performance has upped a little bit. but im still getting pinging. the timing is dead on. i dont think i could have got any closer.

chazzone. what is a spout. and i may have not done that. also idle bypass is clean.

no one answered my question about the single wire ects have voltage comeing from it. is it supposed to or not

 

[Shran]

So you are getting 10mpg roughly, that is pretty terrible.

How does the truck idle? What RPM does it idle at? That could indicate vacuum leaks. One thing to check is the MAP sensor and the vacuum line connected to it, these often develop leaks. Also a failed MAP sensor will sometimes make the engine run very rich, as the computer can't compensate for altitude.

The SPOUT connector is just a little grey jumper in one of the harness plugs near the distributor. Its function is similar to the vacuum advance on an older distributor - you remove the jumper when you set the timing so that the distributor doesn't advance the timing.

For your last question about the ECT sensor(s) - the single wire one you are looking at is NOT the ECT. It is the temp gauge sending unit and is not connected to your computer at all - it goes straight to the temp gauge. I believe it's just a variable resistor and would not have voltage at the wire but I might be mistaken, in any case, it has nothing to do with your issue.

 

[broncobuckinaround]

awesome thanks shran for answering my question about the wire.

i have checked for leaks. i replaced any hose that looked bad or had a loose fit.

idle is fine when it starts in the morning, goes in the 2000 - 2300 rpm range. after like 30 or more secs it starts to drop down. at warmest temps it will stay around 850 to 950 rpms.

but it does do something weird, when i drive say across town and shut it off go do whatever it is im doing. ill come back and start it. it will have a long crank time and when it starts it will sputter and want to die. it will diesel for a few sec and return to normal. and run just fine. i think it might have something to do with the fuel pressure regulator.

ive now replaced the both those ects sensor and the temp gauge sensor just because. i believe i have got a lil better mileage. but i have to wait til i can fill up again. once i do ill do the math and post again. but ill look for your reply to this one. thx again.

 

[kimcrwbr1]

Did you reset the computer when you changed the ECT sensor. Disconnect the battery for at least 20 minutes whenever you clean or change a senser and make sure everything is plugged in when you connect the battery. Then erase the memory on the KOEO test and then run it for around 20 minutes at medium speeds before you do the KOER test.

 

[broncobuckinaround]

ill run the test tomorrow at work. hopefully the codes have been erased or at least dont come back ill let you know tomorrow

 

[broncobuckinaround]

Ok got a new question. I have stumbled apoun a fuel leak. It is the pressure side of the fuel filter that is on the frame rail. Now what are the sizes of the two o rings that are in side if the hose. Or am I better off bypassing it.