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Thread: in town fuel economy
          
   
   

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  1. #31
    DennyW is offline CHR Member Visit my Photo Gallery
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    You need to hook up a fuel pressure tester. I think auto zone will still rent you tools. That way, you can hook it up and test fuel pressure before you start it. You should here the pump prime for about 3 secs before you crank it. Also, with the tester hooked up, and you shut the engine off, you can see if it holds fuel pressure, or is leaking down.
    To see answers quicker, you can refresh the page after a minute to see, that's just in case you didn't know. That way you don't have to wait until you get an email to a new post. Just thought I would mention that... hahaha

  2. #32
    old guy 44 is offline CHR Member Visit my Photo Gallery
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    Now you are trying to make me computer literate, it is a lost cause. At my age it took me a couple of days just to figure out how to turn the d.... thing on.

  3. #33
    DennyW is offline CHR Member Visit my Photo Gallery
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    Don't feel bad. I'm 68 now. When I got my very first computer, that was in 1998. And I got a blue screen, I threw my hands up, and said... NOW WHAT ? Just dug in, and learned, one day at a time. Now, I'm pretty good. Not a pro or nothing, but I can keep my computer running, plus set up, or build one from scratch. A number of other things I've learned. Just take's time...
    NTFDAY likes this.

  4. #34
    old guy 44 is offline CHR Member Visit my Photo Gallery
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    I find it a whole lot easier just to call my computer guy, have him log on to my computer and make it happy.

    With regards to the truck. Been driving it around for a week or so and put 98 miles on it. Stopped for gas, same pump at the same station, and put in 8.4 gallons. That is a dramatic improvement over what I had. I was filling up 20+ gallons at 175 to 180 miles. It may still improve marginally as I have noticed that the throttle response is improving as the computer learns. I believe that the vacuum line to the fuel pressure regulator was damaged before I worked on it causing full pressure in the fuel rail which would be reason enough for the poor economy. The new injectors and O2 sensors probably did not hurt but bottom line is that it is dramatically improved over what it was.

    I still have the starting problem but it only happens if I stop when the engine is at operating temperature and the truck sits for 45 minutes to an hour. It will take around 5 seconds of cranking for the engine to light. If the truck cools off completely first or second piston up will light and the engine runs fine. I haven't had time to wrap my fingers around a fuel pressure gauge to check for bleed down but I still wonder if it isn't the pressure regulator sticking from long time lack of movement. That will be my next task when time permits. It is not critical as the truck is running fine and economy is up to an acceptable level for now.

  5. #35
    firebird77clone's Avatar
    firebird77clone is offline CHR Member Visit my Photo Gallery
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    It sounds reminiscent of heat soak, when the fuel boils out of the carb.

    Bleed down sounds likely.
    .
    Education is expensive. Keep that in mind, and you'll never be terribly upset when a project goes awry.
    EG

  6. #36
    old guy 44 is offline CHR Member Visit my Photo Gallery
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    Got my fingers wrapped around a fuel pressure gauge and checked on a hot engine. KOEO 49 pounds. Running 44 pounds, I pulled the vacuum hose off and it jumped back up to 49 pounds. Shut the engine off and in a couple of minutes it crept up to 55 pounds. I am guessing that it was the fuel heating up in the fuel rails. Within 45 minutes it had bled down to 0. Not sure what spec is but as I recall the police chevy's with TBI ran on 35 pounds and the ones with port injection ran on 50-55 pounds. Ordered a new regulator should be here early next week.

  7. #37
    DennyW is offline CHR Member Visit my Photo Gallery
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    ((I find it a whole lot easier just to call my computer guy, have him log on to my computer and make it happy.)) Well, Tried that before, but, I find it much better after I learned more myself. I was thinking, if I am going to use this thing, I might as well figure out some of the working things to keep it going. I can make actually much better choices after I learned some things. Standard upkeep is key to keeping them working good. But, that's just me. In another way, it's no different than learning automotive things...

  8. #38
    old guy 44 is offline CHR Member Visit my Photo Gallery
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    OK. I hate it when I follow a thread all the way to the end and there is no conclusion so here goes. At the beginning of this thread I was fueling up every 150 to 200 miles 22 to 24 gallons. The last tank I went 293 miles on 23.6 gallons, 12.42 miles per gallon. I believe that I can state that this is the first time since I have owned this truck that it went any where close to 300 miles on a tank around town.

    The largest change was installing new upstream O2 sensors and a new set of injectors. They went in at the same time so I do not know which of the two made the change or if it was a combination. I also found a tear in the vacuum tube to the fuel pressure regulator which I replaced at the same time. The fuel pressure regulator had no vacuum signal for an unknown period of time and when I put vacuum to it the diaphragm ruptured bleeding a small amount of gas into the plenum. This created a hard hot engine start as it was in effect flooding the engine by filling the plenum with raw gas fumes. The running fuel pressure was low also. It was running at 43 psi and with the vacuum signal disconnected it would jump up to 50. I ordered a new regulator and put it in. I rechecked the fuel pressure and it is now running at 51 psi and with the signal tube disconnected it jumps up to 60 which as near as I can tell is in the range it should be in.

    The tank of gas mentioned at the beginning was after installing the O2 sensors and the new injectors but before the new pressure regulator. The pressure regulator went in somewhere in the top half of that tank and for the most part cured the hot start problem. Every change I have made has resulted in the engine running differently until I got enough miles on it for the computer to start re-learning. Right now the truck runs fine but it still occasionally is a little slow starting if I shut it off with the engine hot and leave it sit for about an hour. When it does happen it is the exception not the rule so for the time being I am tired of looking at an open hood and will let it go to see what happens.

    I will continue monitoring the in town mileage for a couple of tanks and if it changes after the computer completely re-learns I will update the miles per gallon.

    I still haven't ruled out a cam change if I can find someone that will grind what I want.
    DennyW likes this.

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