Hello and 1979 EFI Fuel Pump Question
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500, 472, 425, 368 Discussion, Hello and 1979 EFI Fuel Pump Question in Cadillac Engine Technical Discussion; Hello my name's Benny and I'm from Switzerland right in the heart of europe. I recently bought a 1979 Fleetwood ...
  1. #1
    Benny K81 is offline Cadillac Owners Member
    Automobile(s): 1979 Fleetwood Brougham
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    Hello and 1979 EFI Fuel Pump Question

    Hello my name's Benny and I'm from Switzerland right in the heart of europe.

    I recently bought a 1979 Fleetwood Brougham in nice condition as a daily driver (yes! ) but it needs some care as far as the powertrain goes.

    My main fuel pump is failing sometimes (won't turn...a slight knock with a hammer helps) so I just ordered a carter inline replacement pump from Summit.

    Now my question. Since I don't know about the condition of the in-tank pump, I wanted to ask you about a source for an intank pump wich fits.
    I have seen one from Airtex at Summit but I have also read that it is the same pump as in a Volvo 740?
    Can anyone give me some infos on this?
    If some volvo part or something would fit I could save a serious amount of money as I could order it here with a lot of discount (I'm working at an audi dealership)

    Also, I'd need the gasket or o-ring wich seals the tank to the fuel pump/sender unit.

    Any help or input is greatly appreciated!

    Benny

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  3. #2
    BRUCE ROE is offline Cadillac Owners Fanatic
    Automobile(s): Eldorado
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    Re: Hello and 1979 EFI Fuel Pump Question

    I believe the in tank pump is sold as a complete tank unit assembly. My
    notes indicate you need a 25000591 or 25000918 tank unit. However,
    you could get any 76-79 Cad EFI tank unit, and transfer the pump over
    to your tank unit. The tank unit gasket is the same as many other GM cars
    of that era.

    Your fuel injected car has a low pressure pump in the tank, and a high
    pressure pump mounted in the frame. It will run without the low pressure
    pump operating, just pulling fuel through it. But it may lose power taking
    off, if the tank is below 1/3 full.

    All the pump current flows through the ECU connector, wiring, & relay.
    Many ECUs are seriously damaged when worn pumps or defective
    wiring pull too much current. I recommend adding a relay external to
    the ECU, to protect it from damage. The circuit and a way to do this is
    shown on my PHOTOBUCKET, sub album 70S FUEL INJECTION, about
    picture 13 & 14.

    http://s93.photobucket.com/albums/l71/bcroe/

    (that is a lower case "L"71, not an upper case "i"71)

    click on a Sub-Album
    click on a picture to enlarge + explanation

    The whole dual pump system has annoyed me for some time, with
    excessive current drain damaging ECUs, noise, all that stuff exposed to
    road dirt, and difficulty of replacing pumps. I'm working on scheme to
    put a high pressure pump in the gas tank, and just an in line filter in the
    frame. Will be testing the idea on my 79 Eldo (403 EFI) later this year
    I hope. Bruce Roe CLC # 14630

  4. #3
    creeker is offline Cadillac Owners Connoisseur
    Automobile(s): 1992 eldorado. 2007 dodge magnum hemi r/t
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    Re: Hello and 1979 EFI Fuel Pump Question

    Check on rockauto.com for caddy and volvo fuel pumps, very handy website for reference for parts, I looked up fuel pump for your caddy, but dont know what
    year the volvo pump is.

  5. #4
    drmenard is offline Cadillac Owners Enthusiast
    Automobile(s): 95 fleetwood 81 deville
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    Re: Hello and 1979 EFI Fuel Pump Question

    I would just get a walbro 255 pump. get one to fit a GM model, try searching a LT1 motor. With this pump in the tank you don't need the frame pump.. Just run the one pump in the tank..There is a good fuel filter on the front of the motor . The can screws off and the filter is inside... I would put in the extra circuit like Bruce suggested to keep the old ECM from failing..

  6. #5
    Benny K81 is offline Cadillac Owners Member
    Automobile(s): 1979 Fleetwood Brougham
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    Re: Hello and 1979 EFI Fuel Pump Question

    Thank you for your replies!

    I already added an external relay for the fuel pumps. Actually it was my first mod I did to the car.

    As I found out yesterday. My in-tank pump doesn't work at all. Had the gas tank to almost empty couple of days ago and it ran just fine. So no hurry to replace the in-tank pump. I will check the pages you recommended me.

    To Bruce:
    Your images on photobucket are quite interesting but made me worry about my whole ECU
    I'm going to check my map tomorrow too.
    Do you modify ECU's for other people too?

    The whole car was a mess under the hood...vacuum advance disconnected (now works fine)...coolant temp sensor defective...horrible fuel mileage...

    I find the fast idle is quite fast...is there a way to adjust the fast idle valve alone? idle speed with warm engine is ok...

    Benny

  7. #6
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: Hello and 1979 EFI Fuel Pump Question

    The relay is a great idea.

    I've used a regular garden variety TBI pump in the tank like one which would fit a 4.1 liter car. It worked OK with the factory frame mount pump.

    Putting a high pressure pump right in the tank could work well just make sure all lines after it are rated for the 90 lbs deadhead pressure they can make.

  8. #7
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Hello and 1979 EFI Fuel Pump Question

    Quote Originally Posted by Benny K81 View Post
    To Bruce:
    Your images on photobucket are quite interesting but made me worry about my whole ECU.
    I'm going to check my map tomorrow too. Do you modify ECU's for other people too?

    The whole car was a mess under the hood...vacuum advance disconnected (now works
    fine)...coolant temp sensor defective...horrible fuel mileage...

    I find the fast idle is quite fast...is there a way to adjust the fast idle valve alone?
    Idle speed with warm engine is ok... Benny
    A couple of 403 engines have gotten ECUs with adjustable fuel. I can provide
    a drawing on how to make an overall % change in injector pulse width; can
    also make a change here.

    Usually the temp sensors fail open circuit, losing cold enrichment but not affecting
    operation after warmup. A shorted sensor would cause running rich.

    The cold idle air valve on top of the throttle increases cold idle speed. I have added
    a ship about .060" thick to push it farther closed.

    I don't have an ECU listed for a 79 Fleetwood. Could you please check its number,
    which is something like 161 XXXX?
    Bruce

  9. #8
    drmenard is offline Cadillac Owners Enthusiast
    Automobile(s): 95 fleetwood 81 deville
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    Re: Hello and 1979 EFI Fuel Pump Question

    I think 79 was the first year that that have a O2 sensor...

  10. #9
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Hello and 1979 EFI Fuel Pump Question

    Documents suggest the 78 & 79 350 engines offered an OX sensor; don't know
    if any were delivered the first year. I have no listing for 425 EFI in 79. Bruce

  11. #10
    BRUCE ROE is offline Cadillac Owners Fanatic
    Automobile(s): Eldorado
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    Hello and 1979 EFI Fuel Pump Question

    Documents suggest the 78 & 79 350 engines offered an OX sensor; don't know
    if any were delivered the first year. I have no listing for 425 EFI in 79. Bruce

  12. #11
    Benny K81 is offline Cadillac Owners Member
    Automobile(s): 1979 Fleetwood Brougham
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    Re: Hello and 1979 EFI Fuel Pump Question

    Hello Bruce...thanks for all the input.

    I finally replaced the in-line Pump with a Carter pump and it works fine.

    My ECU number is 1612947 C CAL but there is also the number 192935 on it. Is this a California version? I have all the EGR, CAT and airpump systems on it. At the moment the EGR is shut off (vacuum line). I even have the economic lights (green and orange) on the dashboard.

    I realised that even though the heater blows warm after 1 or 2 minutes driving and the water hoses getting hot quickly...it takes forever til the fast idle valve shuts off and the engine goes to normal idle (about seven miles driving outside of town). I have replaced both temperature sensors. I guess as long as the fast idle is active there is air/fuel enrichment too?

    Hope you can help me out. I just sold my second car and until I have something else the Fleetwood is my daily driver (gas stations sure do love me as a customer haha)
    Benny

  13. #12
    BRUCE ROE is offline Cadillac Owners Fanatic
    Automobile(s): Eldorado
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    Re: Hello and 1979 EFI Fuel Pump Question

    Quote Originally Posted by Benny K81 View Post
    My ECU number is 1612947 C CAL but there is also the number 192935 on it. Is this
    a California version? I have all the EGR, CAT and airpump systems on it. At the moment the EGR is shut off
    (vacuum line). I even have the economic lights (green and orange) on the dashboard.

    I realized that even though the heater blows warm after 1 or 2 minutes driving and the water hoses getting hot
    quickly...it takes forever till the fast idle valve shuts off and the engine goes to normal idle (about seven miles
    driving outside of town). I have replaced both temperature sensors. I guess as long as the fast idle is active
    there is air/fuel enrichment too?
    Benny
    According to my notes, a 1612947 is a 1978 ECU, California. Are you sure the car is a 79? The year would
    be stamped on the plate on the right rear of the transmission. 192935 is the serial number.

    If the tiny micro switch arm is broken off the idle air valve heater, it will take longer to close. When the car
    is well warmed, push down on the valve. If the engine slows, the valve didn't close all the way. Cleaning it
    up might help, otherwise I put in a shim to push it farther closed. Or just close it sooner. The mixture is
    adjusted by the MAP, but cold enrichment is adjusted by the coolant sensor. Bruce Roe

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