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Where can I find a wiring diagram for the connections in the trunk of an '85 QV.

Discussion in 'Mondial' started by Albert Penello, Feb 19, 2020.

  1. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    I'm having some hard starting problems (as in, the car won't start) and the diagnosis has left me stumped.

    Right now, my main suspect is a bad Accumulator since a pressure test between the WUR and Distributor drops immediately after shutdown (the fuel pump is clearly new, and I just replaced the fuel filter).

    I've been testing/checking relays and wiring and I can't find anything regarding the wiring on the drivers side of the trunk. It where the thermocouple for the CAT goes, and there are some other relays there but I have no idea what they do.

    I've downloaded some diagrams but I can't seem to find any info on this. Maybe I'm just looking in the wrong place.

    Any tips apprecaited!
     
  2. stekkefun4

    stekkefun4 Formula 3
    Rossa Subscribed

    Nov 22, 2006
    2,164
    Belgium - Europe
    Urs S. has everything you need, he redrawn the electronics in wonderful highly detailed and colorful schemas. He's also on F-chat and I think he will react to this thread pretty soon :)
     
  3. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    On the outlet side of the pump is a non return valve
     
  4. ronfrohock

    ronfrohock F1 Rookie
    Rossa Subscribed Owner

    Aug 16, 2004
    2,816
    MA
    Full Name:
    Ron Frohock
    Steve Mangnussen wrote about this in a thread about two years ago. Was very detailed. I can’t find it......


    Sent from my iPad using FerrariChat.com mobile app
     
  5. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    See if the wiring from a relay goes to the starter motor or its solenoid, there is a mod which may have been fitted
     
  6. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Urs wiring diagrams are an absolute masterpiece. Unfortunately, he doesn't have the US Emissions stuff in his diagrams (although he said he may add them!)

    So in the meantime, I'm just not aware where to find any information on what those units and relays do.

    I'm having the strangest problem - the car just won't start. It's turning over very vigorously - and I have a pump (by previous owner) and the tank was filled with stinky old gas which has been drained and replaced. It would backfire through the distributor ever so slightly if I tried to accelerate quickly (this is all on a lift mind you)

    I'm pretty familiar with these old FD systems since I also work on Mercedes w126 cars which have nearly the identical system. In fact, I had the engine running like and absolute UNIT just yesterday - it was running super lean when warm (over 30:1 AFR!!) and the idle mixture screw was way, way out to compensate. I tuned to have it at 14:1 at idle using my Innovate AFR Meter, then adjusted the idle to 1000 rpm, and it felt like there was another 50hp. Throttle response was quick and instant.

    The next day, I changed the oil and went to restart and nothing! It would sort of sputter but not stay running. I thought maybe the filter was bad due to bad gas, so I replaced that last night and no change.

    Next was a fuel pressure test so I connected an inline gauge to the hose connecting to the WUR (saw this suggestion on diagnosing a 308) and then removed the blue connector at the FD, and turned the key. I could hear the pump running, and the frequency valve buzzing, and fuel pressure rose to + 50 PSI. However, the instant I turned the key the pressure would drop to 0.

    So at this point, all I can think of is that the accumulator is shot and not holding pressure, which is not allowing the injectors to fire.

    I have not checked the spark because I don't have a friend to test it right now. The only other thing I can think of is that some wiring in that control box in the trunk is not signaling something properly - hence the need for the wiring diagram.

    I'm going to try a cold-start tonight when I get home to see if maybe it was flooded or a hot start problem.

    So I'm stumped...
     
  7. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    #7 mike32, Feb 19, 2020
    Last edited: Feb 19, 2020
    As i said previously, have you checked the non return valve after the fuel pump, if the pressure is dropping straight off then the fuel is going back through the pump. Accumulator normally only causes hot start problems.
    You mention it is back firing through the distributor ? Can you clarify this.
    Do you have any fuel in the sump oil ? If so the diaphragm in the injection distributor head may be split and these are available as a repair kit from say a volvo dealer or e bay.
    If this has gone it will full fuel some cylinders and it runs past the pistons into the sump oil, along with a lot of back firing etc.
    I have a set of wiring diagrams but need to know wire colours to id the items
     
  8. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Sorry I missed that. Non return valve? This is not something I'm aware of.
     
  9. BillyD

    BillyD Formula 3
    Silver Subscribed

    Feb 28, 2004
    1,526
    Pacific Northwest
    Full Name:
    Bill
  10. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Thanks I'll read these! I've had the same problem before on the Mercedes and it was always the accumulator. However, it's dropping INSTANTLY in this one which is strange.

    The accumulator will be here on Thursday so I have some reading to do. Swapping the accumulator is pretty simple so at least we will rule that out.
     
  11. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    The non return valve is right next to the accumulator, if you have had old fuel the n/r valve might be sticking. You can try cleaning with electro clean and compressed air. Failed accumulators generally show signs of leaking but will not stop a cold start
    Look on eurospares uk site for the diagrams of the fuel system .instant fuel pressure drop had to be n/r valve
     
  12. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
  13. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    Item 80 is check valve screwed into the outlet of the pump, we call them non return valves
     
  14. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Well interesting news. The car would not start cold today either. I had this car running like a TOP the other day, now no start.

    It will sputter and try to start (likely from the cold start injector firing) but then die almost immediately.

    The fuel pressure test is showing two things right now.

    1. With the engine cold, running just the fuel pump is only building about 55psi of pressure. What's strange, is that it gets to about 55psi then has a sudden dip to about 45 and stays there. IIRC, 50psi is required to open the mechanical fuel injectors.

    2. The wrong pump is installed. I'm not sure how much this matters (and it's a brand new pump), but the Mondial OE Bosch is 69523. What's in there now is a 69435 which crosses to just about every Mercedes from the late 70's into the mid-90's (and it's brand new).

    I would have no reason to think this pump wouldn't at least function, but clearly something is going on unless I'm testing improperly. (I'm using the line between the top of the FD and the WUR)
     
  15. mike32

    mike32 Formula 3

    May 13, 2016
    2,430
    Uk
    What volts are you getting at the coil s when trying to start up. You should have enough fuel pressure at that to start it.
     
  16. theunissenguido

    theunissenguido Formula 3
    Silver Subscribed Owner

    Jan 21, 2004
    1,490
    Argent/Brasil/Blgium
    Full Name:
    Guido
    Are you shure you are get fuel from the tank ? Fuel filter in tank cloged? Try fuelpump and see it is delivering fuel in the first place coming from the tank (between connection with accumulator and pump).
    Accumulator has a membrane inside. The only thing that can happen is membrane breaks and fuel is coming out on the backside of this accumulator. Or membrane is so old and its spring so rusty, it is not working at all.
    Check if the plunger inside fuel distributor is free of travel. 3 bolts on the upper side of distributor. Take care the plunger not drops on the floor.
    Check plate inside air inlet of distributor for free travel.
    Did you check the spark plugs if they are dry or wet ? Dry is no fuel delivery, wet no spark or cold start injector keeps spraying. Disconnect cold start injector if your climat is not cold.Most of our cars dont need this to start.
    Guido
     
  17. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Good suggestions. I'm going to check fuel pressure on the inlet side of the distributor tonight I had also considered that . I also have the accumulator coming and there is no downside to replacing so that will eliminate filter and accumulator.

    The concerning thing to me is the low pressure and the lack of holding any pressure on shutoff. AFAIK, the only things that affect holding pressure is the non-return valve on the fuel pump, and the accumulator. I'm trying to diagnose one at a time, and since the pump was new I didn't suspect it until mike23 brought it up.

    Since the fuel pump is wrong, I was going to install a new one and a new valve since I have to drain the tank for both. But tonight will be accumulator and inlet pressures.
     
  18. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    140
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    FIXED!

    As suspected, it was the Accumulator. When I took the return line off, it was filled FILLED with gas. That's when I knew it was over. Put in the new Accumulator just running the pump, fuel pressure shot up over 60psi, held at 30psi for about 10 min. Turned the key and fired right up!

    I think the diaphragm was shot, and the pump was trying to fill the FD as well as pump fuel back into the tank. May also explain the sudden drop in pressure at a certain point as the diaphragm "popped"

    Anyway, CURRENT problem solved. Now on to the next set of problems...
     

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