240 electrics - no juice getting to fuel pumps

2

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  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    edited February 2017
    So it turns out that the wiring diagram in the Haynes manual for 1989 model is completely wrong, and I've been barking up the wrong tree a bit.

    So the fuel pump relay gets its power from the red-yellow wire coming from fuse 4. But fuse 4 for me is getting no voltage with the key at 2nd position - that can't be correct?

    EDIT: or is is that the relay switching is what provides fuse 4 with power? I'm so freaking confused right now...
  • So it turns out that the wiring diagram in the Haynes manual for 1989 model is completely wrong, and I've been barking up the wrong tree a bit.

    So the fuel pump relay gets its power from the red-yellow wire coming from fuse 4. But fuse 4 for me is getting no voltage with the key at 2nd position - that can't be correct?

    EDIT: or is is that the relay switching is what provides fuse 4 with power? .

    Yes.

    Look at the diagram from Volvo wring diagrams.com - at C4, there is the fuel system relay. When it engages, the second half of the relay brings the red wire (+12v battery) to the yellow-red wire to fuse #4.

    At location D4 on that diagram, the other side of fuse #4 is the power feed to the fuel pumps.

    So no juice at one side of #4 = no juice at the fuel pump side of #4 = no working fuel pumps.

    Now... as to the top half of the relay:

    When the red-black wire at pin 35 of the ECU sees a voltage, it powers up the relay via the black-green wire at pin 20, and the orange wire at pin 9. Unless the ECU sees a signal to say the engine has started, it will then drop the fuel pump relay out.
  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    edited February 2017
    So the plot thickens: the big red wire that the wiring diagram suggests comes straight from the battery and pours into the fuel pump relay, ECU box and EZK box is now confusing me. It was getting 12V after I plugged everything back in: good! I cranked the engine for a couple of seconds, and the voltage on that wire dropped to 2.5V with the ignition off, and 0.7V at second position. There is apparent continuity between the positive terminal on the battery and the red wire at the fuel relay... but fluctuating voltage. The battery voltage is still 12.5V.

    Leaky earth or fried EZK/ECU? What's the best way to test/check? It seems unlikely that the wire itself is at fault, but I guess not impossible?

    EDIT: Pretty convinced it's something funky in that wire, a the ECU is only getting 2.5V on pin 4 now too. There is apparent continuity between pin 4 on the ECU and the red wire into the fuel pump relay (and the battery) so this is making me think that something somewhere must be leaking to earth?
  • bgpzfm142bgpzfm142 (@bgpzfm142) Launceston TAS
    edited February 2017
    Does it fluctuate at all 3 measuring points? (ECU pin 4, as well as the EZK pin 5 and the relay)

    Fluctuating voltage suggests either a short circuit via a resistance to the body, or a high resistance or open circuit joint somewhere.

    You have also swapped out the injection relay at some point? PS: (there is a diode inside it which can fail, as well as contacts which can pit and wear over time)

    If so, it suggests there's a wiring or connector problem somewhere. Wires can rub through and therefore fail, and since you've replaced the ECU and the relay, connections are the next suspects.

    Here is a "generic" wiring diagram for LH 2.4 - I don't know if it a 240 or 740 generic diagram.

    http://ipdown.net/jetronic.info/tiki-index.php?page=LH+2.4+Overview

    The 240 (and all) Green Books are very good at providing exact wiring paths, as distinct from circuit diagrams - an identical circuit can be physically wired up in many different ways.
  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    @bgpzfm142 you're a genius. Thanks to making me understand the wiring diagram, I've isolated to a single component: the EZK. With that unplugged, the relay and ECU both get their 12V happily. With the EZK plugged in, they're getting 2.5V.

    Does this mean the unit is likely dead, or that one of its in/outbound connections is shorted/broken? I guess armed with the wiring diagram, I can check each wire path carefully and try and figure it out!

    Thanks again for all the advice - I'm going to pack it in for today and have another crack tomorrow at finalising the issue.
  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    Ok, back to being super confused again! It feels like a dodgy connection/earth somewhere. With fuse 6 in place, there is continuity between the positive and negative battery terminals (when both are disconnected from the battery obviously!) which can't be right, surely? That would be a short circuit? With fuse 6 out, the resistance goes up to a non-zero but not high number (20 kOhms). So it must be something on the fuse 6 circuit path, but helpfully in the 89 wiring diagram, it says that fuse 6 is not used, when we know that it's related to the fuel pumps somehow...
  • A couple of tips which may assist:

    1. Use your multimeter on voltage, not resistance, You can only check resistances when you're sure there no juice anywhere on the circuit. Any juice on the circuit you're trying to measure will either cook the meter or give you false readings.

    2. Do your voltage checks from the point of measurement to ground.

    That said -

    One side of fuse #6 is the +12V battery rail, which always supplies juice as long as there's a battery. The trick to starting the fuel pump (by jumping fuse #4 to #6) is done that way because there's always juice on fuse #6. Or should be. So jumpering it that way to test proves either the wiring or the pump(s) are faulty. According to the diagram, ordinarily fuse #6 has nothing to do with the pumps.

    You mentioned yesterday that pulling the EZK box out resulted in the voltage measurement going from 2.5V at pin 5 of the EZK when plugged in, to the full 12V at the ECU and the relay on that wire run, when the EZK was unplugged. Do you have a spare EZK which you can plug in?
  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    Ok, progress! It looks like it might be the ECU coolant temp sensor. The wire that runs from the EZK to the ECU via the sensor appears to be shorted to a bunch of other pins, which shouldn't be right (it should just connect pin 2 of the EZK to pin 13 of the ECU). Maybe the sensor has died and is grounding out or something?
  • bgpzfm142bgpzfm142 (@bgpzfm142) Launceston TAS
    edited February 2017
    re coolant temp sender
    it should just connect pin 2 of the EZK to pin 13 of the ECU

    Not quite. That sensor is a 2-in-1 package - the 1 sensor is connected to both boxes, and it provides a varying resistance to ground, to each box, from the same physical point of measurement. (edit: clarified)

    Seriously, I'd go back and look at why you're getting a fluctuation in voltage at the red wire (battery feed) connected to the fuel pump relay and EZK (if I understood that earlier comment correctly).

  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    Yup, you're absolutely correct again @bgpzfm142 - i didn't realise that the sensor grounded to the block, and therefore is presumably de facto linked to a number of other pins.

    So, I've now tested with known good ECU and EZK, and neither of them fixes the voltage drop at the fuel relay pin. I've realised that having either the ECU or the EZK plugged in causes the voltage drop, so it must be something that they're both connected to is causing a short. Back to the wiring diagrams I guess!
  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    edited February 2017
    Well, this is really turning out to be a lesson in frustration. With the ECU unplugged, and monitoring the voltage on the red wire heading into the fuel pump relay, I removed in turn each connection into the EZK box. The only one that did anything was removing the brown earth wire on pin 20, which caused the voltage to rise from 2.2V to 4V. But the earth has zero resistance to ground, and it still doesn't explain the other 8 missing volts! So now I'm completely lost again and throwing in the towel for the day. Any suggestions on how to move forward from here in terms of finding the fault would be very gratefully appreciated!
  • I'm going back to basics here, have you removed the fuse 4 and scrapped and sanded the contacts, replace the fuse and checked that the push on terminal is all good.
    I found nothing but problems with my fuse block and in the end replaced it, now seems really good, starts very easy hot or cold, goes like a shower of ........ or how ever a volvo goes when its going well and gets bloody good economy.

    Tezza
  • .... With the ECU unplugged, and monitoring the voltage on the red wire heading into the fuel pump relay, I removed in turn each connection into the EZK box. The only one that did anything was removing the brown earth wire on pin 20, which caused the voltage to rise from 2.2V to 4V. ...

    Connecting the EZK is loading up the circuit, so you're seeing a voltage drop at pin 5. Disconnecting pin 20 of the EZK is disconnecting the ground for the whole box, and doing that isn't advisable. However, by (partially) unloading the EZK from circuit, you're seeing there's a problem on the +12V battery [30] rail. It should be 12V at pin 5, all day every day - regardless of if the EZK is plugged in or not, or if pin 20 is grounded or not.

    Here is the EZK116 diagram. <p>

    1990-240-ezk.png <p>

    Below are the pinouts for the EZK116 and the signals you should see on them.

    lh24icupinout.jpg <p>

    The description of testing you've done so far indicates to me that there's a wiring problem on the red wire/battery/[30] bus - either a high resistance connection, or a short circuit to ground, somewhere. To find this problem, you need to trace that red wire back to the battery, or the last place you're seeing steady 12V. Then move your way forward, testing at each point, until the volts go AWOL.



  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    @tbro yes - that was my first thought as well, as my old 240 gave me nothing but problems from the fuse block. Sadly not the cause of the current gremlins.

    @bgpzfm142 thanks! this makes things really clear. I'll get stuck in to tracing that wire back. You're right, i've been thinking about things back to front. The potential at the battery must be 12V the whole time, so I need to find out where that stops being the case between the battery and the relay, and then why. That's this weekend's job! Unfortunately due to some shitty unfortunate life circumstances, I only have access to the car on weekends at the moment. I will report back from the next stage of troubleshooting. And again, thank you for your patient advice :)
  • Have you pulled the power distribution block off from the passenger side fender to see if it isnt all fucked up in there?
  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    @Slowbrick That was one of the first places I looked (if you mean the little black plastic case with 3 red wires). All looks kosher in there and the contacts seem ok. I'm not sure what the silver 'can' screwed next to it does, but unplugging the two headers from it makes no change to my predicament!
  • edited February 2017
    Silver can is the highbeam relay. Are you getting a solid 12v on your red feed wire into the relay?

    Have a look at Page 19 in this document. It covers the entire fuel system wiring.
    http://www.volvowiringdiagrams.com/volvo/240 Wiring Diagrams/Volvo 240 1989.pdf

    Here is the full LH2.4 Greenbook. Has some good info in here regarding fault tracing and how to test/fix them: http://www.volvowiringdiagrams.com/volvo/LH 2.4/LH2.4 Manual Complete.pdf

    You can see from the diagram that the orange wires provide power to the injectors. The solid red provides the constant power to the relay. The relay switches the yellow/red through fuse 4 which then provides power to the pumps.

    From memory the ecu needs to see that the engine is spinning before it activates the relay full time. So you should be able to turn the key to the II position and hear the pumps prime for a second or two. Then when you crank the engine the ecu will see the engine is turning and then close the relay which will then give you an injector pulse and the pumps will run.

    Pop the cover off the relay and turn the key to II and see if the two gates shut. They they dont move then something funky is going on with your ECU. My guess would be the ECU is either not grounded properly or its not receiving power.

    I believe the ECU gets it power from a light blue wire that can either come from the ignition barrel or the fuse panel. The ground wire im sure is a brown/black wire.

    I had a similar issue when I wired up LH2.4 into a Kjet car and it was my earth that wasnt connected.

    Vee_Que
  • lasercowboyRico (@lasercowboy) SE Suburbs, Melbourne
    @Slowbrick thanks! This is really useful info, and will help me troubleshoot tomorrow. I now have two avenues to track down, and I'm pretty sure one will prove to be the culprit. Will update with further info/questions tomorrow when I've tried the above, and tracing the red wire back to its power source.
  • this should be easy to diagnose so if you want call me and i can run through a few things with you, what area are you in as you might be able to look at one of my manuals. 240 should be easy to fix.....
  • Here is the full LH2.4 Greenbook. Has some good info in here regarding fault tracing and how to test/fix them: http://www.volvowiringdiagrams.com/volvo/LH 2.4/LH2.4 Manual Complete.pdf

    Just saw something on that which may not have been checked...

    @lasercowboy have you checked the inline fuse? (page 54, item 212) This is the [30] +12v battery feed for the red wire. If the fuse or connector is corroded, it may explain the voltage fluctuations.
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