Fuel pumps were running continuously now won't run at all

Maddenkm · Post by **Maddenkm** » 27 Aug 2018, 18:18

So I was on another Volvo forum asking this but wasn't getting great responses - hoping for better luck here. I bought an 86 240 that had been sitting for a few years, and it would start and idle fine until i tried to put it in gear, then it would sputter out. Turns out all of the hoses were disconnected from the charcoal canister and the PCV hoses were also a mess. I also changed out the IAC valve. I did notice, however, that the fuel pumps were running continuously when I had the battery hooked up to charge, without the key even in the ignition. Once I figured out where all the hoses were supposed to go, the fuel pumps stopped running completely. I have changed the fuel pump relay, both of the fuel pump fuses, the 25A fuse connected to the positive battery terminal responsible for running the fuel system (including the fuse holder itself), and both fuel pumps and still nothing. My next guess is the fuel pressure regulator. I read online that a faulty fuel pressure regulator can sometimes shut off the circuit to the fuel pump(s), but that some have a reset switch somewhere that might turn the circuit back on. Is there a reset on the 240? I could have sworn I saw something like it in the trunk, but now I can't find it (might have been on a newer model that I was searching through at the junkyard). And does this sound like the result of a faulty fuel pressure regulator? I noticed that it doesn't even have an electrical connection on it so I'm not sure how it would cut off the pump circuit...but any help would be appreciated!

Post by **jimmy57** » 28 Aug 2018, 06:43

No. The FPR is a relief valve. When the fuel pressure gets to 35 psi it pushes on the diaphragm backed by a spring enough to open the relief port and fuel goes back to tank. The FPR has a vacuum line to intake manifold and the fuel pressure needed to open FPR is reduced by the negative pressure in intake manifold. This could affect fuel pressure if it is bad but it would not make pump not run.
SO what makes fuel pump run? The fuel injection control module (FICM) grounds the fuel pump relay pin and relay powers the fuel pump. The blue green wire at fuel system-fuel pump relay pin 86/2 from pin 17 of FICM is the grounding wire. It will have 12V on it unless it is grounding the relay if the relay has 12v power supply. The FICM will ground the relay for 2 seconds when ignition switch is first turned on and then anytime you are cranking engine or if it is running. There is a red/black wire at that relay that should have 12V. The 12V supply is from ignition switch and is supplied to ignition switch from the wire attached to the Positive battery terminal. That year range has some history of the transistor in the FICM that turns on ground for pump relay failing. Did you see any strange wiring splices near that rectangular relay behind glove box? Did you see anything in the fuse box that might have been a jumper wire making fuel pump run? When the FICM pump relay circuit fails doing some sort of bypass to power pumps has been a popular way to avoid spending money on another FICM.

Maddenkm · Post by **Maddenkm** » 28 Aug 2018, 09:34

Nope, no splicing by the relay and no jumper wires in the fuse box. I can hear the relay click when I turn the ignition, and I'm assuming it wouldn't do that with a bad ground, right? So my assumption is a short somewhere in the wiring between the relay and the pump.

Maddenkm · Post by **Maddenkm** » 28 Aug 2018, 10:04

Also there's a loose black wore that almost looks like a coaxial cable coming from under the drivers seat, any idea what that's for?

Maddenkm · Post by **Maddenkm** » 28 Aug 2018, 10:47

So I traced the wiring for the fuel pump back as far as I could, until it disappeared under the chassis, and it seems to be fine. So I guess it's probably the FICM like you suggested. In your opinion, is it acceptable to just bypass the FICM and ground it elsewhere? I've already dropped more money into this thing than I was hoping and I haven't looked up what they cost yet, but my guess is it's not a cheap part.

Maddenkm · Post by **Maddenkm** » 28 Aug 2018, 10:50

And from what it looks like in not even sure if you can replace the FICM by itself without just getting another ECU...

Post by **jimmy57** » 28 Aug 2018, 12:38

I was using that acronym for what you may be calling the ECU. There is only the one fuel injection ECU inside car on RH side. The ignition ECU is the black box on RH side in engine compartment with a connector and a vacuum line.

The relay is a two relay built into one relay. One part powers up the fuel system components other than fuel pump and the other part is for fuel pump.
The wire colors and terminals are in the first reply that can be checked with a voltmeter or test light. I don't have a wiring diagram with me now but the fuel pump outgoing wire is connected to terminal 87/2. That terminal is marked on relay and you can figure out which wire if you pull the relay out and look at it.
The blue with green stripe wire could be grounded and the pumps should run any time ignition is on. that loses some safeguard in an accident of having pumps shut down. There is no inertia switch on Volvos like some others (like Ford) used.

Maddenkm · Post by **Maddenkm** » 28 Aug 2018, 12:51

Gotcha, so what you're saying is if I bypass the ECU to ground the relay, the pumps might not turn off if I get in an accident, continue to spew fuel, and possibly cause a fire?

lummert · Post by **lummert** » 28 Aug 2018, 13:27

Bypassing the fuel pump relay may also run the battery down if you forget to switch off the pumps when shutting off the engine.

Post by **jimmy57** » 28 Aug 2018, 19:55

Yes, the risk of fuel spill is greater. How much? I can't say. If the engine runs post accident the pumps would be on as there is no attitude or inertia sensor that cuts them off. On that system the fuel pump relay coil 12V side is from ignition so the pumps go off when the ignition i turned off unless there is some other mods done to wiring.