LH 2.4 fuel injectors losing power

[The Iron Sausage]

This is in a customer’s ‘90 240. It’s been to several shops, they’ve been firing the parts cannon at it.

It starts and runs smoothly, and drives right for 25 to 30 minutes. Then it shuts off like clockwork. I can jump the fuel pumps when this happens, and they turn on. both are still working. The injectors get no power, but the car still has spark. If the key is left in the on position, the car will not restart. If the key is turned off and then cycled back on, it will fire right back up. If the key is left in the on position for a period of time when this happens, it will take longer for the car to start back up after the key is turned off. When the car does start back up, it will run for less time. The second cycle will be 10 to 15 minutes. It will shut off again. Again, this is like clockwork. It doesn’t happen when wires are moved, it doesn’t randomly happen, it’s like it’s on a timer. If the key is left on after it happens for 10 to 20 minutes, nothing is hot to the touch. The coil isn’t warm, nor is the fuel pump relay, ecu, ezk, etc. The car does this if the tank is empty or full. The car doesn’t have a noise suppression relay that I can find.

The previous shops have replaced the crank position sensor, the MAF sensor, the idle air control valve, and the fuel pump relay. I have tried two or three different fuel pump relays I’ve had laying around, cleaning all of the grounds and checking all of the wires I can find. The main fuse next to the battery is in good shape. If I pull that out when the car is running the car also loses spark. I don’t believe this is the problem. I have swapped out the ECU for a known good unit, and the same thing happens. The wiring to the ECU, and the EZK is free of corrosion. Not a hint of it anywhere. Wire insulation in the cabin and underhood is in good shape. There are no codes stored in either unit. I have run the car with every sensor disconnected that will still allow the car to run, and the same thing happens. There are no other symptoms, except for it shutting off at these specific times. It doesn’t cough or falter, it simply shuts off like somebody turned it off.

Any ideas? What powers the fuel pump relay? Ignition switch? I don’t have the wiring diagrams yet. To me it sounds like something electrical is getting hot and shutting down until the current is removed long enough for it to cool down and work again.

Thanks in advance.

 

[2turbotoys]

I would check that the charcoal canister drain hose doesn't have crud in it. That will vapor lock the fuel system. Bugs like to go in there. That kept happening to my 242 a few years ago, it would shut down after 20-30 minutes and not restart for a long time.

Probably not the issue but easy to check.

 

[esmth]

From what you describe, this issue sounds related to the fuel pump relay. Maybe cracked solder joints inside. I know you said it was replaced

Any ideas? What powers the fuel pump relay?

The ignition switch in position 2 and 3 will give 12v power to pin 35 of the LH ECU, which will cause it to ground pin 21 of the ECU to enable the "system" part of the fuel pump relay. That relay then supplies power to the injectors, MAF, and pin 9 of the same ECU.

Ignition is powered with a separate circuit so it makes sense you don't lose that.

 

[The Iron Sausage]

From what you describe, this issue sounds related to the fuel pump relay. Maybe cracked solder joints inside. I know you said it was replaced



The ignition switch in position 2 and 3 will give 12v power to pin 35 of the LH ECU, which will cause it to ground pin 21 of the ECU to enable the "system" part of the fuel pump relay. That relay then supplies power to the injectors, MAF, and pin 9 of the same ECU.

Ignition is powered with a separate circuit so it makes sense you don't lose that.

I’m focused on that as well, but the relay that came in the car does the same thing as the known good used relay I had on the shelf, and the brand new Meyle unit I bought just for the occasion. The car shuts down at the same time no matter what I’ve tried. The noid light doesn’t light after, unless the key is cycled, or the car rests in “off” for some time if the ignition is left on. I can’t even blame grounds necessarily due to the regularity at which it happens.

 

[The Iron Sausage]

I would check that the charcoal canister drain hose doesn't have crud in it. That will vapor lock the fuel system. Bugs like to go in there. That kept happening to my 242 a few years ago, it would shut down after 20-30 minutes and not restart for a long time.

Probably not the issue but easy to check.

I appreciate the response and I’ll check it, but I’ve got a noid light showing no power to the injectors after shutdown.. I’m thinking electrical.

 

[dl242gt]

Since it is happening at a regular interval. If you are losing power to the injectors that is related to the system part of the fuel pump relay as mentioned above. Here is what I would check out. I would check fuel pressure and make sure the regulator is working correctly. When my friends car had this symptom it was a bad fuel pressure regulator. It didn't leak. It just failed internally which made the fuel pressure too high and it would flood the engine after about 20 minutes of running.

The other time I had stalling like that it was ignition related and turned out to be the ignition amplifier was failing by overheating after about 20 minutes of running.

 

[84B23F]

‘90 240. ... If the key is left in the on position, the car will not restart. If the key is turned off and then cycled back on, it will fire right back up. If the key is left in the on position for a period of time when this happens, it will take longer for the car to start back up after the key is turned off. When the car does start back up, it will run for less time.

If ignition switch's plug could be pulled off and hot wired, this would rule out ignition switch.

 

[cwdodson88]

If ignition switch's plug could be pulled off and hot wired, this would rule out ignition switch.

There are easier and much better ways to rule out the ignition switch than suggesting that he hot wire a customer’s car.

Look over a wiring diagram and back probe power in to the switch and power output to the fp relay. See if it looses continuity

 

[esmth]

iirc the ignition switch contact for the ignition system power is shared with the signal that triggers the system relay thru LH box pin 35. so if you've got spark that rules out the ignition switch causing this issue i think.

 

[84B23F]

iirc the ignition switch contact for the ignition system power is shared with the signal that triggers the system relay thru LH box pin 35. so if you've got spark that rules out the ignition switch causing this issue i think.

There are easier and much better ways....Look over a wiring diagram

YMMV, last diagram I saw, quite a few amps runs thru ignition switch. Back probing has been used by shade tree mechanics, and can give false results. There still can be current flowing thru the switch. Oh, the mechanic does the hot wiring, for testing.

 

[cwdodson88]

YMMV, last diagram I saw, quite a few amps runs thru ignition switch. Back probing has been used by shade tree mechanics, and can give false results. There still can be current flowing thru the switch. Oh, the mechanic does the hot wiring, for testing.

Yep, there’s a few amps there. Solidifying the reason for continuity check on the switch, then down the line, main fuse, fp relay, etc.

@84B23F Maybe you just don’t understand a lot about anything. At least that my understanding so far.

Short version, a circuit could pass some amperage, if connections are bad or loose, they build up heat, heat over time increases resistance to the point where they no longer pass current. Could that explain the time thing, maybe. Will it rule out the switch pretty quickly, yes. Will it require removing a bunch of stuff to do, no. Is it a valid diagnostic procedure, yes.

You should really stop giving advice when you really don’t have a damn clue.

 

[bobxyz]

That's certainly a weird failure. Did you check the codes before cycling power when it failed? I don't remember if all the ECU/EZK codes are retained through a power cycle.

You can find a Volvo Greenbook wiring diagram for a similar 1993 at ozvolvo.org/archive, and a Mitchel's for a 1990 at https://web.archive.org/web/20150318194652/http://www.volvowiringdiagrams.com/

When you checked the grounds, I'm assuming that it includes the two front/back ground bolts on the intake manifold and those wires? That's where the ECU and EZK ground to.

When it won't start, you might try measuring the voltage at the ECU and EZK. EZK would be pin 20 ground (brown/black) and pin 6 +12v (blue) from ignition switch; ECU would be pin 5 sensor ground (brown/black) or pin 17 (black) power ground and pin 9 (red/black) main +12v from fuel pump relay.

 

[ZVOLV]

The fuse by the battery on a 1990 240 powers the EFI/Fuel pump relay. It is a common point of failure.

Get a test lamp and do electrical diag at the relay.

 

[The Iron Sausage]

@ZVOLV The fuse at the battery is still fine. When the shut down occurs, it has power both in and out at the wires. If I remove the fuse while the car is running, the spark dies as well. I do have spark while cranking after shutdown.

@bobxyz Both the EZK and ECU have power and ground at those specified terminals during shutdown. Also, thanks for the links, but they are either dead, or show PDFs of a green book cover with no other pages. I’ll try again with an actual computer instead of a tablet to see if there’s something weird going on there.

@cwdodson88 @84B23F @esmth @dl242gt and everybody else: What I’m getting at the fuel pump relay is both fat orange wires (85 and 87/1) have continual power after shutdown as does the red wire (30). Those orange wires are both connected to pin 9 on the ECU, and 30 is obviously battery. The yellow/black wire (86/1) shows 1 volt while running and after shutdown with ignition on. 86/2 is a blue and green wire that has 1 volt while running, and 12 after shutdown. This is connected to the fat yellow/red wire at 87/2 that we all know powers the pumps and injectors. Obviously, this wire loses voltage and the car dies. I can jump the pumps at fuse 4, and they run while I crank the car, but the injectors still don’t fire. If I leave the ignition on, and swap fuel pump relays immediately, the car still won’t start. So, not the fuel pump relay at fault.

The diagram on one of my pump relays shows 85 (fat orange wire with continuity to pin 9 on the ECU [an even fatter orange wire] and 87/1 [same size orange wire as 85]) being the “ground” to switch on the yellow/red wire (87/2) using the 12v source from the blue/green wire (86/2). All orange wires stay hot while running, or after the car dies. Anybody have a complete diagram showing the path of the blue/green wire, and the multitude of yellow/red wires?

 

[esmth]

In the good running scenario, the yellow/black wire and blue/green trigger wires from ECU to relay at ~1v sounds to me like they are working correctly, I think.

The blue/green wire is the ground-enabled trigger wire from ECU pin 20, for the fuel-pump portion of that fuel relay. The ecu will command this line low to ground for a moment right when key is first turned (to prime the fuel pumps), then release. And then again and constantly once the ECU receives a RPM signal into pin 1. Once engine stops spinning for whatever reason, the ECU will quit grounding it and disable the pumps on purpose.

The thick yellow/red wires from that relay should go thru the fuse box to the fuel pump(s) and O2 heater. I dont think it should be supplying power to the injectors. That power should come from the orange wires on the 'other' side of the fuel relay.



How are the condition of the splices where all the orange wires come together a short distance into harness away from the relay?

 

[bobxyz]

The links I posted seem to work fine for me, but the archive.org one is pretty overloaded during prime hours, so trying again in the early morning may work better.

Here's a couple pages of the diagrams, 1990 and 1993:


- The EZK gets powered from the ignition switch.
- The ECU uses the ignition switch as an input (pin 35) to turn on the System side of the main relay, which also provides main power to the ECU.
- When the EZK detects cranking, it starts to fire sparks and generates an RPM signal to the ECU (one of the 3 EZK-ECU wires).
- When the ECU sees the EZK RPM signal, it turns on the fuel pump side of the main relay,
and then starts to fire the injectors (2 squirts per rev during cranking, 1 squirt per rev during running)

I'd check that there is +12v power on the injectors when failed and cranking (I know that your noid light doesn't flash).
I think that bad EZK-to-ECU signals will cause a check engine light and diag codes (the CEL does turn on initially and isn't burnt out?)
Sometimes there are weird failures due to low ECU/EZK voltages. The inline fuse by the battery, and the ignition switch, can be the sources.

Edit: there's a special LH2.4 diagnostic Test Mode 3 that will click the injectors, and the IAC valve. Try running this beforehand to know what it does (the injectors go tick-tick-tick-tick, while the IAC is more of a thwack-pause-thwack-pause), then try it again when failed.

Engine and OBD Diagnostic Codes<

Volvo Engine and OBD Diagnostic Codes<

www.volvoclub.org.uk

 

[84B23F]

Maybe you just don’t understand a lot about anything. At least that my understanding so far.
...
You should really stop giving advice when you really don’t have a damn clue.

Apparently, this video I cited was not watched. Ruling out an ignition switch issue is prudent....

 

[84B23F]

this wire loses voltage and the car dies

Sidebar - Years ago, my 1984-245's alternator shot craps...at some lower battery voltage, engine shut down.

A new ignition switch could be inserted into electrical plug, and manually turned, fwiw.

 

[2manyturbos]

Here you go. This is right out of the 1990 240 Green manual.

 

[cwdodson88]

I'd check that there is +12v power on the injectors when failed and cranking (I know that your noid light doesn't flash).
I think that bad EZK-to-ECU signals will cause a check engine light and diag codes (the CEL does turn on initially and isn't burnt out?)
Sometimes there are weird failures due to low ECU/EZK voltages. The inline fuse by the battery, and the ignition switch, can be the sources.

Edit: there's a special LH2.4 diagnostic Test Mode 3 that will click the injectors, and the IAC valve. Try running this beforehand to know what it does (the injectors go tick-tick-tick-tick, while the IAC is more of a thwack-pause-thwack-pause), then try it again when failed.

Engine and OBD Diagnostic Codes<

Volvo Engine and OBD Diagnostic Codes<

www.volvoclub.org.uk

This ^

Test light rather than noid light.

This would direct me to something ecu related if you have power at the injector.

The fp relay seeming to lose trigger when this happens points me to something ecu related, timer circuits or something there with a connection that’s building resistance. So continuity/resistance checks of power and ground circuits for the fuel pump relay when the problem comes up.