I have a 1990 240 wagon with manual transmission. Recently, something has happened that is preventing electric making its way to the fuel pump. If I hook the pump to another circuit using alligator clips and wire the car runs fine. I thought the relay was shot so purchased a new one but the problem remains the same. Can anyone offer some advice as to what might be the problem.

The car runs and drives just fine “hot wired.”

Is ignition working? For the FI system to work, it must receive timing pulses from the EZK Ignition CU.

And those ICU pulses are derived from the Crank Position Sensor, which is known to become unreliable with age.

If ignition is OK, the 25 Amp fuse can be assumed OK too, as this fuse powers the Ignition CU as well as the FI system.

The Fuel relay itself could be the problem. The Fuel pump portion can be bypassed by applying +12V to the Fuse 4 input (left side) contact. The +12V can be picked up at the left side of any fuse 6 thru 10. The pumps should run immediately when the +12V jumper is connected to the fuse 4 input contact.

If this fuse jumper makes the car run like your other rig mentioned above, the Fuel relay is most apt to be failing, since the more common ECU failure to control the Fuel relay is not known to be a problem with your type of ECU.



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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Dan (pageda, below) is right in noting that I overlooked the fact that the Fuel relay had been replaced. It was late (for me, up since 4:00AM) and I wasn't thinking clearly.

But I'm still reluctant to blame the ECU without further diagnostic testing at the relay, since:

1) I don't believe the 572 is known for failing to ground the Fuel relay, like the 561

2) Relays cause far more no-starts than ECUs

3) The source of the replacement relay is unknown (working car or aftermarket "new"?)

The relay vs ECU choice is fairly easy to make by inserting ("back-probing") a substitute grounded wire where the Blue-Green wire enters the Fuel Relay harness plug. That's the wire the ECU uses to control the relay.

With the substitute relay ground wire in place, the pumps should* run as soon as Key is turned on. If the car starts and runs (as when "hot wired"), then the grounding wire is making up for an ECU problem.

* If the pumps don't run with a good grounding wire at the harness plug, the ECU is not likely to blame—and more voltage checking at the Fuel relay terminals is needed.



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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Bruce
He did replace the FP relay which did not fix the problem. He then got the engine running by applying 12 volts directly to the pump.

To me this seems to be a problem with the ECU loosing the ground for the FP relay as is common with the pink label 561. He does however have an LH 3.1(I did not know when I made my original post) with the 572 ECU. I believe original 572 as with others in the 5xx series suffered from the same failure mode. Dan

fuse in driver's kick panel OK: fuse good; contacts not corroded?

As Jorrell points out there is a 25amp fuse in a holder on the driver's inside fender. It is in white holder if it is the original one and these are prone to corrosion.

Most auto supply stores sell a replacement with a "weather proof" cap that is a good replacement for the old holder.

Yours may respond to a couple of wiggles or a good cleaning if that is the problem area.

If that is not the source Pageda is correct as well it might be equipped with the pink label ECU and they are a known problem item. The jumper wire skirts problem but of course does not solve it.

Post back with what you find out.

Randy

Thanks to all who responded. Have checked all of the fuses (didn’t know about that one under the hood!) and, unfortunately for me, they all are fine. My ECU does not have a pink label, the number is 0 280 000 572. This ECU seems to be slightly rare and far more expensive than others. Can a different number unit be substituted or must I have a 572? I sure I know the answer to this question already... but thought no harm in asking.

The 572 is the only ECU I am aware of that works with the LH 3.1. If your ECU's label is a color and not white I would suspect a bad ECU. Dan

Thanks to all who offered help to solve my fuel pump problem. In the end it was a bad ECU.

I am not aware of what substitutions can be made for the 572 ECU if any, hopefully someone will chime in with the needed information.

One more thing to check on the wire that leads from the battery through the 25amp fuse and on to the relay above the passenger's knees.

I point this out because I had this exact problem and it was difficult to chase.

Sometimes the connection at the battery can become corroded at the point the red wire attaches. This creates a huge resistance and while it may pass 12v it does so at a very low amperage (not enough amperage to close the relay). I found that the corrosion had formed at the connector and spread up behind the wire's insulation.

Take the connector loose (remove 10mm nut on that side) and cut it off of the wire and replace it with a new one making sure the wire you are crimping to is clean and not corroded. Clean the stud it attaches to very well and then reattach the connector and tighten the nut.

Good luck.

Randy

If you have a pink label (last 3 digits of the model #)561 ECU it may have failed, this is common with that particular ECU. First check fuses 4 and six to make sure they are good and have clean tight connections at the fuse panel. Dan

Doesn't the 90 LH 2.4 car have a blue 20A fuse in a white holder in front of the driver side strut tower as well? That should be checked for corrosion and replaced as needed.

jorrell
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92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!