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Old 01-07-2018, 11:51 AM   #1
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Default Lh 2.4 fuel pump issues

I have some issues with the lh fuel pump system
Recently i replaced the main relay, because it started to mallfunction (sparking sounds, no starts). This fixed the issue for some time. But now it does not start again.
When ignition is turned on, the pump stays silent.
I jumped 30 and 87/2 and this turns on the pump, but even then yhe car doesnt start.
Tried using the on-board diagnostics, but it stays silent (ezk diagnostics returns 0 faults)

Where is a possible problem
Thinking either a problem in circuitry (bad contact/ground) or worst case scenario its a faulty ecu
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Old 01-07-2018, 12:02 PM   #2
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Location: California

You will need to get a wiring diagram. Google it. It comes right up: the circuit for the efi/fuel pump relay

Or, what came to mind, is the fuse by the battery. Is this a pre 1992 240?

Get a test light, and confirm current to the fuel pump relay. You could also connect the teat lamp clip to a positive source and then turn on key and poke the (black/yellow?) Wire and see if the Ecu is grounding the relay.

If the diag box is dead, there is likely no power to the Ecu. Which, if you look at a wiring diagram, should be easy to trace.

10 seconds on google:


Item 135 is your relay. Doesn't matter if 740 or 240. Confirm power TO it with lamp and go from there. It's pin 30.

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Last edited by ZVOLV; 01-07-2018 at 12:14 PM..
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Old 01-07-2018, 12:37 PM   #3
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Forgot to add
Its a 1990 940 gle (16v engine)
Also both pump are new
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Old 01-07-2018, 12:45 PM   #4
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Look at the wiring diagram.

Looking at it, the MAF shares the same blue/yellow power wire as the ECU. Therefore, if you went to the maf and checked for power there with a test light....you should have a powered up LH box. That is an EASY access test point. I recommend starting there. If the MAF isn't powered up, your ecu aint.
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Old 01-07-2018, 01:08 PM   #5
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Not all lh2.4 ecus will prime the pumps.

Jumping the pumps at the box will power up the pumps but will not power up the radio suppression relay (i am ASSuming 16v cars have one of these as well..) so even if you have fuel at the rail while jumping 30 and 87/2, your injectors will not fire.

I went through an issue where my lh2.4 ecu was not priming the pumps all the time, but i knew it was an ecu that was supposed to prime them because i had heard it many times before. Both pumps were in good working condition and i had swapped a few relays around. The problem turned out to be a bad ecu that intermittently powered up the pumps. I swapped in a more reliable ecu and have been fine ever since.

It seems that a lot of the early lh2.4 ecus are garbage. In the future, i would tey ri get the later 9xx white label ecu for a 16v if they exist.
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Old 01-07-2018, 03:51 PM   #6
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YEah 928 is the later 16v lh2.4 non turbo ECU.
1988 245 White slicktop M47 Wagon! 2.5L NA 8v going in.
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