1990 240 Wagon Fuel Problems

Nashsurecanpaint · Post by **Nashsurecanpaint** » 22 Jul 2017, 08:42

Ive searched, clicked and trolled several forums for the answer to my problen and havent gotten very far. So heres the deal, my wife was driving the '90 240 and she said the check engine light came on (not sure if that helps) the engine sounded fine, looked fine, oil level was good and the water level was proper. So i told her to just drive it home and it drove just fine. Since then it hasn't run.

Through tossing a few parts at it and some trouble shooting I currently have both fuel pumps replaced and a new fuel relay (the one behind the glovebox ).I'm not getting power to the fuel pumps UNLESS I put a jumper wire from fuse #6 -#4 skipping #5. Once I skip #5 and put the 12v to fuse #4 the car runs fine. The car also has the Lamba Sond (not sure if that's spelled correctly) system with the pink labled Jettronic fuel thing on the passenger side foot well.

Any sugesttions on what wires to test for voltage or trouble shooting help would be greatly appreciated. I'm willing to trade paint and body advice as for I've been a paint and body Tech for about 25yrs.

lummert · Post by **lummert** » 22 Jul 2017, 10:22

Seems that I've read somewhere about an ECU problem work around for a 240 that involved the fuel pumps.

Post by **jimmy57** » 22 Jul 2017, 13:09

The symptoms sound like the fuel pump relay control transistor failing in ECU. One workaround is to use the relay from 83-86 760 V6 that powers fuel pump pin when the same terminal on relay gets coil primary #1 pin signal. You'd cut the blue green wire at rely and run a wire through to the coil and splice to the blue green. If you jumper ground to the blue green wire at the relay and it runs then you know the ECU is not grounding the relay. If that doesn't make pumps run and engine run then it is something else.

Nashsurecanpaint · Post by **Nashsurecanpaint** » 23 Jul 2017, 16:31

What's the ECU look like? Is that the pink labeled jettronic box on the passenger side footwell?

Nashsurecanpaint · Post by **Nashsurecanpaint** » 25 Jul 2017, 16:57

Can anyone tell me what wires should be hot/ground coming out of the ECU that might effect my fuel pumps not getting power? I found a few nice schematics that show the wiring but I'm struggling to figure out what wires should have voltage and which are grounds.

Nashsurecanpaint · Post by **Nashsurecanpaint** » 25 Jul 2017, 16:59

Can anyone tell me what wires should be hot/ground coming out of the ECU that might effect my fuel pumps not getting power? I found a few nice schematics that show the wiring but I'm struggling to figure out what wires should have voltage and which are grounds.

93Regina · Post by **93Regina** » 25 Jul 2017, 19:13

Nashsurecanpaint wrote: ↑25 Jul 2017, 16:59Can anyone tell me what wires should be hot/ground coming out of the ECU that might effect my fuel pumps not getting power?

ECU Fuel Pump Control Circuit Repair.

Post by **jimmy57** » 25 Jul 2017, 21:34

Pin 20 of the ECU is the fuel pump relay operating pin. ECU is behind the RH "kick" panel just in front of door opening at carpet. If you take the connector off and then remove the black cover, the numbers are on the white plastic connector. There are "combs" that slide out of sides of the connector once the cover is off that allow a DVOM probe to touch the pins. You can unbolt the ECU so that both connector sides can be accessed.