Fuel pump relay connector measurement less than a volt

[Cea123]

Hello Javier,

I'm still pursuing an answer to the problem. Here's what I've done since our last correspondence 1) Replaced the current F23 fuse with another one, but disconnected it while performing the following steps, 2) Jumped fuel pump relay sockets 30 and 87, 3) Measured voltage output of socket 30, found a reading of less than 3 volts, and I did ensure that I had a good ground for my multi-meter, 4) Measured voltage at F23, which was zero and I didn't expect anything since socket 30 didn't measure well, and oh by I did switch on the ignition while taking the measurements, 5) Since I wasn't receiving a favorable voltage reading at socket 30, I assumed that there may be a fault somewhere in the B+ cable leading from the battery to socket 30, so I disconnected it from the battery and re-measured the voltage, there was no change still less than 3 volts, 6) Next, I checked the ground for pin 4, it was clean and tight. 7) I checked the fusible link near the battery, it wasn't broken, 8) Out of curiosity I decided to disconnect the fusible link cable from the battery and reconnected the B+ cable, followed by measuring voltage at socket 30 and 12v were present, but changed back to less than 3 volts after I reconnected the fusible link cable to the battery. 9) During the time I had the fusible cable disconnected from the battery, I also measure the voltage at F23 but there was nothing there and I figured that since the fusible link cable was disconnected from the battery, it must have some bearing on the no volts measure at F23, even though there was 12v at socket 30.

Is there some other fusible link that I should check?

If you have any other suggestions, please don't hesitate to send them to me.


Cea123

[Cea123]

If anyone else has some information you'd like to share about correcting the problem with my car, please send it to me!

[genphreak]

If anyone else has some information you'd like to share about correcting the problem with my car, please send it to me!

OK this intrigues me:

I checked the fusible link near the battery, it wasn't broken, 8) Out of curiosity I decided to disconnect the fusible link cable from the battery and reconnected the B+ cable, followed by measuring voltage at socket 30 and 12v were present, but changed back to less than 3 volts after I reconnected the fusible link cable to the battery.

Fusible links are located inside shrink wrap in the 2 largest wires (the main power 1cm one and the 4-5mm one), approximately 8" from the battery post (if battery is under the back seat). If not there, one may be relocated to a large plastic holder behind the battery under the back seat- or very obviously fixed to the front RH shock tower.

Do yourself a favour and replace all the inline fuses* by screwing/crimping/soldering in new ones properly. Even if they are yet to prove faulty, they cost very little and are likely to fail if not replaced after 20 years. The metal simply deteriorates in a way that is only obvious under a microscope. The forums are full of issues with these- and it causes ongoing an challenge whenever anything electrical causes a problem...

EDIT: * If your car is equipped with a 4" plastic holder for any of these fuses, you may not need to be so keen to replace the fuse, I've not seen these fail as often as the inline ones- the inline ones seem to suffer more from corrosion inside the mating surfaces and from micro-cracks in the fuse material. Simply check them carefully for voltage drop and visible signs of oxidation, esp. around the fasteners, as well as cracks. I usually remove the fuse and bench test it under a light and magnifying glass/microscope when unsure.

[Cea123]

genphreak,

Fortunately, after studing the electrical wiring diagram for the car, I realized that I was placing the jumper into the Main Relay sockets (30 nad 87) rather than the Fuel Pump Relay sockets, all due to the fact someone unplugged and switched the places of the Main Relay sockets with the Fuel Pump Relay sockets. I was following the pictures of the locations of the relays from the shop manual, not relalizing that the sockets had been switched around until studing the electrically wiring diagram. So, here's what I found after placing the jumper into the correct sockets (30 and 87): 1.) When I tested the voltage at 30 it read 12v, 2.) The voltage at the B+ measures 12v, 3.) The voltage at F23 read 12v. But, after I replace the fuel pump relay into its connectors in the E-Box the 12v at F23 reads zero volts. Is it possible that the fuel pump relay is bad, even though it's new or maybe I shorted it out somehow? The other anomaly is the voltage at the 30 and B+ are not always consistent, sometimes the voltage is a low as 1.7 and 3.65, respectively, but I assuming that my ground for the multimeter is not quite good enough so I'm going try strapping it down to a good metal source and re-measure the voltages. Lastly, I learned how to test the relay so I will test it to try and determine whether or not its any good.

[Cea123]

genphreak,

I forgot to add that the fuel pump appears to be working fine and I'm saying that because, when I jumper 30 and 87 the fuel does come up to the rail.

[Javier]

Please keep in mind that the Pump relay will only close contact from 30-87 when the car is cranking or when the engine is running, so if you just replace the relay and checked for voltage at F23, it is normal to have 0V unless you crank the engine.

If jumping 30 to 87 in the pump relay starts the pump, the circuitry is Ok, I mean, the fuse, wiring, connectors and the pump. Now if you still does not have a working pump when cranking the engine with the relay installed, it is necessary to check the relay ( just remove the relay and feed 12 V from 86(+) to 85(-) pins, feel the click and verify 0 ohm reading between 30 and 87 pin), If relay test Ok, you may have other issues with the DME control, and a different approach to debug should be started.

[Javier]

This also should be checked carefully, I'll comment using the later info about this being the DME relay and not the pump relay:

I'm still pursuing an answer to the problem. Here's what I've done since our last correspondence 1) Replaced the current F23 fuse with another one, but disconnected it while performing the following steps, 2) Jumped fuel pump relay (now we know it was DME relay) sockets 30 and 87, 3) Measured voltage output of socket 30, found a reading of less than 3 volts (30 is feed straight from B+, just like pump relay, 3 V is bad), and I did ensure that I had a good ground for my multi-meter, 4) Measured voltage at F23, which was zero and I didn't expect anything since socket 30 didn't measure well, and oh by I did switch on the ignition while taking the measurements, (0 V is Ok in this scenario, ignition key in on (not start), does nothing here) 5) Since I wasn't receiving a favorable voltage reading at socket 30, I assumed that there may be a fault somewhere in the B+ cable leading from the battery to socket 30, so I disconnected it from the battery and re-measured the voltage (?? don't see the objective), there was no change still less than 3 volts (Getting more than 0V without battery is weird), 6) Next, I checked the ground for pin 4, it was clean and tight. 7) I checked the fusible link near the battery, it wasn't broken (Fusible link does not feed the B+ post), 8) Out of curiosity I decided to disconnect the fusible link cable from the battery and reconnected the B+ cable, followed by measuring voltage at socket 30 and 12v were present, but changed back to less than 3 volts after I reconnected the fusible link cable to the battery (This is weird, and should be verified). 9) During the time I had the fusible cable disconnected from the battery, I also measure the voltage at F23 but there was nothing there and I figured that since the fusible link cable was disconnected from the battery, it must have some bearing on the no volts measure at F23, even though there was 12v at socket 30 (Now we know that the 30 pin was not in the pump relay).

Note that faulty DME relay operation will shut off the Pump relay.

[Cea123]

Javier,

Thanks for respondng, but please take a look at the reply I sent to "genphreak" at 4:59 on yesterday. I appreciate your commenting ( in red typeface) on the message previous to this reply, but the message I sent to genphreak speaks to being on the right path as opposed to the everything else prior to my 4:59 message to genphreak.

[Javier]

Yes I saw that message thus my first response at 11:12 am. Then I commented in red at 11:52 to your first post with the knowledge of originally mixed relays, because there seems to be some issues at the DME relay (30 pin socked should be 12V no mater what).

Up to know, presuming you Checked Ok the voltage at B+ post, I mean those low voltage readings ( is a low as 1.7 and 3.65) proved to be a reading procedure error, what you seem to have is an issue with the pump relay, if Relay ended being Ok, you may have issues with the DME relay or the DME, as told you, if pump relay is Ok, the debugging takes you to another step. Let's verify first that the B+ post voltage stands solid, and the pump relay is working fine.

[Cea123]

Okay, I'll check the things you've outlined as soon as I get back to the car. I'll keep you posted.

Thanks!