P80 Fuel Pump Relay Repair master thread 9434138 9434225 Topic is solved

[PeteP]

Just taken my relay unit out for the second time in 12 months, this time I got out my old binocular microscope to take a closer look. (The eyes are failing me for close work now). Scanning about the components I found that almost all the surface mounted resistors and capacitors either had dry joints or hairline cracks at the joints. Any one of them would/could have been causing my cold start after short run problem...anyhoo, got the small hot air pencil out and a bottle of reflow flux and restored the joints to perfect shiny ones. Car has been starting well since.

Not everyone has the Hot air surface mount equipment and I certainly don't advise using a standard hot air gun used for paint stripping!!

If you have a decent 25 - 40watt soldering iron with a long fine tip and use 22swg (.7mm) 60/40 solder and use an anglepoise magnifier with a steady hand you should be able to carefully re-make these joints. If you know a friendly electronics engineer used to Surface mount work then buy him a beer afterwards not before he does the job...

[titanvolvo]

I just had this fuel relay switch capacitor repair done to my 1998 V70. Only $11.67 at Radio Shack including the 2 capacitors and the clerk doing the soldering for me. Before the repair, my car would only fire a few times when being cranked, then immediately shut down. It would crank and not fire. Now it leaps to life on every try regardless of weather or temperature. Thanks for saving me hundreds of dollars in repairs and research.

[cwlesq]

Great post. Thank you

[mecheng]

What seems to be the problem with the capacitors? Is it the solder joints and not the capacitors?

I resoldered my relay because I noticed the solder joints for the coil were cracked as it is the heaviest object on the board, but the capacitors were perfectly in tact. I've seen caps explode when they are done, and yes they do degrade with time but that is usually many years later.

[Ozark Lee]

I've seen caps explode when they are done, and yes they do degrade with time but that is usually many years later.

After 10 years they are done. My broadcast clients used to set up analog audio gear maintenance schedules to completely shotgun replace all of the electrolytic capacitors on three to five year schedules. In that case they were mostly audio coupling capacitors and power supply capacitors. In the case of the audio gear you could start to hear it when they were going bad either with a lack of low frequency content and or 60 cycle hum. Having them explode is rare but you can often see when they are going bad when the lead end(s) get(s) puffy. It is much easier to actually see bad ones when they have axial leads.

In the case of the fuel pump relays they are part of the timing circuit and the timing is a bit less critical.

...Lee

[renns]

I put a jumper in for testing tonight, and revived my stalled V70. When I got it home, I noticed that the fuel pump remained running, even with the key off and removed. From reading this thread, am I correct in thinking this is NOT normal? I've pulled the jumper, and put in the re-soldered relay, and it's doing the same thing. When the relay is installed, the fuel pump does not run, but after shut-down, the fuel pump can be heard continuing to run. Any thoughts?

[renns]

OK, found schematics for the electrical system, and it appears the Fuel Pump Relay is fed power from the Fuel System Main Relay (located in main fuse box). I'm not sure if there's a delay in turning off the fuel system main relay after shutdown, but I haven't waited out in the cold to see. I'll try to source a replacement relay today, as I must have shorted something in mine when fitting my oddball capacitors to the circuit board last night.

[renns]

I hit the wreckers over lunch, and picked up a couple spare fuel pump relays (2 for $5...). After swapping in one of the replacement units, the fuel pump turns off with key as it should. I must have damaged my old one in attempting the capacitor replacement last night.

[Kazthebassman]

I did this repair a year or 2 ago. I seem to remember that there was a fuse that needed to be pulled prior to removing or inserting the relay. As I recall in the thread which I had read, there was a person who did not remove the said fuse and had end up with it blown.
Has anyone had any similar experience?
I have the 99 C70 I did follow that other tread's direction and had no issue.
I may be trying this on a 99 s70 tomorrow as well.

[abscate]

You should not need to remove a fuse. Pulling the relay isolates it from the electrical system completely. Ignition off, key out when pulling relay.