99 V70XC driving without fuel pump relay (jumped 87 & 15))

[cn90]

The 850, S/V70 relay design (a bit more circuitry) is different than the Volvo 240, 740 (simple relay).

The idea is this: if you are in a collision and hit a tree and become unconscious:
- If the engine stops running (let's say the front end is crushed), then without signal from the crank sensor, the ECU shuts down the relay: fuel pump stops running.
- If the engine still runs, fuel pump runs anyway.

I have done this jumping before. Jumping a fuel relay in a pinch is not stupid, it is the right thing to do to get home. Now if the O.P. needs to go for some 300-mile trip on Saturday, by all means, do it as long as he is aware of the issues.

Once the key is out of the ignition, the fuel pump stops anyway because terminal 15 is OFF when the key is out. Make sure you use correct in-line fuse and wire gauge/spade connector when jumping (no paper clips!).

His chance of him coming back home alive is 99.999999999%.
In fact, he is at more risk being hit by a drunk driver than running into a problem created by this jumping relay thingy.

For the long-term fix:
- Get a good used relay from local junk yard or ebay for $5, but test it first.
- New is about $50 at dealer. I don't know much about aftermarket stuff.

- The old relay: don't throw it out, search for post by "Ozark Lee" on the cheap capacitor fix. Fix it using Radio Shack capacitor and keep it in the glovebox as spare.

PS: The rumor is that Radio Shack may be out of the business soon, so enjoy Radio Shack while it lasts lol...

[cn90]

This is what I mean by a jumper wire with fuse:

[abscate]

There is little value in adding the fuse because the terminal 15 is fused already, upstream.

Focus on using good crimps and heavy gauge wire and you will be fine.

[cn90]

You are correct, the entire system is protected by upstream fuses (50A, 60A types). See photo below.

However, whenever I jump some electrical component, I always use an in-line because of the "feel-good" factor lol...

Anyway, photo op:

[PatternFlyer]

I looked up Ozark Lee's fuel pump relay repair last night.
Got the capacitors of same part numbers from RadioShack.

Going to work on it tonight when I get back to shop. So far drove around town 30miles on and off. No problem. I will make a new jump cable with 12ga wire and keep it in the car if the repair works on my relay.
I am going to order a new relay anyway.
Thank you all for the reply.

I will definitely be back with more questions about subframe bushings, engine mounts, and oil leak.

I will post a follow-up tomorrow evening after the trip.

Ihncheol

[Ozark Lee]

The relay repair is fairly easy and it has always worked for me unless you find some burned contacts on the relay itself. I wouldn't lose a bit of sleep driving with the jumper wire as long as you use spade lugs and the wire isn't getting hot.

A paper clip isn't a real great conductor and it doesn't fit into the socket real well. Spade lugs fit great.

...Lee

[rspi]

740's had bad wire harnesses and people would knock the insulation off of the wires while working on and around the car. Bare wires would short out randomly and start a fire. A friend of mines 740 caught in her garage and burned the car, garage, and part of her house down.

Chances are, jumping the relay did not start the fire, leaning on or bumping some other wire did.

[northernlights]

740's had bad wire harnesses and people would knock the insulation off of the wires while working on and around the car. Bare wires would short out randomly and start a fire. A friend of mines 740 caught in her garage and burned the car, garage, and part of her house down.

Chances are, jumping the relay did not start the fire, leaning on or bumping some other wire did.

Yep. The magic 1980's extra-biodegradable insulation. That was a mess. It almost gave Volvo's the same charm as a vintage Jag.

Fortunately the Jags wouldn't run reliably enough to catch fire as easily.

[abscate]

Lol....Lucas, the Prince of Darkness

....disturbing that we haven't gotten a trip update, though....

[PatternFlyer]

Ok, Trip on Sunday was just fine. jumper wire made with 12Gauge didn't have any problem or heat issue. Blade type crimps were not fitting tight enough, so I bent a little to make them fit a little better with force.

Replacement of the 2 capacitors were done fine, but relay didn't work.
maybe something else?

Waiting for a new relay.