A paperclip as a Fuel Pump Relay bandaid?

nightc1 · Post by **nightc1** » 01 Sep 2010, 22:53

IS there any danger in driving my car with a paperclip in place of fuel pump the relay?

I've looked around at various forums looking for an answer and the only thing that popped up was that in the case of an accident or the engine stalls, you'd want the pump to stop. But power seems to only be applied when the key is in start & run... so while a possible issue, it doesn't sound really bad if I'm stuck somewhere with a bad relay and want to jumper it to drive on home.

Is there something I'm missing? I don't care if an engine code is thrown, I can reset the codes. Does it drain the battery, kill the pump, hurt some other relay or part of the car?

I just soldered some new capacitors into my fuel pump relay this evening, and if it doesn't work I'd like to go ahead and drive my car home this weekend as it's sat at work for just over 3 months now (wow does time fly). Luckily it's my extra car ... but I'm past ready to have it home and I'd like to do other stuff to the car if my fix fails while I wait for a new relay to show up.

Post by **jblackburn** » 01 Sep 2010, 23:31

If your new, fixed relay won't work, yeah, go ahead and drive it home with the paperclip - it will be just fine for a short time.

Get her on home - wow, it has been a long time without your car!

nightc1 · Post by **nightc1** » 02 Sep 2010, 09:32

Thanks for the feedback. If it would harm something then I'd definitely not want to do it. Looks like a paperclip is going to be standard issue for my emergency road kit from now on

.

Well, I just tested the relay and it still didn't work so either I need a new one or it's not getting the signal to do it's job. Either way I can paperclip'it home and get it in the garage where I'll have more time to work on it.

Post by **cn90** » 02 Sep 2010, 12:01

1. OK to use the paper clip as a bandaid.
BUT remove the clip when you stop the car, this way the fuel pump does not have to run.

2. Personally, I know all about Ozark Lee's famous capacitor fix for the relay, but this is a safety issue (what if the fuel relay fails when you need to accelerate on the highway), personally I 'd buy a new fuel relay for $40.
Sleep well at night.

Post by **Ozark Lee** » 02 Sep 2010, 16:10

If you still have no fuel pressure with the relay bypassed then chances are the fuel pump croaked. You can sometimes get the fuel pump to run again by banging on the bottom of the fuel tank with a baseball bat or a large stick. It only works a couple of times if it even works at all but it might get you home.

...Lee

nightc1 · Post by **nightc1** » 02 Sep 2010, 21:02

Well, for my specific car, the relay (when plugged in) is not engaging (or staying engaged) and letting juice fully flow to the fuel pump. So I'm getting some gas but not enough to keep the car going very long (though maybe it's the engine pulling gas through some kind of pressure and the pump isn't running at all). With the paperclip in, the car runs nice and smooth and I can hear the pump run (if I listen for it).

This means, by my own reasoning (feel free to correct me, I'm a computer scientist not a mechanic), that either...

(A) The relay is not getting the signal that the engine is running and thus isn't engaging the circuit to let juice flow
or
(B) The relay is not working

I see no option for the fuel pump to be bad since it runs perfectly with the paperclip installed.

If it's (A) then no amount of good backup relays would let me drive my car home. But a paperclip would. So I'm definitely going to keep a paperclip in the fuse box (with the extra fuses) from now on. I may even throw a few extras in the little volvo tool bag that came with the car

. It seems like the wise thing to do if it doesn't damage something to use it in place of the relay.

As for the pump running when the engine is off, with my 99 V70 (Base model), I can only hear the pump run when I'm starting the car or while the car is running. It makes NO noise when the engine is switched off and the key is removed. Maybe this isn't true for other cars in the 850/70 line

... but I checked this out first. I can triple check tomorrow by putting the volt meter on the bridged pins and see if any voltage is present with the key out of the ignition as well as every position with the key in the ignition. I'll post back my results. Either way it's probably smart to pull the paperclip when not in use. I may even take this 1 step further and build a kill switch jumper that I can route through the drivers window.

Either way (A) or (B), before I replace the relay I need to get my multimeter out and see if when the engine is on if there is any voltage on the other relay pins that would signal it to engage. Since it's an on or off kind of deal, I gotta think that there should be some kind of voltage that'll show up. My relay could be functioning perfectly but something else could be causing the issue. Throwing money at it blindly doesn't mix well with my budget (though under $3 in capacitors wasn't a huge waste). I'll happily buy a new relay if the upgraded relay really is bad... or a speed sensor or whatever is needed to fix the issue.

I just can't wait to finally have the car home this extra long weekend

. It's kind of funny that a typical MacGyver trick is what is needed for a temporary fix.

The only thing I really wonder here is, will the pump running the entire drive home cause the engine to get flooded thus ruining plugs or burn too much fuel or something bad like excessive pressure in the fuel lines since the pump wont disengage while the car is in run or start mode. I don't mind wasting a little fuel... but I don't want to cause some huge pressure build up and blow a fuel line or something else horrible.

Does the fuel pressure regulator keep the pressure steady no matter how much the pump is running?

Post by **Ozark Lee** » 02 Sep 2010, 21:50

I misread your post and thought that it would still not run with the paper clip - my bad.

You are going to need to pull out the trusty VOM and start tracing wires to find the fault.

The schematics are here:

https://www.matthewsvolvosite.com/downlo ... vo_850.zip

See System Wiring Diagrams.pdf

Don't get into a wreck with the paper clip jumper - the factory system is more or less designed to turn off the fuel pump relay in the event of a collision but beyond that the FPR deals with pressure at the rail so it will run just fine.

...Lee

nightc1 · Post by **nightc1** » 02 Sep 2010, 22:29

Thanks Lee. That's the peace of mind I was looking for.

The route home is peaceful country back roads and I'll probably wait till saturday morning when traffic is pretty much dead to get it home (I'm in rural AL) or in the evening after work traffic has died off on friday. I'm a pretty safe driver. No bumper riding or anything like that as I'd rather get home later and not give my limited income to the troopers or cops.

I downloaded the 850 doc pack a while back (and I highly recommend it to anyone with an 850 or the early 70 series cars. It's not perfect for my 99, but it's guided me to a number of things before. I'll look through it for the schematics, I wasn't sure they were in there. I also have a version of the haynes manual in digital form and um... some other official technical documents (which I haven't fully looked through yet).

I'm feeling confident that I'll figure out what the issue is once i have it home in the garage. I just hope it's the relay or something even cheaper. I'd like this issue to finally be put to rest so I can put some tires on the car (it's in need) and then do a timing belt maintenance, replace the motor mounts (the top one is bad, might as well do them all). flush the transmission (never done this), and replace the heater core (it was leaking and the stop leak worked great but I need to fix this the right way)... as well as do other stuff to bring the car closer to stage zero.

Post by **Ozark Lee** » 02 Sep 2010, 22:47

Check with member BEJinFBK. He may actually have your actual '99 schematics. There was a web site in Poland that had them posted but I only downloaded through the '98 model year - it took hours per model year and the site is now defunct.

...Lee

nightc1 · Post by **nightc1** » 03 Sep 2010, 07:32

Will do. Thanks again for the feedback.