1998 V70 Replaced fuel relay, what's next?

brendandburns · Post by **brendandburns** » 15 Feb 2016, 17:34

Hello folks,
My 1998 V70 Wagon was starting and then immediately dying (1-2 seconds). I read the other helpful posts (thanks!) and I removed the fuel pump relay and jumpered from pins 15 to 87, and the car started and ran like a champ (driving the 3 miles home from where I was stuck...)

I went out and got a new relay (the old one was original to the car), and replaced the relay.

However, now the car starts, runs for longer, responds to the throttle somewhat, but eventually dies. The RPMs look like the idle is hunting up and down in the 900-1200 RPM range.

So why would the car run fine when jumpered, and not with a brand new relay.

I have two guess:
* The relay is connected to some sensor (Cam shaft sensor?) that is failing/has failed, but when jumpered this signal is ignored.
* The fuel pump is failing, and when jumpered it gets more voltage/amps than when running through the relay.

Are either of these possible? Are there other solutions that I haven't thought of?

Many thanks in advance!
--brendan

Post by **theWIFES_S70** » 15 Feb 2016, 22:06

hey brendan, I'm kind of in the same situation. Our car refused to start after I lifted her up to do some brake work. Went through all the motions, jumped wire, starting fluid , lawnmower syndrome fix and got nothing. (Quick question: Have you depressed the schrader valve on the fuel rail? I lost all pressure... giving me hope that it's only the fuel pump...) I am waiting for some decent weather here in NYC before swapping out the fuel pump.

You're right that the camshaft or crankshaft position sensors can contribute to a no-start. (An engine temp sensor, too...) If you look around you can find the resistance settings for the sensors...

I was surprised that something like this happened, especially because the car never gave any sort of hesitation on start up for almost a year. Did you notice any hesitation on start up? And if you did, how long did it occur before the car refused to start?

Post by **erikv11** » 15 Feb 2016, 22:17

What brand is the replacement relay (FPR)? Within the last two weeks someone posted that they got a bad KAE relay. Went to genuine Volvo and problem solved. Here it is: https://www.matthewsvolvosite.com/forums ... hp?t=74320

Even a junkyard relay would be better than one from KAE. 94-00 they are all the same.

The CPS will cause a no-start but no it is not connected to the FPR, so that one is out. Same with the ECT - they are not connected at all to the FPR, so they would be bad all the time, including when jumpered.

Your fuel pump idea is not out of the question, I'd keep it in mind. But my first thought is make sure the relay works like it should.

brendandburns · Post by **brendandburns** » 15 Feb 2016, 22:54

The relay is an OEM Volvo relay bought from a Volvo repair shop (not the dealer), new according to the repair shop, no reason to doubt them but who knows.

The relay itself is dated 2012, I assume that doesn't matter that much, the one I pulled out was dated 1998...

I have a bench power supply, etc, what is the right way to test the relay?

Thanks!
--brendan

Post by **erikv11** » 16 Feb 2016, 00:41

By "make sure the relay works" I meant more that if the jumper wire works but the relay doesn't, then the relay is likely the problem.

I agree would be strange if a 2102 Volvo relay is bad. Puzzling. Grab a couple 103 relays at the junkyard, too.

Post by **abscate** » 16 Feb 2016, 03:43

You test the relay by pulling it out and putting the jumper back in your car. If the problem is solved, welcome to the world iof bad new auto parts.

Post by **cn90** » 16 Feb 2016, 05:44

Let's review the circuitry.
- When key is in position II, and engine is running: current flows from ignition switch ---> "Main Relay FI System" ---> terminal #15 on the socket.
- The ECU grounds the "primary circuit" by grouding 31B, which connects with #15 and closes the "primary circuit."
- Now the "secondary circuit" (#15 and #87) is activated.

When you jumper #15 and #87, you basically bypass the "primary circuit."
The fact that the car runs on when jumpered #15 and #87, it means 3 things:

1. Bad relay (try another brand-new Volvo relay).

2. Something wrong with the ECU terminal #27 wire that runs to #31B.

3. Bad ground that goes to #31. So check this ground for any corrosion. Use an Ohmmeter.

Post by **erikv11** » 16 Feb 2016, 08:37

Great info from cn90, now you have something to test if you want or need to. But remember, many have trouble with that relay, but almost no one ever has trouble with this circuit's wiring in the vehicle. For your sake I hope it's just the relay.

For testing purposes the junkyard relay(s) will be fine, and potentially a lot cheaper and easier than getting a brand new Volvo relay. Like the MAFs, basically every 103 at the yard is working just fine.

brendandburns · Post by **brendandburns** » 16 Feb 2016, 09:41

Thanks for the wiring diagram and the details!

I went back out this morning and tried the jumper again still run (mostly) smooth.

Replaced the relay, still stalling.

But I listened a little more carefully this time. The car runs steady, and then I hear the relay click "off" and then occasionally back "on" and then the car stumbles out.

Also, weirdly, with the jumper in but the ignition *off* I can hear the fuel pump running in the trunk area. From everything I read, I thought that with the key off, the fuel pump should be off no matter what.

So this leads me to believe that there is a harness somewhere that is shorting. or the ECU is bad.

But I will take a closer look at that diagram and poke around more. Will update when I figure out what it is.

Many thanks for all the help!