Yellow boost relay issues

djdawson2 · 03-31-2010, 08:30 PM

My car has been plagued with intermittent fuel pump issues... stopping for no apparent reason. This can happen after hard acceleration, or just when driving steady down the road. It seems random.

However, I took the car for a spin tonight, and this time I unplugged the connection on the meter plate... pumps running as soon as the key was turned on.

Again, it died out while driving. No pumps running. I popped the engine compartment open (key still on) and pulled the yellow relay in and out of its socket a few times, and the pumps came back to life. So it seems this issue is finally isolated to this relay.

As I see this silly relay is now up to $206 from our sponsor, has anyone come up with a decent work-around, or identified an alternate relay that can do the job? Has anyone ever had success opening it up and cleaning up the contacts?

Any ideas appreciated... I'd love to put this annoyance to an end.

Dave

equality72521 · 03-31-2010, 08:42 PM

First, make sure the receptacle part is not opened up so much that the relay pins don't make good contact. That happened to me. Second, those yellow relays are known for having cold solder joints. Many people have taken them apart and re-soldered the cold joints and solved the problem.

djdawson2 · 03-31-2010, 10:46 PM

Quote:

Originally Posted by equality72521

First, make sure the receptacle part is not opened up so much that the relay pins don't make good contact. That happened to me. Second, those yellow relays are known for having cold solder joints. Many people have taken them apart and re-soldered the cold joints and solved the problem.

Thanks... I will look into both possibilities. Unfortunately, I can not duplicate the issue in my garage. I can tap it, wiggle it, etc... and nothing. I was just glad that I believe I determined that it is the culprit.

Thanks

mark '87 930 · mark '87 930's Garage

Dave,

Take the relay apart and re-solder the joints as Mark mentioned. In addition to that, I would recommend you check your overboost switch connection too. Mine was loose and I had to tighten the connector tabs so it fits tightly on the sensor (behind the recirculation assembly).
I had the identical issue, and every bump my car hit seemed to be hit or miss... I did both those things and the problem went away immediately.

djdawson2 · 04-01-2010, 08:36 AM

UGH! I opened it up and resoldered anything that looked questionable. I cleaned the inside of the receptacle 'til shiny, and opened up the male prongs a bit cleaning them as well.

The FIRST time I turned the key on (airflow plug still disconnected) NOTHING. Turned the key a few times... nothing. Left the key on and headed towards the engine compartment and before I even got there, the pumps came to life.

This is killing me. Should I just buy a new relay? I assume the little black box inside the relay is the magnetic contact... perhaps this is just failed?

The post layout is the same on the yellow relay as all of the other "normal" red relays found on the car, but I hesitate to try one of those as there isn't a diagram on the yellow relays that indicates how it works, or if it is normally open or normally closed.

What a PITA.

mark houghton · 04-01-2010, 08:41 AM

Yep, that's all good direction from everyone. Here's a little more that I cut-and-pasted from previous discussions I've had:

You can jump socket pins 30 and 87a on the bottom - pretty sure thats ground and the electro magnet coil wire leads inside it and go without it too (from JFairman)

(you may find that jumping between 87A and 87 also do the trick...I keep a jumper wire in the glove just for that purpose) and the pumps will run when you turn on the ignition. But the downside is that you will lose the overboost protection (from me).

I've also attached a picture of the pin locations on the yellow relays. You can go through a process of decuction, starting with unplugging the connection at the metering plate and unplugging (and grounding) the single white wire at the overboost switch. Drive her that way for awhile and if your problem persists, then it limits it to the yellow relay or the fuel pump relays up front, or the main pump fuse, or dirty connections thereabouts. Short out across the yellow relay terminals as described to take that out of the equation, run her somemore, and continued problems will point to the stuff up front in the fuse/relay panel as mentioned.

Although I purchase 99% of my replacement parts from our host, one can occasionally benefit by price shopping around a bit. That yellow relay can be had for a bit less. I bought one quite awhile ago and am just keeping as a spare.

djdawson2 · 04-01-2010, 08:52 AM

I think mine must be 911 615 118 0 relay. If the post layout and the identified purpose of each post is as you've shown in the diagrams, it seems that it would be OK to try using a red relay. The only part I don't know is normally open or closed, which I could easily test with a voltmeter.

Thanks for the great info, Mark.

equality72521 · 04-01-2010, 08:56 AM

Regarding the yellow version, those came on later cars. The early ones, like my 1979, use a red relay. I think they started using the yellow ones around 1986. I don't think it's an issue using a red one for testing purposes.

mark houghton · 04-01-2010, 08:59 AM

Quote:

Originally Posted by djdawson2

I think mine must be 911 615 118 0 relay. If the post layout and the identified purpose of each post is as you've shown in the diagrams, it seems that it would be OK to try using a red relay. The only part I don't know is normally open or closed, which I could easily test with a voltmeter.

Thanks for the great info, Mark.

I've heard of other's plugging in a red relay in a pinch, but then in the back of my mind there's something about that which says doesn't work (I may have tried it once myself...I may be wrong, though...my memory is lacking sometimes). Jumpering with a short wire certainly does work.

djdawson2 · 04-01-2010, 09:17 AM

Mine is an '89. Even if I know that the post layout and the normal position of the red one is the same, at least I could test... not looking at it as a permanent solution. There is a diode in the yellow one, and it would be difficult to know if the red one would fail if used regularly.

Thanks for the input.

As a side note... is the overboost switch a common point of failure in this circuit?

JFairman · 04-01-2010, 09:23 AM

Red relays won't work in place of the yellow one on my '87. I think there was a change in the wiring or the relay.

My fuel pumps would sometimes just shut off and come back on at times even after checking all the pins on the red relays and resoldering all the solder points inside the yellow relay.

Then I accidentally found out the left most relay under the driver seat is part of the fuel pump relay circuit too. It's the aluminum color "speed relay" or factory rev limiter.
If I touched, tapped, or moved it the pumps would go on and off...

I took it apart and the insides looked like new. There's 2 small relays and some other components on a board inside it. I resoldered some of the connections inside it but I don't think they needed it.
It turned out the male pins on the relay that looked perfectly clean just needed a little light scraping with a knife blade. Apparently one or more of them were not making consistant contact with the female pins in the plug. After cleaning the pins no matter how much I moved or tapped the relay the pumps kept running with the ignition on and the green safety plug removed from the back of the air flow meter.

If you wanted to wire in a hidden anti-theft switch in the car somewhere, this is a good and easy place to wire it in.
4 of the wires going to that relay, 1 red, 2 whites together on one pin, and 2 brown ground wires together on another pin have to be connected to the relay for the pumps to run.

There are other wires going to the multipin plug on that rev limiter relay but they are for something else... possibly to turn off the ignition around 7200rpm.

djdawson2 · 04-01-2010, 09:28 AM

JF... yes... I was very excited to see you post this on another thread. This was the first place I started, as I thought your discovery was going to be the silver bullet, having invested fruitless time on this problem in the past. I tapped/wiggles the speed relay while the car was running and didn't get any response. Just to be sure, I did pull the plug on it, and the car died. I then cleaned all of the terminals, but I've still had failures since.

The plug on that relay sure is a tight one... and in the process, I found about $5 worth of change under the seat from previous owners. Down payment on a new yellow relay, perhaps.

djdawson2 · 04-01-2010, 09:32 AM

I just tried a red relay in place of the yellow one... no go.

JFairman · 04-01-2010, 09:40 AM

Well.. as far as switches and relays go, maybe the alarm system black box/controller that lives behind the glove box under the windsheild cowl dashboard area can cause the problem or maybe it's the ignition switch.

Just guessing because I havn't had to screw around with either of those... yet.

JFairman · 04-01-2010, 09:43 AM

lol... i found some corroded change and an old wine cork from a previous owner in with the relays under my seat.

equality72521 · 04-01-2010, 09:54 AM

Quote:

Originally Posted by djdawson2

I just tried a red relay in place of the yellow one... no go.

Good to know, I won't give that advice anymore.

equality72521 · 04-01-2010, 11:40 AM

Quote:

Originally Posted by djdawson2

As I see this silly relay is now up to $206

They are at $129 right now, might be a good time to get a spare.

Porsche 911 & Carrera Charging System - Page 3

mark houghton · 04-01-2010, 01:10 PM

Quote:

Originally Posted by equality72521

They are at $129 right now, might be a good time to get a spare.

Porsche 911 & Carrera Charging System - Page 3

Yeah...but....well, try adding one to your shoping cart. Shazzamm! The price jumps to $206, and they're out of stock! Too bad, 'cause $129 is a good price. Perhaps our host can give us rain-checks?

jwasbury · 04-01-2010, 01:32 PM

I wonder if you could rewire the circuit to use the red relay, like the older models do...save you poor guys with the newer style yellow ones a lot of headaches and $$

mark houghton · 04-01-2010, 01:53 PM

Quote:

Originally Posted by jwasbury

I wonder if you could rewire the circuit to use the red relay, like the older models do...save you poor guys with the newer style yellow ones a lot of headaches and $$

Worth thinking about...would have to study the wiring diagrams.

Oh, and we're only poor because of the big bucks we spend on those damn yellow relays!