931 relay

[mhewitt]

Hi,

I’m looking for a relay for my 1981 924 turbo (931).

The part # is: 93161511300.

So far I haven’t had any luck. I’d be grateful for suggestions.

Thanks,
Michael

[Monkey Wrench]

rock auto coughed up a cross reference of DENSO 5670045

I cna't be certain that's going to be right.

someone here might explain the schematic on the side, to me it looks like when 15 is energised it pulls in the coil closing 30 and 87. the part at the right Im not sure, maybe it connects 31 and 31B by way of a transistor? a fuse? what is the symbol to the right exactly? im fairly certain the little triangle at the left shows the way the spring presses, its holding 30 and 87 apart until the coil get energized and moves them to a closed position..

you want to be more sure than I am, before you go stick it in and fry something, but its probably not all that hard to use a different relay or two relays in conjunction if its unobtainable. I found reference that it has gold plated contacts.

you can pop the cover and likely clean the contacts but best to renew it and not just hope it stays fixed. Id try cleaning if the car is down but be careful about trusting it , if it dies suddenly that can be dangerous.
sometimes ill take some 400 grit fold it in half to about the size of a paper match, open the spring, put that between and pull it out, do that a lot and then clean with alcohol, this will remove the gold plating , sometimes its silver plating. because the paper is trapped between the spring loaded contacts it will help true them up to each other.

sometimes I need to bend a paperclip so it has a tiny hook on the end to unhook the tiny spring, then you can cut the wire to the contact, its probably uncovered ground wire or solderwick basically, with the contact out you can carefully file it now you have more room to work, then replace fix the cut wire ..

that should make it work unless the coil is burned out, but then its copper or brass contacts and they will not lat as long as the original, good enough to get you home maybe.. Its just a quick and dirty fix to restore operation.

I think if someone were to really be able to wrap their head around what is happening then it may be possible to reverse engineer and use a more common relay even if the second set of contacts is physically in a second relay. i think its explained in the graphics but I'm uncertain how to read them.

there is an update to a solid state relay with diodes for the 944, I dont know quite what the difference is.


if you can work through it, then you could use the old one as the connection base and then solder wires in using the base of the old relay as your new connector. that way what you have done electrically may be done without changes to original wiring up to the relay. you can bet all the connections you need are there.

it might be a situation where taking apart the old one carefully can teach you how it works, once you are certain how it works and what it should do then it may not be hard to do that using more standard parts. relays are very common parts but there is something more designed into this one in order to make it become obsolete ;-) .

you have 5 connections you need two of those to power the coil to pull the contacts in, the contacts close and connect power to your fuel pump, what are the other 2 connections? the wiring diagram might show it.

what is the symbol on the right? it looks like ohms, but square shaped.. which two power the pull in coil? if you feed them 12V the coil will try to close the contacts.. what you can do is just that, pull the relay away from the car.. write down what is connected to what, close the contacts with 12 V to the coil , then check what is connected to what. with the cover off you should be able to tell with a meter if the contacts are indeed closed . there is a bit more to the puzzle but this going to be a solvable problem.

you know the current rating is 16 amps so don't use any parts not capable of carrying at least 16 amps.

[djnolan]

it may be the 31a/b is normally closed and when 15 is energized 31a/b opens. also from the pic there are only 4 pins vs. 5 on the diagram. maybe the pic taken at a bad angle.

[Monkey Wrench]

that's part of the circuit but what are 31 1nd 31 b connected to?

I made a jumper for my volvo's fuel pump relay by just gutting an old one, I put an inline fuse in there and Jumped power to the pump, Its just for testing the pump or "get home mode"

I also started wiring in a very small indicator lamp if I replace a fuel pump, then I can just look if the light is on indicating there is power to the pump. If I'm frustrated by starting problems it's easy to just look and see that way.

I also put a little bulb across the coil wires, the two spade connectors at the coil. how simple is that? if it has ignition pulse then I know. that bulb will flicker as the primary coil is in parallel with the little indicator lamp. If you want you can just leave it there with one wire disconnected then all you have to do is connect one wire and look if the bulb flickers .

if I have ignition pulse at the coil I know the DME has power as it is providing pulses and it is reading the engine sensors, and being amplified by the powerstage transistor..

If I have fuel pump power and a pulse at the coil , or not, than that's already narrowed down and simplified any troubleshooting.

I dont leave it connected but its a very quick and easy check What it does is simplifies the first troubleshooting steps. If I know I have no fuel pump power or no ignition pulse then I don't go spending time troubleshooting other possibilities for no spark. I can verify spark at the plugs sure but usually if the coil has a pulse you most likely have a spark.

it just basically dumbs down the first steps in troubleshooting and all you need is two tiny light bulbs.

That won't replace all the great troubleshooting steps on Clark's garage, I just find it simplifies things a lot , for me.

basically if I'm out and my car wont start and I'm frustrated then I'd check a few things, I may not have a meter or a manual or clark's garage in my pocket. I will make some attempt to figure my way through it before I call a towtruck and tow the problem home for deeper diagnosis.

i can take that little light bulb from the coil and use it for other things, like to see if each fuse has power on both sides, or many other very simple checks. If i put a cheap meter in the car it will surely have a dead battery when I need it, a light bulb is more reliable and smaller, and very cheap. easy to understand, helps to find an intermittent situation. if you are stuck you can do almost every electrical check for continuity or 12 V presence etc with just a light bulb and a bit of wire..

for some a meter scares them, they become afraid and confused because they aren't confident with electrical troubleshooting, everyone understands a light bulb and a hunk of wire.

[Rasta Monsta]

The solid state component there is a rev limiter. Likely takes an on/off signal from the ignition unit.

[originalowner]

Looking at the schematic for an '80, and assuming (danger!) this is the fuel pump relay, the pin numbering does not exactly match (31b on the relay is pin 1 on the schematic, but it makes sense.) It appears the fuel pump safety cutoff in these cars is handled by watching the distributor primary wire for pulses. Since you don't want your fuel pump relay to be pulsing with every ignition pulse, the relay looks for the pulses and as long as they are present, it connects the coil to to ground, closing the contacts from 30 to 87. When the pulses stop (ignition off or crash stopping the motor) the relay disconnects the coil and the relay opens, stopping the fuel pump.

As I don't have one of these cars, nor do I have a relay to examine, use this info at your own risk.

Using a standard relay for this won't work correctly. If it is just the contacts being burned, rejuvenating per Monkey Wrench's advice above may bring additional life while you hunt a replacement. If the electronics have failed, if you or a friend is handy with a soldering iron, the internal components are likely easily available and replaceable. The components will be through-hole mounted.

[curtisr]

Unobtanium. Or at least that's what I thought. Decided to put on my thinking cap, fired up the TOR browser and hoped for the best. Results?
Someone in Wisconsin has listed a new one on ebay.de (Germany) for 277 Euros or $300 US. There's one for half that at fixparts-online.
Best of luck with your search.

[Rasta Monsta]

Originally Posted by gb944

Not likely, turning off the fuel pump is not an effective way of rev limiting (takes too long to make any difference).... most likely a safety measure to turn off the fuel pump when the ecu detects that the engine has stopped turning (e.g. an accident).

Lol, if only there were an ECU. You're opining outside your wheelhouse, friend.

The overboost on these old beasts works similarly, simple fuel cut. In fact, one of those 31 terminals probably goes to the overboost pressure switch on the intake.

[originalowner]

So, I did a little poking around and it appears that the Turbo 93161511300 adds a rev limiter cutoff function to the N/A 433906059 relay's normal function of safety fuel pump shutoff. The relay inside may also have higher current rating (16A) to support the dual fuel pumps of the turbo.

The functions are implemented using common 555 timers, one for turning on the pump if there are pulses from the coil primary, the other shuts it off if they are coming too fast.

Lots of info following this link: https://www.924board.org/viewtopic.php?t=11021

[chuckw951]

Also check out KAE 3.300.300. Not easy to find these days though.

[originalowner]

Originally Posted by chuckw951

Also check out KAE 3.300.300. Not easy to find these days though.

Won't have the over-rev protection, but has the current capability.

[Monkey Wrench]

not sure if this helps or not, Here is a great page but it is based upon the Volvo not the porsche.. what it does offer is some comparison and some good schematics.
One mjor difference is that most volvos of the same era incorporate an in tank pre pump and a porsche 944 only has the one pump.


https://www.240turbo.com/fuelpumprelay.html


as a comparison you can see that written above the 77 shchematic they show that the fuel pump relay is cut off when the "airflow sensor switch detects no airflow.
this is shown where it says "Description of Early Volvo 240 Fuel Pump Relay Function
"

a buit further down it says
"Beginning in 1978, Volvo adopted the below style of fuel pump relay for K-Jetronic to replace the previous dual fuel system relays. This new style of relay added a PULSE SENSOR, which reads ignition pulses. Ignition pulses are the same as a tachometer signal and they are generated by the ignition coil while the engine is running. Since these pulses are only produced when the engine is turning, this added a level of safety, because the new relay would only allow the fuel pumps to pump or pressurize fuel lines when the engine was running. So in a crash, assuming the engine has stopped, the fuel pumps and fuel lines would no longer be feeding pressurized fuel. "


someone smart enough might find that they are able to use the relay from a Volvo in a 944

I noted that some of these numbers are repeating, so I think there is some basis for the numbering conventions.


further down it discusses the adaptation of a "Universal Fuel Pump Controller"

(using a Tach Signal for activation)
You may have a need for a universal fuel pump controller, which will receive your ignition coil or tach signal and then reliably activate your fuel pump(s).
This controller is designed to prime the pump for 5 seconds upon first power-up. After that it will run the pump until the engine stops or is turned off.



so this could be the answer to the availability issue, but it might take a bit of thought to implement it.

https://www.revolutionelectronics.com/Products/Fuel_Pump.html


I'd go here and have a look around. it seems possible to implement this along with a more easily available fuel pump relay and not loose the ability for the fuel pump to shut off when the engine stops in an accident.

i think it's a bit of a puzzle and one might need the help of a wiring guru to sort this out into a more basic schematic that shows what to change to apply it to a 944. maybe if you contact Revolution Electronics they might have already worked this out?

https://www.revolutionelectronics.com/Products/


my brother upgraded 3 volvos to carbs. Eliminating all the unnecessary electronics improved simplicity and reliability. He was able to completely remove the ECU..

it was easier to do there because there were earlier versions to get the manifold and ( points style) distributor from. in that process he wired in an electric fuel pump that isn't a high pressure one. Since the Porsche did not have a carborated predecessor this isn't really an option.

my 66 Volvo has no electronic issues ever because it doesn't have any unnecessary electronics. fuel pump is mechanical , run off the cam directly. Dual SU carbs, very reliable, It can still make 25 MPG or 30 with overdrive on the highway so it wasn't a gas guzzler. with some balancing , polishing ports, hotter cam it really puts out a lot of power but those where heavy and very strong engines. I bored mine from 1800 to 2 litres.

injection did improve efficiency , mileage, power. I assume a 944 could be upgraded to carbs but it might take some custom machining to create a intake manifold. Turbos also created more power at the expense of a lot more complexity. I'm not sure if the VW engines in a 924 used a carb , If they did maybe a carb style manifold was made?

such conversions wont improve efficiency , shedding all the unnecessary electronics does also shed all the electronic issues that are result of overcomplexity. That was the basis of what motivated my brother to convert 3 Volvo 240's . it did work well. my point was just to show other reasons why someone might want to convert to such a controller.

[Monkey Wrench]

here is the installation notes for the revolution electronics controller:
I'm thinking this may be a practical alternative, and maybe you can just use a volvo fuel pump relay.


https://www.revolutionelectronics.com/12003-installation-2.pdf

[chuckw951]

Originally Posted by chuckw951

Also check out KAE 3.300.300. Not easy to find these days though.

Here's one on Ebay...wow buyer beware

https://www.ebay.com/itm/256209312283?hash=item3ba743da1b:g:9OcAAOSwHXdk4fO M

"Please note: All my Relays are defect or they are working, it is your risk to buy them and I don`t pay for returns. Please be so kind and don`t buy if that is a problem for you."

[Monkey Wrench]

what failed in the original relay?
I'd pop the cover off, look at the main contacts for the fuel pump, if dirty , clean them. they handle the load of the pump so may be burned from arcing.

how about run that power wire , instead of to the pump, to a second relay that is capable of more amps and then the contacts will open and close as normal , and instead of running the pump they will simply open and close the coil of the second more robust relay.

that will reduce the load to a minimum on the original contacts. all they will see is a minor load of the second coil , they will no longer see the large amperage required to run the pump. that can be handled by a second relay. in other words, daisy chain them.

I think that if the problem is just that the contacts are pitted this will fix it, but there could be consideration to the what If? so what IF the car stalls due to a bad relay? It is a possibility. There is a possibility of a failure happening at a bad time and a sudden stall causing a fatal accident. new parts may not make that situation impossible but may be more reliable so there is an element of risk.

cleaned contacts may function ok with a lowered amp draw, there will be very little arcing because that load of the second relay coil is reduced significantly..

my decision might reflect my financial position how much I need the car etc. If you have bags of money sure just buy all new OEM parts at any cost.. If you are broke and need to get to work to pay the rent or risk loosing your job .... well then it's the owner's own cost / risk decision.

[curtisr]

Originally Posted by chuckw951

...wow buyer beware

"Please note: All my Relays are defect or they are working, it is your risk to buy them and I don`t pay for returns. Please be so kind and don`t buy if that is a problem for you."

[Monkey Wrench]

I did some searching with the part number in google images and found all sorts of other ones and If I go to the pages that host those pics it seemed to produce info, and then I got so much info I got all confused. I do not doubt there are other direct replacements. a lot of these auto parts sites show the part and list other choices. you can search using each of the choices as keywords..

Im quite confident that if you keep searching around that you "may or may not find it." ;-)

[micah]

Apologies for the several months late reply, but I have been nursing this same relay along for over a year in another '81. My relay has an intermittent prime which leads to an eventual no-start. I'll pull it, clean it, and get another several weeks out of it.

Without going berserk and throwing every relay available at it... I can verify the following:

141-951-253-B-OEM Available on Pelican,
primes fuel pump, fires, dies after 2-3 seconds.

Duralast 19208 Generic (Napa sells similar): primes fuel pump, does not fire.

I would not recommend buying a used (ridiculously expensive) relay off Ebay as, at 40+ years old, I'm thinking that all of these are on borrowed time at this point.

I have written Joe Baumbach at Focus 9 Tech (who makes a fantastic pump/prime/diagnostic relay that I run on a 3 2 Carrera) and he informed me that a solid state relay for 931s is hopefully in the works for 2024.

Until then, perhaps keep an eye on cars being parted and/or look at the 924 Turbo group on FB (I know, I know) for a reasonably priced used example. Please update the thread if you find an alternative that works - I'll do the same.

[originalowner]

Again, I will reiterate that if the relay contacts are still good, all the components in the relay are readily available and easily replaced by anyone competent with a soldering iron. The capacitors, transistors, and 555 timers could be replaced in one operation for a few dollars at most. A replacement relay might be available, but this would require examination of the existing one (which I don't have.)