Hello out there....my car has been dying after getting a good warm up but starts the next morning. The tell tale symptom is that the fuel pump does not run when the stall occurs and even after hours of cooling off it still does not start...but it does in the morning....???
So talk on the street is the relay board is too old to work properly.....the description of 914 LTD's improved and rebuilt relay boards matches the symptoms of my car perfectly so as soon as I scrap up the money I will buy one.....meanwhile I have two spare relay boards and one looks really good. Is there a way to bench test the relay board before I swap the boards ?? These cars sure keep you on your toes and a relay board with fresh soldered connections sure sounds appealing so Brad is holding one for me. So back to the swap out....I hate to go to the effort just to install another faulty board. Look forward and appreciate any and all comments and help....thank you very much!!!!
gg

Yes you can test the board with a multi meter. I have never seen the need to solder the board connections. Quick, simple test is to put meter on resistance test with tone. Put leads at the end of each circuit post and listen for chirp.

with a couple modifications:

There is nothing magical about the relay board. It is actually from the stone age. Just large copper traces inside a plastic housing that runs continuity from point to point.

1) As a former electronics technician it annoys me to no end to see all the forum threads about electrical troubleshooting where the proposed solutions are simply guess work and parts swapping (Note: not targeting @second wind - just a generalization) I've largely stopped trying to participate in those threads because people refuse to use a schematic and a Digital Multi Meter (DMM). I know it might take some time to learn how to read schematics and/or to use a DMM. The reality is that if you're going to play with 50 year old cars, you're going to have to learn sooner or later. Google & YouTube are your friend for learning how to read schematics and to use a DMM. Otherwise:

a)You're going to pay $$ to someone skilled enough to use a DMM, a schematic, and then to troubleshoot properly.
b)You're going to waste $$ on needless parts and parts swapping
c) You're going to pay some other "mechanic" to do the parts swapping and guessing for you which is the worst possible outcome both for time and $$.

2) These boards do have a lot of swagged connections within them as 914 LTD states on the website. However, swagging is a form of crimping that is more reliable than soldering per Auto Industry, Aerospace, and NASA white papers. Yes, it is possible that a swagged connection could be come loose, but it is less likely than one of the soldered connections within the relay board with a cold solder joint, and/or a stress cracked solder joint. Sure you can solder every swagged connector as belt and suspenders, but in reality you're more likely to have a bad solder connection due to a dirty board and/or improper fluxing over the swagged connection than a bad swagged connection itself. If acid core flux is used to do the soldering, you'll have a long term corrosion source on the board itself if the flux is not completely removed. NOTE: I'm not trying to tear down the 914 LTD relay board. I understand why he's offering this as a service as there are bad boards out there with corroded traces, traces screwed up form DAPO's shooting long regulator screw across traces creating shorts, bad potting, and even some with stressed solder joints and/or swagged connections due to corrosion or improper handling over time. I understand why the solder belt and suspenders approach holds appeal and it's not likely to hurt anything. Having de-potted a couple boards myself, his pricing is fair, so is @914sixers for restored boards. It takes a lot of labor to remove the potting, continuity check, redo these boards with new potting

If you really want to do the whole bench test routine, do as @914sixer suggests and simply test all connections for continuity at room temperature.

If you want to go the next level and really think heat cycling is your problem, warm the board in your oven to about 150F - 200F then test continuity again. If you have the board de-potted, you could also use a heat gun (carefully) at the specific swagged connections of interest.

Going back to point #1, you don't have to test all continuity across the whole board, just those traces that handle the fuel pump, the ignition coil, the tachometer (which is also connected to the coil), and the ECU feeds (if fuel injected),

In OP you don't mention if you've already ruled out the relay itself, and whether you've verified the integrity and power feeds to the components (coil, pump, ECU) itself both hot and cold. I'd do that before jumping to swapping relay boards.

Thank you Superhawk....I did some relay swapping and ended up putting all new 914 Rubber relays on the board. Not hearing the fuel pump go on when turning the key makes me want to rule out a bad fuel pump since it works fine when cold and the new relays make me think that is not the problem either. I would love to hear more about these 50 year old relay boards.....do they really go bad or not? And when they do go bad what is the usual culprit? Thank you all very much!
gg

There's a lot of assumption built into what you just laid out. Just sayin'.

Methodical troubleshooting with a schematic and DMM to root cause for the problem at hand is the fastest way to solve the problem.

There really isn't anything complicated in the relay board I'll try to post a picture later. Simply very thick, copper trace interconnects that go point to point. Various relay socket posts and spade connections secured in there with mostly swagged connections and 10 soldered connections, 6 of which serve the voltage regulator circuit. All the relay connections are swagged along with the main harness in/out pins. The other 4 soldered connection go the the spade connectors labeled as roman numerals I-IV in the graphic (below)

Here's a very good internal view of the traces and the circuit connections posted by SirAndy about 14 years ago.

Click to view attachment

Tracking down intermittent electrical problems ain't fun. When we were working on mcm minesweepers, the rule was to suspect cables first, components second. Really it pertains to any junction where an electrical connection relies on physical contact, and those swaged pins in the circuit board fit this scenario. Not saying that's for sure where your problem lies, but it's a possibility. Another rule says to try and pick low hanging fruit first, so easy things that are external don't hurt to eliminate before digging into a complex can of worms.

There's a great reference on Mr. Bowlby's site (absolutely incredible person sharing a wealth of knowledge) dealing with fuel pump troubleshooting. Here's the link. https://bowlsby.net/914/Classic/TechNotebook.htm
There's "Fuel Pump Circuit Troubleshooting Flow Charts" and "Fuel Pump Circuit Troubleshooting D-Jet only". Each is a pdf. Maybe these can give some suggestions as to a path for finding where the problem lies.

Dan

Here you go un-potted board. This is posted as mirror image of SirAndys that is looking from top of board down “thru” the board. This is the physical view from under the board looking up.
Click to view attachment

Note DAPO screws that are too long crossing trace connecting it to the voltage regulator housing

All of the above. Using a dDMM is not rocket science and they really arent that expensive. On these cars a definatly needed tool. Iread all the hype about soldering all of these connections. After stripping the bottom of my board and checking and rechecking the points, from both the top and the bottom found all of the swaged joints to be fine.

Just take your time and check each cirquit one at a time. The problem is most likely not the board. Probably a bad relay or some other problem in the electrical system.

A relay board has no electronics. It is a buss bar to relay and connector pins distributor. If it is intermittent than one or more of these connections is failing. The staking is very good and normally shouldn't fail but if the board is intermittent then the connection IS failing. Locating the connection and soldering it is the best solution. One problem using a DMM is the fact that the meter uses very small current. It can measure zero ohms and the connection can still be bad under load. What is needed is a higher current setup for "Ringing out" the connections. If your card is measured with a DMM as ok but you know there is a problem remaining in the board then one way to ring out the board is by using a voltage source and a light bulb. A light bulb using some power would be best. Maybe a headlight could be used. You need something with at least a couple of amps for testing.

Check the wire harness at the fuel pump....
I have repaired a few in the past where the wires are in bad shape and make for intermittent connections. Sometimes I had to go back on the harness and splice in a new wire to eliminate the bad wires. Leaky fuel lines and pumps corrode the wires and connector.

The word is 'swaged', not swagged.

But I dont think they are swaged, just riveted.

I assume the riveted/buss bar connection fails from time to time. Either this connection, the female sockets or a break in the copper buss bar can be the only potential failure

Basically it is from the stone age, good one Phil

Indeed you are correct. The swage is the tooling used to cold form the metal into what becomes the “rivet” head we can see.

Either way, the result is a sound mechanical deformation that drives the post outward within the hole and compresses downward onto the copper trace.

This is so true.
Get a multimeter and a wiring schematic for the relay board and have at it.

On my 914-6 relay board, I found two (2) of the copper traces that had a break in them that needed a bit of solder and all was good.
If you are seeing sporadic stuff happening during the day, there's a good chance that a trace has a small break in it that shows itself from time to time.

Definitely not rocket science testing this relay board with a multimeter.

I appreciate this info! I have. a fuel pump power issue to resolve soon.

I am so appreciative you guys!!!!!!!!!!!!!! I will end up cleaning up my best looking spare and installing it but going down the Bowsley procedure sure makes sense...I will prevail !!!!
gg

Just to make sure I cover all bases....rumor has it that the ECU never fails....am I maybe overlooking a source of my issue? Thank you,
gg

almost 100% of the electrical problems I found on my car were ground issues burnt brown wire or poor connections good luck!!!

In my best Captain Krusty imitation, offered in the spirit of friendship and a desire to help you solve your problem and get driving your car.

Stop guessing at what it might be. Get a DMM, get a schematic and let's start methodically troubleshooting it and stop the guessing.
@second wind

It’s important to collect hard data on these issues. Otherwise you may think you’ve solved the problem, only to have it crop up again. For example…you replace the relay board and everything works fine. Then, a month later it starts happening again. You finally start to methodically test and realize there was a loose connection in the harness plug and the act of replacing it on a new board improved the contact enough to think the board was the issue. BTDT. Like Ringo….I say this with peace and love, but if you want to solve problems with the least amount of frustration, expense, and rides on a flatbed, implement a testing procedure that definitively identifies the problem. If, at the end of the process you can’t say with specificity exactly what the issue was, you’re only guessing that the problem was solved. If it were me…

-Use known good relays. All of them. Don’t always assume that new=good.
-Confirm that there’s power at the pump leads
-Have a friend repeatedly turn the key to the ACC position while you grip the relay board in various positions. If you hear the pump cycle while pressing relays or the bottom of the board, you’ve found the issue. (This is actually what happened on my BB).

Bottom line…gremlins are crafty. Being able able to re-create the problem at will…or identify the break in continuity on a DMM is the only way you can be sure you’ve slayed this beast!

at Ian's perfect description of what happens when the random parts swapping occurs . Truer words never written

I'm happy to support you in the endeavor to find root cause.

The fastest method of troubleshooting almost anything is the half split method. Know the system you're working with. Find a way to divide it in half, part A & part B Is the problem in Part A? No? Then it must be in part B.

Now divide part B in half. Let's call them parts C & D. Problem not in C? If so, it must be in D. You get the idea.

In the case of your "suspected" issue of not having fuel pressure, the relay board is a perfect place to half split the system.

Let's divide it as power into the board as part A, and power out of the board as part B.

In your case, the intermittent nature of the problem when it's hot makes things a bit trickier but at least we know that you can duplicate the problem when it's hot. That's a great start.

So let's start by verifying (with Schematic & DMM) what all power conditions are when its running cold. Both on Part A (power input) side of the board, and part B (power output)

Then warm it up until you can duplicate your no-run condition.

Then recheck Part A (power into the board) -- if good when hot -- your problem isn't on that side of the system. If not good, then we work to figure out why it changed and where root cause is in Part A.

If the power output in Part B is not good when hot, we'll work our way through the Part B side until you find it.

Bottom line, you can do this, and I'll help in anyway possible, but it needs to be done logically, and methodically.

Let's go back one more step, to the basics.

Before we even start assuming that there are electrical problems, with the fuel pump (only) when it's hot and not running, and you can't hear the fuel pump, have you pulled a spark plug and verified that it is sparking when hot?

Engine needs three things to run
fuel, compression, spark.
(Let's assume for the moment that we can ignore hot compression)

If you just assume that it won't run when hot due to no fuel pump noise, and haven't verified that it will spark, you're potentially missing an important clue on how we might start troubleshooting this. That is to say, we need to know for sure, when it's hot and not running, can we ignore the ignition circuit and focus only on the fuel pump? If we can ignore ignition side, that makes the troubleshooting work even easier.

What's being done here is to half split the system to the fuel side (Part A), and the ignition side (Part B). If by chance both fuel pressure is missing (no pump noise - Part A is bad) and we have no spark (Part B is bad), then we start looking for what is the common denominator between BOTH A & B.

This is a very important starting point.

Hopefully, this is making sense. Logical, and methodical.

Here is an old guy explaining the function

https://www.youtube.com/watch?v=YLgQxpNHzIU

Well guys...thank you again very much and I have a new clue to share. What an automotive hell hole I have had today! So my Chevy S 10 pick up with almost 400,000 miles acts like there is no battery in the car. It has done this once or twice before....I tried charging the battery but the charger fell off the truck and didn't work after that. I figured I could jump it with the 914 but when I started it (first thing in the morning ice cold....but LA ice cold) it only ran 20 seconds and then no fuel pump sound. Hmmm, well I could take the battery out of the 914 and hook the truck up too it and that should work....not even close....barely lit up the dash even though it worked on the 914. So I am standing in the street with jumper cables in my hand and in two minutes I am up and running because of my new best friends that stopped to help me. So the new clue is that the fuel pump doesn't run even when cold.....just sharing. I think I will get the multi-meter out and start following some direction and start testing as an intelligent person....I will report back and I really do appreciate all of the help. BTW truck starts all day long now and might for a few days....but then ?? I am going to disconnect the battery at night and work on that issue later...914 in first spot.
All the best,
gg

Thank you very much George...great video! At the end I thought you were going to show us how to test a relay....is there a procedure for this? I have some of the new 914 Rubber relays....they usually make quality parts....have you had any experience with those? Thank you again,
gg

Take a look at the SirAndy board graphic on page 1 of this thread.


The schematic for the relay is shown.

Pins 85 & 86 are the solenoid coil. I have a good one in my hands it reads 69.7 ohms and draws .15A when connected to my power supply @ 13.6v

Pin 30 is the uncontrolled side of the relay. It is where the circuit to be controlled (usually 12v power) is usually fed into the relay.

Pin 87a is the normally closed contact. It is connected to pin 30 when the solenoid is not powered.
(this should read 0 between pin 30 and pin 87a ohm when the solenoid is not powered

Pin 87 is the normally open contact
(this should read infinity between pin 30 and 87 when the solenoid is not powered)

When the solenoid is activated by applying 12v power across pins 85 & 86, the resistance between pin 30 and pin 87 should change from open (infinity) to zero ohms. it doesn't matter what polarity goes to which solenoid pins - a solenoid doesn't care, it's just there to act as an elecromagnet.

The pins are clearly marked on the old German relays.


The solenoid can be bench tested with a couple test leads and a 12v battery connected across pins 85 & 86 while looking for the resistance changes noted above.
@second wind

I just tested 3 that came off my old relay board. 2 not working. Moral of the story - bench test to know you're dealing with a good relay. And don't ASSUME that if it works cold that it will work when hot. There are electrical connections and moving parts in the relay that may change behavior or become intermittent with temperature. They shouldn't - but they can.

This sort of testing is why a DMM is CRITICAL in my opinion. You could rig up the same bench test to work with a simple lighted test probe, but it's more work. Yes, you could see if the relay is working, but you can't measure resistance with a simple test light.

Sorry to hear about the added drama of the S10.

Going back to not assuming anything - are you ABSOLUTELY sure your 914 battery is good? Based on description above I wouldn't assume that. Yeah, a 914 battery might not be up to the task of cranking a S10 but it needs to be verified. So much of the troubleshooting you're going up against is going to need a verified 12v power source.

It is very possible for battery to show 12v but then collapse when a significant load is placed on it.

Again . . . just sayin' A bad battery could be why you're now noticing that the fuel pump dropped out even when cold. I don't know this for sure, but assuming the battery is solid is not a good baseline to start from given what you've just laid out.

If there is any question about its status, have it load tested at FLAPS.

OK -- so now about the S10.

Sounds an awful like you may have a pretty large short somewhere in the S10.

1) A short would draw down your battery to some level lower than 12v and of course will drain the battery over time if left connected.

2) A short in the S10 COULD have been what collapsed your 914 battery (assuming it was good as you've assumed) to the point that it could barely light the S10 dash lights but yet the S10 could be jump started with a larger current source (the other car's alternator).


By definition a complete zero ohm short circuit will measure 0 volts if you measure the voltage drop across the short circuit.

WARNING - DON'T TRY THIS AT HOME KIDS!

If we were to take a good heavy duty copper cable about 2AWG and directly short the 12v + terminal to the 12v negative terminal while measuring the voltage of the battery with our DMM, it would read 0 volts. There will be a ton of current flowing but the voltage measured across the + and - terminals will be 0v (assuming resistance of the cable is ZERO ohms). The cable won't be absolutely Zero ohms but it will be darn close.

Think about that for a moment and let it settle in.

A short like that - in its most extreme case can pull a 12v battery very close to 0 volts. Lesser shorts can pull it to 11v, 10v, 9v . . . . all depends on the particulars of the short.

I've had to demonstrate this to people (wearing protective gear) because folks refuse to believe it.