Hey guys and dolls (Margie and ??)...I thought my fuel pump was not turning on after running for a while due to some heat expansion issue....then it died again after just running to 3-5 minutes...hmmm? So my college friend of 50 plus years who is a VW lifer and has one incredible 914 that he built from scratch suggested today that it is the fuel pump itself? Mentioned some sort of solenoid or something in the fuel pump...I certainly don't know....anyway the logical test is to test for power to the pump when it stops running....if there is power then it is the pump....if there is no power then the problem is upstream from the pump. Just wanted to hear from the pros out there...thank you very much and I will be under the car tomorrow....
All the best,
gg

Try swapping relays with a known good one. The headlight motor ones are usually a good bet.
Could be that simple.

This is the comprehensive fuel pump troubleshooting process for D-Jet:

Fuel Pump Troubleshooting

This is helpful too as it has a picture of the relay board where the flow chart does not.

http://www.914world.com/bbs2/index.php?sho...p;#entry2414756

Still resisting using a DMM and logical troubleshooting?

My 914 race care was always doing the same thing, cleaning up the electrical terminals solved the problem...seemingly forever.

I've found that electrical connections on the pump, relays, and relay board corrode enough over time to disconnect.

Try pulling the relays off the board and wire brush them with a brass brush to remove corrosion, then coat them with dielectric grease and put it all back together. With this you can be certain you have good electrical contact that doesn't disconnect due to heat cycles. Dielectric grease is the key to kill corrosion and improve connection longevity.

I don't think it's that complicated. Pull the FP relay (see location below) and try a known good one as suggested.

If still non-op then use a 12v test lamp or multimeter (if not you need to get get one) to check for +12 at the relay socket where shown below. This should be hot all the time.

If no voltage there, then it would seem there's a wiring harness or "under the relay board" brass track issue and you'll need trace back from the relay socket to the battery.

However it's more likely IMO that you do have power on that socket. So the next step is to jumper this to the output socket as shown. (I used a u-shaped piece 12 ga. bare copper wire you but can also use a longer wire to run 12v from the battery to this socket) This should turn on the pump.

If it doesn't, then leave the jumper in place and go to the pump. Use your test lamp/meter to see if the + terminal of the pump has voltage. If yes, then the pump is apparently* bad. If no, then there is a wiring problem between the relay board and the pump.

*before I finally replaced my pump it would stop intermittently and restart when tapped with a hammer. Others have reported this also so you might check.

Ron

Click to view attachment

You are right Superhawk...the time has come....thank you and with daylight savings I will have plenty of time to do this correctly...
gg

happy to help ya, but gotta do the troubleshooting with a DMM. The other posts on this page have good info. For me, it's easier to troubleshoot with a schematic but if the flow chart approach works for you, that should get you there too. Success is all about being methodical and dealing in facts not speculation.

Hello Superhawk....I did some Multi Meter testing and some continuity light testing today.....first off when I turned the key to start the car and the fuel pump did not go on....then I used the continuity light on the fuel pump relay socket and there was power....then I tested pin 13 and 14 and there was 12 volts on both, and then I jumped the relay holes on the fuel pump relay socket and sure enough the pump went on....hmmm?? My 914 guru friend has a few more tests for me to perform but I thought I would get your two cents just for fun....I appreciate your persistence on getting me to get on with the proper testing. My 914 friend who has owned his car for 30 plus years is rebuilding a LSD tranny for his '72 2.0 which he rebuilt himself as well. Nice to have friends with strong 914 knowledge....thank you very much!
gg

Great Job. But you're not done yet. Agree it sure looks like relay is suspect.

Here's the catch. As Ian previously suggested, the simple act of pulling a relay and replacing it can sometimes get things to work if the relay socket contacts have expanded open a bit too much and/or corrosion was lightly scraped off allowing it to work . . . for a while. Same could happen just by inserting the jumper wire into the relay socket.

Here's what I'd do next:

1) Inspect and clean the relay board, relay socket pins. Clean them gently with small round bristle brush (spray gun cleaning brushes work great). You want nice shiny brass in there. No corrosion. If you're not getting a decent friction fit when the relay installs, I might tweak the socket connectors SLIGHTLY. Avoid doing that unless you absolutely feel it's necessary. The way the socket connectors are designed they are supported by the relay board plastic and can't really bend outward much at all. Highly unlikely this will be necessary.

2) Replace the relay with one that was bench tested. Use 12v battery across pins 85 & 86. should hear and feel the relay click. Measure resistance across pins 30 & 87 when the relay is powered. You should read 0 ohms.

3) Repeat with the car hot. Warm / idle in driveway. If still good in driveway, drive it locally in close neighborhood WITH A DMM in the car. . . . just in case it reoccurs when the car is hot. Based on your symptoms and troubleshooting thus far. I don't think you'll have a problem when hot unless you're getting into vapor lock or bad grounds that are flaky only when hot. But, even then if I got a hot no start, I'd throw a DMM on it real quick at the fuel pump just to make sure you truly do have 12v and ground there (assuming you can't hear or feel the pump running but just not pumping due to vapor lock).

As I re-read this a 2nd time, I do have a question

Did you have power (12v) on pin 13 BEFORE you used the jumper? How did you determine it had power - with test lamp that lit up, or the DMM?

Pin 13 is the power feed that goes directly to the pump. If you have power at pin 13, the pump should have been running at that point, and you shouldn't have had to jumper anything.

@second wind

If this is the case, we need to dig deeper.

I put the MM in the number 13 and 14 pin sockets....the pin is on the plug...which is unplugged and off to the side....
gg

Hmm.

So let's outline terms to make sure we are on same page.

Male Pins 13 and 14 are on the relay board. Female sockets 13 & 14 are on the wiring harness.

Socket 14 on harness brings power into the relay board direct from battery and transfers it INTO the relay board via male pin 14 on the relay board.

Pin 13 is 12v going OUT of the relay board once the relay is energized. This is transferred to pin 13 socket of the wiring harness to the fuel pump.

if you used the Test light light to probe the back side of the harness with it plugged to the relay board and had 12v there, the pump SHOULD have been running.

I don't really like test lights:

Here's why. if you probed the harness with the test light and it lit, you would ASSUME that you have 12 volts present. However, you would be wrong in assuming that. You could have 10v and still light the test light.

Why does it matter?:
You could have had the relay energized but inside the relay you have a high resistance contact between relay pins 30 and 87 due to arcing, wear, or corrosion. The relay could be closed contacts just enough to have a voltage present but not closed well enough to actually carry sufficient fuel pump motor current to run the pump.

A DMM would be more likely to pick this up by showing you something like 9V or 10V indicating that the high resistance voltage drop is there. A test lamp won't necessarily pick this up.

So what:
it very well still could be that replacing the relay is the solution. However, it could also be that the relay socket contacts are the place where the high resistance connection was occurring (not inside the relay) and the act of using the jumper allowed a good solid connection to occur temporarily and when you go back to the relay, you'll have the same intermittent lack of fuel pump operation. You will then go on a goose chase assuming that the relay was replaced and all is good when in fact, the problem still lies with dirty contact in the relay board relay sockets.

Likewise, there is a possibility that the problem is in the relay board traces and the simple act of disturbing things (replace relay with jumper) is enough to get it working temporarily.

This is the hard part of electrical testing that requires patience and a logical method to get to the root cause of the problem.

What's next:

If it were me, I'd try to see if you can duplicate the condition again where you have power on pin / socket 13 but the fuel pump not running and test some more using the DMM.

IF I could duplicate the condition, i would disconnect the connector at the fuel pump. Would verify I still have 12v at the pump. if i did, I'd switch my DMM over to 10 amp current measurement and probe between the 12v source (wiring harness) and the 12v terminal on the fuel pump and verify how much (if any) current is drawn.

There could also be some sort of funky ground side connection going on but let's not go there yet.

@second wind

Again, thank you for your time. So here is a new twist....my 914 genius friend mentioned the ignition switch yesterday as a down the road possibility....then this morning I tried starting the car with the jumper in place and I could hear the fuel pump running but the car did not turn over....hmmm? So somehow my battery was drained overnight and I took it out and charged it up for 2-3 hours. The MM said the battery was putting out 13 volts or so....so I reinstalled it and turned the key and nothing happened....all the dash lights were brighter and I could really hear the fuel pump just buzzing away...but the car did not crank one bit....absolutely nothing happened....so now I am thinking something else is the root cause of all my woes....but I would not know....maybe you would Superhawk? Do tell...thank you very much.
gg

Relay testing...

If you put 12v to pins 85 and 86 it should click. Briefly. Don't leave it engaged. You could possibly burn out the coil.

If you put a continuity tester on pins 30 and 87 while you give 85 and 86 12v you can hear the connection being made. Should be a solid tone. No crackle. I don't believe there is high resistance between these pins. Should be nearly no resistance. You can put an ohm meter on 30 and 87 while you give the other circuit 12v. It should read like a short when the relay is on. There shouldn't be a voltage drop even if the relay isn't making good contact. It should just read 0v or 12v.

I'm pretty sure you can crack these and clean them. It's a coil. Electro magnet that pulls down on a lever that makes contact between 30 and 87. The contact is quite small.

Ok....enough already...first off you are correct and I was mistakin'.....the 13 and 14 pins are on the relay board....the sockets are in the plug. So I hook up the battery to test 13 and 14 again and maybe to try jumping the solenoid....however when I am taking the plug off the relay board I notice that I am smelling something burning and I see smoke coming off the ignition coil...I quickly disconnect the battery and I am now loosing my shit.....how did all of these things go wrong?
OMG,
gg

I haven't looked at how you're jumpering the fuel pump. There is more than 1 way to jumper it and turn the pump on. It's only designed to power the pump 1 way. The relay is there to isolate the current feeding the pump. The power to the relay is low current. The power to the pump is higher current. If you jumper it the wrong way you're pulling current through places it wasn't designed to go.

Also, while you're doing all this. If you keep your key in the on position without the car running, and your points are engaged. You will burn your points out.

Thank you Dustin...I have a Pertronix and hope it is intact....I am going to recheck where every wire is going and I jumped the fuel pump as in the picture someone had sent in...maybe it was Superhawk? I am going to post some pictures tomorrow and I pushing myself to stay positive....
gg

I have old relays laying around (don't we all?) so I cut the very top cover layer off of one to get to the relay mechanism. Now whenever I need to test my pump I simply push down on the top plate and the pump runs.

Or if I need to keep it running for whatever reason, I'll slide a sliver of cardboard between the top plate and the retention arm, and it stays running.

I keep this relay in the glovebox in case I need to troubleshoot on the road. Still works as a normal relay if I forget to replace it (or use it as a spare).

Negative. Leaving 12v connected to the solenoid (pins 85 & 86) will not burn out the relay. The realy is powered 100% of the time when key is on and all the time the car is running. It was designed for a 100% duty cycle.

Relay solenoid coil is 68 ohms. Per Ohms law it will pull 0.17 amps of current at 12v supply.

OMG is right!

how did all of these things go wrong?

The coil circuit is completely independent of the fuel pump relay circuits. Both in terms of wiring and also in the traces inside the relay board.

This is either a very unfortunate coincidence or could the 14 pin connector have been accidentally put onto the pins out of "index"? There is a plastic guide pin that indexes the 14 pin and is supposed to prevent this but did some thing get shifted when connecting / disconnecting? Just a thought?

This same out of index question applies to the 12 pin engine harness connector. In looking closely at the schematic, I can see that if you mis-index the engine harness 12 pin connector and pin 7 (12v to coil) gets placed on pin 5 (wire to negative side of tach) you would have a direct 0 ohm short between 12v power and ground that would pull enough current to melt the wiring on the negative side of the coil.

The coil itself contains a ballast resistor. It should measure about 3.0 - 3.2 ohms. Ohms Law says that at 12v supply, a 3 Ohm load will draw 4 amps. Not much. An 18 gauge wire is capable of supporting about 16-18 amps without melting. Even with the coil points closed for an extended period of time, you will not melt wiring .

I think two (or more) independent things are going on. A very unfortunate coincidence but not directly related to the fuel pump circuits.

I'm a little bit worried about if you have cracked and/or crispy wiring in your harness that somehow shorted when you were moving it around.

Is there any other sign of melted / shorted wiring other than the coil? Also need to understand which coil wire actually melted. The Positive feed (Black/Red) or the negative tach wire (Black / Purple)?

Let's break this into pieces:

Ignition switch -- let's not get distracted by that yet.

Battery -- is this the same battery that previously went dead and which was swapped into your pickup truck and wouldn't crank that previously? Did the battery get load tested at FLAPS under load? Batteries can and do go bad. They will display 12volts but cannot support a load like a starter motor that draws 50-100A without collapsing. I've had this happen several times during my lifetime.

So now back to ignition switch could it be related to no-crank? Yes, but that needs to be verified before assuming it is the case.

When the car wouldn't crank, I'd jumper the starter motor solenoid high current posts (copper) with a screwdriver. If it still won't crank, the problem is not in your ignition switch. Bad ground strap between transmission and body is a common cause of slow or no crank conditions.

All of this is why verification and methodical troubleshooting is so important before assuming anything with electrical problems.

I agree with the supposition that you may have multiple problems going on. The trick is to verify each symptom one by one in a methodical way before guessing randomly.

To crank and start the car in the short term without the ignition switch, I'd use a remote starter switch from FLAPS to take the ignition switch starter solenoid circuit out of the equation (large yellow wire). This circuit is a notorious problem. We should deal with that separately, and not let it cause confusion about the fuel pump or the smoked ignition coil. Of course this recommendation is based on having VERIFIED the battery is good.

The other thing that concerns me is that the battery drained overnight. This is indicative of some sort of low current draw occurring even when the key is off. Repeatedly drawing a battery down to a dead condition and then recharging them quickly (2-3 hours) will kill the battery very quickly. So I'll reiterate again that the battery should be verified by FLAPS or with a cheap HF load tester.

https://www.harborfreight.com/100a-612v-bat...ASABEgL_4fD_BwE

@second wind

Was the jumper left in the car overnight?

Both pins 12 and 14 are fed direct from battery. They are live all the time.

Pin 14 feeds through the 25A fuse on the relay board and provides power to relays pins 30 for both the fuel pump relay and the rear window defog relay (if heated rear window was optioned).

So if you jumpered relay pin 30 to pin 87 (which leads to fuel pump via Pin 13) and left that jumper in place overnight, the fuel pump would have been left running all night. Even if you disconnected the pump, that same pin 87 from the fuel pump relay also feeds one of the white wires that supplies the ECU, so the ECU would have been left powered all night.

Hello Superhawk....thank you for talking me off the ledge....I will get back to business. First, I just ASSUMED that the battery was worn down when I tried to start the car with the jumper in place for the first time.....so I just yanked the battery and put it on the charger. I had the battery tested a couple of weeks ago and it passed the test. So while on the charger I took the caps off and after 2-3 hours of charge I noticed all but one of the cells was bubbling....so that is not good but I think the battery is still strong enough to crank the car. So the second time I tried starting the car with the jumper in it responded as it did the first time....absolutely nothing happened....so when I back to the engine compartment and noticed the smoke from the frying wire on the negative side of the coil. I though about the long plug being installed wrong and checked it and when I saw the centering points I figured it was on correctly....but maybe it wasn't? I am going to verify where all of the wires go off of the coil and have the battery checked again and I will report back. Last night I did a quick check and the black wire off the negative side of the coil seemed to go through the engine tin down to the starter....I will confirm all of this and report back. Thank you very much.
gg

If you can keep an eye on that cell. I would think a load test should have shown a weak batter if you had a weak cell but I'd still watch it.

About five years ago my wife drove her can to work just fine. Went to come home in late PM and car wouldn't start. Luckily a co-worker was able to help her and jump start it.

Bad battery. One cell went bad. Worked fine . . . . right up until it didn't.

New battery - no problems and that new battery lasted years and years until we finally had to scrap the car due to rust issues.

Check both the 14 pin and the 12 pin (especially the 12 pin from previous posts) connectors very carefully .

@second wind sent you a PM as well

The relay is powered 100 percent of the time. But, there is likely more to the circuit than just the inductor. It could just be attached to the battery. But, why risk it.

There is no risk. Electrical devices are not some magical thing to be surrounded by mythology and superstition. There is no other part of the circuit in play here that makes bench testing the relay with a 12v battery a risk of any sort.

Power is applied to the solenoid and it follows Ohms Law once it is in a steady state condition. If there is any danger at all, it is when the relay is rapidly switched on and off repeatedly at high speed. Only then will inductance come into play. I’ll save that discussion for another time. It is not relevant here.

If there is disagreement; please post the electronics theory and/or data that demonstrates otherwise.

I don't know the spec of the coil. It's connected to the ECU. If you can operate the switch at a lower voltage you're saving heat.

Hello Ron....I appreciate all of your help...so I tried jumping the fuel pump today and it used to work perfect the last 10 times....today all I got was sparks at the relay board...so do you think it is a slam dunk that the fuel pump is fried? Please share your thoughts...thank you very much!
gg

Dr. 914 has a nice video on You Tube how to test the relay board and fuel pump without needing an engineering degree and schematics.

If your car is not turning over, you are looking at issues not associated with the fuel pump. Did you jump the starter solenoid correctly? Hot to the little wire at the top?

Hello Geezer914....would you be able to provide a link? Thank you very much.
gg

Hello Geezer914....would you be able to provide a link? Thank you very much.
gg

Greg - I’m rooting for you. @“second wind”

I think this is the link your looking for


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

Thanks for the link to the good doctor

I agree. The black stuff under the relay board dries out and falls off, ruining connectivity of the traces. My fuel pump conked out on its maiden voyage home, cured with a "rebuilt" relay board.

See if black stuff has fallen off the bottom of your board...

Paul

Umm.. No. The "Black stuff" or potting on the bottom of the board is there to seal or protect the traces. The traces are soldered. Simply its drying out & breaking off does not cause the board to fail. Once exposed for long periods of time corrosion can cause the traces to fail.

Aha! Guess I don't know the tune but I was humming a few bars...I was a lot "smarter" before the internet!

Paul