Hi guys,

Got stranded yesterday with my 1974 2.0 fi... no buzz fm the fuel pump.

Saturday the car started and ran great, only thing I did to the car that day is that I took my steering wheel off as it was a few teeth off center.
Used a impact gun to remove and install the big nut (no idea if this has something to do with my issue). Perhaps I had to be more gentle ...

Before I left on sunday morning I turned the key and heard no buzz fm the fuel pump... tried again and there was the buzz and the car started right up.
Went to fill up the car and no issues with starting. After a 50 km drive I parked the car and when I came back again no start/no buzz fm the fuel pump.

Started switching the relays, even with the ones fm the headlights... no buzz/no start. Switched fuses on the relay board (that's why you see the white in
the position of the blue and vice versa)... still nothing.

Called roadassistance and luckily an older gentlemen showed up. He took his voltmeter and said he could get the car started if he jumpered the relays -
see picture. The car indeed started right up and I headed the 50 km back home with no issue. Disconnected the jumper ofcourse as the pump otherwise kept working.

So where to start fm here... I have the file "porsche 914 fuel pump troubleshooting" but did not go through yet. I just keep wondering what could cause my issue.

The questions I have are the following :

1. Can the removal/reinstalling of the steeringwheel cause this issue (perhaps the connection of the switch came loose ? Pinched a wire so no ground ?

2. Ignition switch was replaced about a year ago (Porsche one, not chinese crap).
If an ignition switch fails, does the car crank or nothing at all ? Trying to figure out if I have a switch failure.

3. My fuel pump has a slight "humm" for a while (assumed it was resonance with the bottom plate (fuel pump is located near the rack) but can a fuel pump go bad "half" ?
I mean can she fail on giving the familiar buzz at start up but still run when relays are jumpered ?

4. Relay board itself was replaced a year ago with a rebuild one fm Bruce Stone

Some advice I received on facebook

1. splitting/widening the relay pins (did this in the past but perhaps have to do it again) - fyi ordered new relays anyway

2. bad CHT sensor ? But once the car starts with the jumpered relays, the car runs fine. Overruled by other members in the meantime

Any suggestions are welcome...

thks

Krgds
Dax

Click to view attachment

Ah, the joy of adventure and mystery with 50-year old cars. Glad you made it back home and got a knowledgeable roadside assistant!

I second that, that has to be about as rare as a winning lottery ticket!

My bet would be it's something simple and the older chap knew how to diagnose? what a rarity is that. Keep us apprised, can you wire the fuel pump direct to the battery and listen for the usual "hum"?

Don’t get distracted with all the other stuff.

Since it runs with the power relay and the fuel pump relay jumpered, you know where the issue is.

Bench test the relays - you’ll probably find they are OK since swapping other relays didn’t help but jumpers did.

If those relays bench test OK, you now know the issue is that the relay pins weren’t making contact to the relay board sockets.

The pins to the relays can be expanded slightly, and, the relay board sockets can be tightened slightly. That will likely fix your issue.

I think your answers are right in your post. To play on words, I think
your steering wheel swap is a red herring or "Post Hoc" fallacy, i.e. "after the the fact, there for because of the fact". I'd bet highly unrelated UNLESS you messed with the ignition switch as well in the process.

Ignition on, no fuel pump buzz means either the switch signal is not getting to the relay, or the relay is bad (or possibly the lead from the relay to the pump is suspect). The fact that the repair fellow jumpered the relays (amazing he knew which ones. I'd have to consult a manual) and you were on your way points to bad relays or bag ignition switch trigger. (but might have also been coincident with a wonky ignition switch playing nice for a moment.

You need to do what roadside repair did and grab a DVM and find the weak link. Hopefully easy like the switch or the relay and not a bad wire or relay board etc, but any should be pretty straight forward to pin down.

Here is relay and board schematic showing what he jumpered.

Click to view attachment

that is amazing he did know how to do that! i bet we would get that in the US!
i had this happen 2 years ago but unfortunately for me jumping the relay didn’t work because it was a short in the board itself. i now have 2 new boards one from Bruce as my spare ans one from 914sixer that’s in the car now. note to self, keep a spare board on board!
Phil

Here's another schematic view of the relay board. Your guy jumped relay K74 (ECU power supply) and K75 relay (Fuel pump). So 2 relays were jumped. K74 provides 12V power to the ECU on Pin 1 of the FI power connector also power to K75 on pin 85.

Follow K74 pin 85 back to the connector to cabin and you see it connects to pin 8 which is from the ignition switch. w/o 12V on pin 8, the power supply relay doesn't work and neither will the fuel pump.

Since your car didn't start up, you don't know if the power supply relay didn't get power from the ignition switch, or it's contacts were not making good connections, or if just the fuel pump relay didn't pull in or has bad contacts.

When the problem happens the only audible feedback you get is the fuel pump not running. You can't hear the ECU running or not.

Since your guy shorted 2 relays, you don't know which relay was causing the issue. Likely only one relay caused the issue.

You can try bending the relay leads out a bit but if the issue is in the wiring or ignition switch, you still have an issue. Until you solve the issue, you should carry those little jumpers with you and your voltmeter. If it happens again, check for voltage from the ignition switch by measuring from the 8A fuse (which also is connected to the cabin connector pin 8) to chassis.

If you have voltage on the 8A fuse, then try jumping just one of the relays at a time to see which one is not functioning.

You may also want to reseat the cabin connector (make sure not to get off by one pin) and the FI power connector.

About the impact tool on the steering column, it may not have done anything or it did. Large vibrations anywhere near wiring/connectors/fuses is not good.

Isn’t there something about the D-Jet controller that can cut off the fuel pump in certain conditions?
Could that function be acting up?

D-Jet computer grounds the fuel pump relay solenoid any time it detects ignition/spark sequences. Opens the circuit when there's no sparky.

It also closes the fuel pump solenoid circuit when the key is in the "start" position.

It's pretty basic.

Thks yr feedback… will dive into it as soon as possible.

Will report back. Just saw the youtube vid of George
going through the relayboard….

THE guy… he was happy he could help (and I was happy
to get home.

Click to view attachment

Rgds
Dax

I had a similar problem last year. It was my hot wire at the battery terminal. I'd start there first. If the connection isn't rock solid, it can cause this behavior. It's a super easy fix, of course. Best of Luck!

you removed the two jumpers after it was running?
if yes, its the fuel pump relay you need to focus on.

It may be a simple as examining the relay and figuring out how to widen it...meaning open up the pins just a bit more.

I also found itsy bitsy wire brushes at a store that sells firearms.
Those, on a drill...do wonders for the sockets.

Get a few, they don't last once on a drill.


Rich

It's obviously in the fuel pump relay area. If you have tested (which you can do with a swap on a headlight relay) relay, you should be able to make it work. Then it should be just the relay. If not, it's on the board. probably at the sockets as some suggested.

Dax,

thanks so much for posting this and your picture. It really helps to put us in your shoes. I too got stranded for a short bit after we had installed a new e-distributor, this weekend.

Car died in a round-about and I diverted for a low traffic lane but in the middle of a middle each/way turn lane. Luckily, some yuts stopped and help push us to the low traffic spur on the round-about, then downhill and out of the way.

After several uncomfortable moments, my son found one of his crimped connections
failed, so the e-distributor shut down, he got it patched up and we were immediately headed home.

clean your contacts on the relay board, and you maybe good.

again, thanks for posting the pic

Hello...I feel your pain....my car was down for six months last year with identical issue....I ended up changing 13 different components and wala it works perfect now....I think the root cause was the 50 year old wire harness but a wonderful world guy walked me through a million tests and they were all correct. Even when I thought I knew what was wrong. he would say "test it first"....he was right. After getting the car running great my fuel lines rotted ad now back up on the stands. One day this war will be over....NOT!
gg

Thank you all for your feedback.

To be on the safe side I have some new relays on the way fm 914 rubber (hurry up Fedex !) as I heard they are better than the Chinese aftermarket ones.

Looking for small wirebrushes to clean the sockets but more difficult then I thought... fire arm stores are not so common here in Europe

I'll let you know what I'll find

rgds
Dax

UPDATE: up and running …

Cleaned sockets with some sandpaper wrapped around
a toothpick… spread the pins slightly and bam…
The familiar buzz of the fuelpump is back…

Anyway, once the new relays are in fm 914rubber I will
put those in and carry the wehrles as spare…

@spoke … thks yr drawing and explanation. That one is
much simpler to understand for a non electrician

Happy it was not more than that (although I feel stupid
as I could have fixed it myself on the road… anyway first
time I used roadassistance and their service has been
tested now

Thank you all
Dax

awesome! sometimes its a simple thing we have overlooked,
i had that happen, about 5 years ago upon reassembly after paint and body work, the ground wire to the fuel pump somehow disconnected, and no start issue, spent 3 hours going thru the whole test and diagostic proceedure for the ignition system and relay board to find out if i hand just checked continuity for the pump circuits id have saved a lot of time, but its never a waste i was able to confirm the rest of the system was working just fine.