Hello out there...my five month fuel pump not going on went away for three glorious weeks of wonderful driving time....then on a very hot day here in Southern California I did not hear the fuel pump go on and had to get towed home...again. So after my usual relay replacement and my tried and true fuel pump jumper wire on the relay board fuel pump relay board position.....nothing...just sparks on the socket holes....hmmm?? Maybe this time the fuel pump did go bad? So a wonderfully generous board member sent me another working fuel pump and I plugged it in and still nothing...damn!! Back to the wiring....only thing I haven't replaced is the relay board and I have a good looking spare right here in my hand. I would love and appreciate any thoughts you fellow teeners might have....thank you very much!
gg

Yeah go ahead and swap relay board just because you have not done it. Next up I would check the ignition switch.

Feel the bottom of the relay board, especially where the fuel pump relay is.
I had an issue a while back where I was fiddling with a plug on the relay board and managed to push one of the pins through the potting so it did not make a solid connection. It took about a week to figure out WTF happened. Once I pushed the pin back into place everything was wonderful again.

Zach

well its a good questions, this is what happened to me a year ago, i had a couple times of no start, pump didnt prime then no issue for months and i thought it was ignition or other issues, but eventually left me stranded and it was a short on the relay board specifically on the FI circuit, in fact i could jump the relay and get pump to fire, but the injectors were not getting a pulse at all, so relay boards do fail and that is what it looks like when they do. If you dont have a spare board to try get one from Bruce Stone or Mark (the guy above, aka 914sixer) i now have 2 new restored boards one from each of these guys, i now carry a spare .

Phil

My relay board failed and the car dies while driving. Couldn't restart. Swapped in a different board and all was good.

Thank you guys very much and here is a tidbit more.....I happened to buy a replacement relay board years ago that the backing was replaced with hard resin....seemed to be an improvement. Well that relay board is in the car and has worked for years....just wanted to share all of the facts in case it explains anything. Thank you again and I will try my spare today this weekend and report back.
All the best,
gg

Hello again...I sure would appreciate any ideas out there just so I can follow instructions....I tested both of the fuel pumps I have, current one in car and a spare I have by putting 12 volts directly to both pumps....they both work. Then I tested the relay board fuel pump socket and it came up with 12 volts. Then I swapped a bunch of relays with the fuel injection plug connected to my multi-meter and there was no movement ....just dead at the plug. So what do I do next? I have a spare relay board and I have already replaced the wiring harness....I'm stumped as the car ran beautifully for three weeks after replacing all kinds of parts so I thought I had solved the "no fuel pump going on" issue but on a recent hot day it relapsed to the fuel pump not going on....I just can't think straight at this point so please share some experience, strength and hope.....thank you very very much.
GG

Here's an idea....how would I check the continuity from the fuel pump plug to wherever it goes? Thank you very much!
gg

You might find this thread helpful:
http://www.914world.com/bbs2/index.php?showtopic=341367

Electrical problems can be really nerve wrecking and for myself I've found it good to step away when I'm ready to pick up the nearest hammer and start swinging. . Not sure if you've said or not, but do you have a volt/continuity meter? Also, have you downloaded a schematic of the relay board yet? There's at least three different versions I've found, each in a different format. If you can't find any, I'll be happy to post the ones I found.

From the diagrams, it looks like the power for the fuel pump comes in from the cabin connector on pin 14. That passes through the 25 amp fuse. In order for the fuel pump relay to turn on, it looks like the fuel injection power supply relay must turn on and then it will turn on the fuel pump relay. The ground needed to energize the fuel pump relay appears to come from pin 3 of the fuel injection power connector. When the fuel pump relay is on, it shows +12v sent to pin 13 on the cabin connector. It also sends +12V to the AAR on pin 12 of the engine connector.

All this may sound very confusing.... it does to me when I read it. So, where I'd start, ignoring all this confusion, would be to short 30 to 87 on the relay board where the fuel pump relay plugs and see if there's continuity with a meter between 14 and 13 on the board where the cabin connector plugs in. If good, remove the jumper and make sure there's no continuity. If that checks OK, then at least the output side of the relay on the board is working. If not, look at the fuse and its connection, and after that it's time to really suspect the traces and connections on the board. Hope this helps a little getting started.

Dan

Thank you very much Dan....I do have a spare relay board that I am getting ready to install. Some when you say "cabin connector" just where are you talking about? Thank you again !
gg

You're very welcome. "cabin connector" is ambiguous, I agree. Here's one of the schematics. The cabin connector is the 14 pin connector of the board and this particular schematic used that term. It's the front connector on front of the board. This schematic has a logical layout, but not physically representative.
Click to view attachment

Dan

Here's a schematic with a physical layout that matches the board. Wish I could remember where I found these. There's tons of resources both here and provided by member's sites.
Click to view attachment

Dan

Maybe this will help. It ain't pretty, but the path I mentioned is traced in red. With a wire jumper inserted between 30 and 87 at the fuel pump relay socket, there should be continuity between 13 and 14 of the front (cabin side) connector on the board.
Click to view attachment

Dan

After verification of the circuit above:

Bench test relays with 12v battery and Multimeter. Assuming you are not getting 12v on pin 13

Swap relay board

I really appreciate all of this help and guidance...thank you very much!! As soon as I recover from my 914 induced severe clinical depression I will try all of your suggestions....
gg

I have had more relay boards fail and result in a no-pump or intermittent pump condition due to one of the solder joints on the 4 pin connector to the ECU failing than any other cause.

Run through the guide on Bowlsbys site, it tests every possible fuel pump failure mode.

https://bowlsby.net/914/Classic/zTN_FI_FPChecklist2.pdf

Thank you so very much!! So maybe I am not crazy ?? I will clean up my spare board and give it a try. Does the heat/intermittent/fuel pump not going on sound familiar?
I appreciate your help and do tell?
gg

lots of good information for you here in trouble shooting this issue, there is a full trouble shooting guide on Jeff Bowlsbys site, and it was already shared above, and i think in the classics section Clay P. had one too, but here just like i said previously, and others have too, is that if your short is one of those tracers on the bottom and its intermittent , then when testing it might seem fine, I had this happen car started and ran the stopped suddenly again, found it because i had the key in the on position, the fuel pump had not primed becaues the circuit was not complete and as i pushed on a relay suddenly pump primed so circuit was complete but the relay was not the issue- that was on a rebuilt board i ran for 10 years, so i come back full circle- - if you have the spare board, it will take you 5 minutes to swap it out and see if that does the job. might save you a couple hours of testing. But then again the experience of doing this testing will help you understand the circuits and test it all thru. . so test the spare board and report back.

Phil

Will do....I need to clean my spare board...is brake fluid ok to use? My favorite is starting fluid but I think brake fluid is a better choice. Thank you,
gg

not sure about brake cleaner but i have heard others here mention using
DEOX R70 electrical contact cleaner.
also before you install it use the guides and test for conductivity on each circuit to make sure on that one too that there is not a back circuit. Clean the pins on the fuses and relays, use emory paper or the like , very small piece int the female receptacles on the board too,

Nope, not crazy, pretty common thing. Run through the checklist, in order, hopefully you can catch it when its not working. Intermittent issues can be a bit more of a PITA to track down, but yes heat and or vibration at any of the joints can cause this. Relay boards are always highly suspect given they contain the majority of the joints and are all 50 years old. Unfortunately new boards are not available ATM (many of us have been waiting) because a new board could in some cases eliminate days of troubleshooting.


As mentioned, deoxidizing chemicals (DeoxIT D5, DEOX R70, etc) can help clean up the boards some but in a lot of cases you will find a cold solder joint or one of the riveted joints that needs to be deoxidized and soldered on the underside of the board