Fuel pump not running Options

[Rand]

75, 2.0, djet. Won't fire. Spark is good. A little starting fluid in the intake and it fires. Clearly a fuel problem. I'm not hearing the fuel pump. Shouldn't I hear it for a few seconds when first turning ignition on? I checked the fuse (#25 on the relay board) and it's good. I'll put a multimeter on the pump terminals to check for power next, but thought I'd throw this out there to the collective for any other input until I can get back to it. Grounds are also on the list. Or put power directly to the pump and see if it runs.
(IMG:style_emoticons/default/beerchug.gif)

[Spoke]

To test the fuel pump drive w/o the FI ECU, remove the FI ECU plug from the relay board and jumper pin 3 of the FI ECU socket to chassis ground. This will remove the ECU from the picture and test the entire fuel pump drive (FI power supply relay, FI pump relay, wiring to the FP, and the FP). When you turn the key to ON the fuel pump should be energized. If you hear it then likely it's the FI ECU or its sensors.

[dralf]

I may be having similar issues.... will try jumping out my relay once I figure out which is the pin mentioned.

[dr914@autoatlanta.com]

usually a loose fuel pump fuse or a relay not making contact

[lierofox]

I may be having similar issues.... will try jumping out my relay once I figure out which is the pin mentioned.

https://i.imgur.com/Nau5VmA.jpg Bottom left corner of this image. The left yellow circled terminal is the one Spoke is referring to.

[Rand]

Hey Al, it looks like we are in this together. Spoke was super helpful, and of course the Bowlsby PDF from your thread.

I thought if I put power directly to the pump, it should turn. Nope. So it makes me think the pump is bad. But I'm still open to the input from the experts.

Funny the Dr mentioned the fuse when we both proved that straight away.

[Specracer]

My recent experience, Had the car running, then stripped for a full resto. Figured it ran before, re installed the 3 port pump, and the relatively complex plumbing at the front under the tank. Luckily didnt install the tank (tank is a coffee can). Direct wired the pump to a battery (eliminating EVERYTHING). Nothing. Took pump apart (again), cleaned it (again), got pump to run. Looking at the return back to the coffee can, barely any fuel. Replaced it with an Airtex, replumbed the lines, and bingo. Running again.

Point is, wiring the pump directly to a battery was extremely helpful, isolating all other potential issues.

[Minerva's 914]

I had the same problem as documented in an earlier thread.

What ultimately got me to the solution was Paul Anders' Fuel Pump Checklist.

Good luck

[76-914]

(IMG:style_emoticons/default/agree.gif) the flow chart will take you right to it.

[dralf]

This morning I wired the fuel pump directly to a battery and it works ! Good news there but then I checked the relay board fuses and found only the blue one (25 amp ? ) had power to it. The red one had no current on either side of the fuse holder. I was then under the impression that this was my problem, but when I look at a 1974 relay board wire diagram it appears that this may not even be connected to anything, thus no current would be measured. I plan to do some more studying tonight and testing tomorrow. At least the cost of a new pump may be eliminated from my repairs. Thanks again for all who have help point me in the direction to get this fixed.

[JFJ914]

Check the pump circuit continuity through the relay plate. The plate has bit me twice!

[sixnotfour]

@Conedoger

I can tell you for one, that right by the brake fluid reservoir under the gas tank is a ground for the fuel pump on the '75

the ground on my 76 was crusty

[mtndawg]

This morning I wired the fuel pump directly to a battery and it works ! Good news there but then I checked the relay board fuses and found only the blue one (25 amp ? ) had power to it. The red one had no current on either side of the fuse holder. I was then under the impression that this was my problem, but when I look at a 1974 relay board wire diagram it appears that this may not even be connected to anything, thus no current would be measured. I plan to do some more studying tonight and testing tomorrow. At least the cost of a new pump may be eliminated from my repairs. Thanks again for all who have help point me in the direction to get this fixed.

The rear 25 amp fuse is the one that needs to have power for the fuel pump to work.

[dralf]

Rainy here in Ohio and a good day to work on the car. I ran through the trouble-shooting flow chart and it shows that my relay board is bad. I had taken it out of the car when I was cleaning and spraying all the electric connections and dollars to doughnuts, I am willing to bet something bad happened to it when I fiddled with it. I will now go and get a rebuilt unit and continue the saga after it is installed. On note worthy of mentioning: I thank all the people who help us shade tree mechanics... the flow chart was a life saver for me and so easy to use. Generally wiring up a lamp is all the electrical engineering I know to do.

[dralf]

Hello. it is me again. Before purchasing a new relay board I was advised to check my relays via the head light circuit. I did that and was elated that one of the relays was bad. I replaced it with a good one but sadly the fuel pump with still not energize. I found a old post by Minerva's 914 that seems to have had similar mysterious running issues and in his investigation found the relay board was bad by checking the continuity of the ground circuit pin #10 to the pump relay socket #86. Mine was OK. I then tried to put a ground wire jumper on pin III. My understanding is that this will bypass the ECU and will eliminate it as the problem. The fuel pump will still not run. I have heard the injectors click when the key is turned on so I am under the assumption that the ignition switch is OK.

I am thus sitting on the fence regarding spending the money for a new board. I will run a few more checks before taking that leap. I may eventually have to seek a professional to work on this. Although we have a Porsche Dealer in town I would prefer to have someone with real experience with the 1975 D Jet system work on it. I was actually told by the dealer that none of their mechanics were as old as my car.

So if anyone has a name of a shop or person in the Dayton Ohio area that could help me if I sink lower into this problem I would greatly appreciate it. Thanks..

[Minerva's 914]

You said in the next to last post that the flow chart showed that the relay board was bad, then you checked the relays, found one that was bad but upon replacing it the fuel pump still wouldn't run.

What was the flow chart test failure? And is the test failure related to the relay circuit, or are the two unrelated?

[porschetub]

I had a dead spot in my relay board,it didn't show until I hooked it all up after cleaning it and resealing it (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif) ,I ended up pulling power from from an unfused supply for the pump and that worked,added 7.5amp fuse and it got me going until I got a replacement board from a member on here.
Recently I had had a non-running pump,found the wiring ok and pump ran with a direct feed,changed out pump relay and away it went...not for long,would work sometimes and not others.
It finally stopped working till I swapped out the FI control relay and problem solved,2 relays in one day call me lucky...not (IMG:style_emoticons/default/sad.gif)

[dralf]

First I would like to thank all the military people for their service. On weekends like this when we get busy it is so easy to take what we have in this country for granted.

Today I had a few ideas on things to check out as to why my fuel pump does not run. I was looking for continuity for the ground wire at the pump. Well as my photo shows the ground wire has come loose from its' post. That will be an easy fix, and the wire may have giggled loose when I first unbolted the pump during troubleshooting. I then thought I would check the continuity of the hot wire from the 14 socket plug to the positive pump terminal. Well as can be seen in my photo that plug is cracked and the plug for fuel pump power is loose. I suspect the previous owner broke it but managed to get it to make good contact. I had taken off the plug from the relay board to spray everything with contact cleaner during my initial repair work. This may have been the start of my GOOSE CHASE. I am not 100 % certain how best to repair the plug but I certainly will be able to sleep soundly tonight knowing I now have discovered the root cause of the problem. Any suggestions from this board will be appreciated.

Before going into the house I decided once again to check the "bad relay" I uncovered following one of the trouble shooting guidelines. Well today it worked using the headlight as a test bed. I will put that one away for I do not want to play Russian Roulette.

I do have a question about sealing the relay. There are many spots of the black sealer that have fallen off. What is the best to reseal these spots, RTV, Silicon or latex calk, or Flex Seal (as seen on TV ) ?

[rjames]

Hey Al, it looks like we are in this together. Spoke was super helpful, and of course the Bowlsby PDF from your thread.

I thought if I put power directly to the pump, it should turn. Nope. So it makes me think the pump is bad. But I'm still open to the input from the experts.

Funny the Dr mentioned the fuse when we both proved that straight away.

If you are supplying power directly to the pump (verified with your mult) and it doesn’t run, it’s dead.