Hi All,
Need a little help to diagnose a fuel pump problem in a 75, I do not hear the pump when I turn the key to the run position.

The car was running, I had a few occasions where it would not start, let it sit for a few days and it was start right up.

The grounds: under the relay board, battery and transmission have all been cleaned.

All fuses are good.

The relay is working as I can hear it click into position.

When the key is in the run position relay terminals 30 and 85 shows 12 volts. Terminal 86 show 0.03 volts and terminal 87 show zero volts.

There is no voltage at either of the fuel pump terminals.

The readings at the relay is counter to to what Haynes states (86 should read 12 and 85 should be ground).

I not sure where to check next, really do not want to pull the tank. Any assistance would be appreciated.

Thanks,
Dan

You don't have to pull the tank to access the pump on a '75. The Cap'n

Cap'n I know this I checked the connections at the pump, I thought that there may be a ground that I may be missing. Any ideas?

One of the two wires connected to the pump is the ground. It should be brown and can be tested for connection to the chassis ground with a VOM.

If your hot wire to the pump isn't energizing, then trace that one back for problems. Also check it for a ground connection in case it's shorted.

D-jet (2.0 manifold pressure type) or L-jet (1.8 air flap) EFI?

Thanks, how do I trace the wire without removing the tank? Also I have D-Jet 2.0L

I have had problems with bad connections at the fuse on the relay board. Even though the fuse was good and the connection checked out ok with the VOM. I finally figured out I was making the connection good when I pressed on both ends of the fuse with the probes. Pulled the fuse out and squeezed the connectors closer together to make the fuse fit tighter...problem solved. Good luck!

I've had problems with the relay not fitting in the socket very well. I used WD40 and spread the pins on the relay and put it in and out a few times to work the wd40 so the tarnish goes away. No problems since.

Most VOM's have a continuity checker that beeps when both VOM leads are shorted together. Turn the VOM to continuity, contact the brown wire going to the pump with one lead, and touch a bare part of the chassis. If it's grounded, it will beep or buzz

Try the same check on the other wire to the pump. If it buzzes too, there is your problem wire.

You are going to have to trace the wiring from the pump to the dash. I have 2 1974's and no front pump wiring on the harnesses. But since I swapped harnesses, there is a part of my harness that extends from the fusebox area into the front trunk area. Some of it goes to the right to connect to the sender on the top of the fuel tank, the wipers, and the blower box. I'd look around there for wires to the pump or maybe on the left side of the depression that holds the fuel tank.

Note the wire color(s) and size on the pump wires and look for a match. Brown is always ground. Have a circuit diagram for a 1975? It should show where the pump wires attach.

30 is power from tha battery
85 is pump on power from the ECU
86 is ground
87 is power out to the pump.

Put a jumper wire from 30 to 87. You should hear the pump. The pump wires should have power. Your relay may "click" and still be bad.

I had a crack in the hot wire next to the pump about 2 inches back of the connector. Inspect it well before you start tearing things apart.....how do I know this?

Also spreading the relay pins and contact cleaner also is a great idea. How do I know this too?

Good luck.

Gentlemen,
Thank you for the suggestions, I will get back to you with the test results.

Regards,
Dan

I’ve had problem with the relay top plate stuck open (1976 2.0 – same setup as yours). Remove black cap from the relay (leave relay plugged in), with keys in “On” position press on top plate, you should hear fuel pump buzzing for 1 sec. I think that this top plate is electromagnetic and there’s a little spring on the side that pulls it down. Sometimes it gets stuck. Hope this helps, good luck.

I had a similar problem a few months ago. Rather than using a shotgun approach, I used pbanders worksheets to systematically check the system:

http://members.rennlist.com/pbanders/FPChecklist.htm

My suggestion is to follow this process. It worked for me.

Eric Read

I got to Brads list after I had torn even the ECU harness out. Went to his flow chart is how I found the bad wire at the pump.

Guys thank you for the pbanders post. I diagnosed a problem with the relay board (went through the procedure 3 times to verify)

I have the board out and will begin the rebuild process. Attached are a few pictures of it's current state.

Regards,
Dan

BTW, what is the best way to clean the tar off of the relay board?

Oh man your terminals are in rough shape. Your time might be better spent trying to find a better one.... or one that is already rebuilt. It' is a time consuming chore, and then to resolder those rivets to the traces ...they need to be REALLY clean.

Short answer is lots of patience and the pick tool set from harbor frieght is what I've used.

I'm sure someone will trump this but I left mine i the sun awhile then gently pried the backing out, in pieces, with a screwdriver. The thimbles or brads seem to be a common trouble spot. Rather than trying to com press the thimbles, I cleaned ad soldered them. After repairs were made I filled the back with a tube of black silicone. That was a year ago and it's still working.

Hi, I finally got around to getting another board and connector for the main harness.

Cleaned everything up checked all traces from the top side of the board and installed the connector and still no fuel pump.

I went through PBANDERS check again and have one question in the problem isolation area. At the point where I'm check pin 87 on relay 74 and I turn off the key I do not get exactly 0 volts (around .4 to .2 volts) does the indicate that I should check the power to the relay board?

Isn't there always some voltage to the relay board i.e. fuel pump relay?? Seems to me I read that here recently.

Dan this may be be an 'of course I know that' comment but...

The djet fuel pump only turns on for a second or two when you turn the key to run. It does not come on again until the starter is engaged. The ECU controls this by switching 86 to ground. When you are troubleshooting you need to remove the 4 pin connector and short pin III (front left) to ground. Or remove the relay and short 30 to 87 as Mike suggested.

oh - and another 'I know that' comment. If you are testing with the key on for more than a couple of seconds you should probably remove power from your coil to avoid problems with you points if they happen to be closed.

Steve, Mike,

Shorting 87 to 30 on the Fuel Pump Relay (ignition is off) activates the pump. I guess it is entirely possible that the second board I purchased is also bad, but I checked all contacts and made sure there was continuity through all of the traces

I'm in the process of rebuilding my original board with hopes that the PBANDERS flow charts are pointing me in the right direction. I followed it to the letter several times and the result point to a bad relay board.....

Steve thanks for the second comment re: points, I did not know that....

so next step - other than working on the old board - is to jump pin III to ground with the key in the on position. If that fails it points to your relay. If it works then we may have to look at the ecu - or more probably the connector to it.

Check your fuel pump. I had a similar problem with my 1976 2.0 liter with stock EFI. The car would start and run fine for anywhere from 5 minutes to an hour and then the engine would die. I spent lots of time trying to troubleshoot (relays, relay boards, grounds, etc.) with no success. I finally started the car and let it run until it stopped. I then used a couple of long wires and ran them directly from the car battery terminals to the pump terminals. The pump was dead. Turns out my pump was failing intermittently. Replaced pump and problem solved.

I have used a heat gun to remove the tar. however most boards I have fixed did not require tar removal. only needed to clean up the front, fine sand papaer and small files and some radio shack terminal cleaner spray.

good luck!

I jumped pin III with the plug in the board and still not fuel pump action. I will check the ECU connector tomorrow. BTW: The wiring harness to the ECU is new from Jeff B.

Toad, the fuel pump worked when I jumped pins 30 and 87 on the fuel pump relay.

I have also attached some pictures of my first relay board rebuild, but suspect (as you stated Red) that there is nothing wrong with the board I see a little oxidation but nothing broken. I will check continuity before I start in on soldering the rivets.

Pin III needs to be jumpered to ground to trigger the pump and the key turned to run. Is that what you are doing?

Steve, Yes that is what I did but the pump did not run.

Sounds like you are getting really close.

This is really sounding like you have a bad relay. Have you tried replacing the relay with a known good one - headlight lift assembly is a good source.

Steve you were right on target. I replaced the relay and drove my car today for the first time in 4 months. Not sure why the PBAnders diagnostics were pointing me to yet another bad relay board. I will probably go through it again.

Now I have a good board and an actual plug assembly for the main harness to the board and some extra good relays....

Thanks for All your help,
Dan

I'm all for being methodical in trouble shooting but you know I'm beginning to think that "check the relays" should be the first step in any diagnostic process. Followed by "check the fuse" and then go to Brad's tools. Relay failure is just so common that the 5 minutes (less if you don't have to steal the relays from the headlights) it takes to check the relays is time well spent.

BTW you can take the can off the relay and expose the actual solenoid. You might be able to see the point of failure and maybe resolder the bad connection. It is the CSOB thing to do

Back on this again. Took the car out a few times today I decide to go a little longer ~20 minutes in 70 degree weather. Car ran fine, shut it off to have some one take a look at doing some PDR sat for about 20 minutes went to start it and it would not start.

The fuel pump was not working, it did not recirculate for 1.5 seconds in the on position and jumping the pins on the relay did not work either. Tried tapping the pump but still no fuel. So I had it flat bed'd to my house by the time I got home it start right up.

Is is possible that the fuel pump is on it's last legs (btw this is a 75 with the pump up front)?

What is a good alternative to the pump, I would guess that a new OEM is NLA?

Thanks,
Dan

I think the 2 port pump (front mounted) is still available at a reasonable cost. Before you spend the mony though I would suggest your get your meter back out and make sure that you have voltage at the pump. The pumps are pretty robust electrically.

Steve,

It is working now I'm sure that there is voltage to the pump but will double check, what am I looking for?

Also where can I get a new pump if it should come to that?

Thanks,
Dan

That's the way mine was acting before I replaced the pump. No problems since...


http://www.914world.com/bbs2/index.php?sho...=105997&hl=

The Summit pump is noisier than stock but it certainly gets the job done.

It is not at all unusual to have 3 problems all at once. And I will throw in a 4th.

I know this is lengthy, but you do mention some symptoms that I have recently suffered, so I will throw it all out there.

1. Relays do fail, and mine by PO were Chinese made and were junk. Replaced them with good working German ones. I later opened up the Chinese relays and they are not even close to the German quality. Worlds apart, really. They were prone to metal deformation from heat.

To test my new board and the pump, I took the opened relays, and would push down to see if the heater fan worked on the rearmost relay with the heater lever pushed forward at the shifter, and if the pump worked with the ignition on and pushing down on the second relay from the rear.

The manual method worked in both cases, so I knew I had a new working board. (The other board did NOT work even with the manual method, so I knew I found an open, but the original board was so thrashed, I just replaced it and threw the thrashed one out.)

2. My similar problem was that the relay board (repaired by PO) would heat up and flex in warm weather with a warm engine (tar was removed and replaced by one hell of a lot of permatex), and stopped the relays from working. I could wait and let the car cool, but once, 10 miles from home, I took the relays out, put them in paper in a cooler I had with me. put another cooler block right on the relay board, and it all started working for a little while, enough to get me home. I was so pissed, the car sat in the garage for 4 months, which caused item #4.

3. The fuel pump can fail, mine started to go (reason shown below), and I got a replacement used one here. But, mine is a 3 port, and it sounds like you have a 2 port, which is MUCH cheaper to get even a new model. People here regularly bypass the 3 way return mess on the front mounted pump and go for a 2 port, but I am not sure which one is best.

4. I had a rusty tank and only by looking at the fuel filter, which was full of rust, did I realize that I had a much bigger problem. You might want to check your fuel filter just to be sure that you aren't suffering my fate.

So, you see, you may not have that much wrong, but those worn out relays can cause the symptoms you mention.

I am almost done with all the knuckle busting, and this week, I think I will actually pour clean gas back in and see what I have.

Hopefully no leaks!

Good luck!

J
avidfanjpl

Thanks for the suggestions:

(1) I just replace the fuel filter and cut open the old one there was nothing in the filter.
(2) All of the relays I have are working German versions that I have checked
(3) The board I just purchased off another member and checked all of the traces with a DVM, I guess it is possible that in a warm compartment something happens to the board but I stripped my old one and realized there was no reason as it was operating perfectly just a little dirty. Not sure that the board is the problem.....

Regards,
Dan

Pricing varies but does this look good;

http://www.amazon.com/Porsche-Vanagon-Bosc...l/dp/B003F1JO08

http://www.pelicanparts.com/cgi-bin/smart/...76%29%2C%20Each

The python pumps are considerably cheaper around $50.00.

Dan you may well be looking at a new pump. I'm just a little cautious because the tapping didn't free it up.

The quick meter check would best be done at the pump itself. Put your meter across the wiring harness and if you have 12V there and the pump is not spinning then the pump is the only possible cause. Is the pump not working now?

I have a suggestion.....


Hook a wire to the positive side of the pump (make sure it is AT THE PUMP) and run it into the passenger compartment. Hook a small light bulb to the wire and ground the other side of the light. If you want to be slick, use the park brake light in the left gauge. Then run the car. When it quits again, see if the light is coming on. IF so, you KNOW it is either the pump or the ground wire to the pump.

Clay that's brilliant! You must be a race car driver

Quick update. I connected a DVM to the pump and turned the key to the start position. As expected the voltage went to 12V and the pump circulated for 1.5 seconds and then stopped and the voltage also went to zero. I did this several times with the same result.

I mistakenly left the key in the on position for a good 5 minutes. After which I turn the car off and turned the key back to the run position:
No re-circulation
No voltage

This is the exact condition that I have every time I was stranded. The car will not start, but if I leave it I bet it will start tomorrow or later tonight. BTW I can hear the relay click (I know this is not indicative).

You guys think it is still the pump?

Something is getting hot and causing the voltage to drop.

Work backward from the pump up the circuit. Check at each connection in the circuit. Example, check the wire where it leaves the relay board headed for the pump. If the problem is still there, then move to the input side of the relay. If the problem is still there, move up the circuit to the fuse, etc....

Steve, Clay am I looking for a constant 12 Volts when the key is in the run position?

I'm a little confused as I expect the 12 volts for on 1.5 seconds unless the car is actually running.

Dan

That's right dan. 1.5 seconds unless you ground pin III. You will also get it if you move to the start position.

This is really intriquing. If we assume this is heat build up (logical) it is not associated with engine heat (car was off). In theory there should be no heat being generated anywhere. The only thing that generate heat then would be contact resistance either through a corroded contact or a partially broken wire. But ... as you point out - the pump would not have been working at that time so that suggests that it is not in the power delivery side of the cct it is over on the solenoid side of the circuit. Can get it to fail reliably by just leaving the key on again? Did it go back to functioning when it cooled off?

Steve,
I will check again when I get home tonight, but suspect it will work and if I leave the ignition in the start position for any length of time it will fail.

I went over every ground in the car an made sure that they were absolutely clean.

The solenoid side that you refer to is this in the fuel pump and hence not replaceable?

Thanks,
Dan

No... it would not be in the fuel pump side.

Think of the fuel pump circuit this way...

You have a battery in the car. From the positive side of the battery a wire runs to a fuse. From the other side of the fuse it runs to the relay. From the output of the relay a wire runs to the fuel pump. From the other side of the fuel pump a wire (in this case the vehicle chassis) runs to the negative side of the battery.

Now in your mind, replace the relay with a switch, because the fuel pump relay is a switch that the computer can turn on and off. So now YOU can turn the switch on and off.

We have eliminated the fuel pump, because it doesn't show voltage at the positive side when the problem is happening. So we move up to the switch (the relay). You say you can hear it clicking, so when the problem happens again, take the relay out and put in a jumper wire from pin 30 (pin 30 is the one farthest forward) to pin 87 (farthest rearward). That will bypass it and if everything else is OK, should make the pump run.

If that doesn't fix it, then check the voltage at Pin 30 on the relay board. It should always have 12v on it. If it doesn't, the pump won't run.

So if it doesn't, check the fuse in the relay board. The right hand contact should have 12v, and the left hand contact should connect to pin 30 on the fuel pump relay. If neither side has 12v, then you have a problem in the wiring harness between the relay board and the battery positive cable.

So now disconnect the 14pin connector, and check pin 14 for 12v. If it is not there, then you have a problem in the wiring harness.

I would suggest checking all of the red wires on the positive side of the battery. They get corroded from battery acid and fail at times.


Another thing to check would be the white wire in the engine harness. It powers the aux air regulator on the D-jet system. If it is grounded anywhere, or the aux air regulator is bad, the fuel pump won't run.

Clay,
Thank you for spending the time to explain, it is much clearer. But unfortunately I cannot duplicate the problem in my garage. I guess I will let the car idle over the weekend for a bit and see if I can reproduce.

Interesting thing about the aux air regulator, why would that cause a problem in the start up?

Dan

ah yes the aux air regulator! It runs off the same fuse as the fuel pump and would be drawing current even when the car is not running. (as would the heater fan and the rear window defogger). Clay is right - it could be on the delivery side of the relay.

In all of this have you replaced the fuse on the relay board? This may well be completely unrelated to the first problem of a bad relay. Just before my car went down for the big sleep I had a problem identical to this - fuel pump cutting out after a while and then coming back to life. It turned out to be the fuse. It had not blown - that would be too easy to spot. But internally the connector was loose and when hot would separate from the end piece. when it cooled down it would make contact again.