Fuel Pump - Need Help, trying to fire up my barn find for first time...no fuel Options

[willimac]

I'll try to keep the story short. I have a '74 1.8 L-jetronic 914 that I rescued from a barn in central Wisconsin almost 3 years ago. It had sat for over 20 years and become a palace for generations of barn mice, who built nests in every available cavity. Since then I've been sporadically cleaning it up, vacuuming mice and their nesting material, dropping the engine, dismantling and rebuilding it, cleaning up rust, shopping new parts (alternator, starter, stainless fuel lines, seals and gaskets) re-boring the cylinders, splicing chewed-through wiring, etc... finally got it put back together this week and am having trouble with the fuel delivery. The fuel pump does not turn on.

There is power to the double relay switch - terminal 86a checks out with the ignition switch on start, zeros out in "on" position , and AFM resistance checks out. The terminals at the fuel pump plug read zero volts unless the ignition is turned to "start" and the AFM is propped open - in which case it reads 7 - 8 volts.

Don't know what to do---is there a way to test the pump to see if I need to replace it? Why would only 8 volts be making it to the terminals for the pump? Is this possibly a problem with the double relay switch?

Any help would be greatly appreciated...I feel very close to bringing this one back from the dead.

[timothy_nd28]

Sounds like a weak ground

[Chris Pincetich]

More tips/advice in this thread http://www.914world.com/bbs2/index.php?showtopic=240820
I am having fuel pump issues too (IMG:style_emoticons/default/sad.gif)
Also, I agree with the advice about improving the ground. My 914 ground post above the battery in back looked OK, but was actually lots of paint and rust. The cooling fan metal shroud/case is a good ground in the engine bay (my battery neg terminal is connected there).
Good luck (IMG:style_emoticons/default/beerchug.gif)

[willimac]

Thanks for the speedy responses. So I cleaned up the ground strap from the battery nto the chassis, and the ground connection by the distributor cap (brown wire from the double relay) and tried again., measuring the voltage at the connector to the fuel pump. Same result - fuel pump gets about 8 volts initially. I let it crank a bit longer (a few seconds) and the voltage it was receiving began to drop. got down to about 5.5 volts before I released the ingnition.

and here's another strange thing that makes no sense to me: with the voltmeter hooked up to the fuel pump connector and the ingition turned off, the meter measures between .125 and .140 volts of juice. when I disconnect the Positive terminal of the battery, the voltage slowly counts down to 0.

I did install a new voltage regulator on the relay board, which looks quite different from the old one (not sure why I purchased it when I first started this project...Not sure whether the old one was good or not) Here's a pic of the new voltage regulator:

confused about what is happening here, and would love some ideas re:troubleshooting where the problem lies.

I'm on a steep learning curve when it comes to electrical components (IMG:style_emoticons/default/huh.gif)

Thanks so much!

[timothy_nd28]

Ok, let's rule out a bad ground at the fuel pump connector. Keep the fuel pump plugged in, and active in the circuit. With your volt meter set at DC voltage, put one meter lead at the negative fuel pump connector. With the other meter lead, put that on the negative terminal at the battery.

Activate the fuel pump, or start the car and report back the voltage on the voltmeter, if any.

[willimac]

Same result - starts at 8 volts and slowly decreases voltage

[timothy_nd28]

From the fuel pump's ground wire to the negative battery post, you are reading 8volts?

[willimac]

Yes. because the plug wouldnt allow me to get in there with the probe while it was plugged in, I jumped from the black/red wire female plug (the hot wire, as I understand it) to the positive terminal on the pump, then from the neg terminal on the pump, through the meter, to the neg post on battery. Reading was the same as when the test didn't go through the pump and just ran straight through the wiring (pos to neg on female plug connector)

[timothy_nd28]

not quite what I had in mind but lets move on. What is the current battery voltage, measuring straight at the battery posts?
Also, is the fuel pump located in the front or rear of the car?

[willimac]

not quite what I had in mind but lets move on. What is the current battery voltage, measuring straight at the battery posts?
Also, is the fuel pump located in the front or rear of the car?

Fuel Pump is in the rear, beneath the engine compartment, under the battery tray - voltage across battery posts is 12.32 volts.

[timothy_nd28]

K, double check the voltage at 88d on the dual relay.

[willimac]

K, double check the voltage at 88d on the dual relay.

I did this by clamping a jump wire on the back of the plastic plug, with the dual relay still attached. 88d is the black/red wire on the ignition harness, right? ran test from that wire, through meter to neg battery terminal

Voltage read 0 with ignition switch "on" and .03 to .04 with engine cranking.

[timothy_nd28]

yep, the bigger black wire with red stripe is the fuel pump wire. So you have no voltage on pin 88D by either attempting to start the car or moving the AFM flap?

If this is the case, lets check the voltage at pin 88y. You should have a solid 12volts from this pin to the negative battery post. If you have 12 volts on pin 88y then continue with this step. Put the meter leads on pins 88y and 88d with the voltmeter set to DC. If you read anything between 0 and 12volts DC on the meter while starting the car, then you have a voltage drop across the points within the relay. 0 volts across these two pins indicates that you have zero loss across the points. 12volts would mean that the relay isn't pulling the points together

(IMG:style_emoticons/default/popcorn[1].gif)

[willimac]

yep, the bigger black wire with red stripe is the fuel pump wire. So you have no voltage on pin 88D by either attempting to start the car or moving the AFM flap?

If this is the case, lets check the voltage at pin 88y. You should have a solid 12volts from this pin to the negative battery post. If you have 12 volts on pin 88y then continue with this step. Put the meter leads on pins 88y and 88d with the voltmeter set to DC. If you read anything between 0 and 12volts DC on the meter while starting the car, then you have a voltage drop across the points within the relay. 0 volts across these two pins indicates that you have zero loss across the points. 12volts would mean that the relay isn't pulling the points together

(IMG:style_emoticons/default/popcorn[1].gif)

Correct. No voltage at 88d moving AFM flap, .03 volts trying to start the engine (might as well be 0 volts, no?)

Yep, solid 12 volts at 88y, without the key in the ignition.
Solid 12 volts between 88y and 88d with ignition key off.
solid 12 volts with ignition key "on".
10.5 volts with the engine cranking.

So there is a voltage drop across the points within the relay. What does that mean?

BTW I am so glad that you chimed in on this post...I'm awestruck by how helpful you've been to others on the site, and have learned so much from reading those threads. THANK YOU.

[timothy_nd28]

You're very welcome. (IMG:style_emoticons/default/beerchug.gif) The voltage drop that you are describing indicates a failing relay. Overtime the metal parts inside the relay start to carbonize and become pitted, which increases the resistance across the internal switch, which robs power from the intended end product like your fuel pump.
A new relay will draw zero volts across the points when the relay is engaged. From the sounds of it, your relay is toast from either being internally pitted or corroded.

If you were to jump pin 88d of the dual relay straight to the positive battery post, does your fuel pump turn on then?

[willimac]

You're very welcome. (IMG:style_emoticons/default/beerchug.gif) The voltage drop that you are describing indicates a failing relay. Overtime the metal parts inside the relay start to carbonize and become pitted, which increases the resistance across the internal switch, which robs power from the intended end product like your fuel pump.
A new relay will draw zero volts across the points when the relay is engaged. From the sounds of it, your relay is toast from either being internally pitted or corroded.

If you were to jump pin 88d of the dual relay straight to the positive battery post, does your fuel pump turn on then?

No. there is a spark at the post when I connect the jump wire, but the pump does not turn on. (The last time the vehicle was licensed was in 1988, so the pump may be gummed up with old lacquered gasoline). Does it sound like I need a new relay and pump? (IMG:style_emoticons/default/blink.gif)

[timothy_nd28]

Maybe both, could of been a domino effect. I'll have you do some more test tomorrow, I'm turning in for the night

[willimac]

Maybe both, could of been a domino effect. I'll have you do some more test tomorrow, I'm turning in for the night

Thanks for the help...they only had one of the dual relays in stock at Pelican - I snatched it up - should be here Friday. Fingers crossed!

[Dave_Darling]

Connect that jumper wire and measure voltage across the fuel pump wires. If it's +12V, that means the pump is getting power at that point and it not running is a defect in the pump. Probably gummed up with lacquer, as you said. You can clean them to some extent--the end cover is held on with four screws. Mark the end cover and the intermediate piece as well as the pump body so you can put it back together the same way it came apart, then you can remove the screws and clean up the rollers and rotor.

The rollers are little metal pucks, make sure not to lose them when you take the thing apart. If you can get them out (they're loose in there) and clean them and the rotor, then spin the rotor by hand, you'll at least have the mechanical parts of the pump freed up.

I don't think the O-rings are available, but you can supposedly find fuel-compatible ones that fit. But it's best not to damage them if you can manage it.

--DD

[willimac]

Connect that jumper wire and measure voltage across the fuel pump wires. If it's +12V, that means the pump is getting power at that point and it not running is a defect in the pump.

--DD

Thanks for chiming in, Dave. Voltage at the pump is about 8 volts, decreasing the longer the engine cranks. I'm hoping that a full 12 volts (which it will hopefully get with the new double relay) will kick it into action.