1974 1.8 L-Jet

There is a single yellow wire from the fuel injection double relay to the engine relay panel and it plugs into one of the terminals of the quad connector on the panel. See the attached picture. I think I have it plugged onto the correct terminal of the quad.

Can someone with a 1.8 L-Jet take a look at their relay panel and see if their single yellow wire is plugged onto the same terminal as mine?

Wiring diagram is useless. Is just indicates that the yellow plugs into the quad connector on the relay panel. It does not indicate which terminal.

Thanks!


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well, I couldn't find a picture, but yes, that is where it should be.

Thanks Grasshopper!

yeah, it looks like you are missing the fuel injection relay up there. Not the fuel pump relay, the other one. You only have the one in the slot for the heater fan. The other three are for fuel pump relay (1.7 and 2.0) and the fuel injection and the optional rear window defroster.

Maybe someone can explain the wiring on a '75 1.8 to me then.

I have a white wire coming out of the 12 pin connector bundle that connects to the
four pin connector, but the next pin over. Also, I do not have a power supply
relay, or a fuel pump relay. This does not seem right to me, but then I do not
understand any of this. My fuel pump runs all the time, and does not shut off after
a few seconds. Is this a fuel pump issue, or a relay issue?

Grasshopper, anyone??

so it runs right when you turn the key on?? On a 1.8, the pump should only run when you are cranking the car. On 1.7 and 2.0 cars, the fuel pump runs all the time. It sounds like someone has hotwired your fuel pump, cause you say you dont have a fuel pump relay. I have no clue what the white wire does...Got a pic?

Sorry, it WAS a yellow wire. I forget easily! Yes, the fuel pump runs when the key is turned on, and does not go off. It WILL go off if the air flow sensor is
disconnected though.

No relays in the board except one. There does not seem to be a diagram of the
'75 relay board in the set of documentation I have! What is supposed to turn off
the pump?

Jeff


Click to view attachment

Ok.. 20 years of working on a 74 1.8L.... You don't need ANY relays in the relay board of an L-jet car. It uses the double relay to turn the pump on and off. The yellow wire from the engine harness plugs into either of the back 2 plugs on the relay board 4 pin connector. They are connected together, and they come from the starter circuit. That wire signals the double relay to turn the fuel pump on when the starter is engaged. During cranking there ins't enough airflow to open the air flow meter enough to turn the fuel pump circuit on.

Speaking of the fuel pump circuit, If your pump is running all the time, and when you unplug the air flow meter, you have a bad air flow meter. The two possible causes of this are:

#1 The metal contact in the air flow meter that operates the fuel pump has broken off the tab on the top. There is a little arm on the air flow meter that separates to copper tabs and opens the fuel pump relay circuit. They get old and break off after time.

#2 Someone has messed with the air flow meter spring to the point where it is so loose that the arm mentioned above doesn't touch the contacts and the fuel pump runs all the time.



The right way to fix this is to get a new or rebuilt air flow meter. Or you can find an air flow meter that has not been tampered with by opening it up and "adjusting" it.

If the pump only shuts off when you disconnect your AF sensor then the fuel pump contact inside the sensor is jacked. The fuel pump on a 1.8 should only run when the starter is operated (current runs to the double relay via that yellow wire) or the AF sensor plate is moved from its stop. It's probably not a huge deal if everything is running fine, but I would not leave your key on without the engine running for very long. If by chance you have a leaky injector or cold start valve you could just end up creating another mess with all that pressure built up.

So yours is a '75? Wonder why your yellow wire is on that terminal and grasshopper's is below it. Can't think of any changes made the the L-Jet between 74 and 75 except for maybe the number of terminals on the AF sensor.

Will

ClayPerrine, thanks for the clarification that both of the rear terminals are connected internally, so I am fine with the location of my wire. I did not realize I did not even need the one round relay with my 1.8. Why the heck do they have it there? I thought it was for the heater air blower.

Next question since you have 20 years experience with 1.8s. I only have one fuse on my panel, the purple one. Why does jd66921 also have a white 8 amp in the front holder? Mine does not have a fuse.

I get confused easily. Excuse me if I repeat:

My fuel pump runs all the time when the airflow sensor is connected. It is NOT
supposed to?

If I disconnect the airflow sensor, the fuel pump does not run. That is NOT normal?

Where is the "double relay" you mention??

Sorry if I am so stupid!!

Clay, are you SURE you don't want a weekend at the beach??

Jeff

Ok.. here we go... Picture time....


The crappy yellow arrow points at the double relay as installed on Betty's car.

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Monted below them are the dropping resistors for the injectors.

(Pict of dropping resistors)

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The factory mounted them to the support for the battery tray. I moved them when I installed the rotary compressor for the AC. For the sharp eyed 914 gurus, Yes, the decel valve is gone and in it's place is an idle up solenoid for the AC.

The L-Jet system uses a different engine wiring harness from the D-Jet.

Here's a picture of an L-jet engine wiring harness:

Click to view attachment

There is an extra plug and connection on the harness to accomodate the double relay. The red arrow is the double relay connection, and the yellow arrow is the wire that connects to the positive battery post.

Click to view attachment

Here's a picture of the factory original, no longer available, official 914 double relay.

Click to view attachment

They have been superceded with the black plastic VW part. A couple of notes about the replacement VW relay. You have to trim the plastic plug on the 914 engine harness to use the plastic double relay on it, otherwise the plug won't fit the bottom of the relay. And there are 2 VW versions of the double relay. The differences is one digit in the part number, and the location of the fuel pump power pin. That pin will be located in connector that matches up to the FI harness, and not the Engine harness. If you get the wrong one, it will plug in and everything but the fuel pump will work perfectly.

Ok.. on to the air flow meters..

Here's a picture of an unmolested air flow meter. The black arrow points at the fuel pump contacts, which are being held open by the little silver arm.

Click to view attachment

Now here's a broken air flow meter....

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Note that the black arrow points to where the fuel pump contacts are supposed to be opened by the little silver arm, but the end of the one contact is broken off.

On a side note, this air flow meter also has slipped it's spring and does not have the correct calibration any more.

Close examination will note that the air flow meters are slightly different styles of manufacture. The late air flow meter (first pict) has a wire retainer in the teeth of the spring wheel. The early air flow meter has a clamp plate (not visible behind the counter weight). The first picture shows a revision done by Bosch due to lots of slippage of the spring.


One last picture... This is a set of dropping resistors with a common failure:

Click to view attachment

The wires break off the resistors. If the common wire breaks, you are left stranded on the side of the road. If one of the other wires break, you lose a cylinder.



I hope that helps your understanding of the L-jet system. Let me know if I can answer any more questions.

Clay, what did you use for an idle-up solenoid? I have a/c as well and an idle-up would sure help. Did you see my question up above in post 10 about the two fuses on the relay panel?

jd66921, you are correct. Your fuel pump should NOT run all the time when the air flow sensor is connected, only when the engine is starting or running.

Thanks!

The idle up solenoid is something I found in my parts box after years of fixing cars. I have no idea what it came from originally. If it ever breaks, I will start scrounging in the wrecking yerds for a replacement.


The front fuse, IIRC, powers the rear window defroster circuit. The rear fuse powers the heater blower and the relays for the D-Jet injection. You don' t need a front fuse at atll, and the rear one only has to be there if you have a heater fan in the engine compartment.

Clay, and others,

Thanks for the explanation of the L-jet. I know there are a million more questions,
but that answers quite a few!! I will have to look for those components today.

It doesn't sound like the "broken" airflow sensor is a big deal, unless it is indicative
of other failures. I can live with the fuel pump running all the time. It is not like it
is running except when I intend to drive the car. The car ran well for the first part
of its trip home with this condition! It might be indicative of other issues with the
air flow sensor though? As far as I know, the air flow sensor has not been molested.

Fuel pressure seems to be good. I measured it at rest, and also running, when I
could get it to run. Little to no change. The air flow sensor itself seems free. No
sticking but seems to seal well. I have a had ay least one very small backfire
near it, but no visible signs of damage. Is there anything else I can check on it
with normal hand/electrical tools. I hate to spend $175 for a rebuilt one without
any guarantee it is broken.

It is fun when I am learning, but I would really prefer to drive!!

Jeff

I am willing to bet money that if you go out to your car and remove ALL the relays from the relay board you will still have a running 914.

Try it....

Just when I thought it was about time to remove "newbie" from under my avatar pic.
You're totally right!!! She runs without either the "power" or the "pump" round relay. But, when my double relay was bad, the only way to run the fuel pump was to physically force round relay# 3 on. I could push down on the top and hear the pump buzz. Got me home and off the side of the road. Never rechecked anything after replacing my double relay. Never yanked the relays while it was running.

The "power" round relay clicks when I plug it back in, but I guess it's contacts are not used anymore.

So, humbly, never mind my earlier advise. <I deleted my post as to not confuse>

Attached:
73 relay board, the board hasn't changed over the years, but I guess its use has.
So, I now have 3 spare round relays. (no rw defrost either).

How that works....

On a D-jet system, the fuel pump relay on the relay board feeds power out pin 13 on the 14 pin connector on the front of the relay board to power the fuel pump, and it feeds power out pin 12 on the 12 pin connector to power the Aux air regulator, thermo-time switch and cold start valve.

On the L-Jet, the same pin on the 12 pin connector is hooked to the double relay's fuel pump output pin. That means that when the double relay is closed, the power flows into the relay board through pin 12 on the 12 pin connector, through the relay board and out pin 13 on the 14 pin connector, then on to the fuel pump (clever of those German engineers).

So if you close the round relay for the fuel pump on the relay board, it will still power the fuel pump. But it's not used by the L-jet system.

If your double relay on your L-jet ever fails to power the fuel pump, you can put a jumper wire across the d-jet fuel pump relay socket and get home.

Okay, lets keep beating this horse. I think he still moving!!

Since I have the fuel pump that runs all the time, and no one told me I couldn't,
I pulled the cover off my airflow sensor.

Click to view attachment

The fuel pump contacts were closed all the time. My first attempt was to bend the
copper arm to get it to operate properly. That worked okay, and now the Fuel
pump only runs when there is vacuum, airflow!! The arm is marked in red.

But.....

I looked more closely at the copper arm. There is a cam type pivoting piece
on the rotating part. The cam thing is marked in green. It ends up hitting the
fuel pump arm and turning off the fuel pump?????? You can even see the bend
that allows that. The plan looks like straightening the fuel pump arm so the fuel
pump keeps running!!! Seems too easy!!!!

Could this be related to my problems with the car running?? The symptom is
that the car will start, then die after a few seconds. If I pump the accelerator, I
can keep it running, sort of. But it will die after a few seconds each time. Maybe
the fuel pump is shutting off as vacuum is building?? I have suspected this alll
along, but couldn't prove it.

Amy I crazy as usual? It looks like the airflow sensor is realatively new,
maybe rebuilt?? Everything else looks clean in there. Anything else to check??

Jeff

It sounds like you may have a slipped spring on the meter. Was the lid for the air flow meter hard to remove? If not, someone may have fooled with it in the past.

I have a 75 Air flow meter that I can send you if you want to check that out. The 74 uses a different pinout so I can't use it on Betty's car.


Let me know if you want to try it.

My post a couple of replies ago was right on the money!!

Once I straightened out the fuel pump contact, the fuel pump operates
correctly. This morning I tried out the modified airflwo sensor, and the car
started. I'm still working on a few other problems, but I think I can do it now,
of course with the help of everyone here!!

I wonder if this will also fix the miss that I had. It might be related, as the car
would cut out momentarily on the way home.

I need to find a few more vacuum leaks, as the car will not start and will barely
idle without my finger in the airflow sensor to hold it open! I think it is the
oil breather line. I need to work on the cold start stuff as well. I don't know if
it is working right. It used to, when I first picked up the car. I also need to
figure out my #2 cylinder problem, but there's hope now!

It's been a long two months! I would NEVER have figured this out without the
help of everyone here. I'm actually surprised I found this at all!!

Thanks to everyone for your help!!

Jeff

Make sure you replace the seals in the oil filler cap too. On an L-Jet car, they cause a vacuum leak that will prevent it from idling.