Fuel Pump relay - 1974 LHD 911 with CIS

[Littleeagle28]

car has been garaged for years, have been trying to start it. However pump runs on ignition only. Have read several topics on this here, and most say for a 1974 model it shouldn't run on ignition only, but on starter.

That's one issue, 2nd issue is, I removed relay to check it, and pump runs on ignition regardless that the relay has been removed.

Would dearly like to hear suggestions on this one

[Flat6pac]

I would start at the pump and work backwards. Sounds like something is crossed on the relay board
Lift the air flow sensor under the air filter for a couple seconds to charge motor with fuel while trying to start.
Bruce

[Littleeagle28]

Originally Posted by Flat6pac

I would start at the pump and work backwards. Sounds like something is crossed on the relay board
Lift the air flow sensor under the air filter for a couple seconds to charge motor with fuel while trying to start.
Bruce

Have already done this with relay in place, engine won't start and fuel leaks out from underneath engine.

How could I check for something crossed on relay board?

[john walker's workshop]

Fix the leak before you go any farther.

[Littleeagle28]

Originally Posted by john walker's workshop

Fix the leak before you go any farther.

I think the leak is the fuel going into the exhaust and not igniting, and discharging out onto my drip tray.

[timmy2]

Fuel pump relays weren’t added until 1976.
If you have a ‘74 the pump runs continuously with ignition on.
Not sure what relay you are pulling, but it isn’t for the fuel pump. (Horn relay maybe)

[Littleeagle28]

Originally Posted by timmy2

Fuel pump relays weren’t added until 1976.
If you have a ‘74 the pump runs continuously with ignition on.
Not sure what relay you are pulling, but it isn’t for the fuel pump. (Horn relay maybe)

Ok, I read a few topics on this here, some say it has a relay, some say it doesn't. As my pump continues without the relay (from the engine bay on the left hand side near the rear), I have to assume it doesn't have one as you say, therefore this relay must be for something else?

Which leaves me with the original problem of car not starting, even though spark is there, fuel is there?

[74-911]

Originally Posted by timmy2

Fuel pump relays weren’t added until 1976.
If you have a ‘74 the pump runs continuously with ignition on.
Not sure what relay you are pulling, but it isn’t for the fuel pump. (Horn relay maybe)

This ^^^ '74's do not have a relay and run continuously with ignition on (Unless previous owner modified it. Is the fuel pump still in the driver side rear wheel well? or has it been moved to the front cross-member?)

[timmy2]

If you have pumped enough fuel into the engine to leak out, then you need to pull the plugs and see how wet they are. May need to swap them out.
Are you getting a good strong spark? Are the Points set correctly?
How old is the fuel? Sitting for how long?
Need more information to be able to help.

[Littleeagle28]

Originally Posted by 74-911

This ^^^ '74's do not have a relay and run continuously with ignition on (Unless previous owner modified it. Is the fuel pump still in the driver side rear wheel well? or has it been moved to the front cross-member?)

On the left hand side, under ther rear wheel well.

[Littleeagle28]

Originally Posted by timmy2

If you have pumped enough fuel into the engine to leak out, then you need to pull the plugs and see how wet they are. May need to swap them out.
Are you getting a good strong spark? Are the Points set correctly?
How old is the fuel? Sitting for how long?
Need more information to be able to help.

Yes, good strong spark.
New fuel.
Car has been sitting for nearly a year, dont know how long before this, probably years?

I am not using the fuel tank, have taken this out and using an auxiliary bottle for fuel.

Can look at the points, but would this stop the engine starting, especially as it has spark. I realise it may not run right though. Just looking to see if the engine will start at all.

[Walter_Middie]

Littleeagle28,

Dennis (Timmy2) is the expert on electrical wiring, and is correct in that your 1974 fuel pump should run with the ignition on - so it sounds like that is working correctly.

You say you are using fresh fuel from an auxiliary tank so old fuel is not your problem.
You say you are getting spark, that's good, your ignition system is working.

You mentioned fuel coming from the bottom of the engine. I'm guessing that your fuel distributor plunger is stuck in an open position, so when you run the fuel pump, you are filling the cylinders with fuel. This is not good. I would remove the spark plugs and turn the engine over by hand a few times, then run it with the starter and the fuel pump disconnected to try and get all that fuel out of the engine.

The fuel distributor plunger moves up and down with the air flow sensor plate. With the fuel pump running, you should be able to lift up on the airflow sensor plate and feel some resistance as the plunger moves up and down. I bet yours has no resistance as the stuck plunger is not pushing on the airflow sensor plate.

If the plunger is stuck, you might have to remove the fuel distributor and pull the plunger out of the bottom and carefully clean it (no sanding or abrasion). The plunger is a very tight fit and can easily get stuck if the car has been sitting.

[manbridge 74]

Good advice here already but also make sure the return line is flowing fuel back to aux tank or it likely won’t run at all.

[Littleeagle28]

Originally Posted by Walter_Middie

Littleeagle28,

Dennis (Timmy2) is the expert on electrical wiring, and is correct in that your 1974 fuel pump should run with the ignition on - so it sounds like that is working correctly.

You say you are using fresh fuel from an auxiliary tank so old fuel is not your problem.
You say you are getting spark, that's good, your ignition system is working.

You mentioned fuel coming from the bottom of the engine. I'm guessing that your fuel distributor plunger is stuck in an open position, so when you run the fuel pump, you are filling the cylinders with fuel. This is not good. I would remove the spark plugs and turn the engine over by hand a few times, then run it with the starter and the fuel pump disconnected to try and get all that fuel out of the engine.

The fuel distributor plunger moves up and down with the air flow sensor plate. With the fuel pump running, you should be able to lift up on the airflow sensor plate and feel some resistance as the plunger moves up and down. I bet yours has no resistance as the stuck plunger is not pushing on the airflow sensor plate.

If the plunger is stuck, you might have to remove the fuel distributor and pull the plunger out of the bottom and carefully clean it (no sanding or abrasion). The plunger is a very tight fit and can easily get stuck if the car has been sitting.

Ok thanks. I have had the distributer out and discovered the plunger was stuck in. Nobody could get it to move out, or had any good suggestions, so I got hold of a strong magnet, and got it out that way🙂
I cleaned it up and was careful not to drop or damage it and replaced it on the car.

When I turn the car over, no fuel gets to the injectors, (but does get to the distributor) not unless I manipulate the air sensor plate upwards. (It has resistance).

[Littleeagle28]

Originally Posted by manbridge 74

Good advice here already but also make sure the return line is flowing fuel back to aux tank or it likely won’t run at all.

Yes, I fed a tube into the auxiliary bottle and return pipe works fine.

[Walter_Middie]

It sounds like you have everything to get the engine to run - fuel, spark, and air. I'd make sure you don't have a fuel leak - where is the source of fuel running out the bottom of the engine?

Once you get the fuel leak under control, you can prime the CIS by lifting the airflow sensor plate briefly (don't let it run too long - or you'll fill the cylinders with fuel).

These CIS systems have a really hard time starting if the cold start valve is not working. Check that your thermo time switch is getting power during starter operation.

Disconnect the connection to the cold start valve. Put a test light across the terminals. Run the starter, the light should stay on for a few seconds, depending on the temperature of the engine. If the light does not work, check for voltage on the yellow wire between the starter and the Thermo switch. If there is voltage to the switch and the light does not work, replace the Thermo time switch.

[timmy2]

Do you have A CIS fuel pressure gauge setup to test fuel pressures and see if you WUR is working?

[Littleeagle28]

Originally Posted by timmy2

Do you have A CIS fuel pressure gauge setup to test fuel pressures and see if you WUR is working?

Sadly, no 😕

[timmy2]

Originally Posted by Littleeagle28

Sadly, no 😕

Time to buy or borrow...

[Dave Kost]

Originally Posted by Littleeagle28

Ok thanks. I have had the distributer out and discovered the plunger was stuck in. Nobody could get it to move out, or had any good suggestions, so I got hold of a strong magnet, and got it out that way🙂
I cleaned it up and was careful not to drop or damage it and replaced it on the car.

When I turn the car over, no fuel gets to the injectors, (but does get to the distributor) not unless I manipulate the air sensor plate upwards. (It has resistance).

I think you need to adjust the mixture screw since you pulled off the fuel distributor and freed up the plunger. The movement of the sensor plate must be coordinated with the opening of the injectors.
BASIC ADJUSTMENT OF MIXTURE CONTROL SCREW AFTER REPLACEMENT OF
OPERATING LEVER
Caution
This test requires that the sensor plate be positioned correctly (rest position).
1. Install mixture control unit.
2. Bleed fuel lines. (Disconnect injectors and hold in a container. Move sensor plate by hand many times).
3. Use adjusting wrench P 377 to initially turn the mixture control screw counterclockwise about 1 - 2 turns.
4. Turn on ignition, pull plugs off safety switch on air flow sensor or fuel pump relay.
5. Turn mixture control screw clockwise until the injectors just barely eject. From this
point turn the mixture control screw back, i.e. counterclockwise, by one half turn.
Install injectors.
Caution
Never apply downward pressure to adjusting wrench during adjustments, since this could change the injection timing.
6. Run engine to ogeratin~temperature (oil temperature 80 to 90 C) and adjust idle speed and CO level to their final specified values.

You should be able to start the engine after properly completing this procedure .

Let us know.