Aurel`s engine rebuild thread

[Aurel]

Allright, that hose connects to a hidden nipple on the cruise control servo. Got the answer on the big technical forum.

Aurel

[Aurel]

John (oldTEE)

I tried to fire it up, but I get no fuel at the injectors. I tried to prime the system, and no luck. Can you give me more details on the procedure? You disconnect the WUR, lift the air sensor plate and crank the motor? For how long? Damn, I hope that old CIS is not going to let me down...

Aurel

[OldTee]

Careful here you could fill a cyl with fuel and lock up the engine. Break the fuel line from the fuel distributor to the WRU. 14mm I think. Then turn on the ignition, then lift the sensor plate. You will hear the fuel pump go. When fuel comes from the line you removed, replace it. The system should now be primed and should fire, all things equal, after a couple of rurrrrs, rurrrs.

Otherwise something else is amiss. To run you need fuel, fire and air. Check for spark. Leave the air filter off for the moment.

[efhughes3]

Sounds like you have good oil pressure with 1 bar during cranking.

[Aurel]

OK I`ll try again. When you say turn on the ignition, you mean without cranking, right?

Aurel

[efhughes3]

No cranking needed, the fuel pump will do the work.

[OldTee]

Originally Posted by Aurel

OK I`ll try again. When you say turn on the ignition, you mean without cranking, right?

Aurel

Did I say to put the fuel relay back in.

You don't crank the engine to pressurize the fuel system.

Check for leaks.

Let us know when it fires.

[Aurel]

So, when I tried to disconnect the fuel line to the WUR , fuel came out of it, so it seems primed. But, when I disconnect an injector and place it in a jar then crank, there is no fuel coming out of it(I tried two injectors). Also, when I lift the sensor plate, I really don`t hear anything going on???

Aurel

[Aurel]

And yes, I put the fuel relay back in.

Aurel

[OldTee]

Originally Posted by Aurel

So, when I tried to disconnect the fuel line to the WUR , fuel came out of it, so it seems primed. But, when I disconnect an injector and place it in a jar then crank, there is no fuel coming out of it(I tried two injectors). Also, when I lift the sensor plate, I really don`t hear anything going on???

Aurel

Cranking does nothing. If you raise the sensor plate you should hear the fuel pump. (Ignition on, relay in, fuel in tank (don't laugh, it happend to me once)). You might crack the fuel line (the one right above and behind #3 cylinder. The puel pump puts out about 80lbs so you should get a spry. One second should do it. Maybe a blockage somewhere. Check your fuses.

[Aurel]

I do not hear the fuel pump at all, so maybe an electrical issue. Where is the fuel pump, BTW? Are there two, one in the front and one in the back? I am going to have to look into that...unfortunately, the car is not going to run tonight. At least I had good oil pressure, and that motor sure looks better than before .

Aurel

Aurel

[mca]

I don't think the fuel pump is supposed to run unless the engine is running. If your fuel pump runs with the ignition key turned, something is wrong.

You can jump the fuel pump relay and turn the ignition key on in order to get the fuel pump running without the engine running. This is how you would perform fuel pressure tests.

Let me know if you need further help with this. See page 240-11 in the Bentley.

[Charlie V]

With the key on, you should hear the CDI box humming. Do you get spark at one of the plugs?

You mention no gas at the injectors. With the ignition key in the on position and the air filter out, reach in and gently lift the flapper valve. You will then hear the gas pump start (it is located under the car near the steering rack - covered by a skid plate). You should then see gas coming out of the injectors. Note - with CIS all injectors will constantly spray gas when the pump is running. Therefore, do not do this too much because the gas goes right into the cylinders when each intake opens.

I would start with this.

[Aurel]

Charlie,

The CDI box is humming. I haven`t checked for spark yet, but since I get no fuel to the injectors, first things first. I did lift the flapper valve, and heard nothing.

Aurel

[Charlie V]

Run a jumper wire at the fuel pump relay socket. This will bypass the controls within the engine compartment. You will hear the pump when you turn the ignition key on.

The Bently manual details this procedure.

Cheers.

[Aurel]

Originally Posted by Charlie V

Run a jumper wire at the fuel pump relay socket. This will bypass the controls within the engine compartment. You will hear the pump when you turn the ignition key on.

The Bently manual details this procedure.

Cheers.

That is a great idea. I could also check the relay by swapping the red fuel pump one with another black one. I assume they are all identical, correct?

Aurel

[Charlie V]

black relay will work - not sure of the difference.

[304065]

Red and black are not the same, red have a "quench" diode across the contacts to prevent back EMF. As such you don't want to back-wind the diode.

More Obscure Electrical Brain Teasers

[Aurel]

I bridged terminals #30 and 87 on the fuel pump relay socket with the ignition on, and I heard nuthin...all points out to a faulty fuel pump. Maybe just seized? I also think the relay is fine, because I heard it click when I plugged it back. Now, gotta dig that fuel pump out.

Aurel

[Charlie V]

Crap - deeper issue.

When you access the pump, disconnect the wiring and apply 12 volts to it to as a last check before pulling it out.

If you replace, I would suggest to also get a new check valve - it attaches to the pump. One of those "while you are there" items.

When I replaced my fuel pump, I took it to the local euro parts store and matched the Bosch part number on the pump. It was the same as a mid 1970's VW Rabbit at 1/2 price for the Porsche pump.