Manual Fuel pump switch, and tips Options

[ONTHEGRIND]

so I am installing a new bosch fuel pump for my factory fuel injection system.. Where my factory fuel pump used to one in the stock location, one of the mounting tabs is gone from a little bit of rust, so I am moving it to the firewall. And mounting it with sheet metal screws.. Any body have a manual fuel pump switch wired up so if that relay crap decides not to work I can just flip it on with a switch.. where do you have it mounted and how do you have it wired up ?

Thanks

[ONTHEGRIND]

Nobody has done a manual switch ? I just put in a new pump and hoses go to start the car pump still doesnt kick on... I jump under the car with my battery charger hit the pump with power just to be sure and of course it kicks on and starts pumping.. so i splice in a manual switch and be done with it or is it not that easy?

[Dave_Darling]

There are two relays that control the fuel pump. One of them powers up the whole FI system, so if "the relay crap" decides not to work your chances are about 50/50 that none of the FI will work even if you convince the pump to run.

Fix the problem correctly, don't hack in a band-aid.

--DD

[ONTHEGRIND]

Dave I am not looking to hack I am looking to fix the problem, as I am the new owner the I am fixing the problems the car is not a junker it is from SILLYCON Valley I would like for the system to work as it came from the factory but if it decide to give me problem during a trip I would like to have the option of manually controlling it. Thankfully I changed the pump and lines they where pretty nasty..

The relay for the fuel pump in the hoto with a working one sill no pump any ideas of things to look at next ?

[markb]

As Dave stated, if the board goes bad, having the pump run will not make the FI kick back in. If the board goes bad, the FI stops working, and it's time to call AAA. Don't bother with a manual switch.

[r_towle]

get two new relays.
Put on in the correct socket for the fuel pump.
Put the other one in the socket for the rear window defogger...

Now you have a spare relay, right in plain sight.

Rich

[ONTHEGRIND]

Hmm instresting car was driving fine took it for a nice drive up mt hamilton not running it hard just cruising, then Monday pulled it out again to take some cylinder heads to jay's machine shop it drove fine then got home parked it.. Went to move in the garage right before night and it didnt run.. Since I put in the new pump and line no fire. So I am guessin I have another problem ?


Is it time to toss on the dells ir is it reasonably fixxable.. ?

[markb]

The car is new to you. It probably has been sitting & needs things cleaned up a bit. Clean up the electrical connections (especially the grounds) and make sure all the components are working. Carbs are a last resort, and in most cases are put on by mechanics too lazy to fix it properly. A stock cam works best with the FI, and carbs will never be optimal for a stock motor. Just my .02

[ONTHEGRIND]

I have been cleaning the grounds as Igo threw it cleaned the one behind the battery still no pump.

[Spoke]

Most folks don't do a manual switch because it is inherently dangerous to have high pressure FI pump on at all times. If you have an accident and fuel lines damaged, a constant on FI pump could pump out a lot of gas.

Why did you put the new pump on? Was the old pump working or leaking?

Did you try connecting a wire from ground to the fuel pump enable wire on connector T4b? If the pump runs with the key on, then the problem is with the FI brain.

With the key on, this will test to see if the relays turn on. With the key on, you should hear a click of the fuel pump relay.

Likewise, have someone turn the key on and check the power supply relay clicks.

[ONTHEGRIND]

Most folks don't do a manual switch because it is inherently dangerous to have high pressure FI pump on at all times. If you have an accident and fuel lines damaged, a constant on FI pump could pump out a lot of gas.

Why did you put the new pump on? Was the old pump working or leaking?

Did you try connecting a wire from ground to the fuel pump enable wire on connector T4b? If the pump runs with the key on, then the problem is with the FI brain.

With the key on, this will test to see if the relays turn on. With the key on, you should hear a click of the fuel pump relay.

Likewise, have someone turn the key on and check the power supply relay clicks.

No I have not tried that yet what do I do take a wire from tb4 in the pics and ground it ? I hate electrics..

[markb]

There's a ground post in front and below the relay board.

[Spoke]

No I have not tried that yet what do I do take a wire from tb4 in the pics and ground it ? I hate electrics..

Yes but be careful. The other spades may have power on them. Just touch the one in the pic to ground.

[ONTHEGRIND]

I put a wire from tb4 to a ground when I put it in the plug in the lower left nothing happens when I turn the ignition to the on pos. I hear a click from the relays.. I toched a wire to the top connectors on tb4 and got sparks

[ONTHEGRIND]

There are two relays that control the fuel pump. One of them powers up the whole FI system, so if "the relay crap" decides not to work your chances are about 50/50 that none of the FI will work even if you convince the pump to run.

Fix the problem correctly, don't hack in a band-aid.

--DD

Where can I find these relays Mr. Darling ?

[southernmost914]

There are two relays that control the fuel pump. One of them powers up the whole FI system, so if "the relay crap" decides not to work your chances are about 50/50 that none of the FI will work even if you convince the pump to run.

Fix the problem correctly, don't hack in a band-aid.

--DD

Where can I find these relays Mr. Darling ?

Not to answer for Dave, but the relays are on the rear relay board (see your posted diagram) power supply relay , fuel pump relay, also the rear fuse(clean) is the fuel pump power fuse. This fuse is shared with the aux. air valve and the aux. heater blower motor. Blower motor circuit may be effecting your pump. Pull this relay (blower)and check the fuel pump operation. Steve

[Spoke]

I put a wire from tb4 to a ground when I put it in the plug in the lower left nothing happens when I turn the ignition to the on pos. I hear a click from the relays.. I toched a wire to the top connectors on tb4 and got sparks

Please elaborate on your findings:
When you say nothing happens you mean the pump did not run. Correct?

You hear a click from both relays?

The spark is good and bad. Good that you had power there; bad cause shorting that pin to ground could damage the FI relay as it provides 12V to this pin from the battery with no fuse.

There is a fuse on the relay board that powers the fuel pump. Is this fuse ok?

Do you have a voltmeter? If not, buy one, you'll need it to work on your 914.

[McMark]

To really solve the issue, you're gonna need to learn to use a multimeter, or at least a test light. Working with wiring/electrical, you must be very thorough and logical. There are no short cuts, IMHO. You have to start at the beginning and check each and every step until you find exactly where the issue is. The members here, myself included, can definitely walk you through a step by step evaluation. But no one is going to be able to tell you exactly what's wrong without you being able to do some tests. (IMG:style_emoticons/default/wink.gif)

Let's get it fixed!

[bperry]

I put a wire from tb4 to a ground when I put it in the plug in the lower left nothing happens when I turn the ignition to the on pos. I hear a click from the relays.. I toched a wire to the top connectors on tb4 and got sparks

Man those relay board photos I did sure are getting around a lot lately.

Yes be very careful here. You can melt wires if you are not careful.

The pins on t4b are numbered:

III I
IV II

With Pin III being in the upper left corner, closest to the drivers side front wheel.
This is the pin that needs to be grounded to get the fuel pump relay to click down
to turn on power to the fuel pump.
See the technical article for a close up photo of the pin that needs to grounded:
FuelPump for carbs

Pin I supplies +12v from the power supply relay. When the power supply relay
is energized (anytime ignition key is turned on) it is a direct connection with no
fuse to +12 on the battery. Short that to ground for very long and you will melt
wires.

Pin II and IV are tied together and are +12v while cranking the starter.
It is directly tied to the line that feeds the solenoid.
The FI brain uses this signal to know you are trying to start the car and turns on
the fuel pump by grounding Pin III.
Ground this pin and you have a dead short through the ignition key while you
are trying to start the car. This could also melt wires as there is no fuse in
this path.

Pin III
The FI brain grounds this pin when the starter is running -OR- only when
it "sees" the engine running. The FI brain monitors the distributor coil to detect if
the engine is running.

The reason that the fuel pump shuts down after a few seconds if you don't start
the car is that the FI brain isn't seeing the engine running (distributor driving the coil)
or the starter cranking.

So in order get the FI enabling the pump it not only has to be able to ground
pin III, but it also has to see the coil being driven.
If the FI brain thinks the engine has died, it shuts down the fuel pump by
ungrounding pin III.

So the ground trick for pin III when using FI is only for testing to see
if the fuel pump will run. I'm pretty sure you can't run the car this way.
I believe the FI brain needs the power that comes from pin I.

A big clue is when things are plugged in as normal.
(Connector from FI brain is plugged into t4b)
Does the fuel pump run then stop when you turn the key to "run"?
If so the relay board and the fuel pump relay is working fine.
Then, if no start, it may be due to the FI brain not seeing the distributor
turning.

Check the wires around the coil, there should be a wire that feeds
into the FI unit. Perhaps it is loose, broken or dirty.
I can't remember the wire colors off hand for that.
Perhaps someone else will chime in.

--- bill

[Spoke]

Pin II and IV are tied together and are +12v while cranking the starter.
It is directly tied to the line that feeds the solenoid.
The FI brain uses this signal to know you are trying to start the car and turns on
the fuel pump by grounding Pin III.

In addition, when starting the car, the FI brain will widen the injector pulses to get more fuel into the cylinders to help the car start.

Nice write up Bill.