HELP. trouble starting 72 1.7L Options

[forzamotorsport9]

Alright.
Look at the positive terminal of the battery.
How many wires are attached?

Get a meter on the fat RED wires going TO the ignition switch inside the
car. I get to these at the front of the tunnel or near the shifter.

What you want to see is two things.
You want to find the RED wire that has power with no key in the ignition.
You want to find the RED wire that has power with the key in the RUN position...basically going back to the relay board.

Use sewing pins and stick them right through the middle of the red wires...then test for 12vdc on each wire till you find it. They are the larger diameter wires...they are the only ones.

If this is positive, you now need to find the RED wire in the tunnel that has power once the key is turned on to the run position.
Use the same process, but this wire will only have power when key is in the run position. This RED wire leads to the relay board.

There is also a YELLOW wire that is the trigger for the starter. While your there, test it.
It will only have power with the key in the start position.


Its kinda stupid, but power goes from the battery, to the ignition switch, then back the the relay board...its a long way.

If this test fails, you need a new ignition switch.


If the test passes, go to the relay board, and find that RED wire and test for power again at the relay board to verify its still getting there.

If you have power at the relay board, its either the relay board or the wiring to the pump...or the pump..or the fuel injection relay.

This is all assuming that you have checked ALL the fuses with a meter, not just visually.
Make sure they all pass power from one side to the other...not just ohm, but 12VDC on each side.

im going out to the garage to do all of this right now, will update soon

[forzamotorsport9]

ok i have power at the relay board. how do i check the wire that goes to the fuel pump. i have no idea which one it is and i looked and i cant even tell where it goes to.

[Spoke]

Where did you measure power on the relay board?

There are 2 fuses, perhaps, a 25A and 8A. The 25A is towards the rear of the car. With the ignition on, you should have 12V on both sides of the fuse.

Check that you have 12V on the 25A fuse and let us know what you measure.

The 25A fuse powers the fuel pump through the relay.

This is only part of the circuit to get the fuel pump running. Let's go one step at a time. Power first, then control, then relay, then fuel pump.

[Spoke]

Here's the circuit for the fuel pump.

When the ignition switch is turned on, the power supply relay energizes and provides power to the ECU on pin I and power to the contact for the fuel pump.

The fuel pump relay turns on when the ECU senses the engine turning via the contacts on the dizzy. The ECU energizes the fuel pump relay by grounding pin III.

[r_towle]

lemme translate.

put a volt meter on the fuel pump, get a helper to turn the key to run...do you see power at the fuel pump?

If you have power at the relay board, and no power at the fuel pump, you now need to get Spoke to explain how to test the rest of the circuit.

Spoke, he just bought his first volt meter last week, be nice.

Rich

[forzamotorsport9]

Where did you measure power on the relay board?

There are 2 fuses, perhaps, a 25A and 8A. The 25A is towards the rear of the car. With the ignition on, you should have 12V on both sides of the fuse.

Check that you have 12V on the 25A fuse and let us know what you measure.

The 25A fuse powers the fuel pump through the relay.

This is only part of the circuit to get the fuel pump running. Let's go one step at a time. Power first, then control, then relay, then fuel pump.

i have 12V at 25A and 8 at the other i think mabe 12 i dont remember

[r_towle]

Where did you measure power on the relay board?

There are 2 fuses, perhaps, a 25A and 8A. The 25A is towards the rear of the car. With the ignition on, you should have 12V on both sides of the fuse.

Check that you have 12V on the 25A fuse and let us know what you measure.

The 25A fuse powers the fuel pump through the relay.

This is only part of the circuit to get the fuel pump running. Let's go one step at a time. Power first, then control, then relay, then fuel pump.

i have 12V at both fuses.

How about at the pump.
It should only have power for about 1.5 seconds when you turn the key on.
It then again gets power once the motor starts.

Rich

[forzamotorsport9]

Where did you measure power on the relay board?

There are 2 fuses, perhaps, a 25A and 8A. The 25A is towards the rear of the car. With the ignition on, you should have 12V on both sides of the fuse.

Check that you have 12V on the 25A fuse and let us know what you measure.

The 25A fuse powers the fuel pump through the relay.

This is only part of the circuit to get the fuel pump running. Let's go one step at a time. Power first, then control, then relay, then fuel pump.

i have 12V at both fuses.

How about at the pump.
It should only have power for about 1.5 seconds when you turn the key on.
It then again gets power once the motor starts.

Rich

no power there. i have another fuel pump that silverteener (scott) let me borrow and im getting nothing...it doesnt click or anything and i tested the power too and got nothing. i stick positive meter into the connector that gets plugged into the fuel pump and the other one to the transmission case as a ground?

[r_towle]

have you replaced the fuel pump relay with a known good relay?
if so, do you have power on the red/black wire from the relay to the fuel pump?

We are down to three things.
wiring from relay board to pump is broken inside the harness
relay board is broken
ecu is broken.

So, if you have power at pin 13 with the key on, then we can assume the relay board is working and the relay works.

Next.
Ohm meter from pin 13 on the wiring harness to the other end of the wire to check if its broken.

If those two test clear those issues, it may be the ECU.

RIch

[forzamotorsport9]

have you replaced the fuel pump relay with a known good relay?
if so, do you have power on the red/black wire from the relay to the fuel pump?

We are down to three things.
wiring from relay board to pump is broken inside the harness
relay board is broken
ecu is broken.

So, if you have power at pin 13 with the key on, then we can assume the relay board is working and the relay works.

Next.
Ohm meter from pin 13 on the wiring harness to the other end of the wire to check if its broken.

If those two test clear those issues, it may be the ECU.

RIch

the wire coming off the relay doesnt go straight to the fuel pump? switched my relay board with scotts and it didnt do anything. How do i check the ohm from pin 13 on the wiring harness to the other end of the wire if i cant find it? lol

[r_towle]

what color wire is currently plugged into the fuel pump?

Rich

[forzamotorsport9]

what color wire is currently plugged into the fuel pump?

Rich

ok with the plug that has pin 13 on it pulled i have no power through the fuses. grrrrr this is really starting to frustrate me

[Dave_Darling]

Power comes into the relay board through the front connector. Power goes out to the pump also through the front connector on the board.

Have you looked at the fuel pump troubleshooting guide on Brad Anders' D-jet website? Look toward the bottom of http://members.rennlist.com/pbanders

--DD

[914_teener]

Dave,

I think Rich almost had him home.......Rennlist may sould like gibberish right now.

Keep at it...... I have been following this thread for a while. It reminds me of my first problem with my car.

It is a learning process.

Keep going........

Rich is like master Yoda.

[r_towle]

what color wire is currently plugged into the fuel pump?

Rich

so, at the pump...what color is the wire.

Rich

[Spoke]

Here's a couple of simple tests to check for proper voltages:

Test 1: Power Supply Relay operation:

1a) Remove the plug from the ECU. This is 4 pronged ECU connector near the driver rear of the relay board with white wires going towards the ECU. We'll call the 4 pins on this connector:

Pin I is passenger front
Pin II is passenger rear
Pin III is driver front
Pin IV is driver rear

1b) turn ignition switch ON. You should hear a low click when the middle relay turns on. (Power Supply Relay; it's the middle one if you have 3 relays or the front one if you have 2 relays)

1c) Measure voltage on ECU connector pin I (passenger front). It should be 12V.

****************
If 1c) is not 12V, then we have to find out why the Power Supply Relay is not turning on. Do not do the next test.

If 1c) is 12V, then proceed to test fuel pump relay:

****************
Test 2: Fuel Pump Relay Energizing:

2a) Keep ECU plug off. Turn ignition switch OFF.

2b) Get a piece of wire 2 feet long or longer with a female spade on it like shown below. Connect this spade to ECU connector pin III (driver front).

WARNING: The reason for the spaded wire is that Pin I on this connector is 12V through the power supply relay directly to the battery WITH NO FUSE. Accidentally touching Pin I to ground (we're grounding pin III right next to it) can cause serious damage and sparking.

2c) Once the spade is connected to Pin III, hold the other end of the wire up in the air (not connected to anything). Turn ignition switch ON.

2d) Touch and re-touch the other end of the wire to a clean chassis ground. Listen for the fuel pump relay to click when the wire is touched to a clean chassis ground.

****************
If 2d) yields Fuel Pump Relay clicking, proceed to test 3.

****************
Test 3: Fuel Pump Voltage

3a) Remove power connector from fuel pump.

3b) Ground ECU connector pin III (driver front) like in 2b through 2d).

3c) Turn ignition switch ON.

3d) Measure 12V across the 2 wires of the fuel pump connector.

****************
If 3d) yields 12V, then the circuitry to power the fuel pump is ok.


Sorry for the length of this post and the detail. If this stuff was easy my post would be like 10 words long and you'd be driving your car now. It is not easy and a methodical approach will lead us to the fault or faults.

Hang in there, we will get you through this.

If you can't get through this, PM me and we can talk on the phone while you test.

Good luck.


Wire for grounding ECU connector Pin III:

[silverteener]

Rich,

If it turns out to be his ECU I have others but I'm not sure what years they are from. Would we still be able to swap one out?

thanks

Scott

[r_towle]

Scott,
I would advise you to brinng a few with you, paul anders site on rennlist will tell you what ECU goes in what car....he has a full chart.
For any of the cars running djet the fuel pump circuit is the same.
The differences in the ECU is the hard coded air/fuel map.

I would suggest that you do a complete test of the fuel pump wiring first and dont risk shorting out a decent ECU if the wire is rubbing or broken and shorted that is going to it.

I would suggest that you do the tests a few posts above this one first.
Then...pull the main plug off the ECU and use an ohm meter to test the whole FI wiring harness...

There are lots of wierd issues when you have a broken wire or wires inside an FI harness...it will drive you mad.

Rich

[forzamotorsport9]

Scott,
I would advise you to brinng a few with you, paul anders site on rennlist will tell you what ECU goes in what car....he has a full chart.
For any of the cars running djet the fuel pump circuit is the same.
The differences in the ECU is the hard coded air/fuel map.

I would suggest that you do a complete test of the fuel pump wiring first and dont risk shorting out a decent ECU if the wire is rubbing or broken and shorted that is going to it.

I would suggest that you do the tests a few posts above this one first.
Then...pull the main plug off the ECU and use an ohm meter to test the whole FI wiring harness...

There are lots of wierd issues when you have a broken wire or wires inside an FI harness...it will drive you mad.

Rich

my buddy and i are going to run the tests above and post the results. i looked and didnt find any breaks in the wire either. im thinking at this point that its the ECU....will update soon

[forzamotorsport9]

UPDATE!

spoke i did your test and got the fuel pump relay to click but am confused as to what to do after that, ill PM me you my number if you would like to call me, but otherwise i can wait and check here tomorrow or later tonight. whatever makes it easier for both of us.


btw scott i swapped out the middle relay with one from my headlights just to be sure