Resolved 1989 Mustang GT no spark, no trigger pump relay

Nine Finger Wrenching · Nov 26, 2023

So I'm not getting spark when I turn the car over, and when you turn key forward the fuel pump relay isn't turning on fuel pump like I thought it should. There is power to fuel pump relay, and you can jump the relay and the pump comes on. The relay is brand new so it has to be good...right? LOL

Pin #4 is dark green/ yellow wire that shows a 22 Kohm resistor on it (ignition coil ballast maybe?) after the resistor that wire splits and goes to ignition coil, tfi module, and back to the dash cluster.

I can't get any continuity through resistor. I think it maybe bad. If it was bad could that be the cause of my no spark?

On wiring schematic it shows its a 22 Kohm resistor. The aftermarket ignition coil ballast I see for sale at auto parts stores don't show that same 22 Kohm, so I'm not sure about how to go about replacing that.

Does TFI have anything to do with triggering fuel pump relay? or distributor PIP have anything to do with fuel pump relay?

Does anyone know what I should look at doing next?

Pictures below of resistor and schematic showing it.

General karthief · Nov 26, 2023

89 wiring in a 91(?) body? IIRC
Does the FP prime when key is turned on?

Mcmahst · Nov 26, 2023

If you have voltage at the relay when the key is in the Run position, but the fuel pump doesn’t prime, that prime function is triggered by the ECU. If you can, check the voltage at the Red/Blk wire at the relay with the key in the Run position. You should get 12v. If you do, then the ECU is suppose to act as the ground, activating the relay. There could be several areas to check. But grounds are always culprits.

Nine Finger Wrenching · Nov 27, 2023

General karthief said:
89 wiring in a 91(?) body? IIRC
Does the FP prime when key is turned on?

Yeah.. This is a basket case I bought. The fella had wrecked his 89 convertible, bought a 91 roller and dropped the 89 motor, engine harness and computer in it. They had bought the American Wire stand alone body harness and partially installed it enough to start the car. From my investigation they roasted a wire on the header, fried the ecu. They tried to figure things out then then put it on marketplace where I came alone. I went and got all 89 wiring harnesses, and sent ecu off to be repaired, and here we are today. 8 months in still waiting to hear it run.

Main power to fuel pump relay is always there. Turning the key does not kick on fuel pump. I can jump the relay and pump kicks on.

Nine Finger Wrenching · Nov 27, 2023

Mcmahst said:
If you have voltage at the relay when the key is in the Run position, but the fuel pump doesn’t prime, that prime function is triggered by the ECU. If you can, check the voltage at the Red/Blk wire at the relay with the key in the Run position. You should get 12v. If you do, then the ECU is suppose to act as the ground, activating the relay. There could be several areas to check. But grounds are always culprits.

I have 12v constant on I think orange wire, then theres two blk and red wires that go to inertia switch, they do not fire when key is turned.

General karthief · Nov 27, 2023

4.) No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – Coupe & hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) 86-90 models only: Blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay.
91-93 models only Blown fuse link in wiring harness. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
The fuse links for all model years 86-93 live in the wiring harness near the starter solenoid.

This is from the 'cranks but no start checklist'. (thanks jrichker) It's best to do the entire list but this covers the fuel pump not priming, I believe if the fuel pump runs when using the jumper under the hood then the computer ground is good.
Someone will correct me if I'm wrong.
Is your fp relay under the hood or under the seat?

AeroCoupe · Nov 27, 2023

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...

stangnet.com

AeroCoupe · Nov 27, 2023

Just a thought but have you checked the ignition switch as they have a tendency to fail. Not the key cylinder but the switch in the column.

Nine Finger Wrenching · Nov 28, 2023

AeroCoupe said:
Just a thought but have you checked the ignition switch as they have a tendency to fail. Not the key cylinder but the switch in the column.

New ignition switch. I had to replace it to get the car to turn over with the key. Seems to be working good now.

Nine Finger Wrenching · Nov 28, 2023

General karthief said:
4.) No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – Coupe & hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) 86-90 models only: Blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay.
91-93 models only Blown fuse link in wiring harness. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
The fuse links for all model years 86-93 live in the wiring harness near the starter solenoid.

This is from the 'cranks but no start checklist'. (thanks jrichker) It's best to do the entire list but this covers the fuel pump not priming, I believe if the fuel pump runs when using the jumper under the hood then the computer ground is good.
Someone will correct me if I'm wrong.
Is your fp relay under the hood or under the seat?

So I jumped wired the inertia switch just incase but it did nothing. I'm getting nothing to the inertia switch. I dont have any power on the red and black wire at the fuel pump relay either. On power at fuel pump relay is orang and blue wire, and its hot all the time, even without key in or on.

Mcmahst · Nov 28, 2023

With the key off, does the inertia switch have continuity? You say key on, jump the inertia switch, and you verified power to the FPR, but the pump doesn’t prime or give any indication it’s running?

So, looking at this schematic, when you turn the key to Run, you should have 12v at the red wire at both sides of the inertia switch, and at the FPR. I say 12v, as measured with your VOM grounded to a know good ground. If not, check that same red wire at the EEC power relay to see if you have 12v there. Let us know what you find.

AeroCoupe · Nov 29, 2023

The EEC relay and fuel pump relay both get power on the contact side from the battery via a fusible link. When you turn the key to run 12V+ should go to the coil side of the EEC power relay which then provides power to the coil side of the fuel pump relay. The EEC then provides a ground to the coil side of the fuel pump relay which then closes the coil and provides 12V+ to the inertia switch. If the inertia switch is closed the 12V+ then goes to the fuel pump.

With all of that said are you getting power on the pump side of the fuel pump relay?

Nine Finger Wrenching · Nov 30, 2023

BIG BREAK!!! Me and a buddy went wild with testers and probes. we realized #1 pin on ECC was getting no power. chased the black wire with orange strip down through the harness. Somehow I had grouped that wire in with the black and green grounds. My computer hot wire was attached as a ground. Once I straightened that out the fuel pump started working, and I started getting spark. The car actually coughed a couple times. Tonight me and my boys are gonna go through checking timing. I'm so excited I don't wanna go to work today. LOL just wanna stay home and hear this thing run.
I really appreciate all the help. Y'all helped me think and chase in the right directions.

Nine Finger Wrenching · Nov 30, 2023

AeroCoupe said:
The EEC relay and fuel pump relay both get power on the contact side from the battery via a fusible link. When you turn the key to run 12V+ should go to the coil side of the EEC power relay which then provides power to the coil side of the fuel pump relay. The EEC then provides a ground to the coil side of the fuel pump relay which then closes the coil and provides 12V+ to the inertia switch. If the inertia switch is closed the 12V+ then goes to the fuel pump.

With all of that said are you getting power on the pump side of the fuel pump relay?

I figured it out. #1 pin which is power to ecc was hooked up as a ground. Ghost found!!

Nine Finger Wrenching · Nov 30, 2023

Mcmahst said:
With the key off, does the inertia switch have continuity? You say key on, jump the inertia switch, and you verified power to the FPR, but the pump doesn’t prime or give any indication it’s running?

So, looking at this schematic, when you turn the key to Run, you should have 12v at the red wire at both sides of the inertia switch, and at the FPR. I say 12v, as measured with your VOM grounded to a know good ground. If not, check that same red wire at the EEC power relay to see if you have 12v there. Let us know what you find.

Found it!! Power to computer got hooked up as a ground.

Resolved 1989 Mustang GT no spark, no trigger pump relay

Nine Finger Wrenching

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General karthief

wonder how much it would cost to ship you a pair

Mcmahst

Nine Finger Wrenching

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Nine Finger Wrenching

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General karthief

wonder how much it would cost to ship you a pair

AeroCoupe

lube between the nut and the face. I know my lubes

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

AeroCoupe

lube between the nut and the face. I know my lubes

Nine Finger Wrenching

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Nine Finger Wrenching

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Mcmahst

AeroCoupe

lube between the nut and the face. I know my lubes

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Resolved 1989 Mustang GT no spark, no trigger pump relay

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wonder how much it would cost to ship you a pair

Active Member

Active Member

wonder how much it would cost to ship you a pair

lube between the nut and the face. I know my lubes

lube between the nut and the face. I know my lubes

Active Member

Active Member

lube between the nut and the face. I know my lubes

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