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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6576
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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1993 Ford Mustang: cylinder..quits..hours, it will start right upagain

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I have a 1993 Ford Mustang 4 cylinder 2.3 engine. It turns off for no reason.
Fuel pump is good. After it quits, and I let it sit for hours, it will start right up
again. All the fuses are fine. Sparkplugs are new.
I attached a Data scanner to the jack. It never sees any data.
Customer: replied 7 years ago.


Yes - When it won't start -we pull a plug wire off and hold it in my hand and turn the starter and I jump )

Hello and thanks for using Just Answer.

I will try my best to help you with your question.

You should do a fuel pressure test when the Mustang will not start. There is a test port on the metal fuel lines for the fuel injectors. It looks like a tire valve stem. Press the needle valve down and see if you get a big spray of fuel.

The fuel pump might seem ok, but it is just and electrical motor. After running awhile it can heat up and not pump fuel to the motor.

We have already verified that you do have spark. Just don't grab the plug wire again and crank the engine. that is just not safe.

Customer: replied 7 years ago.


Sorry for the delay ... Father's Day ..


And thanks for the safe advice on the Spark Plugs wires - you are right . Not really safe.

OK Now back to the task.
We will look for the fuel pressure test point.

SOmeone also told us there is a relay or solenoid in the power chain

to the fuel pump. Is that correct? If so where is that device.

I like your suggestion on testing the pressure.

We will do that (of course car has to fail for us to make that test)...

Will you please hangin here with us as we trouble shoot this.

It could take a few days... as we have to have it happen... get back to you ...

and have you give us more ideas...

I have use this service for other problems and found it has always been very helpful

if we worked closely with the man on your end. We will give you our best - and hope you do the same.


Thank you ,...


The fuel pump relay should be under the drivers seat. The EEC (computer) relay in just above the ECU (Computer) behind the passenger kick panel under the dash.
Customer: replied 7 years ago.

OK... Thanks

I will go take a look at see if I have any more questions ...

And get back.

The computer and the car are in seperate locations... so I can't give you

instant answers.

But will soon



Keep me informed


Customer: replied 7 years ago.


You said:

The fuel pump relay should be under the drivers seat. The EEC (computer) relay in just above the ECU (Computer) behind the passenger kick panel under the dash.

I have looked under the Drivers Seat and don't see it.

Any ideas. There is a box under the passenger seat. Could that be it?

It is hard to see it ... so I didn't work to get it.

If that is the box... is it true that there are several relays inside that box?

While I haven't 'found it' in my car ... I think I found it at the parts store...

and they are telling me that the box contains 3 or 4 relays and will cost over

$100.00. Does that seem right?

I guess we start by asking... could the box under the passenger seat be the box we are trying to locate. Or another question might be... what is the box under tha

passenger seat? It has several small bundles of wires that connect to it.

Your suggestion that the Gas Pump may fail after running for a while and getting hot. Are there other devices in that chain that could also be subject to the same ... and could have the same effect. Do you have a systematic approach to trouble shooting this that we are missing?


It is under the drivers seat. The color wires that are going to it are

PINK/BLACK STRIPED WIRE (should have constant 12 volts from the battery)

DARK GREEN/YELLOW STRIPED WIRE(should have voltage to pump when relay sends it)

RED WIRE(should have 12 volts from ECU relay when key turned on)

LIGHT BLUE/ORANGE STRIPED WIRE(ground wire from the ECU to energize the relay with the key on)


What causes the fuel pump relay to fail is the fuel pump. When the pump heats up after running for a while or if the pump has an internal short which draws more current from the circuit, the relay heats up and fails. Then the vehicle will not start till the relay cools off and reconnects the circuit.

A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6576
Experience: ASE Master Certified, ASE Advanced Gasoline Engine Performance
A. Penland and 7 other Ford Specialists are ready to help you
Customer: replied 7 years ago.

First - We were able to check the 'pressure test port' as you suggested in your answer of Sunday, June 20th at 3:05 pm. We had pressure when we pulled the cap off that port, even after the engine had died.



Today .... we were able to plug in an EZ-SCAN 6000 to the vehicle and saw the

problem occur after the car had been running and was warm, so the scanner would

register a fault.


We observe the following indication:


543 Failure in the Secondary Circuit of the fuel pump control module to positive


What do you think this indicates?

The code 543 points to a failing CCRM (Constant Control Relay Module). This module is a sealed unit that incorporates the cooling fan relay and the fuel pump relay. It is located under the hood mounted to the right front strut tower. It is a black rectangular box with a connector bolted to it.

What is happening is the fuel pump circuit in the CCRM is heating up causing the relay circuit to open shutting your fuel pump off. then after the vehicle cools down the relay circuit resets and you can start the vehicle again. Replace the CCRM and your problem will be fixed.

Customer: replied 7 years ago.

My good friend...

Your help has been appreciated.

I have been trying to figure out the payment part of this transaction with your company.


Despite two questions to them and two responses - I'm not sure I understand precisely.


For starters.. You have been worth every penny of our initial investment - ($23 I think)and I signed off early (accepted) your answer to expedite your getting paid - despite knowing we would have added questions as we had not then repaired the problem we were seeking help on.

I have lived by 'treating others as I would want to be treated" I have tried to treat you the same.


Having set this background...


After I initiated the question on the Ford Mustang - I decided to go for an Unlimited Questions agreement with "Just Answer" and purchased that monthly service.


Then I initiated a 2nd question to a fellow in the legal area - and that was proccessed (under terms of the Unlimited Service)... or didn't cost me added fees.


Then - I came back to the Ford Mustang issue --- had another question - and thought it would either be covered under the new "Unlimited Questions' of at worste case" -- under the original question.


But as I read your latest answer of June 25th, 4:59 - It appears that in order to ACCEPT - I ambeing ask to pay again.

After questioin your HELP LINE - I still don't get it.

When I try to 'Accept' it asks for more funds from my paypal.

I don't think that is right.

It should either be paid from the initial inquiry - or now -through the

Unlimited plan.


You should not be penalized for this...

but nor should I.

The company has my money.

I am trying to help you get paid.

But I don't like paying for something twice.


And worse ... if they end up forcing me to pay twice...

then .. I will look at my options--- but seems like the most probable

one is I cancel the monthly Unlimited service $39 --...then everyone loses.


ISorry for this ... Your are a mechanic ... not a sales/ or PR person.

I am just an average Joe who would never cheat or purposely steal or cheat

anyone. But I also don't like getting 'boxed in' as I feel I have.

I would like to close out this thread of seeking help. But can't do so without being ask to pay more. That's not right.









You have already accepted my answer, and we can keep talking back and forth till your problem is fixed. The "TAG" line under each one of my responses (answers) is automatic. It does not mean you have to accept every time. Sorry if that made you think you had to, it is not intended as such.

As for the fees, that is between you and Just Answer. I have no control over that. I am basically and employee if you want to call it that.

I got on this web site to help regular people fix their vehicles themselves and to help them save the money they would spend at a dealership or repair shop.


So if you still need help with your Mustang issue, we can still communicate back and forth on this page. You do not have to "accept" any more because you only have to "accept" once.

Customer: replied 7 years ago.


This latest response is very helpful.. Thank you ...

I am goind to get you a small bonus (tip) just to say 'Thank You"

I have many skills - just not mechanical -

I also publish a 7x24 online newspaper for my region called


I have a perfect marketing tool to advertise the product and get commissions on

people who use it. I may use 'our story' as part of my editorial endorsement.

Talented "ordinary people helping others in their respective area of most experience ..."

Like having a neighbor who works for Ford...( in thiscase )


You will enjoy the product of one of my skills...


On-Line Web-Cams.



The camera in the top-left is on my deck of my home.

Thank you for your help ..




I'll check it out a little later. I'm a little busy packing up to go to Daytona Beach for the races next weekend. I'll be spending all week there in the infield. I'll still have my laptop running because they are predicting rain for most of the week over there.