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Discussion Starter · #1 ·
Here's problem:
Long crank time before start on 98 Cobra. After starting it runs fine. Usually worse in warm weather.

Does the 98 Cobra have a backup FP relay? One that maybe kicks the pump on at a certain Oil Pressure in case the primary relay fails? This used to be a problem on GM TPI engines way back when I used to work on them.

If not does this sound like a ( one of many) FRPS symptom?

Thanks,
Randy
 

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Unless you are the first I have met with a 98 with a returnless fuel system, you do not have an FRPS, assuming you mean Fuel Pressure Rail Sensor. (Unless it is there only to drive an aftermarket fuel pressure gauge.)

There is one fuel pump relay that turns the fuel pump on.

If your 98 is like my 96, there is also a two stage relay as well. At low RPMs the relay is open, running the fuel pump current through a current limiting resistor, which lowers the output of the fuel pump when you don't need as much fuel. At higher RPMs, the PCM closes the relay which shorts out that resistor to allow full current to the fuel pump for full fuel flow.

There is no oil pressure input to the PCM.

Do you have any mods and/or a tune?
 

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Discussion Starter · #3 ·
Ok, no FRPS. I'm ignorant of this system.

So, I had a buddy listen at the filler neck and he says I have no priming during key on. Are there two relays or just one? Heck I'll replace them both if I knew which and where they are. Help with that is mych appreciated.

Thanks,
Randy

PS: No mods. Bone stock w/ 70Kmiles.
 

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I am pretty sure the relays for the 98 are the same as my 96, but the fuel pump itself is different. That said, I may be wrong about 98 fuel systems...

First off, if you have access to a fuel pressure gauge, you should check to see if you have at least 29 PSI of fuel pressure during cranking. If you do, your problem is probably not with the fuel delivery system. You may want to replace your two fuel filters at 70K miles regardless to ensure they are not causing trouble. If you are not seeing at least 29 PSI of fuel pressure, then you are probably having a fuel delivery problem.

With my car, there are two relays that are labeled fuel pump relays, but they are what I described above. The fuel pump will prime regardless of the state of the second stage relay that just shorts out the current limiting resistor, so that would not cause your problem if it failed. That leaves only the main fuel pump relay. Unfortunately that is a part of the CCRM (Constant Control Relay Module) up under the passenger side front fender. It is a pretty expensive part to replace just for a test.

If I were you, I would take out the trunk liner that goes across the back of the trunk. I am pretty sure that will get you to the inertial shutoff switch that is the final component before the fuel pump. If not, you will also need to take out the trunk liner on the driver's side. Check that there is 8-12V on that wire during cranking. If not, you probably have a fuel pump relay issue. If so you have a different issue, which could be clogged filters or a bad fuel pump.
 

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hey guys just keep in mind that 98 came with both, return and returnless systems.
 

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Discussion Starter · #6 ·
hey guys just keep in mind that 98 came with both, return and returnless systems.
Ok, how do I tell? And does it sound like the relay in either case? I know that the pump isn't priming during Key-On.

Another question: What activates the fuel pump in the event of primary relay failure?

Thanks,
Randy
 

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well the way it goes is 96-98.5 were all return style systems, and 98.5-04 were returnles. The way to check which system u have is, I am guessing, to see if u have a return fuel line ruining back into the tank from the fuel rail.

Also the Inertia shut off switch is located right behind the drivers side brake light. It has a red button on it that resets it, make sure its pushed in. I am looking at the wiring diagram in the haines repair manual, and its only showing one fuel pump relay.
 

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well the way it goes is 96-98.5 were all return style systems, and 98.5-04 were returnles. The way to check which system u have is, I am guessing, to see if u have a return fuel line ruining back into the tank from the fuel rail.

Also the inertia shut off switch is located right behind the drivers side brake light. It has a red button on it that resets it, make sure its pushed in. I am looking at the wiring diagram in the haines repair manual, and its only showing one fuel pump relay.
I have always wondered about the second half of 98 being returnless. Aeromotive sells different fuel rails for 98.5 and up. But I have never had anyone with a 98 on any of the forums where I have discussed this say that they have a returnless system. I find that very interesting. Some say they used returnless-capable fuel pumps in return-style systems in 98. Who knows...

His car would not start at all if the inertial switch had opened. But it is a good place to test the fuel pump power supply.

A fuel pressure gauge would be a fast way to figure out if fuel delivery is the issue.
 

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Discussion Starter · #9 ·
His car would not start at all if the inertial switch had opened. But it is a good place to test the fuel pump power supply.

A fuel pressure gauge would be a fast way to figure out if fuel delivery is the issue.
That's what I thought but checked it anyhow. My fuel gauge is 348 miles north of here. The Ford guy in the vendor forums (Tousley Ford) has the relay which is in the fuse block under the hood for about 11 bucks. Pretty sure that's the problem.

They say they'll check

Thanks,
Randy
 

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Ok, how do I tell? And does it sound like the relay in either case? I know that the pump isn't priming during Key-On.

Another question: What activates the fuel pump in the event of primary relay failure?

Thanks,
Randy
If the pump is not priming, you have a problem with getting power to the pump. Here is the circuit for my 96 Cobra:


As you see, power can get through the resistor if the two stage relay is stuck open and it can get through the relay if it is stuck closed. So it can't be the two stage relay, assuming you even have one.

I am suspecting your main fuel pump relay or the pump itself.
 

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Discussion Starter · #11 ·
I definately have a return on my fuel rail. No I'm really confused. I know that the fuel pump is not priming, but why?

Thanks,
Randy
 

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Check to see if you are getting >=8 volts during cranking to the wire after the intertial shutoff switch. If you are, it is probably the fuel pump. If you aren't, then it's probably the relay. Outside chance of an intermittent wire issue.
 

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I have always wondered about the second half of 98 being returnless. Aeromotive sells different fuel rails for 98.5 and up. But I have never had anyone with a 98 on any of the forums where I have discussed this say that they have a returnless system. I find that very interesting. Some say they used returnless-capable fuel pumps in return-style systems in 98. Who knows...

His car would not start at all if the inertial switch had opened. But it is a good place to test the fuel pump power supply.

A fuel pressure gauge would be a fast way to figure out if fuel delivery is the issue.
yeah it was definitely a mystery. because some people think that all 98s are returnless. lol this caused some big arguments.
 
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