95 Cobra Fuel Issue

1Fine99 · Feb 17, 2016

Lately (and somewhat intermittently) my 95 will have a hard time starting. The engine will crank and not start but if I turn the key off and then try to start it again right away it will fire up immediately. Car seems to run totally fine once it's started.

Yesterday I hooked up my fuel pressure gauge and with the key on and engine off the gauge was not showing any pressure. With the engine running I was seeing 30-31 psi. With the vacuum line removed from the fuel pressure regulator I was seeing closer to 40 psi (also no signs of fuel leaking from FPR). When I shut the engine off the pressure would drop back down to 0 immediately.

I'm curious if anyone has had a similar issue and what the cause was. From doing some research it sounds like it may be the check valve in the fuel pump? Is there anything else that could cause symptoms like this? Leaky injector?

For what it's worth, the car has a new Motorcraft fuel filter, plugs, plug wires, cap, and rotor.

CC'S95GT · Feb 19, 2016

I don't think it a problem with the pump but with the FPR instead.

1Fine99 · Feb 19, 2016

CC'S95GT said:
I don't think it a problem with the pump but with the FPR instead.

Thanks for replying. Do you think the diaphragm inside is bad? I haven't seen any fuel leaking from it when I've had the vac line off and my fuel pressure goes up when I pull the vac line off. That means the diaphragm is working right?

Addermk2 · Feb 20, 2016

this will not be an FPR issue. that much is apparent due to the fact that its doing exactly what its supposed to. You have 40psi running w/o vac ref, and low 30s with vac ref.

Your problem is going to be the small S hose inside the tank. It has likely failed, and you are losing pressure inside the tank. Its basically a fuel leak, but still inside the tank.

Drop the tank and pull the sending unit out. replace the S hose, and im 98% sure your issue will go away.

rz5.0 · Feb 20, 2016

/\ /\ what he said more than likely. Or the check valve on the pump.. Your fuel is draining back to the tank.. When the fpr goes bad it leaks gas from the vac plug and you get a weird idle and rich condition..

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evilcw311 · Feb 21, 2016

Didnt someone else have this same issue recently?!?

Adder has it right. Drop the tank and the problem should be obvious. If your planning any other mods soon it might be time to upgrade your pump while your at it.

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Mustanger · Feb 22, 2016

So Glad you are here Adder !! Thanks for your advice it really helps us.....And all you other members with good advice I & many others rely on you a lot.

1Fine99 · Feb 22, 2016

Addermk2 said:
this will not be an FPR issue. that much is apparent due to the fact that its doing exactly what its supposed to. You have 40psi running w/o vac ref, and low 30s with vac ref.

Your problem is going to be the small S hose inside the tank. It has likely failed, and you are losing pressure inside the tank. Its basically a fuel leak, but still inside the tank.

Drop the tank and pull the sending unit out. replace the S hose, and im 98% sure your issue will go away.

Thanks for the info, I appreciate it. I decided to just order a new fuel pump. Do you know why the hoses usually fail? Just deterioration due to age? I guess I'll find out once I get the old pump assembly out.

Addermk2 · Feb 22, 2016

Most fuel now a days is an ethanol blend.

The S-hose that came with the car from the factory is probably an SAE J30R9 or below. Which means it's submersible, yet still not compatible with ethanol.

For any kind of ethanol blend (even E10) you need SAE J30R10.

96blak54 · Feb 23, 2016

I have to admit adder is a 94-95 sn95 dictionary. Good that so much wealth of info offered kindly!

1Fine99 · Mar 3, 2016

Addermk2 said:
this will not be an FPR issue. that much is apparent due to the fact that its doing exactly what its supposed to. You have 40psi running w/o vac ref, and low 30s with vac ref.

Your problem is going to be the small S hose inside the tank. It has likely failed, and you are losing pressure inside the tank. Its basically a fuel leak, but still inside the tank.

Drop the tank and pull the sending unit out. replace the S hose, and im 98% sure your issue will go away.

I dropped the tank today and pulled out the sending unit. The S hose appears fine. There are no visible cracks or holes in it. The only thing I noticed is the little orange rubber cap has a tear in it...but I'm assuming it's supposed to be like that since it's on the return line?

Addermk2 · Mar 3, 2016

Might as well put a pump kit in.

1Fine99 · Mar 3, 2016

Addermk2 said:
Might as well put a pump kit in.

That's the plan since I already have it. Do you know what the purpose of the orange rubber cap on the return line is?

1Fine99 · Mar 4, 2016

Got the new fuel pump installed today. Haven't driven the car yet but it is now holding fuel pressure after I prime the pump so it appears as if the new pump solved the issue. :thumbsup: