Fuel Pump

[rkm]

Just looking for other possibilities and tips.

I am going to go rent a fuel pressure gauge to test the pump tonight.

Here is what is happening. The car starts up fine, idles fine and under a light load accelerates fine. No check engine light. When I put the pedal down and it hits 3000 rpm it starts to hesitate. It actually feels like the injectors are being shut down or the spark plugs are being shut down. As long as I go easy on it, it does fine. I also replaced the fuel filter first thing.

At this point, only thing I can think of that could be the problem is the fuel pump, because as far as I understand just about anything else would throw a engine code, which right now there are none. Any further suggestions or tips? TIA

[BillBoost37]

Do you have any modifications? Sounds like KR is pulling all your timing.

[rkm]

Yes, it has mods. I acquired this from a deceased family member and I am searching for all the paper work pertaining to it. What I do know, it has had a smaller SC pulley installed. It had a new computer installed to compensate for the smaller pulley. It has a K&N air filter, with what I call an airbox. Basically it has a clear plexiglass shield around the air filter. Performance exhaust. Performance plug wires. I believe that is it.

[BillBoost37]

Take pictures and post them. We can tell you what it is if we see it.

Likely..the pulley is too small and that's causing the timing to get yanked out from under you.

[rkm]

I am not so sure it is the pulley here. It has worked for the last 10 or so years. This started happening within the last 4 months.

[mguzzo]

If it was the fuel pump resistor you'd probably be having issues at startup.
Dirty MAF? unplug the MAF and see if it does it again.
Clogged cat? maybe lots of KR under load because the engine can't breathe.

Flashing MIL? I hope Chip didn't pay you a visit

[rkm]

No check engine light. Which is why I am leaning towards the pump. MAF would throw a code I believe, cat as well?

[rkm]

Book says fuel pressure should be 48-55 psi

Key on engine off = 42
Engine running = 42

That's that then.

[J57ltr]

Could be the pressure regulator. Did you try it by turning on the key a few times and then checking or just once? You should also check with the FPR disconnected with the engine running.

Jeff

[rkm]

I was curious about the regulator. According to the manual the pressure is supposed to drop 3-10 psi when the engine is running. I checked it 3 times. Running or off it stayed at 42 with a slight fall-off, maybe leaked to 41 to 40.5, with engine off. I was going to check the regulator but did not have a vacuum pump handy.

Would the FPR cause the fuel pump to fail the pressure test. As far as I went with the regulator was to pull the vacuum hose off to see if it was dry, it was.

[J57ltr]

It can since it is what keeps the pressure built up in the system. Think of the pressure regulator as your thumb on the end of a garden hose. It's either a worn out pump or a worn out FPR.

Jeff

[rkm]

It can since it is what keeps the pressure built up in the system. Think of the pressure regulator as your thumb on the end of a garden hose. It's either a worn out pump or a worn out FPR.

Jeff

Right, I get that. But I was a little unsure if the schrader valve is before or after the regulator. If before, I feel that the fpr would have no bearing on the pressure at that point. But if it is after I can see where a bad regulator would have an affect.

[BillBoost37]

Book says fuel pressure should be 48-55 psi

Key on engine off = 42
Engine running = 42

That's that then.

Not sure what that's that then is... because they all pretty much sit right at 40-43 and it appears totally normal. If you want to honestly know if the pump is bad, you need to see what happens with fuel usage aka driving and hitting the throttle. I watched one that wasn't a question of a pump at all go down to 7psi when the owner stomped it. As mentioned..it showed it at idle as well.

While you say it's been fine for 10 years... was it actually? Most of the stuff on ZZP's site that is documented says put on a 3.4 pulley and one of our pcm's.. no worries. What many know now is ..they still had tons of KR and heat/humidity play a big part in both. Now..a 3.4 pulley is never recommended unless you have other supporting mods.

I'm not trying to convince you either way, keep poking at it and find the issue... I just tend to be right on my gut instinct while diagnosing over the internet.

[rkm]

Not sure what that's that then is... because they all pretty much sit right at 40-43 and it appears totally normal. If you want to honestly know if the pump is bad, you need to see what happens with fuel usage aka driving and hitting the throttle. I watched one that wasn't a question of a pump at all go down to 7psi when the owner stomped it. As mentioned..it showed it at idle as well.

While you say it's been fine for 10 years... was it actually? Most of the stuff on ZZP's site that is documented says put on a 3.4 pulley and one of our pcm's.. no worries. What many know now is ..they still had tons of KR and heat/humidity play a big part in both. Now..a 3.4 pulley is never recommended unless you have other supporting mods.

I'm not trying to convince you either way, keep poking at it and find the issue... I just tend to be right on my gut instinct while diagnosing over the internet.

Yes, it was working fine. When you hit the gas the car would get up and go and for those ten years the car had no problem going over 3000 rpm now it falls flat. I am positive the mods were all done correctly, the previous owner would have had it no other way. I am not trying to argue with you but things were working fine. However, as you mentioned I will verify the pulley, the components and your comments once I find the paperwork.

PS: However, over the years a few axles have been broken.

[BillBoost37]

That means it does have an aftermarket pcm and most of torque management (programming to stop you from abusing the transmission/axles too badly) is removed.

[chrsmi1]

Yes, it was working fine. When you hit the gas the car would get up and go and for those ten years the car had no problem going over 3000 rpm now it falls flat. I am positive the mods were all done correctly, the previous owner would have had it no other way. I am not trying to argue with you but things were working fine. However, as you mentioned I will verify the pulley, the components and your comments once I find the paperwork.

PS: However, over the years a few axles have been broken.

Just fyi, few people on this site question bill. He's the man here.

As far as you believing it's your fuel pump, I tend to agree that on a car that old, 42psi is about right. I doubt that's your issue.

But it's only a 2 hour job. Spend the 100$ or so, change it out and let us know so we can help others like you in the future, if in fact it turns out to be the pump.

[BillBoost37]

Whoa... question everything is my motto. I just happen to usually be right, so it's faster...often to do what I suggest and hope I'm right.

As for the pump, since when does it take 2 hours? Oh.. comp g.. you gotta drop tank. Still shouldn't take that long

[Scottydoggs]

ill add to the party, when was the last known tune up? get a set of al 104 copper core plugs gap em to 0.50.

if it has copper plugs already they only last 12 to 15,000 miles, for the less then 20 bucks they cost its worth it change em.

i see no headers listed either? got em or no? pulley drops like headers. no headers and they dont like it much. just because it ran fine for 10 years dont mean it was right the whole time. not trying to knock the last owner one bit. but some just take ZZP's word for stuff and blow engines up.

i just did a fuel pump, took 30 minutes or so. not hard at all.

[rkm]

Ok, full stop.

I am going to go dig out all of the paperwork regarding the mods before doing anything else, since that seems to be in question here.

Lets try starting over. It does not seem so cut and dry this time. Never had so much problem diagnosing a fuel pump before.

I will be back with the information if I can find it.

[rkm]

ill add to the party, when was the last known tune up? get a set of al 104 copper core plugs gap em to 0.50.

if it has copper plugs already they only last 12 to 15,000 miles, for the less then 20 bucks they cost its worth it change em.

i see no headers listed either? got em or no? pulley drops like headers. no headers and they dont like it much. just because it ran fine for 10 years dont mean it was right the whole time. not trying to knock the last owner one bit. but some just take ZZP's word for stuff and blow engines up.

i just did a fuel pump, took 30 minutes or so. not hard at all.

It currently has MSD 409s wires on it now.