I have a '02 HO with the 6spd and the guy I bought it from said it was all stock other than intake, smarty and 4" exhaust. He said it had a newer stock lift pump due to a bad batch of fuel but after getting a fuel pressure gauge on it I don't believe it.

The sender is mounted at the bottom of the fuel filter and shows 18-19 at idle, 12-13 under normal cruise and never less than 8-9psi under full throttle pulls. From what I've read there is no way a stock lift pump should be able to do this. The pump is definitely in the stock location on the block, did I just get a freak of nature?

 

You probably have an aftermarket "stock" LP, like an airdog or fass, both of which make a lookalike pump to the carter stock LP as far as location, outlet, inlet and plug goes.

 

Are they as good or should I go ahead and install the Airdog I have? I'm leaning toward the airdog because it's already purchased (bought before I got the gauges on) and because of better filtration than the stock stuff.

 

I think that you should get on the Airdog as soon as you possibly can and then send me the one that you are taking off! I'll gladly pay the postage USPS from your house to mine. That'd be sweet! I'd love to have those kind of PSI numbers!

Cheers!

Mike

 

I get a kick every time people dump on the Carter lift pumps about being junk. There is nothing wrong with them if you use them the way they were intended, to push fuel not suck fuel.

Sure there have been dud pumps made, I have had a couple but I know of a whole lot of junk FASS and AirDog's also.

19 psi, might be possible. My 7 yr old, 120,000 plus mile Carter "lift" pump makes 15/16 psi idling and won't go below 11 psi at WOT. BUT, I have mine mounted on the frame below the drivers seat pushing fuel through 1/2 lines.

And this old pump has had everything thrown at it imaginable during those years down on the frame, mud, snow, gravel, manure, water, rocks, roadkill, whatever I have drive through or over has been chucked at that pump and it still keeps going.

To be totally honest, there is a replacement sitting under the seat for whenever it's needed but it doesn't look like anytime soon. And you can find a Carter pump just about anywhere. It might not be the exact model needed but you can swap parts and make it work fitting wise.

Try finding a replacement part for a FASS or AirDog when your broke down in the middle of nowhere!

In case your wondering.............still working!



Jeff

 

I "upgraded" because the crap factory intank pump was dropping to 5 psi at idle and 0 at acceleration.

I went back and forth and considered everyone's opinion re: Carter, Walbro, FASS, AirDog, etc. etc and finally pulled the trigger on a 95 GPH FASS and mounted it next to the tank and ran new lines. It gives 16 at idle and no less than 10 when I get on it.

Sounds like you are alright with the factory pump you have, just pulling more fuel than pushing, which goes against modern thinking fluid mechanics...

 

good place to mount. I agree pumps should push not pull.

 

Back before I fully understood what keeps the VP happy.....I had a stock lift pump put out 15-16 psi at idle. Seemed odd to me to have one of those fuel pumps seem so capable. After changing fuel pressure gauges from electric to mechanical, and testing the new gauge for accuracy, I found that the old electric gauge was at least a couple psi off. So.....it seems that the OEM lift pump was putting out more like 13-14 psi at most. Thats more like it. Yes gauges are very important but I find it odd to see how many people think their gauges are "perfect" and spot on. Especially those people with GS gauges. So.....if you have an OEM lift pump, dont believe your gauge.

 

Twin mechanical gauges, one under the hood and one in the cab each reading from a different point, what they say is what it makes, sorry to burst your bubble.

Jeff

 

Even if the gauge is a couple psi off it's still making 16 at idle and 6psi at wide open. It may not be the best pressure but it's pretty **** good for a stocker and I'm not worried about a lack of fuel to the injection pump.

 

No problem Jeff.....but you're not the one I was referring too. I was responding to RWDCelicadude, who is under the impression that his OEM lift pump "may" be supplying out of ordinary fuel pressure.

My point was not to assume. I'm not sure what gauge manufacture you have but it could be a couple psi off or far more. With OEM lift pumps rarely putting out 16 psi while located on the block, the odds are that your gauge is more on the inaccurate side than not. The easiest way to solve this dilemma is to have someone test your pressure at the schrader valve test ports.

Also.....fuel pressure is only one variable in VP reliability. The other is fuel volume, which is something the OEM lift pumps are limited to. Then to add insult to injury, the OEM fuel lines and banjo fittings add even more restrictions and further reduce fuel flow. Remember, pressure and volume are not the same and you can have one without the other. For the VP to offer the "best" reliability it should have an abundant supply of fuel volume at pressures over the preset psi of the overflow valve.

 

I'll toss a mechanical gauge on it in the next couple days just to make sure. It may also have something to do with it being before the filter so I'm reading it at about it's highest point. I may also move the sender to the banjo on the injection pump, that will be about the most accurate place and let me know pressure past any obstructions.

You're right, you can have pressure without volume, but only if you have a restriction downstream of your sender. Without a restriction then pressure means adequate volume. It all depends on where you measure your pressure, if you measure it just before the item you're concerned about (the VP44) and have pressure then you have volume. End of story.

 

Not trying to argue but this isnt the case. First off, do NOT pull directly from the VP otherwise you'll put your fuel pressure gauge sender in harms way. Even with a snubber, thats just to close to the hydrodynamic fluid pulses coming from the high pressure side of the VP. With all that hammering, it would be no time before your gauge started acting strange.....or more strange than it may just be now.

Then in regards to volume at the VP..... Your volume is only in relation to the size of the fuel lines and fittings. You can crank up the pressure all you want but if you're still pumping through small lines and restrictive fittings, you'll only reach the maximum flow for that diameter line. Think of your garden hose as a good analogy.

And yes, you need to be reading post the fuel filter. Not because you could be reading higher pressures but because you'll never know if the fuel filter ever plugs up. In essence, you never really know what the VP is getting.

 

Point taken about sender life if mounted to the VP, but it is still the most accurate place to measure as it takes the size of the lines and fittings out of the equation. If the lines are too small to flow the volume needed then you'll lose pressure at the pump, which is kind of the whole point of the sender.

What you're saying is that there is no perfect place to measure with a stock setup. You need larger lines/fittings between the sender and the pump to accurately measure pressure from a safe location?

 

No, what I'm saying is that it doesn't matter where you read fuel pressure from as long as its post the fuel filter, since pre-filter will always skew the true reading. But the closer to the VP your gauge or sender is, the more subject to fluid hammering it becomes. As I mentioned, pressure and volume are NOT the same, therefor this means that reading from the VP is NOT the most accurate as any location "post" filter will provide the same exact psi reading as you'd get at the VP.

Being that pressure is only one issue, having the volume is ONLY achieved by increasing flow. Having pressure "and" volume is the key. The only time pressure will be reduced at the VP is when volume is limited. Increasing fuel line diameter and better flowing fittings will allow for more volume and flow, and keep the pressure up.

The best place to read fuel pressure while using the OEM fuel filter housing is from the post fitting side of that housing. Then adding an additional line from that location running up to the sender or isolator keeps the VP as far from those components as respectfully possible. Then running a short length of wires or isolator line through the fire wall and to the gauge.