Need a little advice here. I went on a 600 mile trip for the holidays last week. 20 miles into the 600 mile trip, my Autometer Phantom ll guage fell from 10psi to 0. Truck ran great all throughout the whole trip. Not really sure if the lift pump went out or not because I had all the normal power. Truck felt fine. Had Smarty on Level 3 and hammered on her a few times up a couple of 5% grades and she ran right up them. Not sure if the CP3 can suck that much fuel, so I'm asking??? Did the sending unit just take a poop, or can the CP3 really suck that much fuel? Is it pretty common for the Autometer fuel sending unit to crap out? Any advice would be great. Thanks


Jason

 

I believe the CP3 can suck the fuel!

Drain your fuel bowl and bump the starter to see how fast the bowl fills.

 

the cp3 can pull fuel but not as much as the GM pumps. they are designed to pull fuel since the trucks don't have lift pumps. I would think that your sending unit took a dump if you were able to hammer it on 5% grades with smarty on 3. Like said above, drain the bowl and pull the cap, have the wife cycle the key and watch for fuel or pull the sender and make sure it is not plugged with gunk and cycle the key to flush the line

 

Thanks guys. Both good ideas I for some reason didn't think of.

 

Tap a cheap gauge on the CP-3 or filter fitting to validate where the problem is. I have had that happen twice on my ISSPRO with the isolator and it has been low fluid every time.

Its not unusual for the pump to perform quite well in no load running and not flow enough under demand to keep up. The presure is the only way to know for sure and is easy to test.

 

Really? You know what we need is a bowl fill time test. Isn't that how a tech checks? Like 1 gallon per minute or something? So maybe the bowl should fill in 10 seconds or the pump is weak.

Let's calculate how much fuel you use when WOT at 60 mph...

Lets say you get 6mpg at WOT going 60mph. That's a mile per minute, six miles to a gallon, so every minute you burn 1/6 of a gallon of fuel. 1/6 of a gallon is about 21 ounces.

So in a minute you will burn through 21 ounces of fuel at WOT. What do you think the volume of the fuel canister is? Lets say it's at least 21 ounces. So if the lift pump fills the fuel canister in less than one minute, you have excess fuel being supplied to the CP3.

These are not measured numbers of course. I bet the fuel filter canister is a quart, so if it fills half way in a minute you're probably good. I bet what you'll find though is a little trickle or nothing, or it fills the canister in 5 seconds.

Hopefully someone can fill in some details, but this is the thinking I'd use to see if the in tank pump is good.

 

The flow test is notoriously inaccurate. It was\is nothing but a warranty denial tool that postpones the inevitable dead truck.

If the pump has failed competely or is only running at partial capacity it will be noticeable but thats the exception to the rule.

The flow test is a single point snapshot in an open system, no other way to perform it reliably. It does not take into account pressure build up over a time period.

Its not unusual for an electric fuel pump to pass flow test at no load and fail test under pressure and time.

Consistent pressure measured at the CP3 inlet is the only positive way to gauge LP health.

 

I ran an 11.73 (multiple times), with no lift pump. Not on purpose of course...

Paul

 

Well my sending unit is right between the GDP MK-2 2 Micron and the CP3. Is there any chance that the filter could be plugged enough to show zero PSI? The filter has been on there for about 4 months now and the gauge went to zero right after I filled up from 4 gallons of fuel in tank to a full 35 gallons. I'll put a guage in the "T" and see what it reads. The wife took the truck to work so I can't do much for now. If the temperary gauge reads zero as well, I'll connect it to the filter housing and go from there.


Jason

 

I had the sender fail many times on my fuel pressure gauge when I was running Autometer's. It acted just as you described, and it was just a bad sender.

 

Well, used two different Fuel "test" gauges today and both read fuel pressure. I called Autometer and ask about a replacement and told them I had the there Gauge and Sending Unit for a little over a year. Has less than
8k miles on it. They told me this is pretty common with these paticular
units. That really makes a guy want to buy another from them. Is it possible to buy another sending unit from Isspro or someone else that will actually LAST?? Thanks

Jason

 

My Commander sending unit has been on almost three years and still works fine....

 

Thanks, I'll check it out.


Jason

 

Hey, you're one of the guys with a 'normal' lope in the idle... Let us know if this fixes the lope too.... I know it's a long shot....

 

Not sure if your joking or not here. I do have the lope at "high idle," but..... not sure where your going with this. And yes, that lope is normal. Some that say theirs do not lope, but most times just didn't notice it until it was pointed out to them, and I'm sure there are some that actually don't lope. I helped a buddy last year move all their Dodge inventory from thier dealer lot to a lot where they could advertice for a sale. It was around 0 degrees. We started all the vehicals (cars, trucks, vans, etc..) and went back in for about 15 min to let the vehicals and ourselfs warm up. The Cummins ranged from brand new to old. When we came back out, all the Diesel rams that COULD enter high idle on thier own had the lope. Some a little more noticable than others. New and older(ish) models.

What I do think is wierd is that if I manually set my high idel, it does not lope. If I leave the truck be and it enters high idel on its own, then it lopes. Kinda wierd