KATOOM

Mike, hate to throw this in there since you just found out your problem but 9 psi is just to low to be comfortable with. Its up to you and I'm sure you're just happy to have solved your issue to worry about fuel pressure.

Mike Perez

Katoom,
9 PSI was at load @2600 RPM the rest of the time it hovered around 12-14 PSi. Are you saying it shouldn't drop at all? let me know your thoughts,

Mike

KATOOM

I appreciate you asking my opinion Mike but I'm not sure you want to open this can of worms because I'm one of the rogue members who have come to realize over years of reading and watching others experiences that the VP is totally reliant on fuel to keep it cool and reliable. Yes the fuel is also there to lubricate but throughout the generations of VP changes, the internals are now strong enough to withstand ULSD but still, the VP needs a minimum of 10 psi at WOT so as not to cause the diaphragm to have to pull its own fuel supply. Remember, these are positive pressure injection pumps. They need a constant positive pressure on the inlet all the time. So the only thing left to worry about is the FPCU (computer) on top of the VP. Unfortunately (thank the environmentalists) the lead free solder used in the computer is notorious for deteriorating over time due to the high heat its subjected to while being bolted next to a 200* engine. When the solder deteriorates it causes intermittent electronic connections and eventual failure. So when the engine is running the only thing that can keep the computers temps down is a constant flow of fuel. Thats where fuel pressure comes in. The VP also has whats call a overflow valve that lets fuel pass through the VP freely after 14-16 psi. If you keep your fuel pressure above that setting then the fuel is always cooling the computer. Now this was the short version of years of combined research and how hot your computer gets also depends on how hot it gets where you live, how you drive your truck, and how aggressive any box you have is. For this reason, I run 19 psi idle and 16 psi WOT with a Raptor 100.
See, thats what I meant by can of worms.

Mike Perez

I see... I had asked the FASS rep if I added the extra heavier spring to increase pressure; he stated that's too much pressure is also bad... He said to pull the original spring out and stretch it a 1/4 inch than put it back in.

How much PSI is too much.


thanks,

Mike

KATOOM

Well not saying that the FASS rep is wrong but.....well.....they sell universal fuel pumps, not VP's. In saying that, as I mentioned before the words "years of research".....there is loads of theories out there which have somehow been converted to fact which still remain today, even though over the years the VP's continued to fail. So what I'm saying is that I'd expect most people to use the words to much pressure is bad because thats simply been the mind set for a long time even though there's nothing to prove it. How much pressure are we talking about and better yet to be asked is how do we know what to much pressure is??? Well I can answer that. WE DONT. There's been countless situations where low fuel pressure has caused the VP to fail but NOT ONE situation where high fuel pressure has caused the same. How many threads have you read where someone said that they were running 20 psi on their "new" VP and it failed? I cant think of any. But I'm sure you've read a few threads where guys have said that they just installed a FASS/Airdog on their old factory VP and it failed. Well thats more than likely not the new fuel pumps fault but because there was a pre-existing conditions which the previous OEM fuel pump created and the new aftermarket fuel pump got blamed for.
They way I look at it is as long as your fuel pressure is higher than the overflow valves 14-16 psi, then your fuel is cooling the VP, but anything over say around 20 psi is a waste of time. Because.....there's only so much fuel volume the return lines can flow and there's no point in overly recirculating the fuel in the tank.

Mike Perez

That sounds reasonable to me, I think I will put the heavier spring in and see what pressure I get out of the fass lift-pump.

It makes sense that if you were at idle traveling down a long grade and the fuel pressure is not high enough to open the by-pass, fuel would not circulate and cool the VP.

Thanks for the info Katoom,


Mike

betsycam

We are having the same kind of problems with our pump, with the exception that the truck doesn't die.

History is in another post, but to summarize, this Carter pump started dropping pressure periodically, then coming back up. I replaced it with a DDRP, which one day seemed to suddenly die after one month of use! Pressure went to zero! So, swapped the old fluctuating pump back in, and it was jumping around from 15 to 5 to 10 to 2, and last week stayed at 2. I'm hearing a sound now up in the engine compartment, worried it's the inj. pump suffering. Truck is parked. Called KLM Performance about getting the DDRP situation resolved, getting a replacement, but after reading the above post, I'm thinking it's electrical, not the pumps!

I had noticed that the connector wires looked loose when I was installing the pumps. My hubby and I did a crude test. I thought the Carter was dead because when I bumped the ignition I got no action from the pump. I put a voltage tester (lamp) at the connector and when my husband bumped the ignition, the lamp lit up and the pump ran for a few seconds. I then plugged in the DDRP and had him bump it again, and got the same, even though when I tested the DDRP this way before I got nothing. So, I suspect it is the connection.

So, where does one find the right female end quickly?!! We need the truck this weekend!

KATOOM

I know this is late but I remember looking for those connectors back when I considered relocating the lift pump but never could find them. Maybe someone knows.

betsycam

Thanks to Bent Valves, the connector can be found here:

Here is a link to Jegs:

http://www.jegs.com/i/MSD/121/8183/10002/-1

Here is a link to Summit

http://www.summitracing.com/parts/MSD-8183/

These are both male and female sides. You will need to cut off the old connector and crimp on the new terminals.

This is a "Deutsch connector" and apparently MSD is the only one who makes them it would seem!

Yesterday I drove 30 mile RT to get the wiring from Dodge, which included the relay and the whole wiring from connector to relay to ground, etc. $55. All I wanted was the socket/female end, so I started another thread and Bent Valves offered up those links. Ah hah, I'll see if I can find it locally, I think to myself. Go to MSD's website and look for local dealers. Everyone I called didn't have it but could get it by Monday from the distributor. Well, there was just one place that actually had it, but that meant a drive across the San Mateo Bridge during rush hour, with a bridge toll on the way back. Pretty cool little connector: you just wire up a new harness rather than splicing wires.

HOWEVER, when I went to do this job, just when I was about to snip off the offending connector, I detected a bit of sheen coming through the insulation of the ground wire! There was a breach where the bracket that holds the cable on at the pump mount had rubbed through! All this hell I've been through when all it required was a bit of electrical tape!!!!

So, for anyone who is experiencing pressure drops from their pump, check the wiring for rubs where the cable is held by the bracket.

Meanwhile, my I suspect my inj. pump was suffering from the low pressure and my check engine light would come on briefly with the chime ringing twice, then off, then on, etc. When I got my pump going again and idled the engine, the chime/CEL kept doing that but thankfully stopped after awhile. Was this the chime of doom for my inj. pump?! Is it possible to just come up short of killing it only to have it be okay once the cooling/lubrication are back to normal? Yikes!

KATOOM

There will be no way to tell if your VP was harmed unless a code was thrown which indicated so. I suspect that the reason your light was coming on and off was because of the exposed wire. The OBD2 is supposed to detect a potential problem and warn of it but if the issue goes away after so many start/runs then the code will clear itself.

riwamiya

I too have been trying to figure out why my lift pump will start and run at 15 psi and than sometime drop to 7 psi. When the pressure drops, if I press hard on the gas pedal, the pressure will jump back up to 15 psi. The drop to 7 psi is intermittent. Sometimes the pressure will stay at 15 psi with normal cruise on the highway at about 12-13 psi and sometimes it drops to 7 psi until I step on it. In the above statement, what triggers the different modes of the lift pump. Is it something in the pump or the ECM. Does this sound like a wiring problem or is this lift pump going out.

KATOOM

The ECM controls the amount of amperage the lift pump receives and normal current flow is 12 amps while the engine is running. There is also two modes for the lift pump. 1) is 100% duty cycle while the engine is running and 2) is 25% duty cycle while the engine is cranking. If the LP is not getting the full 12 amps then for some reason the ECM has a problem or maybe its bad connections or maybe exposed wiring.