sluggo42

Well, after an endless search for the cure to my fluctuating fuel pressure, a fellow poster stated that I had just described the "classic" Carter failure

""You are describing one of the classic failure mechanisms of the Carter lift pump. Inside the Carter pump is a spring-loaded spill-back valve that will limit the maximum pressure to about 15 PSI. This spill-back valve is needed in the lift pump to prevent over pressure to the VP44. The valve is a small ball bearing that will close off a passage in the pump when the VP44 is using more fuel, such as when the engine is running at higher RPMs. or under a load,
but opens and recirculates fuel in the lift pump when the VP44 is not swallowing more fuel.

The problem with this valve is after many miles the spring can weaken from the constant pounding it receives from the VP44. This pounding also wears out the valve seat and causes the ball bearing to not fully close off the passage way, dropping pressure. This pounding is also responsible for many fuel gauge and pressure sender early deaths.

So I will guess that if you change out your lift pump or verify that your fuel pressure gauge is working correctly you will solve the problem.

Good luck.""

Another posted that he had numerous Carter failures right out of the box after I replied that it was a new Carter.

I thought that since my problems were exactly the same from the old pump to the new pump that it was something else...

My point is that I don't want to spend $300 on a Raptor and then see it do the same thing!

So with that thought, I'm wondering if a few of you could describe how YOUR Carter pump failed. Did it do the fluctuating pressure issue that I have, where is randomely falls to 7-9 psi from the 14-16 normal, and jumps back and forth? And when if falls, could you restore the pressure with a quick rev of the engine?
What did your Carter do to let you know it had failed??? Did your pressure fall and NEVER come back? Did it slowly fall as the weeks went by? Did it just quit period?

How did your Carter die???

swordfish

sluggo,
Just out of curiosity, what is your voltage to the pump when it is acting normal and when it drops? Just wondering if maybe you are getting a voltage drop and when you rev the engine you get the alt working harder and giving you the required voltage. Just a thought.

swordfish

sluggo42

Or,

Could this be a symptom of a failing VP$$(44) ?

Random thoughts:
1) Replace the extension harness - maybe the connection inside the plug is shakey - I tested voltage about 6" behind the actual connector
2) Replace the harness with a relay wired direct to 12v - in case the ECM is sending weak voltage - even though I metered 13+ volts
3) Buy another Carter for $119 from Vulcan (is there a 1 year warrenty?)
4) Buy the Airdog FRRP for $299 - and pray there isn't an outside of the pump problem that will cause the Airdog to falter exactly like the Carter
5) Sell the truck and buy a Duramax
6) Ignore the problem and hope it goes away by itself...

sluggo42

Hi Sword,
When I tested the voltage, I wanted to see it when the pressure dropped. So, I spliced my test leads in about 6" above the pump. The voltage never varied from 13+ volts as the pressure jumped back and forth. One of my thoughts was to replace the extension harness in case I have a failing connection inside the plug that goes into the pump. The pressure is ALWAYS full when I start the truck, so testing the leads in the connector would not be conclusive (IMHO), but I haven't ruled out that the actual plug could be the problem.

bent valves

CORRECTIVE ACTION SUMMARY

Below is a brief history of Lift Pump Part Number and associated design/product changes:

3943467 3942802 Initial ISB Production (1998 time frame for Dodge)

3944818 3942802 Added "saw cut" to the motor casing to better detect leaks during production

3944508 Stainless Steel Valve Seat/Bronze Bushing for the Internal Pressure Regulator
3945812 3945813 Some lift pumps were having a problem with the internal wiring shorting to the magnet sleeve. The wiring insulation was inadvertently being
stripped from the wiring during assembly and during pump operation the wires are shorting to the magnet sleeve. Federal Mogul has changed the angularity of the wire lugs in the bottom of the pump so the wires will enter behind the magnet sleeve in a more direct manner, thereby reducing the chances of stripping the insulation. They also changed their end of the line testing to look for this shorting problem during pump operation. Federal Mogul is also adding a radius to the top and the bottom of the magnet sleeve where the wires travel behind the sleeve.

3948431 3948432 Corrosion of the connection of the pigtail at the bottom of the pump was being seen. This was found to be to the result of road salt acting as an electrolyte. The vendor changed the electrical eye terminal from brass to bronze. No corrosion is evident during simulation and salt fog tests with the bronze terminal. The mechanical properties of the bronze meet or exceed that of the brass and the vendor did conduct vibration test for further verification. To further aid in corrosion resistance, grease was added to each terminal at the Engine plant during assembly.

3946151 3948070 The lift pump was updated with an integral electrical connector. The integrated connector eliminates the need for a pigtail type harness on the pump
and will eliminate the exposure of the pigtail to environmental elements. Also updated was EMI reduction for the pump due to an added capacitor to the internal circuit board and a Ferrite bead added to the connector.

3948431 (12 Volt) and 3948432 (24 Volt) where still kept available for service because the wiring harness on older engines where not long enough to plug into the integral adapter.

3938367 3938368 It was found the bearing material used for the MFR. of bearings was not consistently uniform, leading to variance in the pump performance. This leads to change the bearing material to sintered iron from bronze. There was also a change in armature shaft geometry to a straight one to reduce the 100% inspection of the shafts. These pumps have the integral connector.

For service, 3948431 (12 Volt) was superseded to 3938435 (12 Volt) and 3948434 (24 Volt) was superseded to 3938436 (24 Volt). These pumps still maintain the pigtail wiring harness.

3990082 This is a service kit supersedes 3948431(12 Volt). It includes 3938367 (12 Volt) and a jumper harness (4025182) so that it can be used on older engines with the shorter lift pump connection wiring harness. 3938436 (24 Volt) was superseded to 3938368 (24 Volt), but a kit was not created to include the jumper harness, 4025182 must be ordered separately.

3990105 3990106 The lift pumps have been updated to include hardened valve seat to reduce valve wear. The pump also reverts to a prior use RFI circuit board due to components being detached and jamming the pump.

Service kit 3990082 was updated to include 3990105 (12 Volt). 3938368 (24 Volt) was superseded to 3990106 (24 Volt), but a kit was not created to included the jumper harness, 4025182 must be ordered separately.


III. IMPLEMENTATION SUMMARY
The supplier started building pumps with these corrective actions in the first week of May 2001. The latest lift pumps, part number 3990105 and 3990106 went into production

This info is dated and the 3990105 & 6 is no longer the current fix. The latest pump (part number unknown) will allow fuel to be pulled through by the VP44 when the lift pump fails.

From the above summary of changes, it can be seen that the valve seat has remained a problem and is subjected to wear (see red highlight). One good test of this spill-back valve is to "Blip" the accelerator. This will cause the ball to re-seat in the valve and often can make a better seal, at least temporally.

It is often thought the VP44 will cause the lift pump pressure to fall off if its spill-back valve sticks open or gets weak. It is in no way responsible for lift pump pressure but the mythology that it does has gone on for years. I'll stay out of that fight.

sluggo42

This last line is interesting to say the least!:

"""It is often thought the VP44 will cause the lift pump pressure to fall off if its spill-back valve sticks open or gets weak. It is in no way responsible for lift pump pressure but the mythology that it does has gone on for years. I'll stay out of that fight..."""

It makes SO MUCH SENSE!
My problem is that my replacement Carter has sat under my seat for 5 years while my original Carter ran like a dream for 5 years, so it appears to be bad right out of the box, but the warrenty period has come and gone. (If there ever was one)
So after seeing numerous other people posting that they had bad pumps right out of the gate, it doesn't seem impossible.

Well, I still want to hear from other Carter victims about how their Carter died.

I think this topic is important in that a final sticky could be issued that details all of the telltale signs of a dying Carter. This to me is one of the crucial points of owning a secong-gen truck, and I think that a comprehensive sticky detailing the classic Carter/Campaign pump problems (and history - Thanks Dave!!), should be available without having to exhaust the search engine for scattered random cases. Included in the sticky could be some different thoughts about different types of fuel pressure gauges, and just how deeply important they are. And finally, a comprehensive list of possible replacement pumps. From the full blown FASS/AIRDOG types, to the new league of factory replacement pumps, as well a stock replacements like the Carter/Campaign/Airfix 7153

This swath of information really is fascinating Dave, and I can't tell you how much this is swaying my previous love for my good old Carter. Finally, a really plausible concept of what is wrong with my pumps. It would be great to get 4 or five other people to see this and agree that this is what happened to them too. That would pretty well cement my decision to move on to another pump.

At this point, I would be leaning towards the Airdog FRRP, which is basically a Raptor (Rapster hehe) that would mount onto my bracket from my relocation kit, and I believe the same electrical connection could be used. Basically, a 5-minute installation...

Again thanks Dave, and to any other poster who would be so kind as to weigh in with their thoughts and experiences...

Doug

sluggo42

Is this current pump really "failing" ?

As soon as the fuel demand goes up with any load, the pressure immediately jumps back up to the 14-16 psi.

Then, when at idle or "coasting" along it falls back to 8-10 psi.

pressure never goes below 8 psi. So, is that considered to be a "failed" pump?

Would the factory accept it's return if it makes 14-16 psi under load?

***sigh***

sluggo42

I've ordered the Raptor FRRP...

I have better things to do than stressing about a crappy fuel pump.

nkennedy

That's backwards of how they usually work. Mine is 14 at idle, and 10 at WOT. When they get the shaky pressure jumping from high to low, they are on the verge of going out.