danalex

Added some new 'maxtow' gauges. I know some folks don't like 'em, but I don't think that's my issue...

Fuel pressure:
As long as I keep it under 65MPH, the fuel pressure gauge reads reads 14-15 psi.
As soon as I top 65mph, the fuel gauge begins to act wildly...flopping from as high as 22psi to as low as 6-7 psi.

RAPTOR 150 is set to about 13-14 psi @ idle... (is that too high?)

BACKGROUND
The truck has died twice in the last 4 months.
---First time diagnosed as a bad fuel pump (Raptor 150). I believe the diagnosis was true; this is my 3rd Raptor in 6yrs; lifetime warrantee, so replaced it.... Computer showed no codes, and there was zero psi at the VP44. ((VP has 30K miles on it))...
---Second time, I was @ 70mph on the highway and watching the maxtow gauge wildly flopping...until it dropped to 8, 7, 5, 0 psi and --truck died. Diagnosed this time as AIR in the line. My mech bled the lines and truck comes to life!

((both previous times, there were NO CODES)).
new fuel filter. new fuel in tank.

Question: What is happening at +65MPH?? Is the Raptor going bad (again)? Is there air trapped in the line somewhere--how's the air getting in (from where)? Is there something inside the fuel tank that's going bad? a pump? line? filter?

BigIron70

Original fuel pickup in tank being used with the Raptor? Using a draw straw? Possible pickup in the fuel tank plugged.

danalex

When I installed the Raptor, I didn't replace anything in the tank...should I? bigline hose...that was it.

BigIron70

Most likely the pickup in tank is plugged, pull the module out and clean the pickup screen.

danalex

ok...uh... So I'm not the brightest with a wrench... So this is what you're saying (my language).
1) Lower the fuel tank.
2) Unscrew the top-cap on top of the tank. (never done this)..
3) on the inside, there's a tube of some kind with a filter(?) or? That tube is plugged up with something (dirt...gunk...?)
4) Stick something in it to dislodge the gunk...
5) Reassemble it backwards.

Yes?

cougar

Don't feel bad, your in good company here. We all make dumb mistakes or assumptions and most of them are posted here so hopefully we can learn from each others mistakes. Me included .
Before diving into any project, especially if you are modifying is to know what you are working with and/or against. The 24 valve motors have had some factory alteration you have to take into consideration when doing said modification. Like, does your truck have the factory installed in tank lift pump? If it does, that will have to come out or at least bypassed. Also, with performance mods come the requirement to feed them. Stock fuel line are fine for stock trucks, but not when you start upping the power. When I recently did my lift pump, I reluctantly dropped the fuel tank as part of the process. It was a darn good thing I did. There was all kinds of garbage in there. Just do the research ahead of time and ask questions, that way you won't have to do it twice like I'll need to do.

BigIron70

I used shop air and small brush like a old tooth brush, use clean diesel fuel or kerosene, mineral spirits will work. Use shop air to blow off as much of the crud as you can then use a soft brush. You don't have to take apart to clean but if you feel adventurous you can, I never take apart. Some people unbolt the bed and lift up on the left side to gain access to pump. Clean the top of the module really good first so no dirt or mud falls into the tank ***very important***Mark the module so you put it back in the same position, be very careful taking out so you don't damage the sending unit and float. It has to be tilted to come out have a screw driver handy in case you need to pry the bucket a little to clear the tank opening. The wiring connector plug has a red tab that needs to be push over so release lock will move to allow connector to come off. Spray a little WD40 on it and blow off any dirt helps the release to move freely. The lines have a plastic retainer that needs to be squeezed to release fuel lines. Sounds difficult but all and all a pretty easy job.

danalex

Thanks. Is there a way to determine if I do / don't have an intank lift pump without disassembling it? I've had the RAPTOR 150 after-market pump on it for a few years...NOW not sure if I've got BOTH going at the same time ! When I first connected the RAPTOR several yrs ago, I remember disconnecting a fuel line from on top of the tank (blue clip I think); but I didn't do anything else to the top of the tank. IF I DO have an intank pump, I am guessing THAT pump is what gets the fuel from the tank and into the fuel line. and...if I disconnect THAT one, uh, how would the RAPTOR be able to suck the fuel into the line?

I think I can do this...but you're right...I need a bit more knowledge/information. Thanks guys--all good stuff..

HMX-1

It's actually easier to lift the bed than lower the fuel tank. I think it's only for our 6 carriage bolts that hold the bed down, then just unhook the electrical wires and it comes right off.

You won't have all the problems with draining the tank and lifting it back into place, or having to put enough fuel into it to get to a gas station.



-Kris

cougar

Originally, Dodge put the lift pump on the side of the engine behind and below the fuel filter. If it has been retroed with an in tank pump, that engine mounted pump will have been removed and replaced with a block.

DIESELWRKS

HA HA . Not always I have seen a few trucks that have had the pump replaced to the Tank by the dealership but they left the old pump on firewall?? LOL. gotta love some dealerships and the short steps that are taken.
If it has been done by a dealership go to dealership pull the truck up nationally by vin and see if services were done and recorded. if they were done as part of an update, TSB or recall etc. this would be tracked in the star whatever dodge/chrysler calls it now days.

danalex

ok, here's a few updates.
I haven't yet dropped the tank; doing that this weekend.
Have been focusing on the new sensor...troubleshot several times...still having same issue...
ISSUE: Relatively stable fuel psi as long as I keep speed below 65mph (i.e., under 1800RPM). As soon as the engine hits 1800RPM (sitting in driveway with wife pushing the peddle), the needle gauge begins to flop wildly between 4psi-23psi. The needle reminds me of someone gasping for air, getting it, then exhaling to nearly nothing, then sucking deep...
I don't think it's a sensor/gauge issue. BUT what is it about that 65mph line?? Is there a fuel pressure regulator on this truck??

danalex

Considering getting one of these: AIR DOG HIGH FLOW FUEL MODULE UPGRADE KIT http://www.dieselmanor.com/pureflow/901-01-0520.asp ...seems affordable and hey, if one of the intank components is bad, this might fix it... I have the RAPTOR liftpump, so this looks like it would matchup (big line). Thoughts?

danalex

Final for tonight: The 'glowshift' tech support guy was really good...either answered my ph call or called me back. Took great time to discuss and help me troubleshoot. Ultimately they are going to send me a "needle valve" to replace the snubber valve...apparently that has helped some folks tremendously.. But again, I'm not totally convinced I have a sensor problem...seems fuel system problem, but I'm not smart enough to determine otherwise, so I'm just poking around with possibilities...

SIXSLUG

YOur Raptor will not pull fuel thru an intank pump. If your truck had an intank pump it was probably changed out when the raptor was installed.

Do you have the bypass block attached to the bracket for the original engine mounted lift pump, or is the original lp in place, just routed around with fuel line and into the filter housing?

Is there a relay on the firewall near top of the driverside wired to the positive terminal on the battery? This is the dealer installed relay for the intank pump and its lead wire runs down behind the drivers side fender liner and should duck into the wiring harness attached to the frame at that point....

If you elect to drop the tank and add a draw straw, which I would suggest, you will want to leave the internals in the tank for the fuel level sending unit. It is attached along with the fuel pick up tube and screen, and rollover ball(which is required by law) in one unit about the size of a half gallon milk jug. You will want to leave it as well as it also houses the return line. The draw straw will be your new pick up point and is really the only mod.

I lowered my tank with a floor jack and piece of 2X12 quite easily in about a half hour. Be sure you siphon out as much fuel as possible to make it easier.

One more thing, there is no air available in the tank to pick up during normal running operation, if the pick up screen is clogged up by something floating around in there it should just starve out. If the raptor is sucking that hard and pulling air in, you have a fitting problem somewhere in my opinion.....