Engine/Transmission (1998.5 - 2002) PLEASE HELP ME: Raptor 100 Pump Insanity

[Tejas TJ]

I need some help bad, I've gotta drive this truck to work each day and need to fix this pump.



1st pump had fuel pressure flucuation issues the first week I had it and on Friday night the truck left my wife stranded on the side of the road. Luckily I had a replacement 100 pump sent to me by Pureflow. Installed it Saturday morning it started. I then set the regulator on the pump to 18 PSI at idle in park and reved it up a little to make sure it ran right, all seemed fine.



Take the truck on a test drive today and at first the pump seemed fine, once I got into town with stop lights the fuel pressure started fluctuating again and droping to 0 then to 5 then to 0 then to 10 and then creeps back up to 15 which is where it tends to stay at cruising speed.



The wiring harness gets power from the passenger battery which has been tested good, has a 25 amp fuse and relay and runs off the ECM wire that the factory lift pump uses. The fuse didn't blow when the pump died, it just stopped working, put the new one on Saturday and it worked fine for a while, test drove and then 10 miles later it started acting funny in stop and go traffic, mostly under light throttle and taking off.



I set the regulator to 18 PSI at idle with the transmission in park. When I start slowing down to a stop light the pressure rises to 19 almost 20 PSI.



972-658-3219

 

[BDaugherty]

Could you describe your install? Is this a direct replacement or did you install it with the draw straw and larger fuel lines? Does the pump motor stop or does it keep going? You need to know if it's a problem with the electrical supply, the pump/motor itself, or the fuel supply. I think fuel supply is most likely. As for the minor fluctuation in fuel pressure, that may be more normal. I installed one on a 98. 5 about a month ago and it would run up to 20 psi at a traffic light and then drop to about 15 psi under power.

 

[Tejas TJ]

I installed the DSV at the same time. I made for sure nothing was loose in the fuel canister when I put it back in the tank, but maybe I missed something.



Check this video out, he had the same problem I'm having and went with push-locks...



Raptor 100 with push lock - YouTube

 

[twheat]

Are you having 1/4 tank issues?

 

[waltk]

Have you verified the wiring? Two consecutive pumps with the same symptom and failure mode sounds truly odd. Try removing relay from its socket and fashion a jumper to energize the pump; if all is well, then determine whether relay itself or the wiring from the factory transfer (lift) pump to your relay coil circuit is at fault. I just replaced the connector on the engine-side of a neighbor's truck for the similar symptom (intermittent operation of a brand-new FASS DDRP)... If you determine the connector is the culprit: Cummins part numbers are: 3824012 -- CONNECTOR, ELECTRICAL (1 required @ $2. 21 per each) and 3822921 -- TERMINAL, ELC CNR REPAIR (2 required @ $5. 30 per each) (prices indicated are from my invoice at my local Cummins Branch; prices may vary.

 

[jeepit]

Are you having 1/4 tank issues?

If you are at or below 3/8 tank of fuel I'd bet it is the Draw Straw. Especially with your descirption of this occurring at stop lights.

Fill tank up and check again.

 

[Tejas TJ]

First off, I took the busted pump off and found a piece of yellow plastic from the fuel canister wedged in the gerotor gears. So I ordered a 1/2" inlet/outlet inline fuel filter from Oreillys Auto Parts tonight to protect the pump from junk.



I'm going to fill the tank up Wednesday when the paychecks roll in and I'll get back with you guys.



I already bought some pushlock fittings to replace the Jiffy-Tite quick connects. A Raptor 100 owner on Youtube commented that it stabilized his fuel pressure flucuations after his Raptor install. They were cheap so I picked some up from Eric at Vulcan Diesel today.



It's cold and wet so I'm not gonna mess with it tonight but Eric suggested having someone rev the engine to 1500 RPM's and watch the fuel PSI gauge and someone else wiggle the quick connect lines and see if pressure changes. I'll try to do that tomorrow.

 

[Tejas TJ]

Have you verified the wiring? Two consecutive pumps with the same symptom and failure mode sounds truly odd. Try removing relay from its socket and fashion a jumper to energize the pump; if all is well, then determine whether relay itself or the wiring from the factory transfer (lift) pump to your relay coil circuit is at fault. I just replaced the connector on the engine-side of a neighbor's truck for the similar symptom (intermittent operation of a brand-new FASS DDRP)... If you determine the connector is the culprit: Cummins part numbers are: 3824012 -- CONNECTOR, ELECTRICAL (1 required @ $2. 21 per each) and 3822921 -- TERMINAL, ELC CNR REPAIR (2 required @ $5. 30 per each) (prices indicated are from my invoice at my local Cummins Branch; prices may vary.

Thank you for the detailed help. I'm going to run the above tests and then move on to this. Thanks

 

[LDornak]

Tejas TJ,

Did you get your issue resolved?

 

[Tejas TJ]

Not all the way.



I found an air leak on the bulk head fitting on top of the fuel canister. I checked ever single fitting and didn't find any other air leaks. So I haven't messed with it since I drop the tank about a month ago. It doesn't lose fuel pressure as much as it use to but I haven't ran it below 1/2 a tank either.



But, I have this weird issue where no matter how long I let the truck idle, when I start driving 10-45 seconds later fuel pressure will drop to 5 and then instantly bounce back up to 15 psi... Weird huh.

 

[Steve8511]

I suspect the pump itself..... a bad motor which none are made in the US anymore will do this.