I have recently bought an 03 3500 dually from a very good friend that has lots of experience with diesels. The truck started surging at idle and is real bad when in gear only while stopped, but it runs great as soon as your on the throttle. We have replaced the FPR twice with no change, while watching the truck on the computer everything is great all injectors are well within spec and fuel pressure is dead on. The only time the surging goes away is when the truck is warm most of the time or if we are to pump the fuel primer but we have re-oringed the primer. Any help or suggestions will be much appreciated! Thanks
Truck surging at idle after installing new FPR
- Thread starter Whipper Snapper
- Start date
LB7s are notorious for the idle surge. Check your bleeder screw. If priming helps I'd imagine you benefiting from a lift pump.
You think an air dog kit would work?
We are going to try to run straight off of a bucket bypassing fuel filter and everything down stream to see if the problem is stops.
Air Dog is a great brand. Are you plumbing in at the cp3 or fuel lines after the filter? Let me know your findings.
a lift pump will certainly not fix a 'lopey' idle. In all likelihood the Fuel Pressure regulator needs replacement.
A lift pump is a good addition for sure but will not fix the issue.
A lift pump is a good addition for sure but will not fix the issue.
He said he replaced it twice with data logging. The Mprop/FPR was also my first guess.
yeah no kidding is anyone reading his first post? Ive seen this cause by dry crack lines in the valley feeding the pump. rig up a way to pressurize the lines on the motor and isolate the lines come up from the frame and see if it will hold 10PSI from a mity vac/pressure pump. merchant makes an adapter for the bleeder screw that you can connect 1/8" pipe thread to and pump it up. and you will see it lose pressure or even fuel spraying from a cracked hose. you just have to disconnect the two lines and or pinch them off with come hose clamp pliers kinda like locking pliers that pinch off a hose. it works try it.
I had a guy replace his FPR and that did not fix his issue. injectors can make a lope at idle. balance rates won't always show bad on this issue.
Injectors are a great call regardless of mileage I, however, would think they would cause other issues: white smoke, poor mileage, excessive black smoke during acceleration etc.
injectors can fail and not cause white smoke. rail pressure issues are one that doesn't cause the smoke issue.
Rail pressures are right in line with what they are calling for, actually for the most part exactly dead on, it has us scratching our heads. I am bringing to another friends shop this afternoon for him to run some tests and monitor it on his computer to see if we are seeing the same. Thanks for help, all input is very appreciate!
Hmmm didn't think of that. But Id imagine it popin a code or having starting issues. Its a great call and worth checking out. They forgot loctite from the factory in these lb7s.
I have one that does a similar thing and his Baro sensor read way off what it should at idle. it should be reading 14.5 here and it reads 3.4 so his boost is showing 11.1 psi at idle. when put in gear his surges some too. his was workse and he replaced his throttle sensor and that cured some of it but not the baro sensor. we tried a known good baro sensor and it didn't change. Just for shits and grins see what your baro sensor is reading at idle when you have it scanned.
Ok update.... Went to friends shop and on the way there the truck surged at every red light and stop sign until the last red light then truck starts to run just fine. He put his Autel MaxiSYS pro on it and ran the truck through its paces, fuel rail pressures are spot on, FRP is spot on, injectors are spot on, so nothing to be found that's out of line. The truck surged a few times and both guys said that's not a bad FRP surge and that its to quick of a surge(1 to 2 seconds between surges), I explained that if you pump the primer that it will go away for a minute or two and come back so they told me to do a bucket test.
So today I bought a large funnel and disconnected the fuel supply line that goes directly to the FICIM and installed funnel and filled it with fuel, started truck but truck had surge, I stopped because funnel was almost out of fuel. I hooked lines back up and started truck and truck was surging so I pumped the primer and it went away just like before.
Any suggestions?
So today I bought a large funnel and disconnected the fuel supply line that goes directly to the FICIM and installed funnel and filled it with fuel, started truck but truck had surge, I stopped because funnel was almost out of fuel. I hooked lines back up and started truck and truck was surging so I pumped the primer and it went away just like before.
Any suggestions?
Just throwing it out there I had an lly with a surge one time. Replaced the fpr no change after a lot of wasted time I took the 4 screws out of the air box. The second I lifted the lid away from the air filter the surge went away. Removed filter was old but not plugged. Put a new filter in it and cleaned the maf and it was right as rain.