pulsation under mid aceleration

[M.A.G.]

Help!!!!!!!!!! Well here I go, 95 burb remote fsd 3 inch banks hp water pump dual stat tri pod guages KD rv chip. when cold aceleration is the way it should be, warms up mid throttle I get pulsing like fuel starvation go heavy on throttle it gets better, mileage has slipped alittle also. In chicago, winter blend could be some of mileage slip but I think problem is also part of it. 256K on truck no plans of retirement. you guys have been a great help in the past so I`m throwing another one out there thanks. M.A.G.

[Warren96]

Pulsing? With cruise on?

[baker2acre]

Hey MAG...


I had a similar event several months back... it only happend when warm... however mine did not improve with a heavier foot... regardless, have you checked your transfer fuel pump. That's what mine was. When you turn the key on for the glo cycle you should hear a "wood pecker" type sound from under the truck (at least for me) below your seat, if operating. If not running, get one!! They're resonable at the local parts place ($60??) and a snap to R&R. Note: Be sure not to be in the middle of any AC/DC solos when cracking open the fuel lines. :eek: Yum!! Eye protections a good Idea too!! :cool: Two compression nuts on either end of the pump removed and retaining strap loosened the pump should just slide out. Another note: Don't bend the metal fuel lines as they can kink!! There's enough built in slack to carefully push the tubes linearly away from the pump. Also, I believe the electical connection is plug&play too.:D

In my case... the problem was a starvation... but it was effecting timing I.E. make the computer have adjust timing to keep up with the shortage... when the truck is cold, the timing is already tweaked to offset the "cold" performance characteristics but once it warms up it goes all to heck... I'm sure a fish could explain it better, but there it is.... :rolleyes:

Are there any other clues or symptoms??

Les

[baker2acre]

Oh, and mine did do it with or without cruise on... it made no difference.:mad:

[Robyn]

Hmm sounds like some good advice.

With the truck running, be sure its in park and the safety brake set.
Crawl under and see if the lift pump is running.
If the pump is running check to see if fuel will come out of the fuel drain hose at the front of the engine.

Also have you replaced the fuel filter recently???
You may have sucked up some nasties and plugged the filter.
It would be a shame to spend $$$$$ and time chasing this gremlin only to find it's a bad filter.

[Bnave95]

On yor 95. You can also before starting put in drive and turn key to start. Eng. won't crank but lift pump will run. That is if it works:D
This is good for filter change and prime.

[moondoggie]

Good Day!

Boy, are you blessed. It's REAL easy to prime the fuel lines on this truck; too bad this only works on 95's (I asked some time ago, it really only works on 95's).

Your LP is powered by two circuits: relay during cranking, & the OPS during running.



Crack the fuel filter nut (black plastic round thingy on top of the fuel filter housing) a little. Connect a piece of tubing to the port on the top of this nut; drop this in a container.


Set the parking brake or block the wheels. (Maybe better to not use the parking brake on a vehicle you don't know - maybe it never releases, eh? ;))

Put the tranny in any gear EXCEPT park or neutral.

Turn the key to the crank position - the LP will run, but the engine will NOT crank.

Wait for a solid stream of fuel to be pumped out of your piece of tubing. If not, the LP and/or relay aren't working.


Checking the OPS is a little different: While idling in the driveway, slightly loosen the black plastic nut at the top of your fuel filter. If it squirts fuel, your LP is at least working; if the engine almost immediately dies, it's not. (You're almost certain to have a REAL hard time getting it started again if the second condition exists. The fuel just ran backwards down the fuel line towards the tank, & unless you fix the LP system B4 running this truck again, your IP is going to have to pull the fuel from the tank.)


IMHO don't waste time crawling under your truck to see if the LP makes noise - if it does, all you know is that it makes noise; if it doesn't maybe you got a quiet one that isn't well-coupled to the frame. It's SOOOO easy to KNOW if the LP system works right or not.

Blessings!

[baker2acre]

As always, Moon Doogie. Good point. I just assumed that they all made noise... but the sure fire way is to crack the filter nut or the drain valve which will either produce fuel, or stall your truck!! The IP is up stream from both of these appliances and will pump by it's self as long as it is primed. As soon as that prime is lost, there you sit with quitest truck on the planet!! When I bought my truck... I didn't hear the pump. I didn't know it had an LP... but when I developed the driveability issues stated before I went into diagnosis mode (not without consulting here 1st!!!). As soon as I opened the fuel line, she quite and EURIKA!!!

I honestly would check this first, MAG... do a search for LP or Lift Pump and you will find great info on how to do this and maybe some pics of locations. Second I'd follow Robyn and check out that filter, (if you have fuel from the LP) there may not be enough fuel getting through the filter and causing the same results as a dead LP. While you're under the hood, change the filter anyway!! These filters, I feel are a bit too small to run for "normal" intervals. It's way to hard to be sure that what's coming out of the local diesel watering hole.

[M.A.G.]

Well thanks again for all the good troubleshootin guys and gals I should have mentioned I checked the LP, actually replaced it as it served well, but was still working. never did try it on cruise cause the truck stumbled under heavy acceleration one day flat on its face. this was something I had experience before when truck was under waranty. it still ran and was back to pulsation under mid accelleration right after fallin on its face. the dealer had it 4 times before they figured it out the first time (then no mid accel pulsation) just falling on its face. they said it was sucking air through fuel line from frame to motor (steel to rubber line).so with this as a possible I covered the steel to rubber fuel line connection with silicone let it dry over night, drove it to work the next day and it ran perfect. has anyone else seen this problem, it could really screw with your head tryin to find this kind of problem. sorry about the late reply was out of town workin to afford a dmax thanks again MAG

[Bnave95]

Yep, air in fuel will cause different issues. I would'nt trust your repair for long term use though it did help with the cause.
I also just about said that is also sound like a FSD starting to go bad.