My prob happens when starting to accel, sometimes before I get out of the drive way or on a long trip. The eng falls to idle. I have put a fuel pressure gage and watched ther pressure drop to 50 psi--normally it is 53 to 54 psi after decreasing fuel i.e. coming from cruise where it was 58 psi , when it is 53 to 54psi the truck accels normally. But, when it drops to 50 the truck will not accel and the pressure will continue to drop to 44 psi when trying to accelerate and then start to buck-jump-backfire. When backing off acelerator the pressure returns to 50 psi and the problem starts over again. Hold to the floor the eng will die and the pressure immediately returns to 62 psi, place in nuetral, turn the key to start, it starts up. It may go 5 feet or 50 miles before doing it again. Pull off the road let it idle, it will idle all day but still will not accel even with no load, simply racing the eng.

What could cause the fuel pressure to drop like that?

2 new pumps have been installed

When in the faulted state, pulled over to side of road letting the truck idle, I have disconnected the MAF, MAP, evap emmission canister purge solenoid, intake air temp switch, raced the eng it falls so none of these helped.

No fault codes, I have had 2 different people in the cabin with a computer hooked up when the truck faults, the computer says the truck is running normal no problems.

I have replaced the Bank1 sensor1 O2 sensor---no help, now I will put that sensor in bank2 sensor1 position.

Where is the fuel pulsator located? Could this be the problem?

Any help would be appreciated.

 

Have you replaced the fuel filter along the DS frame rail?

 

Yes, I have forgot to mention that.

 

sounds like your spider injector assembly is leaking at the regulator or a couple of injector lines!!

 

308, I like that name, Mine A/M/G--Archery,Muzzleloader,Gun. So, I like the outdoors and so forth, I hunt with all three--what ever season is available.

I have replaced the regulator, it was leaking.

I have also found that I can make it fault on demand. If I put the the pedal to the floor and run the eng hard thru the gears, it is an automatic, once it hits 5k RPM it faults, drops to idle and will not accel until the key is turned off. Then it starts right back up and may fault immediately or may drive it a log time without faulting, or if I run it hard again as soon as it hits 5k, done. I also did it by putting in first gear and going to 5k fault, second gear fault. SOOOOO....... is there a reason it goes to idle at 5k which is redline--some kind of safety switch or something. At 5k it does exactly the same thing as it was doing intermitently, just now I can make it do it on demand. I do not like running it that hard but sometimes it will not happen for 50 miles of normal driving. That is very time consuming.

What ever is causing this at high RPM, I think is faulting intermittently at low RPM also. Anyone know of a sensor or switch that could possibly cause this?

Thanks
A/M/G

 

Ok speed limiter, my vehicle drops to idle and will not accel until the key is cycled. i know it is a fuel issue. I have a fuel gage in front of the windshield. It drives fine until the fuel pressure drops to 50 psi after releasing the gas pedal and starting to re-accel. The pressure drops to 50 and upon increased throttle pressure drops to 40 psi, bucking-jumping-popping, press to floor it dies. Cycle the key 62 psi, it runs again , starts idles 54-55 psi, accel 58-59 psi, when falls to 50 psi faults again.
Speed limiter, is it a physical switch or part of the computer program?

Could the crank sensor cause this problem.

I have been fighting this for 3 MONTHS.

I have read hours on this forum, tried LOTS of stuff including your fuel diagnosis chart in the DIY section. I am at my witts end.

 

Rev limiting is done by cutting out the spark so if you are having issues with fuel delivery, it is not related to a speed or rev limiter.

Have you tried to monitor the voltage to the pump and to/from the fuel pump relay (in terms of the turn on signal as well as the supply voltage into and then out of the relay) for signs of problems?

BTW, don't let your frustrations with your vehicle turn into frustrations with those trying to help you. You may push people away.

 

I am not sure what you are talking about my frustrations toward other people. If I did I did not mean to. I really appreciate this board and information people are willing to share. Please accept my apology if I offended anyone. With that said....

I monitored my voltage at the pump when faulting, 13 volts.

I have also, built a harness, direct wired the pump from the battery and removed the wiring to the input side of the pump from the truck. So, the pump gets no information from the truck, direct power from the battery when I manually turn it on, the harness has a 15 amp fuse and switch. I ran it like this for 12 days no fault until it was under a heavy load, pulling my boat and it faulted, same thing. Any ideas?

A/M/G

 

The only way it could fault with it hot wired like that is either a bad pump or a bad ground. Neither of which make sense when you can simply turn the key off and back on and have it work properly... Unless that is allowing a wire or connection just enough time to cool down...

 

I have changed the pump twice, The pump ground has been removed from the cross member, cross member and ground connect cleaned and reattached.
The pump provides 62 psi on start. As I said this about to drive me crazy.

A/M/G

Throttle position sensor, how do you check it? I read where you said .5 volts closed and 4.5 max open. what pins are you reading, truck running?, iginition on?, tps pulgged in? I looked in the DIY dection and did a search for all forums, I did not see procedures to do it.

Speed or rev limiter, what limits these? Is it the computer? The reason I ask, I am almost positive it is fuel related, but, at this point in time I am open to other options. Since it is doing exactly the same thing, I suspect whatever causes the fuel or iginition to cut at 5k rpm may be my problem. I am willing to replace that item.