As the title says, we have a 19k mile L59 from a 2006 'Burban. We had it tuned by Jim's Performance, and put it in an old International ScoutII. It ran fine for a few miles, but now won't pull past about 4k rpm. We replaced the filter in the suction line, as well as the pump (AirTex E2000) and filter (AC GF822), no love. Any ideas as to what to check? It gets to that rpm level great, then bucks and just won't pull through it.

 

Does it change with load, or does free revving cause the same condition?

Could be ignition, fuel, or perhaps a crank sensor or something. I think the 3400s had a switch point for the crank sensor signal resolution at around 4000 rpm, perhaps the LS PCM does something similar?

 

Pinched fuel line on the suction side! Thanks!

 

We got that fixed on it, but now we're getting lean codes for both banks. Either low fuel pressure or MAF, we figure? FPR and pump are both new...
Any ideas to diagnose it?

 

Try to get a fuel pressure reading when the problem happens. Cell phone video makes a great remote FP gauge monitor.

 

x2 on fuel pressure

 

Airtex is the first place to look.........

 

Here we go again. We fixed the pinched fuel supply line, and it ran like a top...the one time I ran it hard before we handed it off to the customer the next day. Now, we have it back again for some clean up before the Carlisle truck show this weekend, and it's doing it again. Please watch the video and tell me what you think is the root cause of this problem.

 

And if you drive it around all day, no codes are showing up. BUT, if you let it sit and idle after driving it, after about 2 minutes or so of idling, we get a lean code for both banks. It doesn't give a code while its doing what the video shows, though...???

 

Fuel pressure drops to under 10psi during this, confirmed by a gauge this morning. We have had two pumps, two filter/regulators, its a new tank, new pre-pump filter, new lines, etc. Now what?

 

The question is what is causing the pressure to drop ?... you seem to have replaced the pump, filter, etc.. fixed the pinched line/hose..

What about Voltage to the pump and relay.. as well as the Fuel enable signal to the relay from the PCM..? Bad ground(s) ? Where is the power sourse connected too ? (Battery, alternator directly ?)

Have you checked the fuel pickup.. possible that it is clogged or too close to the bottom of the tank ? Also check the hose between the pump and bulkhead.. leaking and alowing air into the system ?

Also.. did you answer the question on it happening if under load vs free of load ?

just a few more inputs to help look into !..

Hope you find it soon.

BC

 

It free revs fine, sitting still. Up hill, down hill, flat ground...all the same results. As long as it's moving, it does it.

The pump ground is directly to the chassis (frame crossmember), and good ground straps from chassis to body, chassis to engine, and transmission to chassis. Also there is good voltage to the pump.

I'm about to go buy a GoPro camera to strap to the chassis looking at the pre-pump filter to see if it stays full when it acts up.

 

I have heard of similar issues with the water pump inlet hose collapsing at high revs. Maybe you have a fuel line collapsing or maybe some debris in the tank that keep swimming in front of the inlet? Maybe all the fuel lines need to be blown out?

Good vent on the tank?

Since you say good voltage to the pump I assume you measured it across the pump pins directly? Measuring it at the fuse won't tell you if the ground is bad. It may not be your issue, but in general I am not a fan of grounding things to the chassis. A dedicated ground wire hooked back into the main harness and with power fed from a fuel pump relay is in my opinion the best way to connect a fuel pump. GM use to purposely build cars to quit working after a period of years and one of the ways they did that was by using the chassis to carry current instead of wires. The few bucks they saved by doing that is totally not worth the headaches it causes older cars.

 

Dropped the tank and found a bunch of plastic shavings in it. Evidently from the manufacturing process. Close to a golf ball sized wad of it, all said. Cleaned it out and about to reinstall it.
Fingers crossed...

Still doesn't explain why the lean codes come after idling, NOT while romping on it...

 

Ok.. two down.. hopefully no more to go..

Keep us posted..

BC

 

I had a similar problem. Probably wise to pull the whole fuel system and flush out all the junk.

 

Did that solve the problem?