Chugging/Hesitation problem

[midnightrumbler]

Recently replaced the PMD on my truck and I seem to be having a slight hesitation/chugging problem with the truck. If I am cruising around 55-70, the truck seems to cut in and out. It will drop down from 3400 rpms to 2200 rpms and come back up while driving. The fuel gauge also seems to fluctuate while the truck is doing this.

1995 Chev Silverado 4x4 6.5 dually 330,000km's

I have been told by a diesel shop that the injection pump needs a rebuild. The rebuild will cost me $500.00 + 4 hours labour. Does this sound about right? Is this something I could do? I am what you would call a backyard mechanic and do know enough about the mechanical aspects of engines but this is my first diesel. I think if I pull the injector pump off I could probobly save an hours worth of labor at $105 an hour or atleast half that.

Excellent board so far guys ;)

[twaddle]

Did you say "It will drop down from 3400 rpms to 2200 rpms"?
Don't think I've ever had to rev my 6.5 to 3400rpm even at or getting to 70mph,mine sits just under 2000rpm at 70mph (K1500 Suburban with the 3.42 diffs).

Could it be that when at those high revs the ECU's cutting in to reduce the revs or is it a fuel supply fault? Is the transmission slipping in certain gears as it changes up?

Jim

[midnightrumbler]

Supposedly the transmission has been rebuilt but I am not sure as of when. I do not feel the tranny slipping in any gears and the problem I am having does not happen when I accelerate up a slope. Only coming down hill or on a straight away.

I have a hole in my fuel tank that will be getting replaced this week. I do not think a hole in the tank would cause this issue but maybe I could be wrong. A reputable diesel shop is saying it is the injection pump but I am not sold.

Let me know your thoughts

[a5150nut]

Have you got any codes? Let us help with the basics before you start thowing $$ at the problem.

And no, it's not that hard to change the pump your self. Do a liitle searching here on TDP and you will find lots of information on it.

[midnightrumbler]

There are no codes at this time.

[tall78]

Try replacing your Lift pump First. It's located on your frame, drivers side, about half way back. your problem sounds to me like your fuel pressure is dropping off. I have been uing diesels sense the early'80s. Most 6.2/6.5 motors have a very tight window o f fuel pressure to work from. Beside that , $130 and 1 hour of time cheaper too. Easy install.

[midnightrumbler]

My lift pump seems to be working. I am can feel it pulsating on idle and here it shut down once the truck is off which would indicate it is working.

I am going through a few issues at the moment to work out other options.

Should I feel the lift pump pulsating or should it feel like a continues flow?

[JohnC]

Pulsating is good, but it could still not be working. Open the bleed valve on the fuel filter while the engine is running. If fuel squirts out, the pump is pumping. If not, the engine will draw air in and stall. (Then you're stuck...)

[midnightrumbler]

I recently changed the fuel tank and installed a new fuel filter. I opened the drain valve on the fuel filter and applied 12 volts to the lift pump directly. There was alot of fuel being pumped from the fuel filter so I closed this and opened up the water drain valve and very little fuel was being pumped through this while powering just the lift pump alone without vehicle running. I statred the truck and it idled well and did not stall. I have yet to take it for a spin.

The lift pump looks old and it did not sound too healthy when I applied 12 volts directly to it.

When opening up the bleed valve on the fuel filter, is fuel supposed to spill over out from the valve or is it suppost to come out of the 1/4" upper portion?

[tall78]

Doesn't sound to me like an IP prrolem. try 1 more thing before you get the IP REBUILT, CHANGE THE OIL PRESSURE SWITCH,it powers the lift pump. Maybe your oil pressube is fluxuating and so your lift pump is too.

[bbudus]

Should only come out the 1/4" hole on top. Hook a hose and drop it in a pop bottle. This will allow you test a bit longer and save the mess.

Bbudus

Ps. I'm on my third one. Common failure point.

[midnightrumbler]

It apperas the OPS was replaced by the prevoius owner as it looks brand new. I have had the truck for 2weeks now.....As for the fuel spillage, it was a misplacement of the rubber gromet from factory.....

Checked my Fuel Pressure at idle and I am at a consistant 6.7 at idle. I have to wait until I get my shifter linkage hooked back up to test this on a good run.

Will keep you posted....