I have a "93 6.5 turbo that runs good overall. It reves with a a slight push of the pedal and idles great. The only issue it has is it doesn't like to come down from a high rpm. It will just stall if you rev it to 2000 rpm and let off. This is a big issue while driving. If you let of fairly slow it is fine. But a sudden drop from 2000 to idle and it will just shut off. It then starts right up. Anyone have an idea?

 

No body has any ideas?

 

How's your fuel pressure (pre-injection pump, of course)?

Might be your lift pump getting weak or giving out. The injection pump itself can pull the fuel through, but it strains it. I know because the mechanical lift pump on the block of my 6.2L was doing nothing for the fuel system LOL

 

I was figuring fuel psi or injector timing.

What should it be and Where do I test it from?

 

Injection pump's dying I've had a few of those old timers do that through the years.

I also had a truck that did that and the throttle cable was hanging up internally. If you had a lift pump failing on those trucks they suffer from looong crank times and low power and heavy smoking on start up because the pump doesn't make enough pressure and it floods down the motor until it finally gets enough fuel to fire then the main pumps internal pump takes over and sometimes heavy smoke under acceleration because they are lean.

 

Well thanks for the good news!!!

Any luck that a fuel filter could be the culprit? Everything you described is happening. Is the lift pump hard to change?

 

No the lift pump is on the drivers side frame rail where the fuel filter would normally be located on a gasoline truck. Turn the key on and you should hear it buzz. Check to make sure it's getting 12v koeo for a few seconds and then while cranking to verify the lift pump is operating.

Fuel filter on yours is located in a housing you unscrew the top off of to change the filter it's located in the V of the engine right in front of the firewall once you take the air cleaner off.

 

Don't replace it with another factory lift pump, they are inadequate for a healthy 6.2 NA diesel, let alone any turbo model. They can barely put out 5PSI at idle and even brand new models have been seen to drop to 0 under full load acceleration.

Buy yourself a decent universal pump that can flow 5-10PSI and flow as much GPH as you can get. I've got a Carter P4070 pump that puts a constant 5-6PSI and 76gph. I bought this pump because I've seen guys running nearly 300RWHP on a 6.2TD with just this pump and still see 3PSI full acceleration, uphill.

 

Typically, with our mechanical Injection Pumps, you will have hard start issues, while warm/hot, or erratic idle/smoking and low power when they start going bad.

I found out my pump was dying when it began taking way too long to fire up, even if I turned it off for 5 seconds, after it was warmed up to operating temp. I got some warm water (don't use cold as it's too much of temperature shock) and poured it onto my IP and the truck fired right up. This was due to internal parts wearing out and when they get warm, the tolerances are loose and the pump doesn't build enough pressure to adequately start up the truck, but can maintain a very weak state of running, if needed.