My 94 K3500 has occasionally had a hiccup under hard acceleration or on a hard pull on soft gravel. Tonight when I headed home from work I had one hiccup then a whole bunch of them about 7 miles from home (soft gravel road) . When I got to the last 2 miles (paved) it didn't get better. I've had some electrical issues wit the truck- bought it with 255k on it, overhauled the engine completely-now has 285k. Tonight when it started this bucking bronco act it runs okay with the throttle feathered but any acceleration brings it right back. It was dark and cold when I got home so I didn't check fuel filter, electrical connections, etc. which I will tomorrow. Just wondered if anyone else has ever encountered this. I've owned about 8 pre 88's with 6.2's but this is my first electronic pump equipped engine also my first 88+ truck. I hate electronics.

 

Do the dual lift pump relay upgrade. You do not have to splice wires to do this upgrade as you will probably find in a google search.
In my opinion it is best to source power to trigger the relay from the plug that goes to the lift pump. Run wires back up to the relay and wires back down from the relay to run the pump.
This is the way leroydiesel.com makes his. I think Leroy uses mountable relays. I prefer mountable relay sockets. Get or do the prime feature. I think you have to request that from Leroy. Use the battery for a power source/Not the orange wire as shown in at least one schematic.
If changing the lift pump or OPS / Oil Pressure Switch use only AC Delco or GM parts.

Use only an AC Delco for a 1993 if changing the lift pump. I think maybe the lift pumps for year 2000 and newer may have also had higher flow, like the 1993's.

If the OPS is bad/won't run the lift pump but still putting out juice, there is usually no reason to change it, if doing the lift pump relay upgrade. It it is putting out any juice at all, it should trigger the relay.

The plug at the lift pump can show full volts, but if the OPS is bad it can put out enough volts, but not enough amps to run the lift pump. The dual lift pump relay will most often cure that without changing the OPS.

Check you oil and coolant levels.

Jumper the lift pump - on a 1994 you can jumper it at the lift pump fuse under the cover on the passenger side firewall - if you still have the cover. It's best to use a jumper with an inline fuse. One end of the jumper goes to a 12 volt source and the other end gets a male spade connector. Remove the fuse out of the fuse holder and one side or the other should make the lift pump run.

Run about 1/2 gallon out the T drain and time the flow.

Check grounds and battery connections, check fuel filter. Possible air leaks or plugging tank sock

You can remove the optic sensor filter and throw it away. They have been determined to be unnecessary and can cause fish biting issues. Plug the harness directly into the Injection Pump/IP

 

Do you run additive in every tank of fuel? IMHO it is a must with the new fuel. Unless you are running BIO

 

I'm running the same lift pump (AC) that I've run on my MF 760 combine -540 C.I. Perkins V8 pumping the fuel 6 ft vertical and 12 ft forward for over 3000 hours. It's run on a divorced circuit from everything else with a remote electrical gauge in the cab. Fuel pressure is fine. Fuel filter housing and filter are from a 3208 Caterpillar 636 C.I. V8 (refuse to use those leaky GM filter housings after replacing 2 of them) Fuel is the same as I use in my big trucks, treated in the 1000 gal barrel. I've been running and fixing diesel engines for over 50 years. It's not an air leak. This truck starts sitting outside at -30 F just fine without being plugged in. It started the next morning just fine - I only had time to run it a couple miles on the pavement that day because I had to take off out of state that morning. Just got home and hopefully will have time tomorrow to investigate some more. I think I'll probably find a broken or shorting wire or a ground broken someplace.

 

Found the problem- a loose pin in the firewall connector. This truck has a tough life- it carries about 5000 lbs. of welder torch air compressor wrenches up to 3" etc. to the woods most every day in all kinds of conditions. Sometimes a machine is broke down where the only way to get there to fix it is pull my truck thru deep mud with a D6 or a log skidder. So far it has taken the abuse really well. We routinely work in places where the mud boggers and rock crawlers like to go. Only found one hill I couldn't get all the way up had to push it the last 30 feet with the cat.