New here, so I look forward to getting roasted.

Have a 93 GMC K2500 with 6.5L, 93,000 miles. Two issues: hard to start when cold and strange fuel pump pressure

Cold starting:
Not an issue until this year. No problem if temperature is above 40. But below 30 blows white smoke like a steam engine, bucks like a horse. Once engine warm, then no issues.

Reviewing the forum I replaced GP with AC60s. Still same issues. I checked everything as best I could, with no change.

Reviewing the glow plug relay I had 12.4 volts across both points, When ignition turn to glow plugs, the voltage drops to 0.4 across passenger side, hear click.

I took a new AC glow plug, attached to GP wiring connection from an existing glow plug, wrapped a wire around the threads then other end end grounded to the alternator. Turned ignition, and can see a slight orange color, but after several seconds, relay clicks very fast. Seems way too cold, no way near bright orange.

I have a feeling the relay is faulty, but wanted to check.

Fuel Pump Issues:
Not a real performance problem, but opening the T at front of the engine to bleed any water, nothing comes out and engine will quit. Re-primed, close T, and starts ok.

But, I learned that with engine off, opening the T, removing the fuse relay and touching a hot point can bleed system. I did, and can hear the LP buzz, and fuel will soon exit from the T.

To check further I got a HF gauge, $19. Attached to end of T hose. Ran engine, opened T and gauge shows a Vacuum. Repeated several times, yes a vacuum.

I then ran engine, crawled underneath and couldn't tell if LP, even used stethoscope, and could not hear it running. LP has been replaced, doesn't seem well done.

To condense this:
Do I need a relay, if so where is a good place to get one?
Of LP, same questions

You guys are really nice, truck runs like a Ferrari, gets 14-15 mpg on the highway. Would like to keep it.

Juan304