Hello All,

Sorry this is long, but I hope all the information will help.

With that said, I just purchased a 1996 B2300 with 160,000 miles for $400 as a second work truck. I got it from my father in law so I knew it had problems I had to fix, but I ran in to one I can't figure out.

I drove it home and it would sputter under load while starting off in first, and for the first few hundred rpms after shifting to second. It would run fine at speed, with just a stutter every once in a while.

He had already told me he drove it for about an hour with old gas in it, and I knew it needed a tune up, so I somewhat expected it to run like this.

Also, the windshield wipers occasionally came on by themselves. I got it home and pulled the plugs, and they were mostly tan-ish with no ash or carbon deposits, both #2 plugs seemed to have the ground electrode slightly melted and the insulators were cracked, I assume this was from the #2 injector causing this cylinder to run lean.

I replaced the plugs and wires, the fuel filter, drained the gas, filled it with 93 octane and added some seafoam into the gas tank for good measure. (I also found a hole in the thermostat housing, so I fixed the weld and replaced the thermostat)

After all that was done, I went to start it. All it did was turn over. After some trouble shooting I found the pcm power fuse was blown, so I replaced it. Tried to crank it again, and the fuse blew right away. I disconnected everything that runs off of the pcm relay (pcm, egr vacuum solenoid, maf, evap solenoid, iac, injectors, etc.) and put a new fuse in. turned the key to the on position, and the fuse held. Then I plugged everything back in one at a time, and the fuse held, and the truck started .

I let it idle a bit, and it seems to idle a little low still, with some engine vibration. After a bit, it will sputter a little then kick up to a normal smooth idle. When this happens, I can hear the fuel pump relay click. I replaced the relay with no results.

I test drove it for a few minutes after it warmed up, and it still sputters a little under load while starting off in first, so I am assuming this is from the fuel pump relay clicking on and off or from the injectors still being somewhat clogged, the seafoam should take care of them in time though.

tl;dr, what would cause my pcm power fuse to blow several times then not blow, and what could cause the fuel pump relay to click like that.

Thanks in advance,
Clint

 

Good trouble shooting on the blown PCM fuse, too danged bad plugging things back in one at a time didn't decisively pan out.

On the random sputter, have you checked the fuel pressure at KOEO & KOER????

Have you been monitoring the fuel pressure when the engine sputters????

The computer actuates the fuel pump power relays coil, to cause it to close & run the fuel pump for a couple of seconds to build fuel pressure at KOEO, before we crank the engine, then it times out & opens the relay to turn the fuel pump off.

After the engine is cranked & the oil pressure comes up & the engine is running, the computer will actuate the fuel pump power relay to close to keep the fuel pump & engine running.

Obviously something in the PCM's fused circuit is intermittently drawing too much current & right now without more clues, with the intermittent fuel pump relay click & having the engine sputter in time with the relay click, sounds like that part of the fuel pump relays wiring belongs on your suspect list.

Maybe chaffed wire insultion in the fuel pump relays coil wire control actuation circuit from the computer, thats shorting out, or opening up, as you may have more than one problem!!!!

Anywhere that wire passes through a metal bulkhead, makes a sharp bend, is exposed to a high heat source, or lays in contact with something that vibrates, or moves or is hot, are good places to look.

So raise the hood, set the brakes & have someone apply some torque to the engine, as if you were moving off from a stop & watch the engines movement & see what in the wiring harness moves with engine torque & concentrate your inpection in that area.

With the brakes set, If the engine will sputter as it rolls a little with torque, maybe you can find & move the suspect wiring by hand & get it to act out & narow it down that way, IF it's a wiring problem.

A bunch of thoughts for consideration, let us know what you find.