Scotty. I really enjoy all of your videos. They are so much more helpful than most of the DIY youtube mechanic videos. Thank you for being succinct and not patronizing the viewer (like most people talking about socket sizes and then unscrewing bolts for 10 minutes).

Anyway, I just bought a gigantic 2000 Chevy c3500 7.4l V8 gas dually pickup to use as a work horse for my business. The guy I bought it from had left it sitting for 2 years. I drove out 200 miles to meet him, picked it up, and drove it 200 miles to get it home (maybe that was a mistake). Anyway,

It only has 87,000 miles on it, but there are a plethora of issues from it sitting and being neglected. The truck takes 2 or 3 cranks and some gas to get it started. Then when it does start, there is a high pitch screech/squeal that sounds like it's coming form the alternator bearing. I don't think he ever trickle charged the battery in 2 years, and at times the voltage meter was reading low. The truck accelerated with the gas pedal depressed slightly, then there is a hesitation/shaking when the gas pedal is pressed further but before it decides to downshift and start picking up again. It also had a few leaks in the power steering lines..

The guy I bought it from said had replaced the idler pulley and serpentine belt as well as the spark plugs and distributor carp in an effort to tune it up to sell it and fix the squeaky belt (to no avail!). He had also filled it up with some fresh gas. I didn't have means to drain the old fuel out, so I filled up the tank along with some fuel additives, and drove it home.

The service engine soon light came on on the ride home, but I kept going slow and steady trying to keep the truck moving without pushing the gas to the point where the engine started shaking. I made it home!

Now the next day, I picked up a set of spark plug wires at AutoZone and went to work replacing those. I figured that might be why the engine was misfiring since I knew he had done the plugs and distributor cap. The aftermarket Duralast wires did not match up in length to the factory wires that were on the truck. Also, several of the wires were very close in length. I was concerned that even after pulling the wires off one by one, and replacing them with what appeared to be the closest aftermarket match, that I may have mixed up a wire and used it on a cylinder it was not intended for.

One of my questions is: is it possible that very slight differences in spark plug wire lengths could make a difference in engine timing assuming they are all hooked up in the appropriate firing order?

The truck did start and run better, and it seemed to have a significant boost in power when I fired it up and drove it around the block. It does however continue to hesitate when given more gas and it takes 1-2 tries to start it.

The truck continues to screech around the alternator/drive belt, when it is started up. The sound is loudest at first, then softens, then goes away once the truck runs for a minute. It also seems to be worse when it was raining/humid. When raining the squeal does not go away, even when driving.

My next thought was to change the alternator and perhaps the belt tensioner. Also, I will change the fuel filter and clean the throttle body, and mass airflow sensor, to see if that helps the hesitation. If that doesn't do it I will check the fuel pressure and think about changing the fuel pump and perhaps check the injectors too. Wow. Sorry for writing a book!

Anyway does that sound logical? Am I missing something? Any advice from your years of experience?

Comments
No. 1-2
Ricardo OG
Ricardo OG

No the spark plug wire lengths do not affect the timing of the spark. One thing o would suggest is test the fuel pressure with a gauge, I'm thinking the pump is sending weak pressure. It's an old truck and all that sitting may have gunked up on the fuel filter, the ethanol in modern gasoline can cause that.

Scotty Kilmer
Scotty Kilmer

Editor

you're going about it correctly, I'd replace the tensioner and use a quality gates belt first. But you probably made a big mistake buying that GM old junker in the first place, sadly.