Bogging down in 3rd and 4th

[MarkPick]

Hey Guys,
I have a problem and want to bounce it off you guys to make sure I am on the right track. My truck was running fine while I had it out the other day. On my return leg I noticed it started spitting and sputtering in 3rd and 4th gear, rev it up and drop down to 2nd and everything was ok. As long as I kept the RPM's up it was ok. Once I limped it back to the shop, I pulled the fuel filter off to inspect it and it was full of rust. Well, we all know whats next, I pulled the line off the carb and pulled the inspection plate on the fuel tank. I used some compressed air to clear the line, changed out the in line fuel filter and the tank filter, cleaned all the crap out of the tank, put it all back together, then figured while I had gone that far might as well dig out my electric fuel pump and install it. Everything hooked back up and working, pulled it out and ran it to see if I got it fixed. No such luck. Same problem as before.
My next steps are to hook up a vacuum gauge to the intake manifold and see what that tells me. I will do a tune up on it since I am under the hood anyway. I am guessing ( I hate to do that) that maybe some of the crap that I cleaned out of the fuel tank made it through the filter and into the carb clogging up one of the ports. Under high RPM (lots of vacuum) it runs fine, higher gears less RPM spits and sputters. Looks like a carb rebuild may be in order also.

I have been reading on the site about timing these beast using a vacuum gauge, I cant locate the post that explains how to do that. Can someone point me in the right direction? Or is it in the manuals?

As always thanks in advance for the help and direction.


Mark

[MSeriesRebuild]

Best timing set is at 4 degrees BEFORE top dead center. Use a timing light.

You may have some rust still clogging a line. If the gas has been in the tank for a while; attend to it promptly. Running stale gas will cause a build up on the under side of intake valve heads. Won't take much until they are lifted off the seats, then it's over. Today's gas starts to separate and cause real problems in a very short time; as little as 2-3 weeks can cause issues with some fuel blends. STA-BIL will help some in a short term, but will not preserve fuel as they claim it will. Ethanol blends are even worse.

[MarkPick]

Thanks Charles,
Gas was at least 6 months old but I did put STA-BIL in it hoping to fight off the stale gas problem. When I was cleaning out the fuel lines I gave them a good long blast of air, also shotgunned it a few times. I hope it is just stale gas.

I have read up on the timing light and using a 12 volt battery to get your power. Got that covered, I have the shielded wires, what do you recommend for getting a signal through them?

Again thanks again for the help and advice.

Mark

[MarkPick]

Never mind my last question Charles. Done some more digging and found the answer I needed. Looks like I will be buying an adapter for using the timing light.

Thanks
mark

[MarkPick]

Back up and running! On top of everything I listed up top, I did a carb rebuild. Good thing, all kinds of crap in the bowl. Installed new plugs and set the timing to 4 DBTC. Just to make sure I covered all the potential issues, I put new gas in also. Checked the vacuume at the intake manifold and got a reading of 20. Good solid needle. . After everything was set, I took it on a test run and I am back in business. No hesitation what so ever, fires right up and powers up on demand.