I posted this over on another forum but I figured it couldn't hurt to post here too.

This past weekend I picked up a 89 4.9l I6 4x4 manual. I ran but if I stepped on it it kinda hesitated unless I let off the gas some. So I decided to seafoam it, Ive used it before (mostly in my bike and tractor) and always had good results. I also saw here and other forums that many people had done it with good results. I followed the instructions on the can, let it warm up really good, then slowly poured 1/3 of the can into the brake booster line, being careful not to pour to fast and stall it. After I poured it all in I turned the truck off to let it sit and went to work on try to get the bumper off the front to bend the brackets back. I let it sit for awhile figuring the longer the better, and thought I had read where someone even let it sit over night, so I dont think me waiting longer than 5 min is the issue.
Anyhow, now it won't start. It just cranks and cranks. I went and got starter fluid and sprayed that in the throttle body and it started up but then it just dies after about 30 seconds. I repeated this several times hoping it would eventually just stay started. Finally I decided to check the plugs and they are pretty bad, but it was running before. I wanted to run the seafoam through it first before I put the new plugs in so I haven't got any yet. I cleaned the ones that were in there and wire brushed them off. I did this one by one so as not to mix up any wires. I got them all in and same result, can get it started with starter fluid and runs shortly but dies. So then I took them all out again one by one and checked the gap. All of them were way wider then the should be so I re gapped them all one by one to .044. Nothing changed, still doin them same thing. The battery is now dead also. Any help would be greatly appreciated. This is my first truck and I was pretty excited, now it's just a big paper weight. What happened!? I was trying to help it! Please help! Thanks in advance!
Oh and I also put little less then 1/3 a can in the oil, 1/3 can in the front tank and Im going to put what's left in the rear tank when there is more gas in it.

Here is what I've figured out so far. The rear tank has a leak, I put some gas in it to try and switch to the rear tank but that didn't help. I've notice smoke coming out from around some of the spark plugs. I'm not sure if this is enough of a leak to keep it from starting or not but I was thinking the crude or whatever that was probably sealing them up before probably got dissolved by the seafoam, not sure though. I replaced the fuel filter and that didn't help. I noticed when I turn the key to on, right before I crank it I hear a click from back by the gas tank, I thought it was suppose to be more of a hum. Not sure if this is the pump trying to engage or what...but both the rear and front tank make the same sound. Not sure if each have a fuel pump or if there is one for both. Hopefully someone has some ideas. Thanks again!

 

Hello there. Congrats on the purchase friend!. Yes both tanks have their own pumps, but there is also a fuel pump on the frame rail, close to the fuel filter, it is the high pressure pump. Check that out and make sure its kicking on. If not, use a voltmeter and make sure you have power going to it first. They are the easier pumps to replace. They are just as simple to change as the fuel filter to change.

 

I hate it when people and the seafoam can says to stop the engine. Stupid. Stupid. Stupid. I have never had any negative results by keeping it revved to about 2000 and feeding the 'cleaner' in. It steam cleans everything just as well and you dont take chances of hydro-locking the engine as much as you would if it kept running and burning everything off...

How easily does it crank when youre trying to start it? Does it sound really loose or sound like it has compression in it? Id look into checking the injector tips also... can you feel your injectors pulsing when you try to start it? Seafoam is pretty volatile stuff since it is basically alcohol. Starting fluid is also volatile and dries out cylinders. Id start with checking the stuff that makes an engine work.. Compression and fuel. We know you have spark cause it starts on ether.

 

It cranks good, sounds like it should, nice and strong. It just won't turn over. I'm not hearing the hum the fuel pump priming when I turn the key on. That led me to believe it had something to do with the pump. The only thing I can think is when I put it in the tank it cleaned some crude loose and lodged in the pump somehow. It just seems odd how me seafoaming it and it not starting now coincided, I was hoping there was a simple answer or if someone had run into this before.

 

Check fuel pressure

 

You should hear the fuel pump relay click. If it doesnt either the relay is bad or the inertia switch is tripped

 

Maybe that's the click that I'm hearing then. Shouldn't that be followed or accompanied by a hum though; fuel pump priming?

 

Like Diesel_Brad said, check that stupid inertia switch. I fooled around with all kinds of other things for a couple of days before I found out about that dumb switch.

 

Ok I'll check it...where the heck is it lol.

 

I found it. It wasn't tripped but I tapped on it to trip it and pushed it back in just to make sure it was working. However I may have found the problem. When I went to look at the relay i looked in the back side othe connector and the one connection looked pretty corroded. I decided to take the relay off the make sure the connections where ok. In doing this I found that one of the wires, the thick green one was basically just sitting in the socket. It had completely corroded through. So now my question is, can I get a new socket or do I have to rebuild this one?

 

Success! It was the relay socket. I rigged it to see if it fixed it but don't want to drive it like that. I have to figure out a more permanent solution. Maybe check the u pull to see if they have a good socket I can cut off with some wire and solder it in, unless I can get a new socket. Thanks for everyones help!