Air,Fuel and Spark ?

[Strike2]

Ok I need some pointers, I have a 75 Bronco 302 all stock it was sitting over 10yrs I drained the saddle tank refilled with fresh gas, cranked the motor by hand and it turned freely so I tried starting it but with no luck then the carb started to leak, so I removed and installed another 2150 from my spare 351w. The motor started right up to my surprise, so I drained the oil and then drove it around the block less than 2 miles just to get a feel for driving a 3 speed on the column. The next day it wouldn't start again so I picked up a carb rebuilt kit/gas filter at Napa only to have the same results it cranks and sounds like it want to but as soon as you disengage the started it dies? Pulled the carb apart thinking I messed something up only to find the bowl had brown fuel. I then flushed the carb and then installed a 3' fuel line after the fuel pump to purge the fuel lines until it was clear hooked back up and she fired right up.

I thought I had found the problem so 2 days later I was going to start her up.I flushed the fuel lines before attempting to start it up brown fuel followed by clear I'm now back to square 1 and cant seem to get it started again. It baffling me because Its started twice and during both time I've let it run for 20 minutes and it idles/sounds really nice,


Here is a list of what I've done/checked so far.
* 3/4 full tanks of gas
* Air screws on carb seated and backed off 1.5 turns
* fuel filter clean
* change all plugs gap to .44
* Check spark on all 8 plugs, good
* New Cap and rotor
* Check all Motor/electronic connections

[Digger]

Sounds like nothing is wrong with the engine, but you are getting bad fuel and need to find the source.

You say you put fresh fuel in the saddle tank, so I assume the rear tank has old fuel in it. Any chance the selector valve is failing and feeding the engine fuel from both tanks or randomly drawing from one or the other?

[Strike2]

Yes the rear still has old gas, it also has an aftermarket rear MTS plastic tank, with a dash switch for the electric pump which I have never turned on. My though was the dirty fuel was just coming from the residue in the fuel lines, I will isolate the rear tank tubes just to eliminate that possibility. I would think if it was pulling fuel from the old tank it would show up in the carburetor bowl which is clean?

[Digger]

Hard to say without standing in front of the truck myself. It is odd that you keep getting brown fuel out. Once the lines are flushed, they should stay clean unless they are falling apart or drawing from another source. The selector switch issue is a long shot, but its hard to believe that your lines are that bad, but nothing is impossible.

[TOOLMAN]

That plug gap seems a little big to me...IIRC it should be around .032 unless you're running an HEI type unit or coil packs.

[Strike2]

The 75 did come stock with solid state ignition and the gap "44" was recommended from Autozone. I could try and re-gap to 32.
When I rebuilt the carb I removed the intake gasket to clean the base, and the new gasket in the carb kit didn't have the cut out so this port was sealed. I cut the gasket thinking it needed to be open. I'm not really sure what this post is for??

[Strike2]

I'm still having no luck getting the Bronco started pulled the carb off several times double/triple checked everything and still not able to get it to fire. It will not even fire up with starter fluid. One at a time I have pulled each plug and all 8 have spark, plugs are sooted but still should be able to fire. I removed the ICM looks to be OEM and took it to AutoZone for testing (not really confident in the guy behind the counter) anyhow they told me it was bad? They did have a replacement one but after looking at it the 3-prong was only 2 and I wasn't 100% sure on the part they were giving me. Stopped at O'reilly's and the couldn't test it and offered the same part.

I Researched it today and seems the 3rd wire "blue" is not needed, so could I have a weak spark? or is the ICM bad and not giving the right signal. what's your thought's as I'm going to another AutoZone after work today to have it tested and will probably just buy another one.

I will set the motor to TDC and check rotor position just incase the timing chain skipped? Although I think this is not the case.

[D&D72]

Those ignition modules are notorious for going bad. so much so that I always carried a spare.

[Strike2]

Well had the ICM tested again and it tested bad bought another installed and engine cranked but no start, checked and have power at the coil, pulled plug wire #1 and install a spare plug and got no spark WTF. Got a beer and the Chilton book and started reading page 67/ 74 about ICM wiring and that some ICM wires were sold with wires crossed and to double check color codes, well my purple and black wire were crossed so I reversed them and checked spark again on #1 . I just barely bumped the starter and she fired right up even with the #1 plug not having the wire hooked up.
Wow what a hard lesson the ICM stared twice and then decided to die!

[Rox Crusher]

Those ignition modules are notorious for going bad. so much so that I always carried a spare.

This is very sound advice !