I have a 1986 bronco that i did a full swap on and had a new 5.0 running last week I changed the throttle body and now it is barely cranking almost like the battery is dead so I changed the battery but its still acting the same way, we have regrounded the engine checked firing order, checked spark plugs. It has spark and has fuel. WHATS NEXT TO CHECK????????????

 

Does the new engine have high compression? That will slow down a starter. You might need a high power starter.

Another trick - crank the engine for 5 seconds. Carefully touch each of the cables, cable ends, and terminals from the battery to ground, battery to starter relay, starter relay to starter and starter to ground ( if you have it ). If one of those connections or cable ends are bad ( high resistance ) the heat from that high resistance connection will burn the ****ens out of your fingers. You might get burnt fingers but you will find the bad connection.

 

would it still be a high compression motor even if this starter has started it before??? I will check the grounds again and the relays

 

use a voltmeter to check them wires.. make sure its getting 14.6 V even simpler and smarter than risking burning your hands

 

bronco - I assumed from your post that you put a different or rebuilt engine in. By high compression I meant an engine with a higher compresssion in the cylinders than you had in the previous engine. It is usually done to increase horsepower. It can be achieved with a longer stroke on the crankshaft, high compression pistons, shaving metal off (milling) the head, installing high performance heads, or raising the boost on a blower. Even a new set of rings can raise compression on an old worn out motor - but that shouldn't affect your starter unless its worn out itself. If your starter started this same motor before I would just start looking at cleaning terminals and checking wires.

I am not sure what brandonhadnot is refering to about using the voltmeter for a check. When the starter motor cranks off the engine it pulls LOTS of amps (like 150+) and the battery voltage will drop quite a bit. Unless you know what it used to read during a crank the new voltage won't tell you a lot.
BTW - the business about burning you fingers is not really that big of a deal. Just touch the wires lightly to see if they are hot before you grab them and you will be fine.

Good Luck and let us know what you find.

 

ok i firgured it out last night there was a ground that wasnt grounded i attached that and it turns like a champ now and runs strong going to time it today and put it on the road tonight thanks for all the help guys