PDA

View Full Version : Hard to Restart



Mike041
04-29-2004, 11:09 PM
" Hey guys, I hope someone here can help me out. I have a 1995 7.4L Mark V Bravo III that I cracked promptly in 1995. After the rebuild (new block with old heads) it never really started right after it heats up. I probably have less then 60 hours runtime on the block.

Startup from cold is fine. The engine cranks with good speed and fires with no problem. After it heats up and I take a trip as little as 15 minutes, shutdown, then try to restart within a couple of minutes of shutting down, the engine does not want to hardly crank at all. It barely rotates. If I let it cool for 10-15 minutes it cranks over with no problem.

When I rebuilt I kind of went a bit over stock with 10.3:1 CR. Looking back there were some things that don't seem right now.

The last piston I put in I had to get repressed because it was pressed on backwards but the place I had press it on pressed it the same way a second time. I had to get it repressed a 3rd time. Also I realized after the fact that I didn't press in the water jacket dowels (from the block to the heads) into the block deck.

Water temp is good at 160. Oil pressure is good at 40-60. There is no steam in the exhaust while running, only momentarily after a restart. Timing is at 10-12 and has also been tried at 8 and 14 BTDC. The plugs are burning perfectly with no water on them or buildup. I replaced the starter with a 10% higher torque starter. Replaced the batteries. Checked the battery cables for good contact surfaces. Battery voltage is good when trying to restart. Still running the stock carb, intake, and thunderbolt ignition.

Some of my theories are:

The compression is too high. I have thought about changing the head gaskets to lower it a bit or getting a high torque marine starter.

I am leaking just enough water into the cylinder because of the missing dowels and am pressurizing the cylinder when I shut down. Along the same lines it could be a cracked head. I tend to rule this out because the plugs are clean with no water and as well as the oil.

I have the connecting rods in incorrectly which is causing them to expand and bind on each other at the crank when the block heats up. This one I am the most unsure about and the most worried. Can the crank still turn without binding the rods when cold? I don't have a problem hand cranking the engine when cold.

It's a bit long winded but I know I hate not getting enough info when I read posts. I hope someone out there has some good ideas.

Mike "

boatrep1
05-02-2004, 03:41 PM
" MIKE

IF YOU HAVE A DIGITAL VOLTMETER TRY THIS TEST.
WITH RANGE ON 0-12 VOLTS, CONNECT RED TO BATTERY POS. POST (NOT CONNECTOR), BLACK TO STARTER POST (NOT CONNECTOR). YOU SHOULD READ .5 VOLTS OR LESS.

CONNECT RED LEAD TO BATTERY NEG POST. CONNECT BLACK LEAD TO STARTER BODY (NOT ANY WIRE TERMINALS). CRANK MOTOR. READING SHOULD BE .5 VOLTS OR LESS.

IF READINGS ARE NOT CORRECT THEN YOU HAVE A HIGH RESISTANCE IN THE SYSTEM.

THIS TEST SHOULD BE DONE COLD AND HOT WHEN ENGINE WON'T TURN OVER.

DIFFERENTIAL VOLTAGE TESTS ARE THE BEST WAY TO TEST FOR RESISTANCE IN THIS INSTANCE. .5 VOLTS IS HIGH END FOR BATTERY CABLES AND .2 OR LESS FOR PRIMARY WIRES.

STEVE "

davism2
02-01-2007, 03:06 PM
"I know it's a long time since this was posted. But, I am new to this site. If Steve's suggestion doesn't work first. Fuel could be getting into the cylinders causing compression to be very high that the starter can't overcome."